Hi, my name is JJ and I'm an overeater, err I mean overheater! ;) Well both! ):h All the overheating discussions have stirred up a lot of controversy on the DP, some swearing their LLY's won't/don't overheat while others swear theirs will. So exactly what is overheating? I've heard several explanations, opinions, theories, etc., but what are the facts? :confused:

While there are several sources we could go to, I chose to go with GM's little handbook they put in every truck. If you haven't read it you should, especially the little Duramax diesel pamphlet, interesting reading. I figure they designed it so they should know the engine/tranny's operating parameters, what to do if things do get hot, plus you won't void your warranty if you follow their instructions. ;)

Here's what GM says:

Owners manual:

Page 3-46: Engine coolant temperature gage: Gage will read 210*F or less. If you are pulling a load or going up hills, normal to approach the 250*F mark. If it reaches 260*F it indicates the cooling system is working beyond its capacity.

Same page: Tranny temp gage: Normal operating range from 100*F to about 265*F. Ally can go to 275*F before
DIC displays a TRANS HOT IDLE ENGINE warning and chimes sound until temps fall below 265*.

There are warnings accompanying these conditions all should read.

Duramax Pamphlet, page 5-34: If you get a low coolant level message, if equipped, but see or hear no steam, the problem may not be too serious. Sometimes the engine can get a little too hot when you: Tow a trailer. See "Driving on Grades" in the owners manual index.

Owners manual "Driving on Grades" pages 4-93: When towing at high altitude on steep uphill grades, consider the following: Engine coolant will boil at a lower temperature than at normal altitudes.... If you do get the overheat warning, see Engine Overheating on page 5-38. Flipping pages....

5-38: Overheated Engine Protection Operating Mode (V8 engines only). If an overheated engine conditions exists and the REDUCED ENGINE POWER message is displayed, an overheat condition protection mode engages(not verbatum). Driving extended miles and/or towing a trailer in the overheat protection mode should be avoided. Flipping pages...

5-40 "If no steam is Coming From your engine": Same as Duramax pamphlet page 5-38.

I haven't see many guys posting engine/tranny temps this high, couple at best. Some guys feel like overheating is anytime the engine coolant gage goes above 210*F, but GM states temps up to 250* are normal when pushing these engines hard. Tranny can go up to 275* before it starts to protect itself.

One interesting point I read was the degradation of engine oil and tranny oil when you run higher temps. The highest engine/tranny temps I have personally seen towing above GCWR were 230/220*F, I slowed down since I thought I was overheating. Turns out I wasn't. ;) Just didn't know any better. :o: Though if I had continued to push it I just may have, this is the $24k question.

Personally I will follow GM's direction until they tell me otherwise. Well, except for towing slightly above GCWR and my mods which should have improved my trucks ability to tow and not overheat. So far so good. Each of us has our own opinions on performance mods. ;)

Take this for what its worth. This is not my personal opinion so no flames please. Those of you following the owners manual, towing within GCWR and still puking your trucks need to take it to the dealership and get er fixed. These are the guys we're trying to help out on the overheating threads. Some of you may have similar problems with your trucks under identical circumstances, so don't chastise their work. This may be a design issue or something that GM needs to address. Cheer them on and support them whenever possible! :ro)

Those towing well above GCWR really don't have too much room to complain. These trucks just weren't designed to pull anything you can throw behind them. That's why GM, Ferd, Dodge, Peterbilt and others make "da Medium and Heavy duty trucks". ;)

Those of you operating within GM's parameters can simply have a nice day and enjoy your trucks! :D

I REALLY HOPE THIS THREAD DOESN'T TURN INTO ANOTHER ONE OF THE OVERHEATERS VS NON-OVERHEATERS. No personal opinions are requested or required. This is GM's data, not mine. Like TxC says: SHIELDS UP! :boxing: JJ :)

ttt

Very nice post JJ:) .
Thanks
DAN

OK, I can live with that IF someone tells me that the Ally temp sender is post TC and on the way up to being cooled.

If in fact the temp I see on the guage is internal temp, then it still goes against what I've been taught about automatic transmission reliablity and longevity.

good post there JJ :exactly:

I have gotten the Trans Temp warning. You get two of them. First one about 250 deg, and the second at 270. This was due to a failed torque convertor, unladen cruising at 65.

I imagine there are 2 for the coolant as well, but I have only gotten the first one at about 245, then I back down.

This might just be for DIC equipped trucks, but I don't know.

McRat, I can't be the only one thinking "no surprise to see you hitting those temps"! ):h Question is has Kat hit higher temps? :D

oilburnr, you might post on the Allison forum, aka MikeL territory! ;)

So far it appears this thread is being received as intended. Thanks! JJ :)

I just want to say to JJ thanks for the great post. As a new owner and just at my 500 mile mark, and getting ready for my first tow, some of these post had me scared to death, but you put it back in light, go by the book and follow the GM guidelines and you can't go wrong. Thanks, Erich

JJ, excellent post! I just returned from Colorado this PM and here are some observations that I would like to note.

1. GCWR is +/- 22500 lbs
2. My truck is a 2005 GMC Crew Dually 4x4 SLT (GMC)
3. MBRP Exhaust and catyrectomy are the only mods.
4. Maximum Altitude was 11,550 over Slummgollian Pass near Lake City, CO. Avg grade is roughly 7% with steepest pitches at 10% around switchbacks:eek: Climbs from 8700 feet to 11550 in only 8 miles.
5. Outside air temp was about 70.
6. Max engine temp was 215 for about 30 seconds till the fan came on with a fury and then the temps settled at about 200-205.
7. Max tranny temp was 220 going down the same hill, and only 200 going up.
8. Max EGT was at or about 1350.

I did not flog the truck, but simply let it do it's thing. I ran right at the posted speed limit, which for most of the pass is 35 MPH.

My fan seems to run a lot, but I am OK with that if it keeps the temps in check. It may hurt the MPG a little, but an avg of 10 is not bad in my opinion pulling this kind of weight.

Thanks for reading.

Very well researched post!

I have read allot of these doom and gloom posts about "overheating" without ever hearing about what D MAX LTD. has to say about What is too hot for the engine they designed.

If GM was having to replace these engines on any kind of regular basis because they blew up from overheating I guarantee they would fix the problem really quick. The crazy thing is, I personally have yet to hear of ANY of them actually breaking because they "overheated". Yet we all seem to be so worried.

The fact is these engines have 100,000 mile warranty's on them. If they do have problems with them they will be fixed one way or the other.
If Isuzu/ GM doesn't have any problem with 245 deg. coolant temp then neither will I.

Just think, No matter how worried we may get It could be worse... We could have bought 6.0 Powerstrokes...:eek: :eek: :eek:

For the record: I tow over 10,000 lbs with the Edge Attitude. According to the digital Gage, my truck has only gotten as high as 220 one time, It usually won't go over 210-215. I tow at altitudes well above 6,000 feet.

I can say the writing on the wall I mean DIC LOLhttp://i17.photobucket.com/albums/b82/socal-lly/100_1693.jpghttp://i17.photobucket.com/albums/b82/socal-lly/100_1699.jpg

Those look like:

The second coolant warning (First says Coolant Hot or something)
The first trans warning (second says to idle truck)

If I remember right.

Those look like:

The second coolant warning (First says Coolant Hot or something)
The first trans warning (second says to idle truck)

If I remember right.the first warning on my truck is coolant hot and the trans fluid is hot I think:) http://i17.photobucket.com/albums/b82/socal-lly/100_1697.jpg

So JJ, what does the manual say determines the tow rating of the truck?

.

TxC,

There is a tow chart in the owners manual that provides this intel for all our trucks. Best to take a look for your particular vehicle. JJ :)

Did the LB7 owners manual have the same language in it about running engine/tranny temps this high? :confused: I read an article the other night on overheating Duramax's, turns out it was a 2001 article. Apparently the LB7 had some overheating issues initially as well. Just found that interesting.

Anybody have this intel? JJ :)

Did the LB7 owners manual have the same language in it about running engine/tranny temps this high? :confused: I read an article the other night on overheating Duramax's, turns out it was a 2001 article. Apparently the LB7 had some overheating issues initially as well. Just found that interesting.

Anybody have this intel? JJ :)

Thats a very good question. If not it would appear GM did test the LLY and knew ahead of time it was gonna crap out so they declared it "normal" for it to do so.

Then again maybe the LB7 has the same disclaimers in its booklets. Who has the LB7 owners manuals?

.

Keep in mind, from an engineering perspective, there is a difference between:

1) The operating temperature range and
2) At what temp the truck was designed to operate at while pulling a load.

The manual has to cover all possible scenarios that the driver can get the truck into and advise the driver what actions he should take (if too hot).

Just because the manual indicates the engine can operate to 245 deg F, does not mean that was the design point where the engineers expect it to operate at while pulling a large load up a hill.

Keep in mind, from an engineering perspective, there is a difference between:

1) The operating temperature range and
2) At what temp the truck was designed to operate at while pulling a load.

The manual has to cover all possible scenarios that the driver can get the truck into and advise the driver what actions he should take (if too hot).

Just because the manual indicates the engine can operate to 245 deg F, does not mean that was the design point where the engineers expect it to operate at while pulling a large load up a hill.

But one thing we know for sure is that they expected it to pull 15k or so right? Knowing that was the design requirement would seem to necessitate including a cooling system that was capable of that task without running into all of the various alarms and such.

Otherwise why not rate it for what it really can handle without issue?

.

I agree 100%. The point being, what temp did the engineers expect the cooling system to be at when pulling 15K pounds (and I suspect it is no where near 245 deg F). The manual is not the design point.

I agree 100%. The point being, what temp did the engineers expect the cooling system to be at when pulling 15K pounds (and I suspect it is no where near 245 deg F). The manual is not the design point.

:exactly:

The manual is more of a CYA document in this respect. I don't know how we could answer your question though.

.

So following your logic GM puts in the owners manual it is perfectly normal to go ahead and operate these trucks up to 265* while towing heavy just to cover their a$$e$. Odd way of looking at it. :rolleyes:

Their owners manual states if you follow their procedures and run it to 265* and the engine blows up they will replace it under their 100k mile warranty. How does that cover GM's a$$? :confused:

Your logic doesn't appear supportable by the facts? If GM were going to cover their a$$ they should tell you to back down at 230* ECT's and not run the risk of even more repairs associated with running up to 265*. Sorry, just don't see the logic! :o: Later. JJ :(

So following your logic GM puts in the owners manual it is perfectly normal to go ahead and operate these trucks up to 265* while towing heavy just to cover their a$$e$. Odd way of looking at it. :rolleyes:

Their owners manual states if you follow their procedures and run it to 265* and the engine blows up they will replace it under their 100k mile warranty. How does that cover GM's a$$? :confused:

Your logic doesn't appear supportable by the facts? If GM were going to cover their a$$ they should tell you to back down at 230* ECT's and not run the risk of even more repairs associated with running up to 265*. Sorry, just don't see the logic! :o: Later. JJ :(

I meant it was CYA in the respect that they have to establish limits that the truck can get into that they will cover. The computer takes it out of your hands anyway after a certain point, so GM doesn't trust you to do whats "right" in the first place.

I am also saying running the truck up against those limits should not be considered "normal". Why do you think they put in all the DIC warnings and such? They don't want you up in those areas because you are in any area that just might cost them $$$ under your 100k warranty plan.

You are your own worst enemy Tx. Same back at 'cha. Good luck.

Ed

Can a mod please ask these guys to get lives and stop bothering me? The purpose of this site is NOT for you guys to harrass anyone

You sure got snowed by this pack of losers JJ. Too bad.

.

I will go down to a used lot JJ and see if any LB7's have the manuals inside to see if there is any difference.

.

Ok guys, since most are adults here, how about acting like it.

Harrassing PM's aren't going to help and may be hurt YOU instead.

I hate to be a PITA but that's it.

If running at 230* plus is OK, then why don't the other year D-Max's run as hot all of the time ? I have a 04.5 and it consistantly runs hot, only when pulling a trailer in 95* plus temp and up a grade of 2% plus. If I do not back off at 230* plus, I can get the DIC to display a warning everytime.

Bodine, did u ever tow w/ stock tires?

I now on mine it makes the truck work harder to pull the higher overall gear ratio.

I've also posted here about how much my attitude temp is lower 10-20* than my truck temp gauge.

How much power are u running and egt * ?

If running at 230* plus is OK, then why don't the other year D-Max's run as hot all of the time ? I have a 04.5 and it consistantly runs hot, only when pulling a trailer in 95* plus temp and up a grade of 2% plus. If I do not back off at 230* plus, I can get the DIC to display a warning everytime.
If you didn't back off how hot do you think? Is it a slow climb or a rocket.
Mine will slow climb even with the fan, if I happen to hit the hill w/o fan , look out 1/2 mile could jump 30+ deg ECT.

TxC, thanks for running that down. ;)

Bettered, moving on please. You've got work to do! ;)

DMax Tim, thanks for the support and oversight.

It's been a long day, emotions running high, tempers flaring. Hopefully tomorrow is a better day. JJ :)

Nevermind JJ, I have better things to do so I won't be seeing what the LB7 manual says. Sorry. It is irrelevant to the issue anyway.

I am tired of all the crappy games being played over this thing. There are better ways for me to spend my efforts than what this has developed into.

Good luck trying to beat it. I am sure others truly want it solved, which is the correct thing to do, we'll see where that goes.

.

TxC, you have mail. JJ

I have owned both rigs lb7 and lly as many other members on dp. I can honestly say I am sorry I sold my lb7 for this pos lly. These temps are definetly much hotter than what my other truck performed. Gm must have figured it out that running these trucks this hot will let them get to 102,000 miles and then the works comes apart! I have a few buddies who had the 100,000 mile blues with cracked head gaskets and oil pump pickup tube coming off, surely this wasnt caused by excessive temps. Or? Any way not to beat a dead horse any more than it possibly can be beaten... oh well lets beat the horse some more when your truck flat out shuts off that must mean it is too hot, If gm had more gauge to use they would use it! I have been around many of fords and dodges that have no trouble reaching high mileage but good luck to all the suckers with the lly!

"I REALLY HOPE THIS THREAD DOESN'T TURN INTO ANOTHER ONE OF THE OVERHEATERS VS NON-OVERHEATERS. No personal opinions are requested or required. This is GM's data, not mine."

From my original post. The intent was just to provide the intel, that's all. But if anyone wants to vent, have at it! lol JJ

To reply to the thread topic, I will add my piece then go

Overheating: a state or condition in which the vehicles coolant rises, after the full open status of the thermostat(s) is (are) commanded, that leads to a momentary or progreessive deterioration of the coolant temperature, or a condition in which the vehicles heat load, if not reduced, will create an uncontained rise in system temperature. Of or pertaining to the characteristic of a cooling system that cannot control the coolant temp so as to maintain it at or below the temperature of the hottest thermostat, or, in an elevated state, in a state of equilibrium that represents stabilization.


by this definition, 211 is an OH situation, but only if it is rising. assuming a 210 stat
,

To reply to the thread topic, I will add my piece then go

Overheating: a state or condition in which the vehicles coolant rises, after the full open status of the thermostat(s) is (are) commanded, that leads to a momentary or progreessive deterioration of the coolant temperature, or a condition in which the vehicles heat load, if not reduced, will create an uncontained rise in system temperature. Of or pertaining to the characteristic of a cooling system that cannot control the coolant temp so as to maintain it at or below the temperature of the hottest thermostat.


by this definition, 211 is an OH situation, but only if it is rising. assuming a 210 stat
Thats exactly the correct explanation from an engineering point of view!
The temp can got for a short period of time above the thermostat settings - thats when the roaring fan comes on. That fan has the task to cool the engine below the temp of the hottest thermostat (which is does in normal condition). After that temp is reached the fluid clutch will disengage the fan and the thermostat will fully open again and maintain 210 F - until its getting hot again, the fan comes on again and so fort... Steady rising temps above 210 F without coming back down is overheating - whatever that manual may say IMHO.
Those manuals are NOT writting by engineering at GM but from Marketing people - engineering might take a quick look at it but thats all...

Maybe we should draw a distinction between "overheating" and "overheated" LLY's? Overheating being ECT's above 210* up to 260*, overheated at 265* or when the engine goes into protection mode whichever comes first.

By the engineering definition my LLY technically overheats every time I tow a small grade or accelerate with the 5ver in tow. What I find unusual is how close the LLY operates to its upper cooling capacity at all times. I can make my ECT's go up 6*-8* just on a hard acceleration, that's awfully fast for ECT's to climb don't you think? JJ

once again I point to inherrent airflow weakness, apparently more prominent in the Chevy.

Then the "dumb" T-V fan comes in with a lag behind the problem. It can be significantly out of "cycle" with the heat onset. That is the cost of having no direct input on the fan. The variable that engages it, hot air, is at issue. Anything can trigger it, even recirc heat in the engine bay.

Notice it's gone for 06.

Agreed.

Short comment:

This "Fan" is an Analog device, the coupling is Linear and Progressive, as apposed to Incremental.

The fan coupling is controled by a variable orfice that is then controled by a bi-metal strip (linear switch).

The Stack Air (discharge) Temps (SAT), heats/cools the fan hub (bi-metal strip) controling fan coupling, (and is a Linear function).

Fan coupling follows the rate of change in SAT.

When the SAT change, the fan coupling change, Every Time. When the change is slow, there is no perception of a change in Fan Load (RPM), but there was.

When the fan appears to "Turn On/Off" quickly, "Roar", there was a temp "Spike", up or down, (linear, but quick in time).

I like the "Water Pump", "Casting Residual" point, thinking........

FWIW

Idahofox

Agreed.

When the fan appears to "Turn On/Off" quickly, "Roar", there was a temp "Spike", up or down, (linear, but quick in time).

I like the "Water Pump", "Casting Residual" point, thinking........

FWIW

Idahofox

I never seem to experience modulation, not that I can sense anyhow. Could be I just never see "hot".

Agreed.

Short comment:

This "Fan" is an Analog device, the coupling is Linear and Progressive, as apposed to Incremental.

The fan coupling is controled by a variable orfice that is then controled by a bi-metal strip (linear switch).

The Stack Air (discharge) Temps (SAT), heats/cools the fan hub (bi-metal strip) controling fan coupling, (and is a Linear function).

Fan coupling follows the rate of change in SAT.

When the SAT change, the fan coupling change, Every Time. When the change is slow, there is no perception of a change in Fan Load (RPM), but there was.

When the fan appears to "Turn On/Off" quickly, "Roar", there was a temp "Spike", up or down, (linear, but quick in time).

I like the "Water Pump", "Casting Residual" point, thinking........

FWIW

Idahofox

There is nothing linear about that fan, its a simple 2-point regulation principle - ON or OFF, which means the fan is freewheeling with 45...50 % slip disengaged or only 5 % slip when engaged. There might be some kind of short time between the 2 conditions but thats very short - within seconds once the bimetal spring finally opened the orifice to let the fluid into the outer clutch part the fan speed will be between 45.....5 % slip but that time is SHORT!
Therefore the only really controle over ECT is via the open/closed thermostats, the fan follows that slowly (too slow) via low or high speed cooling. :exactly:

RDL has commented that he felt it had 3 distinct levels of loud, with rising ECT

Count JJ as one that hears the fan engaging at different intervals. Sometimes I can hear it starting to engage if I'm climbing a grade. If I am pushing it and temps start to spike it will engage with a roar. Not sure why, totally SOTP's impression. JJ :)

I agree, both my Wife and myself hear 3 levels of "hookup" as it is, normal, turbine type and rocket- I can't hear in the truck.

John is probably someone who can clarify this.

Fingers commented that on one of his runs testing the dam that when he got to the top of Ballbuster, the fan was On but he never heard it come On.

FWIW

Idahofox

KB,

Would this fit in your Christmas stocking ? (Http://www.ngclark.com.au/Products/HortonVmaster/ViscousFanDrives.htm)

Idahofox

Therefore the only really controle over ECT is via the open/closed thermostats, the fan follows that slowly (too slow) via low or high speed cooling. :exactly:

Our thermostats are analog devices, with infinite range from Open to Closed.

FWIW

Idahofox

Idaho, If that clutch you linked, can pull harder at lower rpm, I am all for testing a sample.

I have a suspicion they are oem suppliers though, probably not much interested is us small time.

Our thermostats are Linear devices, with infinite range from Open to Closed.

FWIW

Idahofox

If you're refering to the fan thermostat, I don't know if I can explain it, but its not like that. It is a very
definate and predetermined setting, almost like a gear change. When its
kicks up to high it feels like your truck downshifted. Its pulling that
much power away from the motor!

in my opinion then, the first stage is too much. Could be slower and quieter, say at 205, than step up at 210, then at 215. Problem is, the air temp is so whimsical, that's what sucks. Trying to make this clutch "logical" is like trying to potty train mice.

Added to the eq is that the clutch is forever creating it's own heat (that's what the fins are for) the more slip the more heat, it's not unlike a TC.

Our thermostats are Linear devices, with infinite range from Open to Closed.

FWIW

Idahofox
I did NOT say anything about the linearity of the thermostats - just the fan clutch (fluid coupling).
The infinite range from open to closed does NOT necessarily make the thermostats linear either - linear would mean that for a certain temp change the thermostats would change a certain amount on a linear scale (like inches/degree Fahrenheit) - I am sure thats not the case, this are simple cheap devices and they don't need to be linear to function properly.
As for the clutch operation there are NO possible 3 conditions of speed but just 2. The third one your are hearing is the transition phase from low to high speed (which is in theory any value between 45....5 % slip)
BUT thats just the theory - I will measure the rpm when I got the tool and clarify this.

As for the clutch operation there are NO possible 3 conditions of speed but just 2. The third one your are hearing is the transition phase from low to high speed (which is in theory any value between 45....5 % slip)
BUT thats just the theory - I will measure the rpm when I got the tool and clarify this.

When you get the tool to clarify this, please do so. Myself and several other members have posted hearing 3 definite and pronounced speeds. If not the transition you speak of will last hours, and is consistent and locked to engine RPM.

NOTE; This post was edited to remove piss & testosterone.

mahalkita,

Maybe we're saying the same thing just differently? Your saying two speeds, either fully engaged or disengaged and free spinning. What I think Rick and I are hearing is a gradual engagement due to heating up on the viscous coupling due to heat coming across the stack while towing, a low roar. Sometimes on flat ground I will hear the fan start to increase, but not fully engage to a roar. If the viscous fluid gets cooled while before full engagement it will back off.

I've mentioned before that I can tell when my fan is starting to engage, it isn't always an abrupt engagement and HP stealer! Things just heat up, it starts to pull air but things cool off quickly and it releases and goes back to free spin. Make sense? If that isn't the way it is supposed to work then mine is broke. JJ

When you get the tool to clarify this, please do so. Myself and several other members have posted hearing 3 definite and pronounced speeds. If not the transition you speak of will last hours, and is consistent and locked to engine RPM.

NOTE; This post was edited to remove piss & testosterone.
Thanks for the removal! I don't try to be a smartass but thats how it should work in theory - I could never feel or hear more than 2 speeds on mine but thats just me.

Hope that the tool works on the fan (its designed for another purpose) - that will prove the possible difference between theory and reality!

Thanks for the removal! I don't try to be a smartass but thats how it should work in theory - I could never feel or hear more than 2 speeds on mine but thats just me.

Hope that the tool works on the fan (its designed for another purpose) - that will prove the possible difference between theory and reality!
I hope so too. We are still at a loss for definite information. So much of what we are doing is limited by lack of test equipment. We need a GM engineer Traitor! :D

with what we HAVE measured, the fan can spin a hurricane, it's still not as effective as it can be because of design limitations of the vehicle, I posted my measurements on the orig solutions thread today

mahalkita,

Maybe we're saying the same thing just differently? Your saying two speeds, either fully engaged or disengaged and free spinning. What I think Rick and I are hearing is a gradual engagement due to heating up on the viscous coupling due to heat coming across the stack while towing, a low roar. Sometimes on flat ground I will hear the fan start to increase, but not fully engage to a roar. If the viscous fluid gets cooled while before full engagement it will back off.

I've mentioned before that I can tell when my fan is starting to engage, it isn't always an abrupt engagement and HP stealer! Things just heat up, it starts to pull air but things cool off quickly and it releases and goes back to free spin. Make sense? If that isn't the way it is supposed to work then mine is broke. JJ

I pulled heavy for the first time this past weekend and mine did the exact same thing. My fan speed (and noise) would increase then followed by full engagement within 5 - 10 seconds.

Agreed.

Short comment:

This "Fan" is an Analog device, the coupling is Analog and Progressive, as apposed to Incremental.

The fan coupling is controled by a variable orfice that is then controled by a bi-metal strip (analog switch).

The Stack Air (discharge) Temps (SAT), heats/cools the fan hub (bi-metal strip) controling fan coupling, (and is a Linear function).

Fan coupling follows the rate of change in SAT.

When the SAT change, the fan coupling change, Every Time. When the change is slow, there is no perception of a change in Fan Load (RPM), but there was.

When the fan appears to "Turn On/Off" quickly, "Roar", there was a temp "Spike", up or down, (linear, but quick in time).

I like the "Water Pump", "Casting Residual" point, thinking........

FWIW

Idahofox

This is not a thesis, promise.

Viscous coupling with Silicone Oil:

An engine driven plate (attached to the water pump shaft, engine RPM), with fine grooves, rotates within the fan clutch housing, also finely grooved (to which the fan is attached).

Between the housing and the plate is silicone oil. A property of Silicone Oil is that it's viscosity is less dependent on temperature (as with normal oil), than on velocity. The greater the oil velocity the greater the viscosity.

The greater the difference in speed between the oil layer on the housing and the oil layer at the plate, the thicker the oil becomes and the result is tighter coupling.

As the coupling increases the fan speed increases, the speed difference (plate/housing) decreases and the silicone oil gets thinner, thereby less coupling. This phenomenon limits the fan RPM to a percentage of engine RPM.

The plate/housing coupling is also controlled by an orifice that is then controlled by a bi-metal strip (analog switch). Inside the fan hub, this switch moves a small pin that controls the amount of silicone oil that is allowed to flow between the grooves. Increasing stack air temps, results in more silicone fluid entering the grooves, resulting in more coupling between plate and housing and giving a higher fan speed.

Summary:

Two elements control the degree of coupling: engine RPM and quantity of Silicon Oil between the grooves.

FWIW.

Idahofox

I did NOT say anything about the linearity of the thermostats - just the fan clutch (fluid coupling).
The infinite range from open to closed does NOT necessarily make the thermostats linear either - linear would mean that for a certain temp change the thermostats would change a certain amount on a linear scale (like inches/degree Fahrenheit) - I am sure thats not the case, this are simple cheap devices and they don't need to be linear to function properly.
As for the clutch operation there are NO possible 3 conditions of speed but just 2. The third one your are hearing is the transition phase from low to high speed (which is in theory any value between 45....5 % slip)
BUT thats just the theory - I will measure the rpm when I got the tool and clarify this.

I stand corrected. Let me change Linear, to analog.

My bad.

Idahofox

If you're refering to the fan thermostat, I don't know if I can explain it, but its not like that. It is a very
definate and predetermined setting, almost like a gear change. When its
kicks up to high it feels like your truck downshifted. Its pulling that
much power away from the motor!

Rick,

I was referencing the engine thermostats, and I have posted a correction to my statement.

What you are saying is clear and I agree.

Idahofox

OK, I can't believe I'm gonna say this. If you guys can get a vendor to donate an electric water tempature gauge and 2 senders I will make adapters and put them in my radiator hoses.
I will not at this point un-due what I have done, nor will I stop doing modifications I think will help. But at least we will have a starting point and I will make a second set of adapters to install in another truck if needed.

Is there a correlation with OH'ers and battery replacement?

Does the PS battery fail more often than the DS?

Wandering minds !

Idahofox

This is not a thesis, promise.

Viscous coupling with Silicone Oil:

An engine driven plate (attached to the water pump shaft, engine RPM), with fine grooves, rotates within the fan clutch housing, also finely grooved (to which the fan is attached).

Between the housing and the plate is silicone oil. A property of Silicone Oil is that it's viscosity is less dependent on temperature (as with normal oil), than on velocity. The greater the oil velocity the greater the viscosity.

The greater the difference in speed between the oil layer on the housing and the oil layer at the plate, the thicker the oil becomes and the result is tighter coupling.

As the coupling increases the fan speed increases, the speed difference (plate/housing) decreases and the silicone oil gets thinner, thereby less coupling. This phenomenon limits the fan RPM to a percentage of engine RPM.

The plate/housing coupling is also controlled by an orifice that is then controlled by a bi-metal strip (analog switch). Inside the fan hub, this switch moves a small pin that controls the amount of silicone oil that is allowed to flow between the grooves. Increasing stack air temps, results in more silicone fluid entering the grooves, resulting in more coupling between plate and housing and giving a higher fan speed.

Summary:

Two elements control the degree of coupling: engine RPM and quantity of Silicon Oil between the grooves.

FWIW.

Idahofox

Looks good - nice pictures!

I measured 2 different speeds on mine and posted the result in the conference thread. Since yours is 2 years older maybe we both are NOT talking about the same thing....

Looks good - nice pictures!

I measured 2 different speeds on mine and posted the result in the conference thread. Since yours is 2 years older maybe we both are NOT talking about the same thing....

I believe we are talking the same thing.

I need to qualify. The change from low to high speed may (probably is) quick enough to appear as an Off/On event. By design (characteristics of viscous coupling) the event is analog/over time; I accept Quick Time !

We're on the same page.

Idahofox

I'm resurrecting one of my previous threads to use to provide some additional intel. The bullets below were obtained from a technical article I found on the internet. Some we have discussed, some we have not. I'll try to highlight any areas that are new intel or provide emphasis to something we have already discussed. If I make any comments I'll bracket them.

Here tis:

Thermal overload also puts tremendous stress on the cylinder heads, and in particular aluminum heads because aluminum expands at a much higher rate than cast iron when it gets hot. This, in turn, may crush the head gasket between adjacent cylinders causing the gasket to fail and leak. A hot head can also succumb to warping and cracking if it gets too hot, causing even more problems that will be expensive to fix.

Lubrication is another area that will suffer as a result of overheating. The viscosity of the oil gets thinner as the oil heats up (I had this backwards :o: :D ) and if it gets too hot it can start to oxidize (burn) causing a breakdown of the lubricant. The parts most likely to suffer are the rod bearings, rings, cylinder walls, valve guides and upper valvetrain components.

Fortunately, water has a tremendous capacity for absorbing and carrying away heat. For every degree in temperature rise, water can absorb 10 times as much heat as cast iron and five times as much heat as aluminum. Ethylene glycol, the main ingredient in most antifreeze, has about a 25% lower heat capacity than pure water. That’s one reason why a cooling system should never be filled with straight undiluted antifreeze - it increases the risk of overheating during hot weather. But antifreeze raises the boiling temperature of the coolant when mixed with water, so as long as the coolant is at least a 50/50 mixture of water and antifreeze the cooling system should be able to handle normal loads with no problems.

Overheating can also be caused by anything that increases the normal heat load on the engine and cooling system. This can include a slipping clutch or automatic transmission, (I'm still not convinced the Ally isn't part of our problem), a dragging brake, an exhaust restriction (plugged converter, muffler or pipe), running the A/C at maximum while sitting or creeping in heavy traffic during unusually hot weather, pulling a trailer, hauling an unusually heavy load of cargo or passengers, mountain driving or extremely aggressive driving.

To provide maximum cooling, the coolant obviously has to be maintained at the full level. Many cooling systems today will overheat if the coolant level is low because steam pockets that form in the cylinder head can prevent the thermostat from opening. To function properly, the thermostat must be in direct contact with liquid coolant, not steam. So if there’s air in the engine, the cooling system will have to be bled to get the air out. Getting all the air out can be fun if the radiator cap isn’t the highest point in the system. Some vehicles have special bleeder valves to help you vent trapped air, but most do not. If the heater is the high point in the system, you can loosen and burp a heater hose to release trapped air. Another trick is to raise the front end of the vehicle to tilt the cooling system so the radiator cap becomes the highest point in the system (aka the Fingers method ;) ).

Sometimes a lower radiator hose will collapse under vacuum at high speed and restrict the flow of coolant from the radiator into the engine. This can happen if the reinforcing spring inside the hose is missing or damaged.

A bad thermostat is often blamed for causing an engine to overheat. But in many cases, the thermostat is a victim and not the cause of the problem. Severe overheating can often damage the wax element in a good thermostat, which is why it should always be tested following an episode of overheating even if you’ve diagnosed something else as the cause (like a coolant leak). (Good advice)

If the thermostat needs to be replaced, install one with the same temperature rating as the original. Using a cooler thermostat (160 or 180) in an attempt to "cure" poor cooling performance can increase fuel and oil consumption, ring wear and emissions. Vehicles with computerized engine controls use engine temperature to go into closed loop and to control other emission and drivetrain functions, so if the engine never reaches a normal operating temperature it can cause additional problems for your customer.

If the fan has a clutch, inspect it for signs of fluid leakage (oily streaks radiating outward from the hub of the clutch). If the clutch allows the fan to spin freely with little or no resistance when the engine is off, or you can make the fan wobble by wiggling it, the clutch is bad and needs to be replaced.

On an unrelated note, does anyone have a chart or know what the final drive ratio is for our trucks in 3rd, 4th and 5th gears while in TH? TC locked/unlocked? That dyno run at PUSU in 5th gear at 2100 RPM's has me thinking..... dangerous I know. :D JJ :)

I failed to mention that I read in another article that a clogged or restricted exhaust can also cause overheating. Logic there was that if the heat can't exit the engine fast enough the BTU's will build up in the engine and transfer more BTU's to the coolant. IIRC we started seeing the overheating issue moreso with the LB7's that had CAT's (California and NE) and the LLY, interesting? :confused:

I know we have discussed this before and said there isn't much of a correlation between exhaust gases and overheating, but this kind of makes sense to me. Not a totally obstructed exhaust, just slowing exhaust gases down too much. I'll leave that one up to the technical types. JJ :)

I am a big supporter of exhaust restriction, lowering available HP, thereby a potential OH exacerbation. Been wanting folks to do before/after cat removal to determine effects. That and the turbo were the big changes for LLY.