Is anyone running a 180 deg t. stat. and is this a good idea. From what I know about engine temp if you keep the coolant in the engine till 195 it is also at the same time staying in the radiator longer getting cooled back down, so what's the advantage of trying to keep the engine down at 180. Give me some insight. Thanks.

I think you want the engine as close to 200*F possible to keep it running right.

IF YOU KEEP THE INTERNAL ENGINE TEMP TO THE STOCK 195 WHEN YOU APPLY MORE LOAD TO IT, LIKE A BIG HILL WHILE TOWING IN SUMMER, THE MOTOR WILL HIT THE ELECTRONIC FUEL CUTBACK POINT OF 220 FASTER THAN IF YOU KEEP IT AT 180.

My truck used to sit mostly at 180F, but would creep up to 210 in traffic in moderate temps (80-85F OA) and go towards 230 in higher VA temps with AC on. <?:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" /><st1:place>PO</st1:place> had put on a 17" direct drive (no clutch) flex fan.<?:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

I removed the flex fan and installed a 20" DMax plastic fan with a new OE GM HD fan clutch that I had moved the bimetalic tang 1.omm or so CCW on.

Now shes sets closer to 165F most of the time and gets up to 180 with moderate internal load or AC use. Truck runs just fine - though I admit it ran fine before at elevated temps, but I got concerned.

Lower thermostat setting may not be beneficial. In a 95, unless you've upgraded the rest of the coolant system to 97+, you're really not going to buy much. Engine likes 195° from the stuff I've read.


Are you fightin' heat with towing or something?

I have been running two years with the 180 t-stat and have no ill side effects. My temp gauge never goes past 200 deg when pulling up hills. But then again I only pulll about 4000 lbs. I use half of my winter front cover to combat low temps closer to winter and my full front to combat winter temps.

Can anyone give me a good reason to not close the coolant bypass hose from the water pump to the t.stat housing. If I do this I will be able to put in a normal high flow t.stat. which should eliminate the need for dual t.stat's. I'm probably going to try this regardless, but again I'm asking for a good reason why maybe I shouldn't.

i've thought about his before and it seems that the bypass is benifical for warm-up as it keeps the coolant flowing through the heads but just in a smaller circuit while you are warming up. a better solution to blocking it off may be reducing the size of the passage. the dual setup has the bypass but it is smaller to allow less flow forcing more coolant through the radiator. if you were to eliminate the bypass and your t-stat were to stick closed you would be left with no flow and the truck would overheat almost immediately.

From what I can see the only purpose of the (interesting) factorty T.stat design would be to alow coolant to flow up thru the valve which would be open when the t.stat is closed allowing coolant to flow through the crossover manifold into the heater core line which then is returned to the lower radiator hose feeding the pump, this is the only circuit of coolant I can figure out when the t.stat is closed\valve open. This might speed warm up time as coolant is not flowing through the entire engine to feed the heater core. This design in the single T.stat seems rediculous as the t.stat is fighting against two spring systems to stay open when it should, which seems to me like it would contribute to premature failure leaving it in the closed position. The more I look at it the more I'm convinced that a single (regular) high flow t.stat would solve a number of overheating issues with the single t.stat design.

Matt I think if it was a T Stat only change, GM would not have gone to the dual thermostat and 130 gpm waterpump in 97+ they would have just swapped Stats, from all I read cooling flow was always marginal in earlier trucks, which is why many over at TDP & some here upgrade to the later system. Something you can try though is JKs fan clutch it will kick in the fan earlier, simple 4 bolt swap, if that doesn't get you all you need, I'd go with aux trans cooling to help pull out some heat & maybe hi-cap finned pan for 3-4 qts more fluid & a little more fluid to heat up, then if it still doesn't work about only thing left would be to upgrade to HO pump and dual therm.

the bypass on the bottom of the housing that is blocked by the factory t-stat is a coolant return not a feed. it keeps coolant flowing back to the water pump even when the t-stat is closed (blocking off the radiator). when the t-stat opens it closes this bypass off forcing all of the hot coolant back into the radiator. the heater core lines feed from the crossover, through the core and back to the passenger side top of the radiator.

The factory cooling system holds about 3 gallons of fluid. So by my quick math the factory 78 GPM pump on my 95' should be able to completly exchange the engine with the radiator in about 2 seconds. This makes the pump seem adiquate even if it took 10 secs to make the exchange. GM does not use high flow design t.stat's so it does not surprise me that instead of utilizing new high flow designs they would just incorporate two of the designs thy've used for years.
Thanks Lupey, for the flow direction information you've just given me another idea! :D

Lower thermostat setting may not be beneficial. In a 95, unless you've upgraded the rest of the coolant system to 97+, you're really not going to buy much. Engine likes 195° from the stuff I've read.
If the engine likes 195 then it will run at 195 under load. The 180 stat will allow the cooling process to began sooner but should not have much change when it's worked. In colder temp you will notice it running cooler. I would be looking toward the cooling system upgrades, as I am myself soon.

It is better to use a 180F stat and modify the fan clutch to on at about 210F. Setting the engine up this way keeps it operating in an envlope of 180 to 210. The 6.5 does not like high engine temps both coolant or exhaust because it has 34 head bolts and they are streach type. The part number for a Stant 180 stat is 45476. A 180F stat will give you enough heat in colder temps. If your engine still gets hot then have your engine timing checked and set to the highest advance position prior to setting a SES lamp and code. If you have a high exh temp but coolant is normal then check the CDR valve located on the right side valve cover. This valve, if not serviced properly will allow engine oil into the air intake causing high exhaust and combustion chamber temps. If the valve is faulty then you will see oil residue at the hoses connecting the turbo to the air plenum. The oil is being injested into the turbo then emulsified and pressurized and forced through the hose from the insi9de. If this is the case replace the CDR valve.

... If you have a high exh temp but coolant is normal then check the CDR valve located on the right side valve cover. This valve, if not serviced properly will allow engine oil into the air intake causing high exhaust and combustion chamber temps. If the valve is faulty then you will see oil residue at the hoses connecting the turbo to the air plenum. The oil is being injested into the turbo then emulsified and pressurized and forced through the hose from the insi9de. If this is the case replace the CDR valve....
I wonder if this isn't where some of my oil is disappearing to. I ordered a new one from the dealer just to be on the safe side. They don't give them away though! Looks like it'd be a cheap part, but cost me $48 and some change.

CDR, being a high-volume low-pressure flow-thru valve, is designed to allow crankcase vapors into intake system.
Diesel fuel is a light oil - crankcase vapor is a light oil - engine has no problem combusting either\both.

High intake vacuum, via turbo, regulates excess engine oil intake by restricting CDR when necessary, but as vapors also lubricate intake valves\seats, concern is to valve's operational status.

Read all about it in FAQs.

gmctd: So what are you saying? Is it possible my CDR is malfuntioning, letting excessive amounts of oil vapors into the intake, or not?

I've read your post on the CDR in the 6.5 FAQ's section. Good stuff, but I didn't feel like spending an afternoon gathering up the tubing, building a manometer, and testing mine for myself. It looks like it'll only take 10 minutes to replace with new.

Yes, I took the slacker way out on this one.

CDR is designed to pass vapors, but not pull raw engine oil under high vacuum levels.
Vapors condense when cool - that's where the oil in the turbo and manifold comes from.
Except for the seep and drip, it causes no other problems.

Possibility yours is bad, if hi mileage, but don't be disappointed if the seep and drip continues, with the replacement, because high mileage wear results in more vapors.

I clean and wash my engine every three months, or so, as the seepage becomes noticeable, with A**o Z**e engine cleaner in the white can.

Anyway, who sez slackers are bad people, anyway - we're just...........practically motivated. ;)

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It would probably help to remove the valve cover and wash out the wire mesh underneath the CRD, I've seen some of these get plugged full of sooty oil and give fits.

It would probably help to remove the valve cover and wash out the wire mesh underneath the CRD, I've seen some of these get plugged full of sooty oil and give fits.
Do they sell valve cover gaskets for just the passenger side?

I guess that depends on who 'they' are, if you call the dealership, they'll probably tell you what they told me, that there is no valve cover gasket for a 6.5, as they don't come with one from the factory, cork ones are only available from the aftermarket, which, strangely, some dealerships sell. They're pretty cheap, good excuse to pull them both and give them a good scrub and fresh paint, thats what I did anyway.

Then I guess I need to go take a look under the hood and see how much stuff is in the way to make it a pain to pull them off.

I'll get the new CDR first, and when I put it in I'll take a gander at the valve covers. I'm sure my bro-in-law (owns his own shop that specializes in tranny rebuilds) can get me a set of gaskets.

Matt I think if it was a T Stat only change, GM would not have gone to the dual thermostat and 130 gpm waterpump in 97+ they would have just swapped Stats, from all I read cooling flow was always marginal in earlier trucks, which is why many over at TDP & some here upgrade to the later system. Something you can try though is JKs fan clutch it will kick in the fan earlier, simple 4 bolt swap, if that doesn't get you all you need, I'd go with aux trans cooling to help pull out some heat & maybe hi-cap finned pan for 3-4 qts more fluid & a little more fluid to heat up, then if it still doesn't work about only thing left would be to upgrade to HO pump and dual therm.
I bought the high volume pump to replace the OEM when I changed out the timing gears and chain and trying to get that phoney quick connect out I ended up messing up the Stat housing so I had to change that out and did so with the dual. The change made a big difference. IMHO it's worth the bucks and effort. Again if your going to change either timing chain or water pump do both as you most of the way there and it's not worth the head ache to do it again a short time later.

It has been said that by keeping the engine hotter you will get better fuel economy. My understanding of this fuel injection system is that it is not regulatory, meaning that it gives you the same quantity of fuel per pulse reguardless of load or RPM. So if I'm running 75mph at 2000rpm how could my fuel consumption be affected by the engine coolant temp. Whether I'm running 180 or 195; I'll still be running 2000rpm at 75mph:confused:

It has been said that by keeping the engine hotter you will get better fuel economy. My understanding of this fuel injection system is that it is not regulatory, meaning that it gives you the same quantity of fuel per pulse reguardless of load or RPM. So if I'm running 75mph at 2000rpm how could my fuel consumption be affected by the engine coolant temp. Whether I'm running 180 or 195; I'll still be running 2000rpm at 75mph:confused:
You're fogetting about throttle position, if you're running 2000rpm@ 70 and mash the pedal, you get more fuel even though you haven't increased speed yet right? If you're more efficient(warmer) at 2000rpm /70mph you'll need less pedal and save fuel.

I pulled my pass side valve cover 8 months back to clean the cdr condenser mesh inside the valve cover. The oil buildup on the turbo inlet and the drip off of it have been dry since. I cleaned my dad's turbo externally but not inside the valve cover and his turbo is as greasy and dripping as ever. Cleaning that condenser should help.

Also, slackers have it right seeking a stress free existance, within a sence of self.