Well, I changed the thermostat tonight, hoping that it would fix my no heat problem. Bought a 180, and then found it it had a 190 in it. I get 'warm' air out of the heater, but nothing hotter. I used one of those infared laser guided temp probes, and found the radiator hoses to be about 105, same as the air coming out of the heater. exhaust manifolds were only at about 175 sitting there idling after about a 15 minute trip. Its about 20 outside. Do I need to cover my grill with something? I dont understand why my engine isnt creating heat. I really wouldnt think that there is anything that can go 'wrong' with an engine that would make it run ok, but not generate any heat.

Does anyone have any suggestions? a new radiator cap was suggested here, but it seems to have some pressure. What pressure should the cap be? What temp should the stat be?

How does the engine sound? Should be a very defined detonation clatter, hard to talk over with the hood up, especially when the cold advance is on. Maybe you need to advance your timing a little to compensate for timing chain wear.

Actually I think it sounds fine... but I do notice on acceleration that I hear a faint 'pinging' noise. sounds kinda like the randomness of ping in a gas engine.

How does one advance the timing? And how can I check it?

Should I be using a grill cover? See alot of diesels with them in the winter...

That would help, but you should still be able to drive it and get the engine up to operating temp. 180 thermostat will make it run a little cool, really need to get over 195 to make these engines run right and get best mileage and power out of them.
Do you get any smoke out of the exhaust when the engine is warm? A little black would be good, any white would be bad.
I say, try advancing your timing a little bit, only takes a few minutes...

Sorry, I missed your first post...
Should be pretty pronounced, more than faint, these engines are quite noisy when they're running right.
All you have to do to advance the timing, is loosen the 3 15mm mounting nuts that hold the injection pump to the timing cover, rotate the top of the pump to the driver's side and retighten the nuts.

How can I be sure not to go too far? Is it possible for the timing chain to be that bad with 90k on it? Its an ex mil, did they run them with the timing retarded some for durability reasons? It seems to be every bit as noisy as I remember my brothers... but its not quite as snappy. Although his was a brand new crate motor....

Just bump it over a hair, We commonly advance them a lines width. If you scratch the dirt off where the pump meets the timing cover, you should see a line on each, just advance it the width of the line from where it is.

90k isn't a lot your right, GM says replace them at 100k IIRC. Being a military truck, it likely idled a lot, and did a lot of low speed hi-revving with Joe at the wheel (been there ;)) Just try it, if you go a lines width or so, you can't hurt anything at all. If you go too far you'll get black smoke and excessive clatter.

BTW, are you still using the 24v electrical system? Just curious, if the pump is original mil. spec, you might consider having it rebuilt to civilian HD specs.

still bone 'stock'... I just picked it up this weekend, and it came right from the mil.... was the civvy pump different than the mil?

minor parts and calibration differences...been a while since I did a mil spec pump.

Advance the pump timing, if you don't like it, just put it back, but I'm pretty sure you will. Put a big piece of cardboard in front of the rad while your at it. These engines really need heat not only to warm up your toes, but to run right.

Did you happen to pass that heat gun over the block? I wonder if your Water pump is just not moving coolant around and thats why your not seeing higher temps? Is your temp sender on the front crossover or on the head?

not sure where the temp sensor is... being a mil, its only lights...

we didnt move the probe around too much, but I can try that tomorrow. I am looking at maybe buying the Mil canvas to put on the front of the truck. looks alot better than cardboard.. ;-)

BTW, the cardboard didnt help much the other day....

Does your fan clutch disengage like it should? I'd just take the whole fan out and run without it for the winter. Do that while your advancing the timing and installing the cold front :)

isnt taking the fan out a little extreme? Esp since I plan to plow with it next winter? I am not sure if the clutch is disengaging.

I ran my old '90 Blazer without a fan as long as I owned it, only overheated once, sitting in traffic on a 100+ day...course I upgraded to a huge 4 core radiator.

Your right though, safest thing is to have one in, but that clutch should be disengaged until you get to 200 degrees or so.

any chance the mil used the 4 core in theirs? wonder if maybe it has a 'better' cooling system than the civvy.

very good possiblity of that, can't say for sure though. Military purchases from lowest bidder, not best quality or performance necessarily.

Put in a 195 degree thermostat and you should see a change, but remember that diesels do not put out a lot of heat in the winter when it is cold. I would not change the timing. I have about 225K miles on my 6.2 and the timing is still fine.

I don't block my radiator in the winter and I live in cold country. Your 195 thermostat should keep your engine at 195 unless it is opening or leaking. Most of your coolant will be going thru the by-pass from the crossover to the water pump and also thru your heater. Very little will be going thru your thermostat into your radiator.

Only thing that doesnt make sense there cougarjohn, is that I should at least be achieving a 180 degree water temp now... and I am not.


What do you suppose the new stat was junk to begin with as well??

Well I tried advancing the pump today. moved the line maybe 3/16" of an inch. there was not multiple lines to use. This did not seem to help the temp problem it all... BUT!! HOLY **** did it wake the engine up!!!! It runs amazingly better now..

My only worry is that I might have gone too far? How can I be sure that I didnt over-do it?

Put cardboard on the grill, gets kinda warmer now. Maybe I should buy another 'stat' and see if that helps? wonder if the new one was just as junk as the old.

Aha! I told you you needed to advance the timing. Judging by your emphatic 'HOLY ****' then your just timing is just right ;)

Higly unlikely that you replaced a bad thermostat with another bad one.
Is the temp gauge on the dash showing heat? Have you checked the heater vavle to see if its opening? I've seen them break and blow warm air all the time, more annoying in the summer than the winter I think.

Should I not worry about maybe having gone too far? Would it be wise of me to have someone dynamically do it, now that I know it was off? it is awfully loud when its 'cold'.. like almost painfully

While the engine is cold, your Cold advance and Fast idle solenoids should be engaged, and they will make a lot of noise, thats a good sign, means they're working as they should, that should help warm the engine up too...

There are tools to 'dynamically' time these pumps, I have found the most effective way to get them to run right, is to time them by eye (smoke) and ear (sound). My old man and his guys have been doing it that way for decades, never have any problems with it.

so basically as long as there isnt copious amounts of black smoke? I am fine?

black smoke, excessive engine noise and you will start to lose power if you go too far.

Your basically just guesstimating at how much compensation you need for timing chain slack and the condition of your injection pump, supply pressure, fuel quality etc. Adjust to where its got the most power, then its right.

Are you getting black smoke out of this rig? Hows your air cleaner?

not seeing any smoke... I have not had a chance to check the air cleaner yet..... been too busy driving it home from kansas, and struggling with the heat problem...


which reminds me of the topic on this thread...... any other ideas on this??

Maybe your just not getting enough fuel? Not enough heat is a better problem to have then overheating. If your brave enough, you could try and turn the fuel up a bit, if you got the cash, you could send the pump in for rebuild and put a new timing set and REALLY wake this bear up ;)

I could try turning it up, but how can I be sure i dont go too far? I do have a haynes manual for diesel engines at my disposal, but I doubt it says much about that... after all for the timing it said use tool such and such... ;-)

I have done crazy things before... like put a turbo on my deuce...

Moving the IP 3/16" is farther than I've ever gone. I would be concerned with burning up glo-plugs. I've seen it several times and traced it to IP timing moved too far. If you have to move the pump that far, the timing chain is worn and retarded. Most often, If you put a timing meter on it, you end up advancing the mark about a line-width or maybe two. That's about a 1/16 of an inch. Yes, the engine makes more noise and power with advanced timing, but it's not always a good thing. Be careful!

What do you figure it is that causes the glow plugs to burn up when the IP is moved too far?

Excessive heat? I'm not sure, I just found them (mostly) on the 6.2s with 9G or 11G glo-plugs. These plugs fail easier and the heat seems to be a factor. In my dealership days, I replaced glo-plugs repeatedly in certain hard-working trucks that had the timing advanced for more pulling power. Didn't seem to have anything to do with cold starts, etc. Just put them in and after pulling a loaded trailer on some long trips, next day, truck wouldn't start. They would tow it in and I would find the newly-installed glo-plugs burned out. Finally, on the vehicles that the owners would let me, I retarded the timing back to the factory setting and the problem stopped, abruptly.

This may not be an issue with the newer style 60G plugs, but it still indicates something different is going on in the combustion chamber when you advance the timing too far. Just information. Fred

Any way of checking the timing and making sure its right without a dynamic tool?

There tools available, but not easy to find a shop with one, it would have to be a fuel shop.

Replace the timing chain and put the pump back line to line and you'll be dead on. And still have same power, won't help your low heat problem though.

Talked with someone who used to work at the local truck dealer that specializes in stuff like this... they dont even have the tools!!

He said that they were 'supposed' to put them on the mark, but they commonly put them around 1/16" advanced from the mark. I need to move mine back, and will do so tomorrow night when I am fixing the dead alternator. Really sux to have an alt die on the military 24v system!!!

Do you really think my timing chain is ready? are they every bit as easy in the SBC? How much do they cost?

Hard to diagnose from here, open the oil filler cap with the engine idling and listen. If it sounds like somebody's taking a chainsaw to a piece of steel, then yes you need one ;) Also if you have to advance the pump a lot to make it run right you probably need one.

do you suppose that could be the noise that I refered to that sounds like 'pinging' ? not the normal diesel engine sound?

hard to explain to a 'gasser' guy what a diesel is 'sposed' to sound like. But they don't sound like gassers thats for sure, back it off just a touch if your worried about it, but if you were too far advanced you'd probably have overheating problems.

yeah yeah yeah... I know what its 'sposed to sound like.... my point is, I hear a more 'random' noise, that doesnt belong.... sounds almost like a ping in a gas engine, and I know this noise isnt normal diesel noise... My guess is, its what you are refering to, and mind you, i hear this from the drivers seat. once I get it started again, I will pop the oil cap off and listen. I was just wondering if the worn chain would have the noise I described...

Can't hear the chain from inside the cab, does the noise sound something like marbles bouncing on top of the pistons? That would be detonation clatter, and thats good/normal.

hard to describe...
and I dont think a tape recorder will pick it up... its faint compared to the normal clatter.... its nothing that really bothers me, just wondered if the chain might be the noise.

Is it only under hard accel? Full Throttle? Idle? Cruising? When? Since its random its probably just right, if it were very pronounced and constant that would be too much.

under any accel I think.... I meant random in its pattern of noise... maybe it is normal... who knows... :-) I dont remember it in any other diesel I have driven

6.2 is a unique animal, and its certainly not a stealthy one ;)

this is true... but at least it doesnt sound like a 'come-a-part'..... well not usually at least.. mine does right now when its on the cold circuit... LOL

Thats good, means your cold advance is working ;) If I could actually hear it, this would be alot easier, but judging by your description, I think you've just heard a 6.2 run right for the first time. Army mechanics put them line to line and won't change them ever, but if you think its too much, back it off a touch. You know that where it was it was too far retarded, and now it might be a little too advanced, so play around with it.

btw... the noise I am talking about was there before too... almost sounds like it could be a bearing in an alternator, or water pump or something.... but I really only notice it on accel... might just be normal 6.2 noise, and i just dont remember it from the 4 different engines my bro had...

he had a 6.2 that ran PERFECT.... was a brand new crate motor installed at the dealer... sold it this summer for $2500 in the old rusty 84 3/4 4x4 with maybe 10k miles on the engine.

I would not advance the timing more than 1/16th in. from the mark unless it proven that it needs it by using a timing device. My engine has 225K miles on it and on a dynamometer it still puts out max horsepower and torque with minimum smoke. I set my pump at the 1/16th in. mark when I installed a heavy duty pump at around 67K miles. My philosophy is don't fix it if it is not broken!!!! Replacing the timing chain is not a small chore.

As I posted earlier, diesels don't put out much heat in cold weather. I have had my windshield ice up because the defrost air couldn't keep it melted. And I have been forced to wear my coat too because the heater didn't put out enough heat. A 195 or more degree thermostat is a must for winter time in you live in a cold weather area.

It could be your heater is plugged so that coolant flow thru it is low. You might try disconnecting the heater hoses and flush the heater core out with a water hose at full flow. I don't think your vehicle has a shut-off valve for the heater.