bought '82 gmc suburban 6.2 first diesel i've ever owned it does great on flat road but when i start going up steep hills i lose power and it over heat any help would be great or at least where to start checking.

Is there any smoke out the tail pipe?

Welcome to the forum! :welcome:

Well, there are a number of things that could cause that problem. There are also a few more symptoms that would most likely be associated with it...

Does it smoke at all (any color under any circumstances)? Is it easy to start (short crank time)? Does it run smooth or does it misfire a bit? Does it surge at all under any conditions?

I think the most likely cause would be a clogged fuel filter... When was the last time it was changed? If it hasn't been done in a while (or you don't know when it was changed last), you should change it. Just remember to bleed the fuel system out when you are done before you attempt to start it (see the stickied thread on air leaks at the top of the forum, post #4 explains how to bleed the system out).

Other possible causes would be cooling system issues, such as a clogged up radiator or a bad fan clutch.

Hope this helps! :)

1 ,when i rev the engine light black smoke followed by grayish blue smoke,
black smoke is more noticable when i floor it & going up hills
2 ,truck fires right up
3 , runs pretty smooth
4 , yes i change the fuel filter about 2 months ago as well as the thermostat.

Sounds like a cooling system issue. I would recommend draining and flushing the cooling system and replacing the thermostat. While the coolant is out of it you might want to take the radiator out and have it checked by a radiator shop to see if it is clogged up.

You might also endup replacing the fan clutch... It is rather critical to proper cooling and if it is malfunctioning it could cause problems.

will cooling system rad.,fan clutch , etc., cause it to lose power ! i ' ll be going 70 mph or so and when i reach very steep hill (hyway) half way up i'm bearly doing 35

Definitely. Overheating engines suffer a dramatic power loss...

Crank up your fuel at your IP put some antifreeze in it and shovel the coal to it on the hill lol. Sounds like you got a Cooling system issue on your overheat problem. Hotter it gets the less ponies your gonna have. Check your thermostat!

And by the way if you see wanted posters by mosquitoes on the trees, then you know your pumping enough fuel to it...more black smoke the better!!!!:D

something else to check.. make sure you have a fan shroud.

And by the way if you see wanted posters by mosquitoes on the trees, then you know your pumping enough fuel to it...more black smoke the better!!!!

The only thing about black smoke is that there is a lot of heat when there is a lot of smoke, so you've got to be careful...

how do you test the fan clutch , i remember when i was a kid my family went on a trip and our car over heat we pulled in this shop and mechanic tested the fan clutch he grabbed the fan and held and told my dad to crank the engine dad look at him like he just escaped from a mental institute so another mechanic did it the engine turned over but the fan was'nt turning.

... we pulled in this shop and mechanic tested the fan clutch he grabbed the fan and held and told my dad to crank the engine dad look at him like he just escaped from a mental institute so another mechanic did it the engine turned over but the fan was'nt turning.
so if the clutch is bad, then the fan spins with the motor... right?!?! :eek:
I have never herd of this test. it would seem to be dangerous if you did in fact have a bad clutch

bought '82 gmc suburban 6.2 first diesel i've ever owned it does great on flat road but when i start going up steep hills i lose power and it over heat any help would be great or at least where to start checking.

Since you mention you are new to driving 6.2 diesels, keep in mind that you're driving an almost three-ton vehicle with the power of a 305 gas engine. I don't know what size tires you have, axle ratio, overdrive trans. or not, etc. A 1/2 ton Suburban with 3.08 axles, 700R4 trans. and 31" tires will work very hard climbing a steep hill. And, if it's a long climb and it's hot out, the cylinder head exhaust temps can get very high - unless you back off the pedal and downshift. Back in 82, when the 6.2 diesels first came out - I knew of several loyal Chevy truck owners that bought them - and in disgust - quickly got rid to them for being gutless. Usually this would happen with someone who had experience with 350 gassers - and figured a 379 diesel would have MORE power - but they do not. Non-turbo diesels just about always have much less power than gas engines the same size. That's why Chevy had the 6.2 designed as a power equivalent to the 305 gas engine. The diesel also has a much narrower power curve - and it's just about done gaining power after 2500 RPM. A stock gas engine might keep gaining good power up to 4000-5000 RPM. On the other hand, the diesel seems to hold pretty good torque right down to idle speed - so in that respect - it's nicer to drive than a gas engine.
That all being said - I 'm not trying to insult your intelligence or the 6.2 diesel - I love them. But, I saw many good running 6.2s get pulled and scrapped for being "gutless" back in the 80s.
Now -back to your Suburban - I don't have any of your specs. 3.73 gears work very nicely - with the 6.2 in a Suburban - especially if you pull a lot of hills. If you've got 3.08s, at the least - use the stock size tires and do not use oversize.
One thing I've found that often that make things worse. Mufflers. If anyone has bought replacement mufflers - e.g. from NAPA - they can almost ruin an engine. NAPA will sell you a gas-engine muffler with very high restriction. They sell it because it fits. I bought a truck that had them - and it heated something awful climbing long hills in the summer. I could literally smell the paint cooking on the cylinder-heads.

how do you test the fan clutch , i remember when i was a kid my family went on a trip and our car over heat we pulled in this shop and mechanic tested the fan clutch he grabbed the fan and held and told my dad to crank the engine dad look at him like he just escaped from a mental institute so another mechanic did it the engine turned over but the fan was'nt turning.

Don't grab the fan. Sounds like maybe the guy really did escape from a mental institute... ):h You can try cranking the engine, but most of the time the fan will turn with it. If you reach in there with the engine good and hot (gloves on, ignition off, keys in your pocket - safety first) and try to rotate the fan it should be pretty difficult to turn (if you can turn it at all).

The best way I have found to check the fan clutch... Replace it. If nothing else is wrong, that is really all it could be... The reason that seems to be the best method is because the fan clutch won't necessarily lock up or completely unlock if it is bad. They can do all kinds of funny things when they are on their way out...

thanks everyone for your help just went out got a fan cluth ,radiator is in order( to many pin holes)also went out and got new water pump,hoses etc., JDEMARIS , i was running 31"tires with 3.42 gear swapped axels from my blazer k5 with 3.73 gears & 35" tires .detroit lockers in the rear auburns up front

hi i'm new to this site and diesels but all you guys are so helpfull this is a great site and keep up the good work and thanks

i think the fan clutch is designed to grab when it gets hot and release when cold... so, if the truck is cold and the clutch is stuck, or if the truck is warm and the clutch spins freely, then the fan clutch is bad... never hurts to replace it though... or better yet switch to electric fans, which could be turned off for deep water crossings

i think the fan clutch is designed to grab when it gets hot and release when cold... so, if the truck is cold and the clutch is stuck, or if the truck is warm and the clutch spins freely, then the fan clutch is bad... never hurts to replace it though... or better yet switch to electric fans, which could be turned off for deep water crossings

I've never found the fan-clutch to be an issue on any of my diesel trucks - as far as diagnosis goes. First - I can hear it when it's working - there is no mistaking the sound of it. Second - in most cases - a fan is not needed except for times when driving very slow or stopped.

I know that in my trucks, if it was not working at all, or it was engaged all the time, I could easily hear it. Maybe there are certain applications with better insulation where you cannot hear it? But, I've got diesel trucks, K5 Blazers, and Suburbans - and I can hear the fan in all of them. I must admit though, that over the years the mice have stolen a lot of the insulation from under the hood.