Question: 1st Time Diesel Owner Questions

[oldblue92]

Hey guys I just bought a 91 gmc single cab 2wd 5-speed 6.2 diesel. 265K on the ticker. What are some things I can do to it just to clean it up. Maybe some sensor's, I heard running sea foam through it helps clean it out a bunch. maybe headers. Its got dual exhaust. Truck runs fine but would like to keep up on it.

Also The gas tank leaks, can i use a tank out of a gasser of does it have to be a diesel.

The truck does not want to get warm. I have not had it running for over a hour but gets lukewarm at best.

Truck is slow as molasses can i change the rear gears. Is it worth the effort?

Thanks guys cant wait to hear from ya!

[acesneights1]

A 91 with a 5 spd ? Factory ?
Never seen one. Post some pics. That is a first for me. Headers will do nothing and at 265k miles you are nearing the end. Leave it alone aside from maintenance .
Gasser tank should be the same as long as capacity is the same, just use the diesel sending unit assbly.

[roadhog0]

5 speed was a Getrag instead of an NV4500, it wasnt much of a tranny. With that many miles not worth doing anything to it other than maintenance. Also these trucks are slow. Mine with 4:10's would take 2 miles to get to 60 pulling 5000lbs...

[happypunch]

My family has owned a couple of 6.2's that were well over 300k miles before they were either sold or wrecked. Its a real guess how much life to expect out of these, some people's go forever and others dont, real good to keep up on things like a good harmonic balancer and keeping topped off with oil.

These arent like the cummins 6bt's with a b rating of 500k (meaning that half of the engines made it to at least 500k miles before needing serious repair) but you never know how many miles you can get before needing a rebuild/replacement.

Nice thing is that you can usually find 6.2 engines from the military with low miles and for pretty cheap. My brother-in-law was an army mechanic and says that most of the 6.2's they pulled had less than 40k on the clock and were running great, just got replaced with the 6.5.

And something to really wake it up is swapping on a turbo! I did that to mine and it was a night and day difference. used to take about 25 seconds to get up to highway speeds and freeways were scary since it couldnt get up to speed fast enough to merge with traffic. Now with my 6.5 turbo I can romp on it and pass people without worry and easily keep up with the flow of traffic. You can find 6.5 turbo setups for fairly cheap and I recommend it

[oldblue92]

I agree truck is slow as can be. 1st gear is good to 10mph. Truck's top speed TBD but i had it going 60mph @2500rpms. just bought it a few hours ago. drove it home only. SO what is some good basic maintenance to keep her up? I will post some pics in a few.

[NO TREAD ON ME]

As far as being luke warm, is your temp gauge going up? Mine wasnt blowing real hot so I bled it and helped quite a bit, they also make a gas tank putty that you can use for a short term fix, I used it before and it worked for about 6 months on a wrangler. Good luck No Tread

[oldblue92]

The gauge moves a little bit. so i think its working. going to check the thermostat in the morning. I just checked the vin and it said

MM4 TRANSMISSION,MANUAL 4-SPEED(MERCHANDISING OPTION) 4-SPD MANUAL TRANS PROVISIONS(MM4)
M20 TRANSMISSION,MANUAL 4-SPEED(MUNCIE) 4-SPD M/TRANS(M20)

So not a factory 5 speed.

[acesneights1]

Originally Posted by oldblue92

The gauge moves a little bit. so i think its working. going to check the thermostat in the morning. I just checked the vin and it said

MM4 TRANSMISSION,MANUAL 4-SPEED(MERCHANDISING OPTION) 4-SPD MANUAL TRANS PROVISIONS(MM4)
M20 TRANSMISSION,MANUAL 4-SPEED(MUNCIE) 4-SPD M/TRANS(M20)

So not a factory 5 speed.

That's what I thought.
Is the engine temp up and just no heat ? I had that problem when I replaced my heater core with a Chinese made POS. I took my original one and had it fixed and put it back in.

[oldblue92]

Originally Posted by acesneights1

That's what I thought.
Is the engine temp up and just no heat ? I had that problem when I replaced my heater core with a Chinese made POS. I took my original one and had it fixed and put it back in.

Temp gauge moves a little. Engine seems to not be getting that hot. I can hold the upper radiator hose.. I will post some pics of the motor later on. MAybe you guys can tell me whats been replaced and what a few things are on the motor.

[smackzed]

I just had this happen to me as well. I'm sure th et-stat just fell apart. Only 2 months old and an AC delco which is supposed to be good. Drove for 1 hr noticed 1/2 hr into the trip that the gauge was reading 110-120F and no heat from the heater. Got where I was going and upper rad hose soft and lukewarm. Both heater hoses were lukewarm also.

It's sunday and it's supposed to be -20C/-10F for highs all this week. Hopefully I can find one today