Excessive cooling system pressure!! Blown head gasket(s)?

[Tahoe Joe]

I just picked up an '83 Suburban with a Banks turbo. It has been running great for the last few days. I just changed the oil and filter, checked the antifreeze, etc. and everything looked good. Tonight, on my way home, it started to overheat! I stopped and checked things out and saw that the overflow bottle was full and had been leaking due to it overfilling. I thought that maybe the radiator cap may be bad, so I stopped at AutoZone and bought a new Stant 16lbs cap. I refilled the radiator and everything looked good. I had another stop to make and when I shut the engine off, you can hear coolant percolating in the overflow bottle. Once again, it looked as if the bottle was overflowing. I went back to AutoZone, and out of desperation, tried an 18lbs cap, and it's the same thing. There are no other leaks, I pressure tested that radiator and cap, they both check out fine. The radiator holds 16-18lbs pressure for about 10 minutes with no drop whatsoever.

I'm wondering if the excessive pressure, which is evident due to the fact that you can actually see the overflow bottle filling up with the engine idling, is due to blown head gaskets? Something else I also noticed was that the cooling system pressurizes very quickly...maybe within a minute or two of putting the cap on. The truck has no other signs of a blown head gasket...ie. water in the oil, white smoke, signs of water in the exhaust, etc. etc. This Suburban runs really good with the exception of this issue. I'm almost to the point of hating 6.2's/6.5's. I've not had a lot of luck with them, and if it weren't for the time and cost factor, I'd ditch the 6.2 and go to an old 12 valve Cummins!

Until such time, or when I hit the lottery, lol, I guess I have to make the old 6.2 run! Any thoughts on this? Sorry to be so long winded, but I need to figure this out and get it fixed, FAST!

[NEVEREASY]

Is the engine getting HOT? are you getting hot air out your vents? Before you tear into the heads try changing the thermostat and checking your water pump. I recently had a problem with my powerstroke where it was overheating, I changed the thermostat and cap + $40 worth of coolant and it still overheated. out of desperation I pulled the water pump and found the impeller had spun loose of the shaft.

Josh

[Tahoe Joe]

It only gets hot when the coolant overflows out of the bottle...usually after it loses about a gallon or two....

Thermostat is new as well, water pump looks like it was just done

[turbovanman]

Yep, it sounds like the head gaskets are done or you have a cracked head. Be very careful you don't hydrolock it one day. Had a customer do that, bent a rod and broke off the starter bolts in the block,

[Diaric]

been in the exact situation. and if i took it on the highway, it would run ok. till i had to idle or move through slow traffic. was a blown head gasket

[Dan-karnut]

Yep, blown head gasket. Very common on the early 6.2's. Pull heads to verify. When replacing gasket make sure you use the newer TTY head bolts. (torque to yield)

[Tahoe Joe]

I pulled the heads the other day and it definitely looked like both head gaskets were blown, as well as #3 cylinder had a major crack that I'd say went through to the water jacket. The heads that were on there were the early large valve heads, which I gather are prone to cracking even worse! I built my spare set of heads, a set of late '80s small valve heads. Should have her all back together tomorrow night after work.

If that doesn't fix it, there WILL be a Suburban up here for sale CHEAP!!!

[ah-kay]

I am new to this forum. I have the same problem with my 1983 6.2L suburban. It is overheating with excessive gas build up. How easy is it to replace the head gasket? I am intimidated by the engine as I have never done a 8 cylinders diesel before. I am thinking about using Bar Seal to try to seal it. Would it work? Also is it OK just to replace 1 side if I manage to locate which head is blown?

[Tahoe Joe]

Don't let this engine intimidate you!!! I have worked on quite a few of them and have built a couple of them as well, and they are pretty simple. If it were mine, I'd replace both sides and just be done with it. I believe that there was a problem with those head gaskets and GM actually sued the gasket manufacturer, or so I have heard. Make sure you replace the bolts and torque everything to specs and you should be good to go. I wouldn't use Bars leak...it's just a "bandaid" for the problem.

Really though, this engine isn't much harder to work on than a gasser. Just be patient, take your time, get a good shop manual, and pay attention and the job will turn out fine!

[turbovanman]

Originally Posted by ah-kay

I am new to this forum. I have the same problem with my 1983 6.2L suburban. It is overheating with excessive gas build up. How easy is it to replace the head gasket? I am intimidated by the engine as I have never done a 8 cylinders diesel before. I am thinking about using Bar Seal to try to seal it. Would it work? Also is it OK just to replace 1 side if I manage to locate which head is blown?

Read thru a manual before you start. Yes, its alot of work but if you have any degree of mechanical inclination, you can do it. Take lots of pics, notes etc.

I wouldn't not use any type of sealer, they don't work and your simply masking the problem.

Do both heads, if one is gone, the other one isn't far behind. False economy to do only one.