Blown head gasket? - Diesel Bombers



Chevy/GMC 6.2L and 6.5L Discussion of Chevy and GMC Trucks with 6.2L and 6.5L Diesel Engines

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Old 09-12-2017, 06:55 PM
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Default Blown head gasket?

Hey bombers, 6.5 N/A 24 ft 1997 P-30 school bus homemade rv conversion here with 154K on it. It's been a great ride for a couple of years now, very fun to camp in and work on, and has given me no trouble other than the usual maintenance.

Driving back from some friends down south my low coolant light came on, so i pulled over at a rest stop to check it out. After a few minutes, i opened the cap with a towel and gloves for protection, and it had a bit of pressure in it but no spray. I had to put about 2 gallons of water in it which was first sign of bad news. I noticed a puddle under the overflow hose. Driving back home after about 30 miles the light came on again, filled it again. It kept spewing out the overflow hose. It never overheated as far as the gauge was reading and we made it home with two refills.

Once home I replaced the radiator cap, started it up and let it get hot. brake torqued it a bit and it happened again, blowing water out the overflow hose hot and fast. Looking down into the reservoir i can see it blowing bubbles and from what I can tell, this indicates a blown head gasket, blowing combustion gases into the water jacket and overpressurizing the coolant system. The oil looks clean and black, and there doesn't appear to be oil in the coolant, but i've had to replace it so much that might not be saying much.

So before I go getting estimates or trying to do this myself, I wanted to check with the bombers here to see if there is any other plausible explanation, or if there is any advice I should get on doing the job myself. This board has always been super helpful to me in the past with my diesel burbs and I hoping for some good news. In particular, if it is the head gasket, any thoughts on how difficult it is to do the job myself? I've got the tools, and the engine is reasonably accessible from the doghouse and I like to think I'm not entirely an idiot.

Thanks in advance and I hope you all are doing well,

-Mike

Last edited by pythonguy; 09-12-2017 at 07:07 PM.
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Old 09-13-2017, 02:33 PM
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I hate to say it... but cracked heads are also common. Usually in the combustion chamber, emanating from the valves and pre-cup pocket. In the very least, have the heads magnafluxed for cracks before re-installing.

There are aftermarket cylinder head castings now... Brand New 6.5 Diesel Cylinder Head :: SSDiesel Supply :: GM 6.5 TD Specialists
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Old 09-14-2017, 06:00 PM
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Originally Posted by u2slow View Post
I hate to say it... but cracked heads are also common. Usually in the combustion chamber, emanating from the valves and pre-cup pocket. In the very least, have the heads magnafluxed for cracks before re-installing.

There are aftermarket cylinder head castings now... Brand New 6.5 Diesel Cylinder Head :: SSDiesel Supply :: GM 6.5 TD Specialists
Thanks for the reply! Been doing research and it does look like cracked heads and other internal damage is a real issue. I have I think 3 options:

1. fix the head gaskets, have the heads checked, maybe buy new ones ($1500+)

2. Pull the engine, have it rebuilt at a local rebuilder ($2700+)

3. Found an ad on craiglist for a rebuilt 6.5 here in town, owner wants $4000 for the engine which is still at the rebuilders going through assembly, and a whole box of parts including turbo and IP (https://portland.craigslist.org/clc/...291763266.html)

4. get a whole new engine from SS ($5500)

I'm inclined to go with 2 or 3. $4K is a bit steep given that the second option is $2700, but I don't have a turbo or a decent IP (one I have is limited to 120hp) plus all the manifolds and other new components, including the dual termos that I also don't have, and 4k starts to sound like a good deal.

I'm still weighing my options, in the meantime I got he front clip off the bus and got the radiator removed, it looks like it will be a pretty straightforward pull with my friends shop crane.

Last edited by pythonguy; 09-14-2017 at 06:04 PM.
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