Head Gasket problem?

[Cartoondog]

Hello, I have a 6.2L "J" vin Chevy P20. The odometer says it has 50k miles. I've had it for about 9months and have been working various issues. It starts and runs with no noticeable white smoke from the exhaust, except on initial start-up and then only a little. Recently I have been blowing coolant out of the coolant overflow bottle. I also noticed that the upper radiator is rock hard after the vehicle warms up. Since ownership (9 months) I've replaced the thermostat, coolant, radiator cap, fuel cap, lift pump, and most hoses. Temps also seem ok(as long as there is coolant) All was fine until recently. I do not see coolant in the oil or oil in the coolant. I need this vehicle to work reliably, so if this is a head/gasket issue, Id just assume to get'er'done now before the problem manifests into something that leaves me stranded. When I bought it, it had the wrong style rad cap on it and would collapse the upper hose.

Thanks!

PS what I keep thinking about is, "what could make the upper radiator hose so pressurized". The only thought I have is the heads/gaskets/ cracks...

[Robyn]

The pressure is leakage of compression/combustion gases into the cooling system.

This can be from a couple things.

Head gasket/s
Cracks in the head/s

Any sealers are pretty much a waste of time and $$$$$

Bottom line is you need to find out where the pressure is coming from.

Easy way is to get the coolant crossover off of the engine and fill the head passages with coolant.
Start the engine (WATER PUMP BELTS REMOVED) AND SEE WHICH SIDE SHOWS BUBBLES

A bad gasket is a likely culprit.

One caveat though...as the gaskets erode and fail the cylinder block decks erode too under the stainless steel ring that seals the compression/combustion gases.

Once the deck has been eaten away, getting a new gasket to fix the issue is pretty much a lost cause without machining the block.

The other possible is the cylinder head has cracks between the valves that have finally found their way into the coolant passages.

Do some snooping as see what you find.....

Best of luck

[Yukon6.2]

Yes good luck
At least parts are cheap and you can work on it yourself.
When you get it sorted you should have the truck you wanted,cheap to drive,dependable and Vintage Cool

[Cartoondog]

Thanks for the reply's guys. I took it out for a drive yesterday up and down the coast. I was all ready to tear into it. But when I got back, no leaks, no missing coolant, no nothing. I could slightly dent the top radiator hose with my hand while at temp with the engine running. How stiff is your top hose?

[Yukon6.2]

Drive it as is for a bit...
Maybe you got lucky and it just needed a good burp.
Keep an eye on things,drive it for a while.
If it acts up again,there is lots of help here for you if you need to tackle removing the heads

[More Power]

Thanks for the reply's guys. I took it out for a drive yesterday up and down the coast. I was all ready to tear into it. But when I got back, no leaks, no missing coolant, no nothing. I could slightly dent the top radiator hose with my hand while at temp with the engine running. How stiff is your top hose?

That's how it is in the beginning... We all hope for the best.

How stiff is my top hose? Gotta be a joke in there somewhere... :) Fill your kid's bike tire with 10-psi air pressure. That's how stiff your top rad hose could be. These cooling system normally run with 8-10 psi pressure at operating temperature.

Luckily, these sorts of problems have been solved with certainty a long time ago, using the right procedures, gaskets, bolts and sealants pioneered by The Diesel Page.