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High pressure in cooling system

That kind of pressure and it holding overnight cant be from just the water heating up/air pocket. If that WAS the case the pressure would dissipate and be completely gone after the engine cooled.
Something has gone wrong with what you did,defective/damaged head gasket,debris on block or heads causing it not to seal- something of that nature.
Best bet would be to run it with the crossover off and figure out which bank is the issue,then pull the head and look at everything very carefully.
 
jake 03 said:
That kind of pressure and it holding overnight cant be from just the water heating up/air pocket. If that WAS the case the pressure would dissipate and be completely gone after the engine cooled.
Something has gone wrong with what you did,defective/damaged head gasket,debris on block or heads causing it not to seal- something of that nature.
Best bet would be to run it with the crossover off and figure out which bank is the issue,then pull the head and look at everything very carefully.
Click to expand...

Deja vu. I have exactly the same engine and exactly the same problem (though yours sounds more severe). Coolant test indicated no combustion gasses, but it will hold pressure for weeks at a time while stored. After thinking it over for a couple years, I have concluded I must be getting combustion gasses into the radiator. However, my problem has been coming and going for about 2000 miles. It went away for this whole summer and just reappeared on the last day of the offroading trip. No visible contamination in the oil, nor do I see steam in the exhaust. I have though that it's possible I'm getting clean air from the turbocharger, but that would be less likely. And it definitely would not be giving you 28PSI. Mine doesn't seem to actively burp while running, it just holds pressure after it cools down. It's been minor enough that I've just been driving it. And, like I said, the problem went away for about a thousand miles before reemerging briefly on the trip. It's weird.
 
Jonah Gregg said:
Just a little information on waterless coolant... I dont run it (yet) but I think it's a pretty awesome product!

https://greengarageblog.org/17-waterless-coolant-pros-and-cons
Click to expand...

It sounds cool, but this blog posting is overstating the advantages. Firstly, waterless ethylene glycol and propylene glycol are readily obtained at any automotive store. That's what full-strength automotive antifreeze and RV antifreeze are. So there is no need for the expensive product. Secondly, traditional antifreeze mix does not boil at 212 degrees. The mixture will boil at somewhere near 250 degrees. The pressure valve in the radiator cap allows pressure to build, restraining internal boiling even when it is running hot. When heat gets excessive, the cap opens and allows some coolant to boil and leave the radiator. This removes heat from the radiator and provides a safety backup cooling method if your water pump does fail. The non-boiling pure glycol cannot take advantage of this ability until it reaches 375 degrees. They are advertising this as a safety feature, but what that means is that the boil-off mechanism won't engage until the engine is thoroughly ruined by excessive temperature. The higher boiling point sabotages this important safety feature. Fourthly, scale buildup is a function of chemical interaction. Use clean water, and periodically flush your glycol (as the corrosion inhibitors break down), and it should not be an issue. Fifthly, as stated towards the end of the post, propylene glycol only carries about 60% as much heat energy as water (80% as much as a proper mix). Do you really want a cooling system that is only 80% as effective as stock? Yes, it warms up faster. But that's not actually a good thing unless your cooling system is significantly oversized. Reduced carrying capacity is particularly harmful to head castings, where heat gradients tend to build up.

The post also indicates that this particular coolant is prone to corrosion issues. So the auto store glycol might be better, as it will come with additives to manage corrosion. But, either way, pure glycol is not going to remove heat as well as a traditional mix.
 
campfire said:
Deja vu. I have exactly the same engine and exactly the same problem (though yours sounds more severe). Coolant test indicated no combustion gasses, but it will hold pressure for weeks at a time while stored. After thinking it over for a couple years, I have concluded I must be getting combustion gasses into the radiator. However, my problem has been coming and going for about 2000 miles. It went away for this whole summer and just reappeared on the last day of the offroading trip. No visible contamination in the oil, nor do I see steam in the exhaust. I have though that it's possible I'm getting clean air from the turbocharger, but that would be less likely. And it definitely would not be giving you 28PSI. Mine doesn't seem to actively burp while running, it just holds pressure after it cools down. It's been minor enough that I've just been driving it. And, like I said, the problem went away for about a thousand miles before reemerging briefly on the trip. It's weird.
Click to expand...
One of my first thoughts was that maybe somehow pressure from the turbo is getting in the coolant.
I am still investigating this.
I will be soon changing the water pump and at that point I will first try to check the 2 sides by removing the crossover pipe and belt and see if anything is coming through there.
If I see one side has a problem I might deal with it and fix it.
If both sides are a problem then I will pull the bolts and put studs and probably the thicker head gasket
 
jake 03 said:
Did you have the heads checked?
Click to expand...

That was my thought. I seem to remember that 6.2s had a tendency to warp the heads, but maybe that was only the early ones. There were rumors that driving them hard before being fully warmed up would blow the head gasket, but I'm remembering way back to when new square body diesels were for sale.

imiceman44 said:
One of my first thoughts was that maybe somehow pressure from the turbo is getting in the coolant.
I am still investigating this.
I will be soon changing the water pump and at that point I will first try to check the 2 sides by removing the crossover pipe and belt and see if anything is coming through there.
If I see one side has a problem I might deal with it and fix it.
If both sides are a problem then I will pull the bolts and put studs and probably the thicker head gasket
Click to expand...
I thought you described the pressure as building at idle, where the turbo wouldn't make any pressure. Stock boost is what - 7psi? So you would need quite a modified setup to open the radiator cap with turbo boost. Plus, how would you pressurize the coolant with the intake charge, but not burn coolant when not in boost?
 
Blue85 said:
That was my thought. I seem to remember that 6.2s had a tendency to warp the heads, but maybe that was only the early ones. There were rumors that driving them hard before being fully warmed up would blow the head gasket, but I'm remembering way back to when new square body diesels were for sale.

I thought you described the pressure as building at idle, where the turbo wouldn't make any pressure. Stock boost is what - 7psi? So you would need quite a modified setup to open the radiator cap with turbo boost. Plus, how would you pressurize the coolant with the intake charge, but not burn coolant when not in boost?
Click to expand...
It doesn't start building pressure until I start driving or revving up then it's a steady stream.
And I didn't say I know what is happening just throwing ideas out.
Now I am thinking maybe the turbo does have something to do with it.
The tty bolts and the torque setting is for a normally aspirated engine and I put a turbo on it and I was pulling 8psi after I put it together maybe that's what is making the pressure escape?
 
imiceman44 said:
It doesn't start building pressure until I start driving or revving up then it's a steady stream.
And I didn't say I know what is happening just throwing ideas out.
Now I am thinking maybe the turbo does have something to do with it.
The tty bolts and the torque setting is for a normally aspirated engine and I put a turbo on it and I was pulling 8psi after I put it together maybe that's what is making the pressure escape?
Click to expand...

Your 8psi turbine is not capable of pushing into a 28psi cooling system. The water would be flowing into the intake, not the other way around. It can't be the cause of this problem.

21.5:1 compression means 316psi in the cylinder even without ignition. I can't think of anything else with sufficient pressure to insert air into a pressurized radiator.
 
campfire said:
Deja vu. I have exactly the same engine and exactly the same problem (though yours sounds more severe). Coolant test indicated no combustion gasses, but it will hold pressure for weeks at a time while stored. After thinking it over for a couple years, I have concluded I must be getting combustion gasses into the radiator. However, my problem has been coming and going for about 2000 miles. It went away for this whole summer and just reappeared on the last day of the offroading trip. No visible contamination in the oil, nor do I see steam in the exhaust. I have though that it's possible I'm getting clean air from the turbocharger, but that would be less likely. And it definitely would not be giving you 28PSI. Mine doesn't seem to actively burp while running, it just holds pressure after it cools down. It's been minor enough that I've just been driving it. And, like I said, the problem went away for about a thousand miles before reemerging briefly on the trip. It's weird.
Click to expand...
Well decided to do one more test.
I pressurized the system to 25psi and let it sit for a couple of hours, if the head gasket was blown it would hydro lock the engine.
It didn't, so with the pressure still there I started the engine and it immediately started rising in pressure, which eliminates the theory that steam is building up the pressure so I am changing the water pump which turns out has a bad bearing, and I pulled the valve cover on the driver side to check the head bolts...
5 were not tight enough.
I had a mechanic friend helping me and I believe he missed the last round of torque on the 5 bolts.
He swears he got them but well...
I torqued them
I will do the other side tomorrow and run it.
My theory is that under the combustion pressure gasses are escaping where the bolts were not tight enough but coolant can come in
 
JoshHefnerX said:
Hopefully that does the trick, and running w/ some bolts loose didn't warp the heads.
Click to expand...
I didn't run it long, I am still in the testing phase, so when I replaced the radiator because of a leak I was making sure it was just the radiator and I was right to check. All I was doing was warming up and driving around the block for 5 minutes.
We will see once I work the passenger side head and check.
 
JoshHefnerX said:
Hopefully that does the trick, and running w/ some bolts loose didn't warp the heads.
Click to expand...
Looks like I am out of the woods.
Definitely an unorthodox way to fix it but it was worth the try.
I did have a few little obstacles to overcome: cracked crossover pipe so I replaced it but the thermostat housing was pitted so broke both bolts trying to remove it so a couple of days of soaking in liquid wrench and tapping it with a hammer and I was able to get both with a vise grip.
By the way both sides had bolts not tight enough around the center area, 5 or 6 bolts.
Also changed the temp sensor in the head, off course it had to break in the head and I had to use a big bolt extractor and got it out.
Tested good for idle and a 15 minute drive up the hill and down
 
When I got the 83 GMC C1500 pick-up from Can Can it was doing similar to what you were describing. Eventually a few months after I brought it home it hydro-locked. I bought head gaskets and all the other gaskets I was gonna need and started the dis-assembly. I also found three or four head bolts near the center loose on both heads. IMO the TTY should be called TTF (tq to fail).

I splurged on ARP head studs, and the peace of mind was worth it to me. TTY suck
 
tRustyK5 said:
When I got the 83 GMC C1500 pick-up from Can Can it was doing similar to what you were describing. Eventually a few months after I brought it home it hydro-locked. I bought head gaskets and all the other gaskets I was gonna need and started the dis-assembly. I also found three or four head bolts near the center loose on both heads. IMO the TTY should be called TTF (tq to fail).

I splurged on ARP head studs, and the peace of mind was worth it to me. TTY suck
Click to expand...
Well if it falls now it's going in for a full blown makeover but I am hoping I get a year or 2
 
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