Pushing coolant what else to check before pulling the heads

[Dozerboy]

So my LBZ has been building enough pressure to push coolant out the overflow for the 7k miles. The thing is it only does it when I lean on it hard and if I keep the coolant 2" low it won't push any out. I even pulled my 9k lb camper 3k miles without a problem other then a very hard coolant hose. Never got hotter then 220*. EGR isn't the issue. Anything else I should check before I tear into the engine? I have some black (soot?) in the coolant. I fear I have a cracked head or block since it's only a problem when I push it hard. Any insight y'all have is appreciated. I'd hate to tear this thing down and stud it only to have overlooked something in my lack of experience.

Truck has been tuned for 90k+ and 500hp+ daily 15k with a bigger cp3 and Marks stg2. Compression test 6k ago was good.

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[jedenbeck]

If your pushing coolant and have black soot in the tank. 9.9 times out of 10 it’s headgaskets. Cracked head or block would be a issue all the time. Mine was like yours. Only causes issues when I really pushed it. It’s time for headgaskets.

 

[Dozerboy]

If your pushing coolant and have black soot in the tank. 9.9 times out of 10 it’s headgaskets. Cracked head or block would be a issue all the time. Mine was like yours. Only causes issues when I really pushed it. It’s time for headgaskets.

Well that does give me hope. Seems like all the HGs I hear about are pushing coolant even at idle.

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[rcr1978]

Nope my buddy's LLY would only push coolant with a trailer pulling a hill, all other times it was ok other than the hard hose syndrome.

 

[NC-smokinlmm]

Yep, just gaskets, replace and roll on with it. I'd stud it since you will have it apart.

 

[clrussell]

I sousing check anything else.

Just pull the heads off, get them surfaced, and regasket and send it

 

[WVRigrat05]

Yep, mine passed pressure test and only puked on hard pulls, after 20-30k it puked a gallon as soon as it was over 2500 RPM and idling any amount of time, sounds like they're not too bad yet, surface the heads and slap gaskets in it.

 

[Dozerboy]

Thanks yall.

Ya definitely doing studs. I got some research to do, because I want to do it right not just slap C HGs on it. Going to look into porting and other up grades to do while the heads are off. Probably 100overs since my balance rates aint great. Got a leaking front diff and steering box to address too.

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[Chevy1925]

Make sure the shop that decks them, pressure checks them under high pressure and in a hot tank. Sometimes they don’t open up and leak unless the head is hot and got decent pressure under them

 

[kidturbo]

Also be sure to use the good Victor Renz wave guide gaskets. Not the GM LML release version from the dealership. I learned that one the hard way...



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[Bdsankey]

Make sure the shop that decks them, pressure checks them under high pressure and in a hot tank. Sometimes they don’t open up and leak unless the head is hot and got decent pressure under them

Also be sure to use the good Victor Renz wave guide gaskets. Not the GM LML release version from the dealership. I learned that one the hard way...



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Both of these posts cannot be stressed enough.

 

[Chevy1925]

Also be sure to use the good Victor Renz wave guide gaskets. Not the GM LML release version from the dealership. I learned that one the hard way...



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They outlast LLY heads with 150ft lbs torqued head studs

 

[kidturbo]

Having buddies who work at GM dealerships can be a good and bad thing..

Dustin convinced me to use those new GM gaskets because they were half price of the Victors with his GM discount. Then about 8 months later once both engines are assembled and setting on stands, he says to me "those GM gaskets we used are junk, I've changed four sets on trucks with under 20k miles."

"We? Ya got a little man in your pocket??"

 

[Dozerboy]

Anyone got any suggestions on ways to clean the soot out of the coolant system? I would think the build up is going to affect heat transfer.

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