Hydrolocked

[DAVe3283]

I built my motor 1,200 miles ago. For the last 500 or so miles, I've been noticing my coolant go down every time the truck sits (but not while driving, even hundreds of miles). After sitting, it would sometimes smoke white. I suspected coolant leak, but the radiator hose wouldn't stay hard, and no bubbles in the coolant tank.

I got one of the coolant pressure testers, and put 15 PSI into the system with the motor off for 10 minutes. It leaked down about 5 PSI. Released the pressure, and went to turn it over. Nope, hydrolocked.

So, the coolant is going into one of the cylinders (I will figure out which one this weekend). But how? Normally with bad cups or headgaskets, you get bubbles into the coolant. But mine is not doing that.

How would I know if a cup or headgasket is the problem? If I can just replace/reseal a cup, I would rather do that. (Pulling a head off sucks.) Do I just hope the cup comes out with the injector, then assume that was the problem?

 

[DIESELMAFIAPER.LB7]

cracked head? pull glow plugs see which is wet then pull that injector see what you find

 

[DAVe3283]

cracked head?

How would I tell? Rip them back off and have a shop pressure test them?

They are SoCal stage 1 heads, so in theory SoCal pressure tested them before they shipped them to me.

pull glow plugs see which is wet then pull that injector see what you find

That is my plan, if there isn't a better/easier way to see what is wrong.

 

[DIESELMAFIAPER.LB7]

that's bout the best way to tell on the head and to test

 

[x MadMAX DIESEL]

Yeah pull the g plugs and look for wet. A shop will be able to pressure check the heads. Plenty of stock ported heads leak, even "the new performance heads" are cracking


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[Awenta]

Sounds like a small leak that makes its way when the engine cools and contracts but there is still pressure in the system.

Warms up and seals itself. Thinking out loud.

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[DAVe3283]

Sounds like a small leak that makes its way when the engine cools and contracts but there is still pressure in the system.

Warms up and seals itself. Thinking out loud.

Yeah, it seems to leak most when the engine is cooling back down.

I'll pull the glow plugs and try and narrow it down to a specific cylinder tomorrow. I might see if I can throw some compressed air into the intake and see if it ends up in the coolant. That would certainly answer some questions.

Thanks for the input so far guys, even if I don't like what I am hearing

 

[Awenta]

Any leak sucks. Good luck buddy. Hope it isn't too bad.

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[Ed04zf6]

Could it be a lifted injector cup?

 

[Duramax One]

Could it be a lifted injector cup?

If it were a lifted cup I would expect pressure in the cooling system. At least that's what would make logical sense to me; I would think that the combustion pressure would force gases backwards into the cooling system just like with a blown head gasket.

 

[DAVe3283]

Yep, it appears to be a cracked head

I built an adapter to pressurize the intake (basically a boost leak tester), and put 5 PSI into the intake. Within 10 seconds, I had 1 PSI in the coolant.

A summary of my findings so far:

• I can idle the engine for 15 minutes and it won't build any pressure in the coolant, which indicates to me that the head gaskets and cups are fine.
• If I pressurize the coolant to 15 PSI, it leaks out enough coolant in 10 minutes to hydro-lock the motor.
• If I pressurize the intake manifold, I get pressure in the coolant immediately.
• Oil analysis showed coolant in the oil at the first change (836 miles). That is what made me start this whole investigation (and the disappearing coolant).

I'll give SoCal Diesel a call on Monday when they open, and get this all sorted out.

Dang, I had just received my first tune from Rob last night, and I was excited to try it out.

Thanks for the help everyone.

 

[DAVe3283]

[YOUTUBE]JKWdH5cw93M[/YOUTUBE]

 

[DIESELMAFIAPER.LB7]

Dang bud pull your y bridge see which head it is

 

[S Phinney]

Could be a gasket or cracked intake port. If you pull the bridge and it's a cracked head you should see some water somewhere and the oil fill cap will have moisture under it.

 

[DAVe3283]

Aah, forgot to update this. It was a cracked head, #2 cylinder, at least one of the intake ports. Stuck a borescope in and I could see coolant pooled on one of the intake valves.

I just sent the heads back to be looked at, and I am curious what they will say.

I found a few unrelated things when I pulled the heads off, so I need to look into them as well. Once everything is sorted out, I will do a proper build thread (with pics!) of the whole process, and what I learned along the way doing the build myself.

 

[Burn Down]

Man that really sucks Dave.

 

[WVRigrat05]

That sucks man. How are these heads cracking? I've had my old LLY so hot it should have done worse. All I ever got out of it was melted valves.

 

[DAVe3283]

It might just be a casting defect. I have never overheated this motor, and never even got a big tune loaded into it. Highest EGT was 1300*F a couple times on the break in tune, which is lower than I would tow at before.

I will let the machine shop look at them and see what happened, then report back.

 

[Chevy1925]

Ignore this lol

 

[Burn Down]

I wonder if they can be welded? I know the gassers weld them up all the time.