NitrousMan

I'm having an issue with coolant pushing out the overflow tube on the coolant tank on my LS7 when I'm on the boost. I can drive it around town normal without getting into the boost and it never looses coolant. Nothing in the oil and I don't see or smell anything in the exhaust. I've done a leak down test and all cylinders look good with no bubbles in the coolant. I did the leak down test with the motor warm and then again with it cold to see if there was a difference but it still tested ok. I've replaced upper and lower coolant hoses plus added a spring to the lower in case it was collapsing under boost. Any ideas on what else it could be? Motor temp is always good and the system will still have pressure in it after the car has sat for more than 24 hours. Running 10 lbs of boost and the motor is all forged with ARP head studs. I know under boost its seeing way more than 100 psi like the leak down test uses so anything else I should check before pulling the heads to install new gaskets and check for warpage? Would a bad thermostat cause something like this? Short bursts of throttle don't seem to be an issue its more when I stay in for more than 4-5 seconds. It may be the heads are lifting after a while under boost but I'm hoping to avoid pulling the heads if it could be something else. Thanks for any ideas to check.

SPIN20

Just a shot in the dark, but maybe try a new resovoir cap?

realcanuk

Agree... test or try a new cap... if not that sounds like lifting heads a bit.

maustin195

My guess is lifting a head gasket under boost. I have a turbo sled that only does it above 15 psi. Stay below that and no leak. Has never gotten better or worse.

NitrousMan

Sorry I forgot to post I replaced the cap too. Do the reservoirs ever get warped at the neck? What about torquing the head studs again? It's been a few years since the motor was built.

5 Liter Eater

Sounds like it's detonating, creating excess cylinder pressure and lifting the head. The MLS gaskets are usually good about resealing provided they aren't torched. I had this happen on an overly aggressive tune once.

sr71bb

Well It is almost certain you have hurt a head gasket. This condition unfortunately will only get worse. To properly fix this you are going to have to remove BOTH heads and check them to make sure you still have a perfectly flat head surface. It is VERY likely that you will need to mill the heads to get them perfectly flat again. Usually a .005 pass on the heads will do the trick. The block side is usually OK.

In the meantime, go easy with the car. Try not to do any full throttle runs. If it were my car I would make sure I kept it under 3000 RPM until I get things fixed.

NitrousMan

I didn't see any signs of detonation on the Pistons or plugs when I was taking a look with my bore scope. Dr. Phil did the tune a few years ago and he was pretty conservative with the tune since I street drive it a lot on pump gas. Would I be able to see if it's pulling timing out with HP tuners connected while making a run?

schpenxel

Yes.

Arctic Vette

Why dont you replace thermostat and burp system again first before you rebuild. Would suck to do a rebuild or pull engine when there is no need. I had this happen to me on my bike it would spit out coolant when rev hard, i replaced radiator, rad cap, thermostat, replaced coolant flush n fill, replaced thermo sensor.. Not sure which one it was but never ever overheated after and never spit out fluids again.. I think my thermo was stuck or had air in system..

Louis Gigliotti

Is that how you "drove your car 5k miles with no issue" after RR?

sr71bb

Whats your point? You obviously know more about my car than I do. LOL Hell maybe I have just been driving the SOB in my dreams. Regardless of what you may think this car was certainly faster than anything you or your customers had at RR,,,,,,,,,,,,PERIOD,

Louis Gigliotti

Actually, the car I tuned beat your car in the final.

I was simply asking a question. I saw the water pouring out every pass, and if your "recommendation was to keep it below 3k, and not beat on it till you can fix it" was from experi mce, it was obviously hurt more than anyone led on.

sr71bb

I deleted my response to this because after thinking about it , I was being as *******! LOL

Louis Gigliotti

Boy, your shop and scare tactics.

The car didn't break out, it had a stock motor, it exceeded the customers expectations. It's
No fault of mine he took it elsewhere. He wants to drink that coolaid, he can. He has no money to build an engine if it breaks, and no need to make the power level its at.

No need to tread lightly. Your car hurt a head gasket, tuned by the same place he took his car to? Ok!

sr71bb

Well frankly, my car also exceeded expectations. With the exception of a ECS supercharged C7 corvette, it was a little underpowered with the F1R and it certainly was alot heavier in the *** than the other cars that AMP had a hand in, We thought that it would be good to get in at least the top 16 but it ran better than expected and we ran 7th fastest in qualifications.

Logically the car SHOULDNT have made the finals but it was very consistent within 1MPH on each run (final was exception) despite what you were seeing between rounds. The final round was a disappointment because the SOB wouldnt go into 4th gear at 7700 RPM which I blame now on the Centerforce DYAD clutch. THAT is being changed out now as we speak.

Louis Gigliotti

I agree. Your son can drive!

NitrousMan

So since you guys are done with the thread hijack do you have any other ideas besides a head gasket as to what could cause it to push coolant out under load?

schpenxel

Cracked head/block?

I can't think of anything good that can be causing it, assuming the cap is in good shape and holding pressure. The only way it should overflow is if it's seeing too much pressure. It can only see too much pressure by getting way, way too hot, or from something else pressurizing it. i.e. cylinder pressure.

There are test kits that you can buy that will test for the presence of combustion gases in the coolant if you want to be sure that's what it is.

Louis Gigliotti

Take some timing out and see if it still does it.

Most likely it needs head gaskets. MLS gaskets seal
Up well, but they are not invincible.