Coolant bubbling during BLT

[berberjp]

Hey everyone I just got done a boost leak test on my car (95 tsi) since its been running like absolute garbage (4" vacuum at idle ). It turns out the throttle shaft seals are shot and its leaking pretty bad from there. No problem; I can fix that relatively easily. Now what I'm worried about is the coolant I can hear bubbling underneath the head when I apply pressure to the tester (which is connected to the turbo compressor housing) There is no water in the oil and it doesn't seem to smoke or anything. Should I be worried about this? I would imagine that the air wouldn't come in any contact with the antifreeze whatsoever unless there was a bad gasket/seal somewhere.

Also, the compression was a consistent 130 +/-2psi across all 4 cylinders on a COLD motor (I know its supposed to be warm but this was before the car was running). I have no symptoms of a bad head gasket so is there somewhere else I should look?

 

[ToughTalon]

Thats strange, Im assuming your leaving the throttle body attached to the UPIC pipe and pressurising the engine, Im suprised your even able to build pressure with that method.

While im not completely sure how your doing you test, it is possible for compression from a running engine to push past the headgasket and leak into the cooling system and not burn coolant or mix coolant with oil. A way to test for this is with a kit that is typicaly called a "block test kit". The kit contains a special tube with a rubber fitting that attaches where the radiator cap goes on the thermostat housing. The block test kit has a special liquid that you put in the tube and then you use a little hand pump to suck air from the coolant through the test liquid. If there is any combustion byproducts in your coolant (signifying a leaking, cracked engine block, cylinder head or gasket) then the liquid will change cooler, typicaly from yellow to blue.

This is a test you could consider. BUT, I feel like we might be missing somthing all together, like your running your boost leak test wrong or missinterpreting somthing. Somthing just seems weird to me about this.

And if you figure this out please edit the post so it reads resolved in the title so other people can learn from this too.

 

[berberjp]

Im doing the boost leak test just like the vfaq. Removing the intake pipe and attaching the blt to the turbo inlet. Sorry for the confusion.

I will have to look into that test that you are suggesting. Thanks for the info

 

[JonathanNL]

While im not completely sure how your doing you test, it is possible for compression from a running engine to push past the headgasket and leak into the cooling system and not burn coolant or mix coolant with oil.

I had the exact same problem, but only found out because the temp gauge would start rising drastically due to airlock in the coolant system.
When having the engine running with the radiator cap taken off, there was a clear constant flow of airbubbles in the coolantstream. This was a clear sign that the headgasket was leaking.
The car had no white smoke whatsoever, no coolant in the oil, nor oil in the coolant... must have been one tiny leak just under compression...

Headgasket to be replaced this upcoming week...

 

[Jeff99GS]

Yeah that's definitely a bad Head gasket.

 

[berberjp]

Thanks for the replies everyone. I sort of figured it was a head gasket but i wasnt sure if there was a seal or something in the turbo that could be bad.

....and i found out why i have poor vac.... Timing belt is off 2 teeth!!!!