it was my coolant cap

[volks88]

so after the car went stg3 it was fine for awhile then i developed a coolant leak. i knew it couldnt be my aux pump cause i replaced it at that time. it was leaving a puddle sometimes right in the middle where you would think its the aux pump. i started thinking it might be a head gasket cause it was building pressure and i was getting coolant residue right outside the coolant cap. i threw it on the lift and the pass turbo coolant line was leaking coolant and running down making its way over to the middle. i tightened it up but i knew that was not the issue of the pressure forcing it out the cap. i decided to buy a new coolant cap and check my old one. sure shit it was a bad cap. it was holding almost 20 psi and im pretty sure thats high. anyways no leaks anymore

[RusS4]

Holy old thread! Sorry to bring it back from the dead but I need help with a coolant leak. I have coolant that keeps puddling up in the valley. I just reinstalled my aux pump with my 605 install so I know its not that. It dosent seem to always do it but I replaced the coolant cap with another one I had and it seemed to stop but now its doing it again. Im thinking its a pressure issue but I think I bled all the air out. Anyone have any ideas?

[RusS4]

Anyone want to take a stab at it???

[2Point7]

Coolant reservoir.

[2Point7]

There is also some O-ring located in one of the coolant hoses behind the motor...

[RusS4]

Ok so after more research I'm thinking its the o-ring that's on the pipe that goes to the heater core. Its the hard line that sits in the valley on the drivers side. How many others have experienced this problem? Could it be air still in the system causing it to leak there?

[sa_seahawker]

I don't know, but I had a similar problem as the OP. I just happen to read this after I found the problem. I looked at the inside of my coolant cap and it was missing the o-ring. Replaced the o-ring and I will see how it goes.

RusS4,

I don't think air in the system will cause a leak, per se. If there is air, it would just circulate with the coolant. I would recommend a good thorough engine cleaning. Get as much as the old grease, oil, dirt, etc off. Let it dry thoroughly. Then run it for a bit and see if you can find the leak either bubbling out of a connector or follow a drip trail.

Or if you can find an engine coolant dye. Like this: clicky click

Then you could use a UV light to find the leak easier. However, I ask around to make sure the dye is compatible with G12/11 first. I've never used it in an Audi before. Hopefully someone else has some experience with it in Audis.