KingHamer

I had a pretty good coolant leak from the front of the engine. Ended up being a cracked plastic thermostat housing. Replaced with the aluminum one, also replaced thermostat and water pump as well as TB, roller etc etc.

Now I have coolant leak in the rear of the car... Passenger side, pretty far back. Is this the Auxiliary pump or maybe the hoses around it? If so, how do I know for sure?

I don't know how to find the darn DIY articles on this site.. I know thats weak but I legit can't find it. Where are those at? Thanks guys.

deviantirish

On the back of the motor there is the coolant bar that goes from one head to the other. just below that is the coolant line for the secondary pump that is located under the fuel rail/ intake manifold. Then below that is 2 coolant lines that travel into the car for the heater core. The very bottom 2 are hard to get to and held on with a retainer clip at the motor.

clancy

AudiWorld Tech Articles This is the aux. coolant pump replacement tech article. Also there have been many posts in the past 24 months about this issue. Search this forum.

SloopJohnB@mac.com

That pipe is held on with two socket head cap screws, prob 7 or 8 mm wrench.
I could barely get in there with a cut-off allen wrench to tighten them.

Just about impossible to get off without pulling the intake manifold (on my 4.2). Have to pull the intake manifold to get to the aux coolant pump on the 4.2 anyway…there is a pipe from that pipe to the front of the passenger side head…the transfer pipe has an O-ring in it too that may or may not work with the OEM O-ring…one tech on my 4.2 had to put a larger cross-section O-ring in there to stop a leak.
Point is that pulling the cross pipe from the back of the V8 can loosen or cause a leak in the transfer pipe to the front of the passenger side head so be prepared to replace ALL the gaskets, seals, O-rings involved when you mess with that cross pipe.

devinsixtyseven

KingHamer, what engine?

FWIW, the TB cut through the plastic coolant manifold on my BEL 2.7T...huge mess. Audi does offer a cast aluminum replacement, YMMV regarding the belt, I'm getting ready to check mine at about 10k miles post-repair.

jseklund

Check the CTS - the gasket on this often goes bad and coolant will come out when the car heats up. It is located in the top of the pipe mentioned by the others above. You will see coolant pooled in the top of the sensor....

You seem to know a lot, so maybe that was obvious and you already checked it. If that isn't it, then I would be pulling the air intake to take a look....it isn't that big a job and takes me about 30-45 minutes and I am slow.

raj99

+1 on this...it happened to me on my previous C5 and it was the gasket that was the issue.

KingHamer

Watch out, we got a big man here!. God forbid someone wants to know where the link is.

KingHamer

My bad, its the 2.7t!

I did replace that Thermostat Housing with the aluminum one, worked like a charm it was cracked with the plastic one.

KingHamer

I'de like to think I know quite a bit about this particular model (2.7t) as I have replaced so many parts on it... but, I don't know what the CTS is..