*1999 Audi A6 Quattro 2.8L

I have coolant slowly trickling out of the cap of my coolant reservoir and I can't figure out why!?! I replaced the coolant reservoir, reservoir cap, water pump, thermostat, serpentine belt, timing belt, tensioner, radiator, and radiator/auxiliary fan Switch all less than a year ago.

About a week ago I had a mechanic change the valve cover gasket on the driver side because I had a burning smell coming from my engine. After he changed the gasket he noticed there was oil in my spark plugs so I changed the spark plugs myself. I'm somewhat mechanically inclined and I checked all of the hoses from the coolant reservoir and everything looked good. When I started the car everything seemed fine, but about 5 minutes later coolant slowly started trickling from the top of the expansion tank where the cap is.

I figured it was just a bad cap so I went to the Audi dealership and bought a new cap. I installed the new cap and within 5 minutes the coolant started trickling out of the cap again!! Like I said I checked all hoses and everything is good to go.

The car seems to be running great, it's just the coolant leaking out of the cap of the reservoir! I'm not sure what to do because I've already had so many things done to the car that relate directly to the cooling system? Please HELP!!!!

 

If it isn't the cap, its the reservoir. ALthough you changed it once, it looks like it is time to change it again. But, look at the sealing surface closely and see if there is a burr there that you could sand down. The reservoir is pressurized so the seal needs to be tight and clean in order to hold the pressure.

 

Thank you so much Bob! I truly appreciate you taking the time to reply to my post! I had a gut feeling it might be the coolant reservoir so I ordered a new one online last night along with a new thermostat (both OEM). I got both parts for $52 shipped so that's not too bad.

Please excuse my ignorance but I'm not sure exactly where the sealant surface is located?? I'm assuming it's where the cap screws on to the tank? I'd like to try and salvage the tank that's currently installed on the vehicle if at all possible and simply return the new one I bought. If I need to replace the tank can I do it myself or should I hire a mechanic? Also can any mechanic do this job or should I hire a "AUDI or VW" mechanic? Thanks again

 

I put some blue silicone instant gasket around the top of the coolant reservoir cap where it meets the reservoir. Is that ok for a temporary fix until the new coolaant reservoir gets here? I didnt start it or try and see if that fixed the leak because I don't want to doany major damage. Does anyone know if that's ok for a couple of days until the new reservoir gets installed?

 

Paul,

Your blue silicon idea should work until your new reservoir arrives. The top surface is the sealing surface. A person with reasonable mechanical skills should be able to replace the reservoir themselves with a phillips head screw driver and a pair of pliers.

Where did you get your replacement reservoir from?

Good luck,

Bob

 

I put the blue silicone around the area where the cap screws into the tank and the coolant still found a way to leak through the cap. The new reservoir came in the mail so I'm going to install that and see if it fixes the problem. Any other ideas of what it could be?

Once again I didn't have any coolant issues until I replaced the spark plugs. When I went to move the coolant reservoir out of the way to get to the spark plugs 2 of the hoses came loose off of the coolant reservoir. I simply refastened the clamps and reapplied them to the reservoir and I thought everything was fine. After I got the new spark plugs installed coolant started slowly leaking out of the cap after the car had been running for about 5 minutes. Like I said I never had any coolant leakage problems before I changed the plugs.

 

Paul,

After your incident, did you add coolant? If so what kind and how much? Maybe you just overfilled it....

Bob

 

first check coolant levels .. make sure you are at the full mark when the engine is COLD.
The coolant does flow past here when circulating in hot mode but a couple of things to consider.
The cap is designed to release excess coolant or release pressure in an overpressurrized enviroment.
The system will become over pressurived and leak if you have a leaking head gasket.

Not saying this is the cause, just things to consider ...