Recently sprung a coolant leak. It appears that on the bottom of the expansion tank there is a valve/vent. coolant is leaking from this, and it will continually leak out. I can find no other leaks, and I have pressure tested the system. and when I pressurize, this is were the system is leaking.

so, my question is, is the hole on the bottom of the expansion tank a valve, or is there supposed to be a cap and mine is missing? looking on audiwholesaleparts, the parts diagram only list the expansion tank without going into detail about the function of the valve onthe bottom of the tank.

any help really appreciated.

thanks - dan

 

Neither. That's where the coolant bleeds out when the cap thinks there's too much pressure. Your cap is the "valve". Buy a new cap.

 

so if I pressure test the system, it SHOULD bleed out the bottom? thats the only place it is leaking that I see. that would be a great simple fix.

thanks

 

replace the tank and cap. the tanks crack. maybe

 

Depends on how your tester fits in there. If you look down the mouth of that tank, you'll see where anything that escapes the inside ring is going to end up going down that drain hole. The bottom line is that the cap is the safety valve for excess pressure. If the cap lets pressure out, it's going down that drain hole.

 

can we agree that there is not a bleed valve on the bottom of the tank?

 

They do. They also "leak" out the bottom, by design. If it's coming out the tube circled in red, it's just the overflow.

 

I've only got 205,000 miles on my 1.8 so I stand corrected. cheers

 

I only know because on a 2.8 it leaves white coolant residue on my heater hoses and makes me think I have a leak when I don't....

 

no, you have 207,000 and I have only 205,000 miles. more experience, you.