Hi guys!
My 2001 Audi a3 1.9tdi(ALH) is leaking coolant from radiator cap.
This happened after replacing the thermostat, expansion tank, radiator cap and coolant after the previous expansion cap had cracked(all new parts are OEM).
Radiator cap seems to be sitting flush, I even cut the ears of the cap to make it sit deeper. I also tried the old cap and the one from my dad's tdi but it keeps leaking.
Coolant temperature heats up to 197.5°F and stays there (Normally should be 194°F but I don't think that this is enough to cause this problem). This has maybe to do with the thermostat opening at a higher temp than normal even though it is supposed to be a OEM product.
Car doesn't leak coolant from somewhere else.
Car was bought new by us in 2001 so I'm sure the car has never overheated before (Except for when the expansion tank cracked then it saw 212°F max, I was on a busy highway so had no choice but to continue for 5 minutes).
Except for this and the AC the car runs perfectly fine, has been serviced regularly his whole life.
Could it be something else other than a bad new expansion tank? Old one never had this problem.
If not I'm going to buy another expansion tank and maybe thermostat from another shop.
Because this car doesn't get driven that often anymore we don't want to go to a mechanic with it.
Thanks in advance and have a nice day!
Cutting the ears off the radiator cap renders it useless. You need to have the correct pressure radiator cap securely locked to the radiator and opening at the appropriate psi. My experience with thermostats is that they function depending on who made them and it is not and exact science. Expansion tanks have no moving parts, it's just a container that holds coolant. Are you certain that all the air was properly bled out of the system?
Thanks for you're reply! When replacing the coolant I usually let the car run with the cap off for 5-10 minutes until the car is warmed up and squeeze a bit on the lower radiator hose to let air out, then top it of with coolant. I have done some other thermostats before but never had this problem before.
I know you are not supposed to cut the ears off but I tried everything I could before and a OEM radiator cap is like 10 euros so no big deal. I also noticed that my radiator cap sits higher than other VAG cars with the same expansion tank so I thought this might solve the problem.
I still think the system has air in it.
How can I fix this? Most guides online tell me to leave the cap off, turn the heater on and let the car idle until it is warmed up and coolant flows back to the expansion tank.
I always jack up the front of the car, open the heater selector to "high" and use a burp funnel -
https://www.youtube.com/watch?v=odDJ8idW9QE&ab_channel=LiveFree
Okay thank you for the advice!
I will bleed the system when I have time.
But I don't think a burp funnel is going to work tho as the expansion tank has a mark where the coolant level should be ideally, and it is well below the radiator cap.
Thank you for you're time!
That doesn't matter, they're all that way. The reservoir is supposed to be filled to the "Full" (Max) line when the engine is hot. If the reservoir is overfilled, the coolant will expand when hot and be expelled out the tank overflow tube onto the ground.