magwa

1993 100 CS. i just replaced the heater core and things went well. i then added coolant and bled the air out of the system using the bleeder valve at the back of the engine. however, the car is over heating so i must of missed something. i try to bleed more air from the system and i still have a problem. is there another bleed valve somewhere? this is what happens.

car heats up to operating temperature fine. it then moves into the position near the first "dot" on the themp gauge. then the cooling system makes a thumping noise and the cooling hose from the coolant tank shakes like hell. is this the thermostat that i hear? it is obvious that the system is not flowing properly and therefore not cooling. what have i missed?

thank you for the help

audiqv8

Air in the system. Did you bleed the system?

Jim02351

Look under the cowl just before the heater core tubes. That's another bleeder valve. You should only have give it 2-3 turns counter clockwise run the engine at elevated rpms to get the air out then close the valve. Don't go crazy tightening it! If it breaks it's about $50-60 for a replacement.

Chase GT

Definitely sounds like there is some remaining air in there somewhere. Cool VW guys refer to this as "vapor lock" Which has to do with the increase in pressure, throwing off the thermostat, making it not function properly when it should after heating up to normal operating temperatures. Try that other bleeder valve and see how it goes from there. And be sure not to break it. I ended up having to spend that $50 and waiting a week, for something that I could have easily avoided.