Hello, new guy here starting to fix up my 91 Firebird 3.1L. The heater control valve was cracked and was leaking coolant. I put on a new one and now it's leaking from underneath the round top part. The only thing I can figure it could be is the vac. line but not sure. How do I check it? Is there a certain procedure to changing this part ? Thanks for any help.

 

if it's leaking coolant, then you have a defective heater control valve. That round part on top is a vacuum diaphram that open when you set the inside temperature control to heat. That's all it is, if there's coolant coming from it, it needs to be replaced.

 

I have had to replace this stupid little thing several times now because they are so cheap they constantly break/fail. I just ordered another one, this time an actual ACDelco, so maybe OE equipment will last longer than the others.

 

It you don't use your heat often and only in the cold months, junk the HCV and put a ball valve form a hardware store on the heater core line.

As is int he summer I bypass the core as that heat still travels up and inside, got no ac and it gets warm in a black car. Every bit counts.

 

easy to crack them during installation...