I recently changed my waterpump and waterpump housing and devoloped an erratic idle issue. The car will idle up to 900-1000rpm when its cold but once it gets hot the idle will fluctuate 1200-1700 rpm while stopped. What i did notice is there is no presure in the coolant lines running into the BAC and up to the thermowax or leaving the thermowax. Could this be a cause of the idle and if so how do i blead the air out of there.

 

If your idle bounces, it's bound to be TPS related. I doubt the thermowax is expanding and contracting over and over again.

 

You can search about bleeding the air out.

The coolant hose that goes into the side of the BAC casting is mostly to keep the valve from freezing up in very cold climates. The coolant has no noticeable effect on the operation of the valve. I have cut a BAC valve in half and observed its operation off the car. It's just a magnet operated by 12 volts that pulls a plunger open, which is then returned to position by a spring.

The coolant hose to the thermowax moves the fast idle cam to lower the idle speed from the cold position.

 

ok wasnt sure if the coolant was nessecary to making either of these really control the idle. Guess i will have to check the TPS and go from there

 

ok coolant is all bled, fixed to vac leaks, i adjusted my TPS per the LED method, and i adjusted the idle screw. idle is about 900 normally and when my e fan kicks in the idle drops to 700, this still doesnt seem right to me as before all this work the idle was 700-750 all the time and even when the fan kicked on the idle was 650 at the least. The only thing else i did besides all this was clean out the TB of the years of carbon build up. guess i will keep at it so i can find the issue