Can anyone tell me where to get a lower pressure AST
cap for the Pettit AST? I need the Stant # for a 13lb cap. Mine came with a 16lb cap.

 

It's a generic cap. Just go to any auto parts store and get one at whatever pressure you'd like.

 

I know its generic but they have different diameters, tallness of spring. I dont want to guess at this. Does anyone with a Pettit Ast have the number for their 13lbs cap.

 

ST-13 13LBS KPA90

 

Thanks HDP using those numbers these are the parts numbers;
TVI / STANT
PART # DESCRIPTION MOTORAD GATES ROBERTSHAW

TVI 10329 RAD CAP ST-13 31511 RSP-29

 

If you want the one with a Pressure release its #11329

 

I quite using the pressure release caps because the seal around the vent lever was always the first thing to wear out and then they wouldn't hold pressure. The seal under the cap was fine, but the seal where the release goes through the cap wouldn't hold pressure after a while.

 

Just wanted to second what DamonB said. I was having problems with my coolant level dropping after every drive and filling up the overflow tank. Turned out to be the seal around the pressure release valve. This was on a new AST with a new cap.

BTW: I was able to test the pressure releae seal by removing the overflow line and attaching a pressure pump there, then pressurized the AST. I could actually hear the leak at that point.

Replaced it with a non-pressure release and haven't had a problem since.

 

I went to CSK to get a Stant Pressure Release Cap and he said they no longer sell them because of leaks. Although, they sell the Prestone Release Caps, which the manager said haven't had any problems and are better than Stant.

 

i've noticed my 16lbs motorad cap isnt locking down as firmly as it used to. I also have some of the coolant leaking out of the overflow tank sometimes. Maybe i'll try a 13lbs one.

 

I just dealt with the whole overflow issue. Ended up being the filler cap, but in the process of troubleshooting I learned my 13lb AST cap was opening at just 7lbs....