ok i think my Cap is not sealing well on the AST.. due to age and the plastic getting chewd up by taking on/off the cap. has anyone else had this problem?? iam trying to fix a coolant leak ( air leak )
i pressure test the system with the mazda cap on the AST with pressure tester on the filler neck. @ 11 psi i can hear air escaping thorugh AST cap i have ALL new water/heater hoses and new caps from mazda
next question if i get a new AST why would one buy the metal AST that uses the stant ( bigger type ) rad caps? as they do not work as well?

 

The metal AST and cap works just as well. The advantage is that it will not crack. But low mileage stock ASTs are also pretty sturdy and much cheaper. Or of course you can go with an elimination kit.

Dave

 

Because a metal one won't burst, causing you to lose most of your coolant, and overheat your engine.
I've never had any issue with my Stant cap...

 

"ok i think my Cap is not sealing well on the AST.. due to age and the plastic getting chewd up by taking on/off the cap. has anyone else had this problem??"

 

Most either go with an aftermarket metal one or as mentioned eliminate the AST. If your still running the stock one your just asking for a cooling system failure.