So when i bought my car last year, I got the engine rebuilt by a place with a pretty good rep. The filler cap looked like a radiator cap and had a spring in it.

then, I started losing coolant. It seems to pee out of the overflow tank vent after driving. I took it to a different rotary shop and they told me they pressure tested the system and that the ast and filler caps were bad. so they replaced them. and they both have springs in them.

Whats the deal? does the spring matter in the filler cap?

 

The filler neck above the water pump (not the AST) should have a cap. Not a pressure cap with a spring.

 

It seems like it wouldn't matter so long as it seals but ?

 

The filler cap isnt supposed to have a spring. If it seals, the spring wont hurt anything.

 

Make sure the hose in between the AST and overflow tank is good. I had the same problem and it was the hose. Also you can get the proper cap for Roy at Malloy Mazda.

 

^ *Ray at Malloy

 

Doesn't matter if both are pressure caps as long as the seal is in good order! I have been using pressure caps in both location for the past four years without any problems.