OK, on my previous post I was talking about my overheating problems at the track..............could this be my problem.............????

My last time at the track, my radiator (not really, I guess it 's more of a thermostat housing/filler neck cap..) cap was spewing, and the rubbing gasket under it was pretty much toast.................so my only choice at that moment was to run to Discount Auto parts, and get what they had so I could limp home...............

My question is...........the old cap was a cap only, not a pressure cap with the spring thing under it...........I figured "no biggie" because all it does it basically seal the neck, right?..........but a buddy of mine suggested that might be the problem.............it should just be a cap, with gasket under it...........not a pressure cap........

What difference could that make, other than it seems that it would prevent the fluid from entering the neck area, since it's sealing off that area...........

Am I on to something here? I sure hope so since this would be an easy fix............I'll run to Mazda and get the right one...............Those bastids at Discount!!! Here it was that this cap came right off their cross reference list...........!!!

Thanks,

David

 

IMO, a bad radiator cap could definitely cause overheating problems at the track. If the pressure is not being held by the cap, the coolant can boil and air/gas can be introduced into your cooling system not allowing it to function properly (especially at the track). Get a new cap ASAP. I forgot the psi rating of the cap, but it think you should be fine with anything above 13, or just go with the "solid" cap that you had before.

 

I see in your mod list you have the Pettit AST. You should have a pressure cap on that. Your filler neck should have the non-pressure cap (whatever it's called). There has to be a pressure release somewhere in the system, and in your case it should be the AST cap.

This would not cause your car to overheat, unless the cap was leaking before, and the temperature of the coolant got so hot that it began to boil.

 

Spring cap instead of plain cap = no problem (assuming it still seals at the top).

Plain cap instead of spring cap = overheat.

Unless the new cap you got just doesn't seal well around the top, that cap should not be a problem.

-Max

 

After getting my car running from a 3 year wait to find the right used motor, I inadvertently switched the caps. After the first run of about 1/8 mile down the road and back, I pulled off the road only to find that my coolant buzzer was ringing and lost all my coolant. I refilled and ran again just a few miles (never overheating the car) and brought it back. Ended up blowing all the antifreeze after shutting down.

Eventually noticed the caps were switched. The one on top can be either one, pressure or flat cap as long as you do not have the earlier year filler neck with a tap line in it. If it has that line, you will need a pressure cap.

But the key is that the AST must have a working pressure cap. My car had no restriction there, so it was happily dumping all my antifreeze from the engine to the overflow with no restrictions, then leaking out the overflow neck where it attaches to the tank.

Good Luck
Tim McCreary