Ok. I've been losing coolant. Well, not losing. It's all in the overflow bottle. The other night I turned the motor off and went to listen for leaks, and I hear the radiator cap hissing. Is it supposed to make noise? I did the coolant seal test last night. The water level rose just a little bit and slowly poured over the top, but no surging geysers or anything like that.

 

Radiator caps are cheap...go get a new one...before installing make sure the neck of the radiator and the seat on top where the cap seal sits is clean and smooth with no kind of build up....you might want to check the cap on the thermostat neck too....I use a 16lb up there and it will leak a drop or two...I need to find a plain cap with no pressure rating....get a Stant or other known brand...Stant is pretty reliable...good luck

 

PS....I think the cap on the Radiator calls for a 13lb...dont put a 16 there...

 

I only have one cap. It's on the thermostat neck. There's no cap on the radiator. As for the result I got from the coolant seal test, that means they're still good right?

 

Could be...but for 7$ I would get a new one....no kidding...are you losing coolant? Both my 88's have lost coolant,,,but not getting into engine....I don't know where it goes....they been doing that for a long time...how much are you losing?

 

PS...have you replaced your thermostat lately ? Thats a good Idea especially here at the beginning of summer.

 

That's the thing. I'm not losing any from the cooling system. It just all goes into the overflow bottle. From there it leaks out when that gets too full. Thermostat was installed late this past winter, when I discovered there was none to begin with... I'll try a new cap today. I know that happened this past spring with the last cap. The light kept coming on, and the bottle was full. I put in a new cap and the bottle just about drained itself and the light turned off. The cap that's on there now is from pep boys, I'm pretty sure. Will that make a difference as to good cap/crap cap?

 

Go with mazda OEM rad cap. Stants have been known to fail.

 

Yep...definately sounds like a cap problem....you sure its the right spec for the car...any part can fail...including OEM parts....I've never had a Stant to fail.....Yet anyway....they probably contract and make them for Mazda....but you can't go wrong with a Mazda OEM part...

 

Get the good stuff... Get the Mazda cap
... and if you buy it at a dealer... ask the parts man to pressure test the cap in front of you before you buy it.... you would be surprised how many caps can be defective... even brand spankin new!

 

Should I try a 15lb cap? The manual says the cap can range anywhere from 11 to 15 psi.