1st things 1st. This pic isn't my car. I googled it, so if it's your car. thanks for the pic!

I just bought my FD and love it. The power compared to my N/A FC is unreal. The car runs great, but it's got it's quirks. One of 'em is that when I turn it off, even after driving nice and mellow, this thing begins to "squeal" like it's losing pressure, and my coolant boils.

Are these two problems related? I have a feeling they are. I put on a new radiator cap, but that didn't help.

The cap says on it "Do not remove" or "Do not loosen". I don't remember which, but I got the point. How should I go about replacing this cap?

Thanks in advance. I'd search, but I don't know what the part is called.

 

looks to be the air separator tank (AST) to me, time for an aluminum one.

 

It's called the AST cap. I recommend buying a new AST cap and water pump housing cap (the other one near the middle of the engine bay) from Mazda. OEM only.

I do know that it's supposed to vent pressure to keep the system at a particular pressure. There are radiator cap testers that measure exactly that - it might be that yours works fine but happens to be noisy.

If you're getting a great deal more pressure in the cooling system, it's possible that your engine has bad seals, and that it's combustion gases driving up the pressure. I hope that's not the case, but be aware of it.

Dave

 

Thanks for the info.

That other one's the water pump housing cap, huh? I though it was the radiator and replaced it. I'm gonna contact my Mazda dealer and see about getting a new AST cap....and a service manual so I can quit asking stupid questions.

 

There is a PDF of the factory service manual available here, it's one of the sticky posts at the top of the 3rd Gen forum. If your local dealer doesn't have the cooling caps in stock, you'll get better prices ordering from Ray Crowe at Malloy Mazda. His phone number is in the 3rd Gen FAQ: https://www.rx7club.com/3rd-generation-specific-1993-2002-16/faq-3rd-gen-other-useful-links-68640/


-s-

 

you can just get the cap at your local auto store its just a radiator cap.... The radiator cap works on the ast and the filler neck... I would recommend using a pressure release one there like 10 bucks

 

yea dude and also get the stock duct back for that IC. That lil thing isnt all that efficient with the duct, so chances are its gunna be even worse without one.

 

Not his car, remember? But very good advice nonetheless. I can't imagine that stock I/C would do much of anything without the ducting.

 

This is a common mistake I've sen on several cars recently. The cap on the filler neck (closest to the air pump) is not a pressure cap. The one on the AST (closest to the Intercooler) is and should be a 13psi (.9 bar) some have gone back to the 16psi (1.3 bar) cap but it's not recomended due to the hose failures it's caused. The noise your hearing is most likely the steam/coolant being puched into your over flow (recovery tank) which most likely means there's air in the cooling system and it needs to be purged as well.

 

The cap on the AST says in big yellow letters to not loosen at all. When I tried to take it off, it wouldn't budge. When I turn the car off, it makes a boiling sound and a sound like it's purging air, but never has it leaked even a drop of coolant. I was at Karack's shop yesterday and he said that the sound is coolant being pushed from the AST into the radiator overfill tank and that the whole system needs purging(at least I'm 99% sure that's what he told me).

heh, the car's getting rebuilt right now by the guru himself anyway, so I don't think this'll be much of a problem in a couple o' weeks.

Thanks for the info!