So, my car drives fine, but when I shut it off, it spews coolant out of the reservoir. I believe this to be a bad AST/Rad cap. SO, I've never had a bad cap before. Is this what it looks like?







Also, to replace this AST cap (RE Amemiya), I believe I would need a stock, or import sized cap correct?

Thanks in advance,

Jeff

 

I've never noticed what a bad pressure cap looks like. But if it's leaking, then replace it, lol.

The one thing I do know, is that you're not supposed to use a pressurized cap on both the radiator and the AST. So if your radiator has a pressurized cap, buy a standard cap just to cover the AST.

 

My filler cap isn't pressurized. This cap doesn't seem to leak, but when I pull it off of the AST, it just looks like it's barely if at all properly sealing.

 

You can use a regular pressure cap instead of the filler cap all day long, there's no problem there.

The rubber seal on that cap looks goofed up. I'd try a good new cap just to double check. Just get a cap for a Mazda at the parts store or whatever, shouldn't be hard to find.

If you're barfing out of the reservoir, it's going to be just one of a few things -

- bad radiator cap
- hole in the line going from the AST/radiator cap to the overflow tank
- Bad water seals in the engine

Unfortunately, many times it's #3. Might want to do a champagne test. A buddy's FD just had his go out, we're fixin' to rebuild soon.

Dale

 

I appreciate the chime in Dale, but if it's number 3, shouldn't I have issues with hard starts, and overheating?

 

^nope, not necessarily.

 

What AST do you have? Some AST doesn't seal well with pressure cap over time.

 

Thanks Rich

RE Amemiya

Well, I bought a new cap from O'Reilly's and filled the radiator neck. Warmed up the car, and it spilled out of the reservoir again. Could also be, because I filled the neck. OH and my AST is in a relocated spot. Could that be it? It's closer to the front of the vehicle.

 

Might want to pressure test your coolant system to rule out the coolant seal first.

 

Mine did the same thing. My problem was number 2 on Dales list except I never found a hole but the hose was really old and I think it stopped functioning correctly. Changing the hose is really easy and so is the pressure test. Id inspect that hose and maybe just replace it since its cheap to do.

 

I believe you want the AST to be at one of the highest points in the system...otherwise it defeats the purpose.

That's why the AST is normally mounted right near the top (front area) of the motor.

I see you have your AST mounted slightly lower and also angled forward...that could be part of the problem...

 

I'd just delete the AST altogether if I was you. It's easy to do.

 

- I agree with this imo the height of the AST is important. The coolant recovery tank height doesn't seem to matter from what ive found its not under pressure like the AST.

 

When my coolant reservoir started to overflow my coolant seal blew about a week later..

 

So, the replaced AST cap is holding up. two days so far with no coolant buzz or adding of any coolant. I'll follow up next week. I didn't move the AST to a higher point either, which I was thinking could have been the issue. We'll see, but so far so good. If all goes well, I can finally replace my clutch...HAHA I wanted to wait, because if my seals were gone, the clutch would be the least of my worries...

 

For fun, notice the cheap Radiator cap. No label on it haha.

 

no problems so far

 

Keep up updated.... any new songs ?