okay I opened my ast only to find it was almost completley empty. So I filled it again and I checked the filler neck also and it seemed to be okay maybe a hair on the low side. I topped that off too. I went for a drive and came back home. Next day just out of curiousity I opened the ast again and it was empty again. I checked the overflow and it was beyond the full line (like it's always been) but didn't seem to be higher on the stick though. I could be mistaken since I have a hard time reading the overflow dipstick because the coolant loves sticking to the dipstick. Could this be a coolant leak? I don't think it is since I don't see any coolant on the ground. And I don't really smell any coolant burning. Any ideas. Sorry if this is a repost but I couldn't find any answers in the search. Maybe I was using the wrong key words or something. Thanks.

 

Don't worry about the AST. The only thing you really need to pay attention to as far as coolant level goes is the filler neck. The level of the AST and the overflow tank will vary - that means they are doing their job.


... That said, I hope you have an Aluminum AST. If not, go get one - like now.

 

cool.... I didn't think it was a big deal. The car has never ran hot since I bought it. I feel better now thanks.

 

Aluminum AST a must? I've seen people say the the plastics are preferred (to these people) because they show signs before they burst, and the metal ones do not.
Not saying aluminum is bad though

 

Oh, and if anyone was wondering where I heard this, it was in referral to someone asking why a very modified japanese FD kept the stock plastic AST.
And no I'm not saying the plastics are better. Just adding

 

Your symptoms are typical for a hole in the line between your AST and your overflow tank.

As for the Stock plastic vs. AL AST debate, I'll take the 3rd side and say eliminated it. Simplier is better.

 

I had the same exact problem only a month ago and here's how I fixed it:

1) Replaced the filler neck cap with a new OEM cap ($18)
2) Replaced the overflow tank with new OEM tank ($120)
3) Replaced the rubber hose connecting the overflow tank and AST. ($8)
4) Replaced the stock sh*tty plastic AST with a aluminum AST. ($80)
5) Replaced the stock sh*tty radiator with a all aluminum Fluidyne radiator. ($435)

Ok, so that may have been overkill, but I didn't want to take ANY chances with overheating my FD and suffering an unfortunate O-ring failure.

I'm happy to say now that my car does not overheat even after running in 80 degree sunny weather for 6 hours straight. My coolant levels are constant and stay topped off in the filler neck and AST. Before that my car would mysteriously lose coolant overnight. There was never any visible leaks from hoses even after putting the car on jackstands. Another funny thing is the car use to smoke for a minute when starting in the morning, but interestingly doesn't do that anymore. That may be related to the precat though, since I installed a downpipe at the same time.

Oh yeah, another thing you might check that caused my car to overheat - make sure the caps are in the right places. The pressurized cap should be on the AST. The non-pressurized cap should be on the filler neck.