I apologize if this question has been asked before or it's just an overall stupid question. I haven't read anything on the boards specifically like this before and have found nothing searching.

Basically my FD will only hold so much coolant...I go out to the car and put in about a liter of coolant or water in both the AST and radiator caps but then as soon as I start the car, that liter of coolant dumps out of the overflow tank. Only a little comes out of the overflow tank, like the exact amount I put in before it stops. If I don't add coolant and run the car, nothing dumps out and the level stays the same.

I expect I have a coolant leak somewhere and air is getting in the system or my turbos are burning coolant, but why exactly does it dump out of the overflow tank as soon as I start the car?

Any input or suggestions on stuff to check would be appreciated.

Thanks guys.

 

radiator cap might be bad, coolant seals might be bad or you are just over filling it....

 

Guess I'll order a new cap. I doubt it's the coolant seals as I just replaced them 2k miles ago. As for over filling it - Both the AST a filler neck shouldn't be topped off?

 

Am I correct in assuming the turbos could be burning the coolant and letting air in? I get a nice puff of white smoke in the morning for about 10 seconds

 

AST cap. Mine hung once too.

 

Where did you get your AST cap from? Looking on rx7store.net and only see radiator caps.

Thanks

 

Sounds like you just need to get all of the air out of the system. Take the coolant line that runs to the back of the throttle body off so the air will bleed out. Fill up the filler neck with the AST cap off, let the AST fill up, then cap it. Then continue filling the filler neck and squeezing the radiator hoses. Big bubbles should come out when you do that. You may have to drive the car up to operating temperature a few times and keep topping the filler neck off over time to get it perfect.

 

Get the caps from Malloy Mazda - shouldn't be that much for new stock caps.

Are you sure you aren't overfilling the overflow tank? You have to use the dipstick to see how much coolant is in there - you can't just fill it to the top. The cooling system, like anything else that's heated, expands and contracts. You fill it cold, and when the car warms up, the coolant expands and the extra coolant goes into the overflow tank. Once you shut the car off and it cools, it sucks the extra coolant back into the system.

Dale

 

sounds like you have air the system. so everytime you check it after driving it will look low. iirc

 

I haven't put any water in the overflow tank at all, so I know I'm not overfilling it.

It's been doing this for months, so it being low after everytime I drive it should have eventually stopped and it hasn't, if it was as simple as air in the system. Air has to be getting in somewhere along the way, don't you think? Or does it really take months of doing this daily to get the bubbles out?

EKTwin93, I'll try what you suggested. Thanks for the detailed input

 

I understand that when the system cools down, it's supposed to suck coolant back into the system to keep it full. Mine isn't doing that - I top it off at the filler neck when the car is cold, then run it. After it cools off again, the upper radiator hose is caved in - when I open the filler neck cap, the vacuum is released and I need to add coolant to bring it up to the filler neck rim. Is there a one-way valve (other than the spring-loaded seals in the AST and filler neck caps) in the system?