My FD3S overflows antifreeze when parked hot after being driven
 

I drove my 93 FD3S for five miles today, when I parked it in my garage the antifreeze overflowed from the overflow tank all over the garage floor. I checked for a damaged to the tank and the fill spout to no avail. This has happend several times now but it does not overflow every time. Does anyone have a solution to this problem? :scratch:

Sorry to break it to you, but that's a symptom of a weak/leaking water seal.
Search the forum and you should find more info.

Before you jump to any conclusions, change your thermostat. It's a sub $10 piece, and takes 15 minutes to change. I had the same problem last year.

Wow...Not necessarily. It is more than likely the result of an overfilled coolant system. As the Coolant heats and expands it overflows the overflow tank which isn't sealed. It can also happen as a result of a poor seal on a Coolant Cap, either at the filler neck or the AST. I have had this happen many times. Let the car get completly cooled then pull the dipstick out of the coolant resivoir and check for proper level. If it has too much in it, get a small piece of tubing and syphon it out through the dipstick hole.
Here's a link to the Big Fat Cooling thread...a must read for all FD owners...
https://www.rx7club.com/3rd-generation-specific-1993-2002-16/big-fat-fd3s-cooling-thread-571088/

I just checked the dip stick and it shows the tank full. The top of the tank is all wet with antifreeze. The floor has a huge green bloodly puddle. The engine is dry with no leaks present. I suspect a cracked overflow tank, but doesn't leak when cold. Any thoughts?

I already told you to change the thermostat. I can almost guarantee that's your problem.

+1 to coolant cap and/or AST cap. I had same problem last year and was assuming the worst.

Thanks! I will replace the Tstat.

Thanks!

I will replace both caps. Did you have to replace the overflow tank?

+2

my previous car was like that when the previous owner exchanged the 2 radiator caps
i was loosing coolant everytime it was getting at operating temperature

Did it stop after you replaced them?

i live in FL what temp stat shpuld i put on

Hopefully it is just a bad coolant cap for you but my car exhibited these symptoms when a coolant seal was failing. Exhaust gases would make their way into the cooling system and overpressure the system and push coolant into the overflow tank. A sign of this happening is black goo on the overflow tank dipstick. When the car cooled off the exhaust gases in the cooling system would prevent it from pulling coolant back from the overflow tank. The net result of that problem was a coolant tank that overflowed more often than not after the car was parked. If a new coolant cap doesn't fix the problem then definitely do the champagne test.

The stock one, I suggest giving Ray Crowe a call.

i didnt even need to replace them, just exchange them

make sure that the cap with the valve goes on the AST

How would a thermostat cause this problem?

i had this happen to me a couple of weeks ago.it dumps the coolant to the reservoir because it cannot hold pressure.I bet it only overflows when you try to add more coolant because your thinking that it must be low from leaking all that coolant.. turned out to be the ast cap not sealing right..

Sam exact thing happened to me with the same fix. New ast cap.:icon_tup:

There's a good thread somewhere that explains the way the FD cooling system works. Basically in a nut shell the coolant expands as it gets hot hence it goes into the overflow bottle. Normally when the car cools down it will draw or suck the coolant from the overflow back into the system only if the system is tight and sealed - which is why you need proper radiator and AST caps.

If you open your filler cap you will see the coolant sitting there. Under normal circumstances if you then open your AST cap your coolant will start to slowly go down - where does it go? Into your overflow bottle. If you put the AST cap back on it 'should' stop going down.

So you can see where I'm getting at. If you open your filler cap and your AST cap is on but coolant level is still going down, then most likely its your AST cap but just to be sure replace both of them while your at it.

I replaced my AST too at this point as well as the hoses to it and problem solved. Just remember how old they are now.

+1 if its not the ast... i got this problem as we speak and im getting a rebuild in a week or 2 hopefully all the parts arrive

+1 for too much coolant in the overflow.

Here's "The Big Fat FD3S Cooling Thread"

https://www.rx7club.com/showthread.php?t=571088

The best I've read on this issue!!

it can also happen if the stock coolant overflow line is pinched off or deteriorated, so that coolant overflows but is not sucked back into the system...that was my problem a few years ago

To be on topic....I just bought my FD and its leaking coolant. The previous owner replaced the overflow tank. My friend and I checked out the car yesterday and the previous owner put in way too much coolant because he said it was leaking out. Okay so we do the pressure test on the radiator and there are no leaks, we suck out some coolant so its on the full line ( not over full ) and as I was driving...it beeped like mad crazy telling me to add coolant but its already full. So replacing a thermostat and radiator/ ast cap will solve my problem? I added coolant but it doesnt seem to be sucking into the engine. Im talking about the little resevoir on the right. Please help me guys and sorry for being a noob......

well just read the sticky and it answers everything i suppose, just wanted feedback of others please