Bad coolant seal?
 

Hi all!

My pretty stock FD has been starting and running fine until it is time to slow down due to stop'n'go traffic or it is time to park the car. I can drive for one and a half hours, no problem, but when slowing down the car dumps coolant into the overflow tank, buzzer goes off and temps rocket. Sometimes the temp start to rise without the buzzer going off, manually starting the fans on high level only has a slight effect in preventing this from happening.

I watched this and decided to do the "champange test". In the video it is mentioned a lot about "hard to start" and "tail pipe smoke", which I have none of. Also found where the car isn't hard to start nor smokes.

My champange test sure produced bubbles. Watch here.
The car is cold started (18 deg C). At 9 minutes when the bubbles start pouring out my temp gun says about 40C. The stock temp gauge has been linearized so it shows about 60C at the end of the video. The horrible noise that comes after a while is probably due to water spilling on the drive belt, it is not normally there. And I know, I need to do a coolant flush.

Any chance there is another reason than a bad coolant seal??

/Thanks in advance!

https://www.rx7club.com/3rd-generati...ystem-1068344/ If nothing else helps, check posts #13 and #21....kind of sounds similar to you. Regardless, I would pressure test the system asap.

Had similar symptoms. No white smoke smoke or hard to start at first, but eventually.

Sounds like the coolant seal is failing. The bubble test isnt great because the water pump will churn up the coolant. Get the car to operating temperature and then pull the belt off and run it for a few seconds. The best way is to pressure test the system with a dedicated coolant system pressure tester.

Test for CO2 in the cooling system, like a head gasket on a piston engine, coolant seals usually fail gradually. Combustion gasses being pushed into the cooling system displacing coolant is usually the first symptom. When it gets really bad it'll start running rough blowing coolant vapors out the exhaust.

Thanks for input.

I did a pressure test last year (had the problem then already) after changing all coolant hoses to silicon hoses and a new AST. My symptoms sounded awfully similar to those in the link SgtBlue gave. I have, on occasions, heard a boiling sound after shutdown as well.

Haven't smelled the plugs or done a CO2 test. I guess I look in to that, but things do not look very bright...

If you become convinced it's a failed seal, try not to wait too long. Over time coolant can sit in the seal grooves and they pit/erode, making them unusable for a rebuild.