Coolant Issue Overflow Tank Dumping
 

I have filled my car with coolant twice
Both times what ends up happening is my fc would drive a couple days fine then randomly would almost overheat the next day and I would check to see what's wrong and I would notice that the overflow tank would be filled to the top almost and coolant would be dumping out of the hose that's on the cap of the overflow tank.
Any thoughts appreciated.

My Friend's 7 had the same exact problem at first then it got worse with time. It ended up being a coolant seal... Needed rebuild.

You can check by taking the belt out of the water pump and open the cap where you fill up the coolant (do this when the motor is cold) and turn on the car. If you see bubles while engine still cold it is because you have a water seal problem. I hope I am wrong!

I hope this helps

Andrew

You need to include more info about your car.
What kind of car is it? is it an FD? You should really post in the 1st, 2nd or 3rd gen section - whichever relates to your car.

Anyway, I can only comment on the FD, but if the hose that goes from the AST to the overflow tank does not hold pressure/vacuum; when the car cools down it cannot suck the coolant from the overflow tank back into the engine...(it gets sucked back in under vacuum as the coolant cools and contracts)

This means if that line is no good - it will keep pushing coolant into the overflow tank as the coolant heats up & expands. But it will not get sucked back into the system as it should. Leading to a low coolant buzzer & an overflowing overflow tank...

The other options are too much coolant in the system or dead coolant seals. Don't be so quick to assume the worst though.

Yeah probably should have been in the generation specific,
Sorry
And it's a 1987 Fc3s s4

There probably is too much coolant in the system, but after it dumps it out the temperature just rises above 1/2 then it goes back to normal, then goes to 1/2 maybe a little more, then normal
And repeats this throughout the drive. It only stays cold when I fill it with coolant all the way and burp the system.

Do a block test to be safe and it does sound like a bad coolant seal or the engine is overheating in general and blowing it out. The factory guauge are not very acurate and could be flaking out on you.

Does the coolant have a slight exhaust smell or smell like fuel are other signs of a bad coolant seal.

Never heard of this method but it sounds like itll work :)

Damn good point! The s4 have aluminum water necks but the nipple that feeds coolant to the reservoir is plastic and tends to crack with age. IF that nipple is cracked it will not suck the water back to the engine.

Another thing is to check compression on both rotors. Even if you use a shitty piston compression tester, you can compare one rotor to the other.

Pressure testing the cooling system is also a good idea.

What everyone else said, coolant seal, bring the engine to operating temp (to thermally expand the engine internals), slowly bleed the system, then open the cap, and with a pressure tester (rent or buy one from a local parts store) and do a leak down/pressure test on the radiator, if the positive pressure bleeds off within 45-60 seconds, its failed. also, smell the exhaust to see if it smells sweet, visually look at the exhaust to see if it has white smoke coming out of it, coolant seals internally failing is a common problem I run into with the FC's at my shop.

Pressure test the cooling system.