Hey guys,
i just got my car back from bodywork and paint,...yay!!! but i noticed a prob today....ive researched on rx7club and found some similar hreads but not quite the same prob........my fc does NOT overheat but the coolant reservoir seems to fill up and not return any coolant back into the radiator....my temperature goes up to about halfway and not any further.
All the other threads ive researched had the same prob but theyre cars were overheating....i have a koyo radiatorwhich eliminated that funky fill cap by the goose neck....if anyone can help me out here itd be great....

faulty or weak rad cap and or damaged sealing lip where rad cap seals against come to mind.








Or you're pushing combustion pressure into the coolant.....

thats what i figured, i dont see no visible leak....no "exaust smell" coming from filler cap....maybe waterpump going bad?....well i hope not...i swear if its not one thing its another. ill have drive down to advance to get a cap now...maybe a tstat too...wonder how much itd cost.

Well if the rad cap has failed when the coolant heats up, and expands, it will push coolant past the cap without any visible leak.

A rad cap should only be $10 bucks or so at any local parts store, pretty cheap. A t-stat is only about $23 from Mazda.

cool....i hope it solves this problem.

I agree with replacing the radiator cap first.

If the problem is combustion pressure in the coolant, you will have bubbles in the coolant all the time. You can remove the radiator cap and let the car run. You would have an endless amount of bubbles coming out.

I just bought a 1990 and had this same exact issue. You won't want to hear this, but after doing the "champagne" test, I confirmed I have blown coolant seals. I did the new tstat and rad cap hoping this would make the problem go away....then had to hear the fat lady sing...

do you have any coolant in the oil?