My 1987 rx7 na has overheating issues going on. I have replaced the thermostat and radiator cap. Car runs for about anywhere from 10-20 minutes and then starts to overheat. I am thinking it is either weak waterpump or bad clutch fan but not sure. I don't leak any fluid just pushes it out the overflow and boils in the radiator. Any ideas as i am new to this motor.

 

That sounds like blown coolant seals. If so, the fix involves an engine rebuild. You can do the "champagne test" which involves starting the engine, then removing the radiator cap (ONLY WHEN COLD). If there is a steady stream of bubbles coming up, there's a good chance air/exhaust is being forced in.

 

Blown coolant seals, bad fan clutch, bad water pump, clogged radiator, bad t-stat, no undertray, external coolant leaks: Various things that could be causing your car to over heat.

 

I did the champagne test and only when the thermostat opens do I get a mad rush if bubbles and it gets worse the warmer the motor gets to the point it blows antifreeze all over the place. This is why I think the seals are bad.

 

Just to let u guys know that when I drained the antifreeze it was mostly water. Also looking down into the motor from the fill spout you can see the rust stains. So I could be a bad waterpump?

 

will it overheat while driving?

 

Yes. But will not overheat if you have the front of the car up in the air on ramps though. Weird.

 

Here is a video after i topped off the coolant without opening the air relieve plug.
http://smg.photobucket.com/albums/v4...=VIDEO0007.mp4
Looks like coolant seal bad?