My car, for a 93 RX7 runs great. I decided to go with a Koyo rad radiator not because of any issues but to protect my car for future fun!


Replacing was easy, I think I have bleed the system correctly but I took the car to get gas after and when I got to the pump the overflow leaked out antifreeze on passenger side, looked like 1 quart or less.


drove it another 5 miles to see if anything happened and the car drove great never over heating or beeping that it needed fluid, I even double checked and the fans are working.

got home left the car in the road running and nothing leaked, pulled it into my garage and well lol it leaked again about the same amount. This time the light went off saying it was low on coolant, this may answer my own question but I wanted to ask some of the pros here.

Any advice would be helpful Im going to bleed it again tomorrow and see if I just have air in the system still.

 

I've encountered this before. Typically, it is a pinhole in the line between the Thermostat Housing and Overflow Reservoir, but can also be caused by loose hose clamps too. This will push out coolant when heated up and suck in air during cooldown. The resulting air in the system will then force out more coolant from the Overflow Reservoir exactly as you described when hot, then suck in even more air during cooldown. Renting a Coolant Pressure Test Kit from your local parts store will put a spotlight on any weakness in the system that causes this behavior.

When I pumped the system up to 10psi, I found that EVERY SINGLE CLAMP was leaking. Tightened them all, then re-tested at the regular 15psi. No more leaks.

 

Ok, I went back out this morning and looked at all my connections and found two loose connections at the air separator tank.

I fixed them and then started the car and had a no spill coolant filling funnel tank which is really nice to use, I added a little radiator fluid and I mean less than 1/2 a quart.


let the car run at idle for 20 min and when the radiator fluid started rising in the funnel i shut the car down.

the raised radiator fluid went back into the car upon shut down and I waited for the over fill to spill coolant but nothing happened.

I then pulled the car on the lift and again let it run for about 5 min, lifted the car in the air and waited, no over flow or spillage at all.

I think you were right and I appreciate the advice, I will take it for a test drive later today and see if anything changes while under boost.