Correct me if im wrong about coolant
 

once a day the overflow fills up and wont go back into the enigne. If I don't pour the overflow back into the engine, it will buzz me and overheat the next day. I'm pretty sure this means coolant seals. I am going to try the open filler neck cranking test tonight, but any info would help.

'86 fc n/a stock except for exhaust and intake

change you rad cap..get a new one..OEM (mazda) cap..not a cheapie..good luck

Im confused because I have done a pressure test and the system held 13psi for 25 minutes. I don't think i have a leak so i tried a new cap from napa. I guess i should get an oem one. thanks

You have a coolant leak...a real tiny one.


-Ted

The 86 had a coolant tank retrofit kit put out by mazda. It moved the overflow tube from the water spout above the thermostat to the water level sensor. With a seprate pressure cap device. My dads 86 had the same problem for years and he thought it was a seal. I eventually spotted a car at the junck yard with the retrofit kit, and picked that up. Instead of installing it he bought brass radiator with the cap on the radiator, never had this problem again.

So yeah if your really lucky, and you find that there is no leak it may not be a coolant seal.

thanks alot. I have a new radiator coming because i thought it was leaking. so hopefully i will install it this weekend.

I actually just found a TSB for the '86 rx7s with a coolant leak problem. They have a retrofit kit with a different radiator cap, hoses, overflow, filler neck, and some other things. A TSB means that the manufacture has recieved alot of the same complaints with the same repairs necessary, so they come up with a revision that is usually required to repair the problem. I have a plan to avoid buying the kit from mazda and i will let everyone know how it goes. Sorry if this is common and written up a bunch of times, but it seemed pretty unheard of on the forum, so whatever, i'm rambling.

The other possible culprit is that you have a leak after the rad cap.
Check the overflow hoses and especially the plastic cap of the overflow reservior itself.


-Ted

If you buy a radiator with the cap on the radiator than you don't need the kit. The kit is merely intended to move the overflow location to the top of the radiator, thats it. Every aftermarket radiator I've ever seen has the cap on the top of the radiator, which is effectivly the same thing. After you get everything installed pressure check the cooling system to make sure there isn't also a leak somehwere else.

that was actually my plan exactly. aftermarket radiator. thanks for the help guys