OnlyRotary

I have been looking more at my 10th AE rx-7, and I have noticed some differences that are not in the service manual. For example, there is a coolant cap (radiator cap) on the hose leading from the engine to the radiator (like there should be), and there is another one on the actual radiator right to the right of the radiator level sensor. Why is this? Is this an aftermarket radiator? Basically, my problem is a leak. While running the car, the coolant usually does not leak out of the system. However, when I turn the engine off, the coolant reserve tank fills to the brim and then overflows. And I know the coolant level is correct because I added the liquid prior to driving and made sure that the reserve tank had not too much or not too little in it. I even turned the car on and let it idle (while the cap was off the hose going from the engine to the radiator) and could see the coolant flowing through the tube. What is going on? Should I simply start looking for cracks along the hoses, testing the coolant level sesor, and testing the thermostat? Any imput would be fantastic. Thank you for your time.

Icemark

all 88's are like that, with a coolant cap and pressure cap, pressure cap being on the radiator.

Sounds like a bad pressure cap (make sure it is a Mazda OEM one) or a bad coolant seal.

OnlyRotary

What would happen if you switched them?

Lets say the problem is a bad coolant seal.....what next.....(thinking anything but a rebuild)

pip

Bad coolant seal would require a rebuild, start small and work your way big, if you think the leak is the pressure cap replace it, if that doesnt fix it its rebuild time.

Icemark

Well the coolant would flow into the overflow tank, evey time the coolant warmed up and was under pressure.

One cap will have a .9 bar on it. That is the one that should be on the radiator on an 88.

opelbits

iTrader: (5)

I dealt with similiar problems, recently.

If you have coolant filling the catch tank, then you have to look at how much and how fast. Mine was slow. It would take a couple of days before the level dropped low enough to set off the warning buzzer. It did not seem like it would suck the coolant back in when it cooled down. I replaced the radiator caps with new ones from Mazdatrix on the theory that the caps were not sealing properly and that instead of sucking the coolant back in it was sucking air. Coolant heats up, expands into catch tank, car cools down, cooling system sucks air in.
But it did not solve the problem. Lessened it, but did not solve it.
Other possibilities are that it is a combination of issues. Bad water pump, slipping belts, bad fan clutch, bad radiator, bad seals on bleeder screws/drain screw/low coolant sensor/, anything that would allow the engine to run hot and/or might provide a type of 'one way valve' for coolant or air.
Do you have a temp gauge that cycles between a high and low reading? If you get on the gas going uphill does you gauge then show the car getting a little hotter or does it stay steady all the time?

I mostly solved my problem with a new radiator, new caps, new water pump, new thermostat, new belts, new hoses, and a different catch tank (there is a rubber seal on it's cap, too, that can cause problems, or the rubber hoses could have splits, both would allow air to be sucked in instead of coolant).

I no longer have the coolant filling the tank and not returning. But my gauge does cycle slightly and the seal on my low coolant sensor weeps a bit.

If you are getting alot of coolant, quickly, then have someone check the coolant for combustion gasses. If I start my car, the coolant will slowly expand and flow out the thermostat housing filler neck if I leave the cap off. Takes about 30 seconds to a minute. I thought that might indicate bad seals (impending rebuild) but when tested, there were no combustion gasses indicated.

OnlyRotary

I want to give thanks to everyone who has helped me with my coolant problem. I am so grateful that it was not a seal, but those damn radiator/coolant caps. I went to my local automotive shop and picked up two of the ones made for the 1988 RX-7. This solved the problem and now the coolant is flowing from the reserve tank back into the system when the car cools down. Thanks again everyone.

hondahater

iTrader: (2)

sorry to bring this tread up but I was wondering what you guys mean by radiator cap(s) and not cap? I have a koyo radiator so I have to caps but on stock insn't there only one cap? Thanks.