I have a 91 rx7, new radiator, new thermostat, the temp stays fine for awhile then starts to get hot. When this happens it fills the reserve resovior and starts to overfill it. could there be air in the system? If so how is it getting there, and what should i do to keep the reserve from being overfilled? could it just be that i dont have enough coolant in the system?
With the rotary engine its common for the coolant seals to give out. especially if they are original seals. when that happens compression and combustion leaks into the water system causing the water system to have pressure and blow out the cap.
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Re: 91 mazda rx7 cooling problems
Run the car with the rad cap off until the thermostat opens[top rad hose will be warm] then shut off the engine.wait a couple of minutes and recheck the fluid level,this should get rid of the air.if ithis does not fix the problem then the head gasket may need to be replaced.
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it could be you have an air lock in the cooling system
remove the rad cap from the rad, start the engine and let it run until the coolant drops (add to fill it back up) or until the coolant boils out of the rad spout.
maybe pull the heat sensor. -replace it OR clean it off, reinstall it.
This might sound like too simple a solution, but after owning 5 expeditions, I think I may have an idea.
It is possible that the cooling system is simply not full of fluid. If, when changing the thermostat twice and other service, the system was not sufficiently bled or burped, this can happen. What happens is that people do these repairs, and then fill the radiator, but fail to completely flush the cooling system. My son had the exact same problem on his Mazda 3 (Mazda was owned by Ford then), and flushing his cooling system solved his problem.
Think of it this way: If your heater works fine, then goes cold, that usually means the heater coils which the air blows over have no hot fluid in them. As for overheating, your thermostat opens when your engine reaches a certain temperature with the intent to exchange the too-hot fluid with water cooled by the radiator, but if there is only air, or insufficient fluid in the engine after the exchange, you will overheat.
Ask your mechanic to flush/burp the cooling system completely. I hope this works.
Blown radiator hose? Might have blown a head gasket right there,which would continually send hot bubbles into the cooling system and degas bottle. If you see bubbles continually,it's a head gasket probably.
Might be the degas cap not releasing at 16 psi or your cooling system has air in it, OR your cooling fan is not actuating. Many things.
Also I have gotten 3 out of 5 bad thermostats from aftermarket stores. Get a Motorcraft thermostat. Did you replace with a NEW radiator?
Most engines don't fair well under extreme heat. It's apparent you might have some electrical issue's. Your rpm's or mph arm going up and down could be faulty speed sensor would cause arm problem. I think you may have more than one problem, the car shutting off is due to engine over-heating. Check cooling system-thermostat, water pump, radiator, engine fans and coolant temp sensor and fan relay's. It could be as simple as blown radiator hose.
If you replaced the thermostat I would look next at the electric cooling fan thermostat.. Its likely located in the radiator itself and is in charge of turning on the electric fans.
To check. start the car and listen for the fan next to the radiator to kick on. It should start running before the car gets over heated.
Also when the temp gets really high is the radiator hot? if not then you still have a coolant flow problem. If the radiator IS hot then you have a problem with the coolant not getting cooled. Either an electric fan/thermostat of if you have an engine driven fan maybe its clutch is bad.
Have no idea, but it's not hard to trace the hoses... they basically consist of an out from the water pump, and into the radiator, the out from the radiator and into the thermostat water jacket... then there will be 2 heater core hoses, in and out, which will be located on the firewall to the rare of the engine compartment. But if it's overheating the likely cause wouldn't be clogged hoses, unless of course you are leaking coolant which I'm sure you'd have noticed already. While the car is running and warm feel the coolant hoses, if they feel pressurized and hot then your water pump is likely good, and the likely cause would probably be the thermostat. Easy fix and cheap, too...
the coolant should flow from the radiator into the reervoir as it heats up. When it cools, the fluid flows back into radiator.
Check to be sure your cooling fan is coming on when the engine gets fully warmed up, and when you urn the a/c on.
CHECK COOLANT LEVEL.CHECK THERMOSTAT.IF TOP RADIATOR HOSE DONT GET HOT IN 10 MINUTES AFTER FIRST STARTING CAR IN MORNING .AND JUST THE BOTTOM HOSE.THERMOSTAT STICKING CLOSE.IF THERMOSTAT FINE.PROBLEM COULD BE CLOGGED RADIATOR OR ENGINE BLOCK CLOGGED OR FAULTY WATER PUMP.
the engine overheating after a shutdown could perhaps be addressed by installing a time delay off on the relay of the radiator fan. The idea is after absence of Ignition B+12 (engine off), the fan/relay should still be energized for a number of minutes so as to cool the radiator;
idling the engine for about 5 minutes before shutdown is a good practice. this enable the engine to cool slowly rather than an abrupt change in temperature of the external but the inside is still rather hot;
the opening of the thermostat is triggered by the temperature of the water above it not below (where the spring is);
in my country, where it is relatively always hot, some mechs remove the thermostat (of course not applicable in cold climates);
a more helpful idea would be the installation of an electric water pump in lieu of the mechanical one. There are several after market models. Pls try here, here or here for a start;
it is also possible to wire the electric water pump to still run for a minute or more similar to the proposed time delay for the radiator fan above.
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