My 89 is overheating but only when I'm driving around town. The gauge fluctuates very rapidly to max hot, then to norm once I start to drive again. I was told its probably the gasket between the water jacket and combustion chamber and that the engine isn't worth squat anymore. Any chance its just a clogged radiator? I flushed the system and checked the water pump. Also, a while ago, my radiator light came on and the water level was full. So to turn off the annoying horn, I just grounded the wire on top of the radiator.....

 

The overflow tank is just that; a place for coolant to overflow. The radiator, if working correctly, should never need to pull coolant from the over flow tank. That buzzer was telling you that the radiator and motor were low on coolant. The motor pushed all of its coolant out of the exhaust and into the overflow tank and is now running dry. Depending on how long this has been going on, your motor might be toast (literally). That annoying buzzer was made to be annoying for a reason!

 

Some basics: You are driving a car whose engine makes more than 2 hp per cubic inch.
It will not take neglect and still run.
Overheating any aluminum (especially a rotary) engine is serious.
Disabling an alarm will not fix the problem.

So - maybe start with this.
1) Replace the thermostat. Make sure it fits. The spring loaded disc under the stat valve must close the bypass port, or guess what?
2) Replace the radiator cap. Low pressure = steam bubbles = spit out coolant.
3) Look for leaks. (same symptoms as #2) Some can be very hard to find. You may have to pressure test it. A common failure spot is the 3/8” coolant line that runs from the top of the rear housing (under the intake runners) to the throttle body, to the BAC, to the water pump. Another one is the heater hose under the oil filter.
4) The fan clutch will slowly start slipping as it ages. The fan should U]pull really hard up to about 4k[/U] when the motor is hot. It should maintain about 4k as the motor revs higher. Sometimes you can get more life from it by bending outward the bi-metal strip on the front of the fan clutch. The cut-in for the series 4 fan clutch is gradual – it pulls some even when cold.

 

thanks guys, sounds like that fan clutch may be the answer. There are no leaks in the coolant--except for a little residue next to the sensor on top of the radiator. That's partly the reason I grounded the wire. Is there a simple way to check the fan clutch without a torque-meter?

 

Just make sure it's full. Loosen the top bleeder screw and make sure fluid comes out. I've never heard of a failure of that sensor. If it's coming on then it's probably low. Grounding it would be absolute NO NO in my book no matter what.

 

https://www.rx7club.com/forum/showth...hreadid=151556

 

Thanks for the link, I checked it out and replied with what I was told is wrong with mine. Its all bad. But, I think I'm gonna give that fan clutch a whirl. (get it). As long as I am cruising the freeway, thing runs great. Only gets 14.5 mpg though! (cty or hwy) Is THAT normal?

 

http://www.aaroncake.net/rx-7/cooling.htm

 

That mpg is normal.

Have you done the rad cap check? It's quick and free.

Give your system a once-over as I suggested in the other thread. How would you feel if you later learned that you'd junked an engine that only had a bitched thermostat or rad with clogged fins?

The sensor went off yet the rad was full? Air bubble. (Sorry I didn't mention this b4 - mind was on other things.) There are a couple of things you can do. Try this: with the engine cold, remove the rad cap (does this sound familiar yet? ) and place the palm of your hand over the opening. Make it tight so no air gets in or out. Now hold the lower rad hose with your other hand and repeatedly and steadily squeeze it. Not too quickly. Squeeze it about 5 or 6 times. Remove your hand from the rad cap hole. Has the level gone down? Top it up and then repeat the procedure. Keep repeating it until the coolant level stops dropping.
You may not get all of the air out, but you will get the worst of it.

 

I'll try that--thanks! So, I drove my car just now and sure enough, it got hot at a stop light. The elec fan came on, and the temp cooled a little, then dropped when I started driving agian. Anyway, right when I got home I opened the hood and spun the fan. It spun without ANY resistance. Didn't someone say that it should have some when its warm? The more I think about it, the more that seems like the problem. I was also thinking of trying to slow it with a piece of wood on the shaft when the car is running-too check resistance. It almost looks like its just free-wheeling when the car is running....

 

Check the other thread again and read the e-fan 411 I posted...

 

Its not such a mystery as you would think. The cooling system is a pretty basic one, and it has some simple rules. The mechanism is also very simple, so you can diagnose whats going on pretty easily. I have said it before, but I'll say it again:

1) If the coolant light goes on and off, then two things could be happening: either there is air in the system (so, as the air bubbles circulate, they "pass" at the spot where the sensor is, and this triggers it), or the sensor is malfuctioning. Fill up the radiator using the proper technique (top it off, then start engine with rad cap off, and fill it up completely, go for a drive, repeat at least one more time). If the quantity of the coolant stays the same, and you dont overflow, its almost certainly an air bubble or a malfuctioning sensor.

2) If you are overflowing all the time, then this means that air is produced inside the cooling system. This "air" could be just air (i.e leak in the cooling system, like a torn hose, cracked thermostat housing, bad seal), or it could be exhaust gases, which is almost always a water seal, but sometimes its even worse (corroded housing). This is also easy to diagnose, provided you can test the coolant for exhaust gas. You can perform the simple test of leaving the rad cap off and checking the coolant for bubbles after the thermostat opens, and see what you get.

 

I hope its not what we all think it is...