My father just bought a 1990 gxl for 1300.00, it has a problem though, we just had a friend do a tune up, also had him flush the radiator. When he did alot of rust came out, thing is when he drives it the car will run fine, but all of the sudden it will show its getting real hot, then it will go normal, then it will get real hot again, water will start over flowing out of the over flow tube on the resivor, anyone know what this is, do we need a new radiator or water pump, we also just replaced the thermostat. Any help will be greatly appreciated. Any test well help too.

Peace
Buddy

 

Did you replace it with a stock thermostat or aftermarket? What temp was it also?

 

Yea i have heard if you dont use the mazda thermostat that it can do some wierd ****.

 

Damn not sure, had a mechanic do it.

 

Check the t-stat, rad cap, water pump, and radiator fan (the mechanical one). Any or all of these can cause the symptoms you're describing (other than a bad engine).

Brandon

 

Here is my overheating check list:
1) Replace the thermostat. Make sure it fits. The spring loaded disc on the stat must close the bypass port under the stat, 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 pull really hard up to about 4k when the is hot. It should maintain about 4k as the 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. Your series 5 fan clutch is more on/off.