overheating prob

[punkbek3886]

the ex is overheating now on the street. sometimes it wont even overheat when im offroading, but once i hit the pavement the temp gauge shoots up. i changed a radiator hose and the thermostat and it seemed like it was fixed, then after about 25 min. of running it just gradually heated up to above the normal area on the gauge. does anyone know what might be causing this?

 

[Alec]

I'm thinking a faulty radiator cap, did you replace it with the thermostat (you always should just to be safe)?

 

[Crankcase]

Did you pay extra attention to which way you installed the T stat? If your reversed it, that could be your problem...

 

[JDraper]

Also check the fan clutch to make sure it's not shot....

 

[punkbek3886]

how would the radiator cap cause this? i think my fan clutch is good cause the fan is always going, plus it will still overheat even when i speed up to about 55. the first time the ex overheated the cap's safety valve went off and all the coolent went out, do the caps need to be replaced after they do that?

 

[Alec]

Like I said above, it is a good idea to replace the cap whenever you replace the tstat. Honestly, it can't hurt to try replacing it since it is a cheapo part. It may be letting too much coolant into the overflow tank.

 

[Slick Rick]

Punkbek3886, is this a new problem? Does it normally do this when you drive on the pavement?

 

[Maniak]

Just becuase the fan is going, doesn't meant the fan clutch is good.

I finally replaced the fan clutch on our '92. It would sort of overheat as I merged onto a freeway, but that was it.

I finally just grabbed the fan, and turned it when everything was cool.

then I did it again when everything was hot.

The fan rotated almost a full turn when everything was hot which told me it wasn't really locking up.

With my new HD (towing) fan clutch, even with everything cool the fan only turns about 3 inches.

In AZ this is great, in other parts of the country the HD fan clutch may be a little much.

I also read that the fan clutch looses(sp?) 10% of the fan speed every year. Seeing that you have a '91, might was well get that thing changed. Its a $50 part and nto hard to change. I would recomend that if you don't have an air hammer to take off the old fan clutch, get a strap wrench to hold the water pump pulley (easier than the correct too is).

Also, if your boiling over when you overheat, your radiator cap is bad. Water only in the radiator with a good cap is good to about 260F. Add anti freeze to it and your up to 280F+

~Mark

 

[Texan01]

Mine would overheat at highway speeds, you could putter around town and it would never run hot. Turned out to be the radiator was 60% clogged up according to the radiator shop.

That was after I bought a new water pump, fan clutch, hoses, 2 t-stats, flushed it 3 times, replaced the radiator cap ,installed an electric fan and called it every name in the book. (needed all of it anyway previous owner never changed the coolant in 100,000 miles, it was nasty when I first drained it, didn't know rust could flow like water)

 

[punkbek3886]

texan, that sounds like my exact problem. the last flush i did on it was about a year ago. i just changed the rad cap and it hasnt overheated yet but it seemed like it wanted to once, but i got to the place i was going to before i could see if it would or not. ill try a flush, i know the coolant level is good, tstat is good, assuming water pump is good. a flush would be an inexpensive way of testing the radiator for blockage.

 

[Maniak]

A flush won't fix a plugged radiator, it only keeps it from getting plugged. Once its plugged, you need a new core (or new radiator)..

If you overheat on the freeway (50mph+) you either don't have enough flow (water or air).. If turning on your heat helps, then you have enough water flow, not enough air flow.

If turning on the heat doesn't help then the water pump is possible (but not always, it still could be the radiator). This is assuming its not the tstat

~Mark

 

[punkbek3886]

yeah that makes sense but i know theres airflow. i think maybe the radiator is partially plugged to where its pretty close to keeping the engine cool but sometimes it gets overwhelmed and the heater core gives it just enough boost to bring the temps back down.

 

[X~FACTOR]

Overheating is very hard to trouble shoot and pinpoint. If you need to start replacing things just start with the cheapest ones first.