97 jeep cherokee overheating at high speeds (over 65mph)


#1

I have replace 1: water pump (was beginning of problem, 2: electric fan was replaced, 3: thermostat was replace, 4: Mechanic said was a head gasket issue, head was machined as was warped, however did not fix problem.

I can drive the car at 55 MPH not problems but as soon as reaches 70 car will overheat - Help


#2

I think your mechanic has been doing a lot of wild guessing along with a little BSing.
It would be interesting to hear from him why he thinks a head gasket would be a problem at 70 mph and not at 55 mph and lower.

This kind of problem is usually caused by one of the following, more than likely.

  1. Bug clogged condenser.
  2. Clogged radiator.
  3. Broken or missing airdam (radiator dam, whatever)if so equipped. These are usually narrow plastic dams mounted under the lower radiator support and they are intended to force more air upwards through the radiator. When missing, a vehicle will not overheat at at idle or slow speeds, but will overheat on the highway. Curbs and critters do them in all the time.

If the vehicle is not equipped with an airdam then I would suspect No. 2.
Your mechanic might also be a bit suspect IMHO.


#3

I second OK4450’s advice.


#4

This is a classic case for a bad radiator cap. The system is not holding pressure. I think you will find that it will overheat even at 55 if you are going up a long grade too.


#5

Examine the radiator closely, Are the fins corroded from road salt? They will eventually pull away from the tubes and cooling capacity is then greatly reduced. The cure is a new radiator…


#6

Have 92 Cherokee,doing same thing but pulling light trailer or small boat. Tried flushing, new cap & thermostar. Good but still would run over 200 summer against wind. Changed out “aluminum” rediator which gets age corosion been fine since. (3yrs) Should have done radiator first. Had 90k when trouble started.