Jeep: motor running hot, mud work, coolant temp

Question
QUESTION:  I just had 96 jeep cherokee with the 4.0 six get hot on me. I was towing my boat which weighs about 1000 lb into a 20 mph wind on rolling hills between 65/70 mph. When I noticed the temp gage in the red area. I pulled of the road at the next town and poped the hood. I could see no problems so I turned the motor off for 1/2 hour checked the radiator fluid and it was full. I turned it back on and let it ideal 15 min and the temp gage stayed in the normal range. The elect fan did not run when I turned the motor off. I got back on the interstate and kept going but this time I drove 55 mph and everything was fine. What's your best guess has to what is  going on? One other time it got hot after just a little mud work. neither time was I abusing it.    THANKS     jerry

ANSWER: Jerry,

I would do some basic checks. Check your oil and coolant to make sure there is no mixing. Check for any play in the pully on your water pump. Check to make sure your coolant temp sensor and thermostat are operating correctly.

Since it doesn't sound like this is a regular thing, it may have just got a little hot from working too hard.

You may want to install an external trans cooler before anymore towing. It's a pretty common modification for XJ's when towing.  It's pretty common for the XJ's to get hot under hard loads because the trans cooler is currently inside the radiator. The extra heat from the trans can cause the coolant to overheat as well as not cool the trans properly. You may also want to consider a K&N (or similar) intake or air filter as well as a more free flowing exhaust which will help add a few ponies and make it a little easier on your engine.

Hope this help!



---------- FOLLOW-UP ----------

QUESTION:    When is the elect fan suppose to run? Mine runs only when the air conditioner is on. Is this normal?
         THANKS   jerry

Answer
You electric fan is controlled by the temp sensor. IT should turn on around the same time your thermostat opens. If you look, towards the front of the motor, drivers side, on top of the block, should be a wire that plugs to a sensor that screws into the block. That is your temp sensor. That would be the first place to start. They are inexpensive to change out.

If you turn on your defrost, the fan will probably cycle on as well since your defrost is hooked up to turn on when your AC is on and vice versa. This keeps your AC condensor from getting that mildew smell from not bring used all winter.

My wifes Cherokee, the temp sensor was malfunctioning and when the defrost was on, sitting at idle, the fan would cycle on and off, on and off, continuously.

I would start with the temp sensor and see if that helps. I would say to check the relays as well, but since the fan is working sometimes, I would have to guess they are probably okay.