I have a 1994 XJ with 4.0, automatic transmission. My jeep has been overheating (up at 260, in the red) both when I am driving and when it is idling.

I have replaced the thermostate, radiator, both sensors, electric fan, both hoses, AC Condenser ( AC is not charged yet).

I replaced the water pump about 7 months ago.

The electric fan is not coming on when the AC is on but works when I unplug the Sensor to the thermostate housing so I know the fan works.

I any advice will help.

 

How's the fan fan clutch ? and what Radiator did you use ? and did the problem start when you changed the water pump ?

 

The problem started prior to the Water pump replacement. After I replaced the water pump it ran a little hot about 220-230. I wanted to get it back down to 210 or below so I started replacing parts. Now it jumps up in the red.

I will check the fan clutch tomorrow but because it overheats when I am driving would that make a difference?

I just installed a CSF Radiator last night.

I know this is an open system. Do I need to burp the system? I have not done this yet.

 

The fan clutch is used when driving and when sitting still on a xj the air flow though the radiator is very important because the size of the radiator is short in height .

 

Fan clutch issues usually show up during idle, but can also cause problems going down the road. It's a maintenance item anyway, and should be replaced if you're unsure of its age and having overheating issues. When you pull it, if you see a puddy expanding from this hole:




There's no doubt it's bad. Here's a good video showing replacement:

 

I just put in a new fan clutch. I rechecked both sensors.

My jeep temp. went up to the red just idling. The electric fan didn't come on. (I unplugged the sensor at the thermostat housing and the fan came on so I know it works). Even with the electric fan on the jeep still was in the red.

I noticed that the upper radiator hose was not hot as the temp climbed. Even after i turned the jeep off hot the hose was not hot. I am about to go but a new thermostat and water pump unless someone else has any ideas.

any ideas are welcome. Thank you,

 

I would warranty the water pump because it new , and it is always a good thing to change the thermostat .

 

There could be a clog somewhere. You need to flush the system. I would first drain and wash all the coolant out of the radiator, heater core and lines with a garden hose. I would then fill the system up using only distilled water and Prestone AS107 radiator flush, then drive the car as you normally would for a few days. Drain and wash again. If you're satisfied with how the water came out of the flush then go ahead and refill with a 50/50 mix of antifreeze/water. Most importantly, always back fill when adding water and or coolant to the system as to minimize incorporating air into the system. By that I mean don't add the liquids at the top of the radiator where the radiator cap is located but, rather through the hose(s) of the heater core and the through upper radiator hose leading into the radiator.

 

Not a bad idea there.... on your earlier post regarding the burping.... yes... basically all systems like this need that. If you have air bubble pockets in the system you're going to get it running hotter as air obviously has different thermal properties than your coolant does. either use ramps/stands, or find a small hill and park it with the vehicle facing up the hill. Will help when you purge any remaining air in the system as it will want to rise to the highest point.

 

So I replaced the Water Pump, flushed the system, new thermostat and I put a better (thicker) lower radiator hose on and it is still running hot.

I am starting to think the temperature gauge is not working properly. Is there anyway to check that?

I was also wondering if there is a way to make sure the computer that controls the electric fan is working. I have replaced the sensor (in the back of the block) but the electric fan is not kicking on until the gauge is in the red. Obviously if there is an issue with my gauge the fan might be turning on at the right temp.

I appreciate any ideas.

 

The sensor in the back of the block (Drivers side, original was 13mm with a single prong) is the sending unit. It controls the gauge and has nothing to do with the electric fan.

The fan not turning on is a problem. Smarter folks than I have indicated it is supposed to kick on at around 218-223 or so.

Have you replaced the sensor at the t-stat housing. That's the one that the computer uses for engine management.

 

So I have replaced both sensors. I bought an infrared thermometer and I took the temperature at the visible part of both sensors. The temperature only was at 213.

Does anyone know the best way to take the temperature with an infrared gun?

 

I would think the best place to get a reading is right at the t-stat housing.

 

I measured the temp at these spots using an infrared temp gun -





My gauge is measuring right above the red and the infrared temp gun is saying 213 degrees.

At this point I think the gauge is wrong. Has anyone had problems with their gauges? Is there a way to fix them?

 

I was having the same issues. Last year. Literally replaced everything on my cooling system. From fan clutch to new cylinder head cause mine cracked. Turned out it was my aftermarket aluminum radiator. It was a 2 row. One of the guys at naxja told me to try the spectra radiator off of amazon. Was like $100 and it fixed my problem now it runs cool.