freeworld71

In the spring I changed thermostat and water pump. I mainly drive on highway When I'm on highway, the temp guage runs cool, probably 170. When I get into traffic or city driving, temp goes up to 200-220. Any issue with it running cool?

Also, upper radiator hose feels very pressurized while car is on..... to the point you couldn't squeeze the two rubbers together. Is this a bad thing?

4.3L XJ

It is supposed to build up some pressure, makes the boiling point of coolant higher. Usually it is 16 pounds per square inch. I think you need to check to see that the fan clutch is good and that you have shrouds on your fans

freeworld71

My fan clutch is good. I do not have a shroud on it at moment. I'm more wondering why it's running cool or if that's even right,

Bugout4x4

No shroud??? what year is this? You sure it even has coolant in the engine to make contact with the temp sensor? They tend to look like they are running real cool when there is no liquid in contact with the sensor.

4WD4EVER

Ignore the gauge reading (for now). You need to measure the temp with an IR thermometer at the thermostat housing.

4WD4EVER

This is actually false. It would read higher temps since air heats up faster than water.

freeworld71

I'll get a thermometer and do that. Thanks for the heads up. I know there's fluid in it the radiator. I guess I could take of the radiator hose and check too.

Bugout4x4

I have been in the repair and towing industry in one of the hottest places in the US since I was born. You have no idea how many times I have heard "Well it did get hot but then it cooled back down before it blew up and quit running?" as I was hooking it up to a towtruck. Yeah, because there was no more liquid in it to make contact with the sensor yet it was still getting hotter and hotter because it was empty.

Same with cylinder walls, if the coolant foams for some reason along your cylinder walls it might read normal at the gauge, but it is indeed running too hot at the cylinder walls because it is imperative that they are in contact with a liquid rather than a gas caused by the foaming.

This foaming is a very common problem in heavy truck engines. Everything looks good and cool, but it is foaming along the walls under the proper conditions and by the time you do get an indication it's getting hot it's too late for the rings and walls.

freeworld71

So are you saying I should get the thermometer and check temperature of sides of wall?

4WD4EVER

Don't care.

If the OP's coolant temp sensor is functioning properly and the system is filled with air it will constantly read high. He needs to verify actual temp before moving forward.

Bugout4x4

That was tech talk, disregard that. it is right to do as suggested and check it at the thermostat housing. I asked only because it has happened many times before. Just making sure you do indeed have enough coolant in it. An empty system will read cooler on the gauge than it is actually running. And from my experience 170 is cold for these even without a thermostat unless it is absolutely frozen outside. But you really need a shroud on that...

4.3L XJ

Geting back to the original question, the reason he is getting warmer sitting still is that he doesn't have fan shrouds. When moving the force of the wind on the radiator pushes air through the radiator, and if fact if the system is in otherwise good shape that will keep the engine cool. When stopped, the fan is not pulling enough air through the radiator because the shrouds are missing. Put some shrouds on and fix the problem.

4WD4EVER

Agreed.

freeworld71

You guys, I'm not overheating. I ran it today sitting still for 20 min and it barely got to 210. I'm wondering why when I'm on the highway, it seems to run cool, definitely less than 190 which is what thermostat is rated for

4WD4EVER

It's your XJ, if you want to run it w/o a shroud, that's your choice to make; it's not recommended.

Do not rely on the gauge to give you an accurate temp reading, it's not a finely calibrated tool. If you really want to know the answer, use an IR thermometer. You may have multiple issues, who knows until you verify?