91 xj running constant at 240 doesn't drop doesn't red zone. Replaced tstat, tstat housing, upper and lower hoses, radiator, new coolant. Clutch fan feels good has resistance and doesn't wobble back and forth. When it gets up to temp the thermostat is opening and I can feel coolant in the upper rad hose so the water pump must be doing its job. The aux fan comes on at about 220. It's not leaking or overheating just running too hot for my blood any ideas. Ac is currently not working either so Im not using AC at the moment.

 

I would start by verifying the temp with an I.R. temp gun aimed at the t-stat housing. Just to make sure that you are getting a true temp reading and that your sending unit or the gauge isn't giving you a faulty reading. Then I would start looking at other possible problems.

 

I put new sensors as well and I bought a laser thermo gun but it doesn't feel accurate. It reads 150°F when I get it up to temp and I point at the thermostat housing. If I'm cruising in daily traffic it will go about 220-240. When wheeling it starts to creep close to the red zone. Jeep is running good too good compression plenty of umph. Previous owner said it never overheated on him but it had the dummy light cluster. I put a gauge cluster and that's when I noticed that the jeep runs hot.

 

Nieko? Temperature sending unit, on the rear of the block next to the valve cover. I had one on my 91 that gave the exact same temperature readings.

 

If you verify that your getting a high temp reading you may want to consider a new clutch fan. You can't tell their condition by feel as they can wear out gradually. Mine felt fine to but was my high temp problem. It wouldn't over heat as the fan was still good enough to keep it out of the red.

 

You need to check your water pump. I started running up in the 215ish area, no noise, no leaks until my radiator decided to give out from old age and I overhauled the entire system. This is what I found on my 01 when I pulled the water pump

 

Yikes!


How many miles on that pump?

 

163k and change. Original pump from 2001 lol

 

Well its still running hot and I've been driving it like that due to lack of funds. This weekend I will be doing a heater core flush. Heater is not working but not leaking i suspect it may be clogged. PO really neglected the cooling system its a damn shame he was running it on straight water. I will also be replacing the water pump and clutch fan just to hit the problem with a shotgun blast and hope it fixes my problem.

 

Anybody know what year zj fan clutch will work with a 91 xj??? And any input on this mod would be appreciated. Do recommend or are against it lmk please.

 

http://www.napaonline.com/Catalog/Re...Dp%3d3%26N%3d0

 

The guage in my '89 says mine runs hot too but the IR thermometer says otherwise. I'm going to keep driving it until the overflow bottle starts violently gurgling or the motor blows. Gives me a great excuse to swap in the lower milage motor/ transmission.

 

Running that hot is going to lead to problems down the line, so you really have to fix this.

With your water pump being that borked, you really need to consider a full coolant system rebuild. I think you're going to need a heater core, a radiator, and hoses, but you really should flush out that engine block as well.

 

That's not my water pump ha ha but I will see how bad mine is when I pull it this weekend. Guy said he changed it but at this point his word means bull doo doo. It had the original chrysler thermostat in there from 1991.

So far I've done:

New radiator
New t stat
New t stat housing
New upper and lower hoses
New 50/50 coolant
New front and back temp sensors

Next on the list is the fan clutch and water pump. It's a sketchy situation because the gauge will show 240 but the fan won't come on until a few minutes later. So my aux fan is working and if it's supposed to come on at 220 that means my gauge is reading wrong. I also have pointed an ir thermo gun right at the thermostat housing and it reads 180-190 tops. When I point it at the temp sensor that's located on the thermostat housing it shows 211-215 never above 220.

 

I'm in the same boat right now. I replaced everything, did coolant flush, etc.. Thought maybe cat was plugged up and casing it to get too hot. Took cat off and did the exact same thing. I'm at whits end trying to figure it out. Mine is reading a tad cooler than yours but 220-235 is what it says for me. Both fans are good, water pump flowing. just don't get it.