Temperature Heating Cooling problems

[myke]

Hey guys, im just lookin for some input regarding my situation.  I have a 92 XJ and i have recently put a new motor in it after blowing the head gasket.  I seem to now have some problems with it still heating up higher than i would like on my guage.  Im sure i am just gun shy with it because i dont want it to overheat again and blow another gasket.  Right now when im driving it on the highway or in town, my temp guage goes from about the middle (100) to around the next tick mark which could be around (112) or so.  Im wondering if there is a chance that when my new motor was put in, the guage might read a little bit off from the original motor.  It doesnt seem to be really hot in under the hood, or at least any hotter than when it reads under (100) on the guage.    What im trying to say is that even though my guage is telling me its getting close to overheating, maybe it actually isnt.  Are the number on my temp guage in farenheit or celsius.  Im sure they are celsius seeing as how we are in Canada, so yea, i guess im just looking for some input. 

I also purchased a tent trailer and it would be a real shame if i cant tow it with my jeep, its around 1500 pounds dry and i know the jeep can physically do it, but i dont want it to overheat on me while im on vacation or something.  Any input is appreciated.

Thanks

[yjcanibul]

I'd check the following

- nothing obstructing the rad or mud/dirt/leaves or bugs nesting in it
- make sure you have a good antifreeze mix 50/50
- try a new sending unit,  it should be located at back of head drivers side,  replace w/eng cold,  think their like $10
- thermostat might not be able to open fully I suppose ...

I too think guage is metic,  100c is temp water boils at (212F) ,  does it have an external trans cooler on it ?

not sure how to test guage accuracy ...

[rws]

The temp. sending unit is connected to the temperature gauge and these gauges can be very inaccurate.

To find the true temperature that your engine is running at you have to find the temperature sending unit that is hooked to your vehicle's computer, it will be on the block someplace.  Disconnect this unit and attach a DVOM, set the meter to read Ohms, then take several readings as the engines warms up to operating temperature.  Next you have to search the internet to find a graph that represents your vehicles sending unit vrs ohms, plug your numbers in and you will now know the true temperature that your XJ runs at.  All this info would be in the factory service manual.

Sometimes rebuilt motors will run a bit hotter till they are broken-in but that temperature increase should not be that noticeable.

[rws]

On the DVOM an engine temp of 212F(100C) should read around 185 ohms.

[yjcanibul]

how'd you make out ?

on my setup the only temp lead I could find going to computer is on theromstat housing ... is that possible ?

[86 irocz]

DID YOU PUT THE FAN SHROUD BACK IN THE SHROUD MAKES A BIG DIFFERENCE AS I FOUND OUT  WHEN MINE BROKE

[rws]

The temp sending unit on the thermostat housing may be connected to the computer, you would have to look at a wiring diagram to be certain. Lots of knowledge on this fourm so maybe someone else would know.

Some Parts Source stores have on-line manuals and could print the necessary wiring diagrams and test procedures for you.

I thought the orginal poster was referring to a 90 xj when it was actually a 92 xj so the procedure that I outlined is correct but the numbers may be wrong.

[myke]

Hey, so i have still been having the problems with the cooling and now after trying to get a rad flush done at mr.lube to see if that cleaned it up, they werenèt able to do it and ièm thinking it was because of a vapor lock or something like that.  I decided to just suck it up and take it to a rad shop, and the first second the guy looked at my rad and the fins on it just fell off, aka.....rotten, so ièm thinking that is my problem and he kinda voiced that if the fans are rotten, then there is no flow in the rad.  I am gettin a brand new rad as we speak and im really hoping that will solve all my problems!  Thanks for the help and insight guys, i will let you all know how it turns up.