Hi all,

Quick question for you. Was driving my '96 XJ 4.0 (162k miles) to work today when I noticed the heat in the cabin get really hot. Took a look at the gauge and it was showing 210. Sitting in stop-and-go traffic I watched it and slowly but surely it was creeping up. At one point the battery voltage also started to drop and a terrible rattle came from under the hood. Turning the heat off seemed to make the voltage go back up to 14 and the temp needle drop a bit, but it was still sitting high. Made it the remaining 1 mile to work with the the needle moving between 210 and the point marked in the picture below. The ambient weather condition was about 20degF and moderate snowfall if that might have anything to do with it.



What could this be and what should I do? I'm going to check the radiator before leaving work to see if I can see any oil in there. Anything else I should look for? I have access to company cars so I could potentially leave it here and not drive it back for a while.

Thanks,

Stop and go traffic issue , main suspect would be fan clutch.

Hmmmmm.

Good thing I work wayyy past rush hour in the evening, so I can get it to my mechanic's garage with minimal stops.

That is good news though, I was starting to worry about the head gasket or cracked cylinder head. And if my understanding is correct, a struggling fan would cause the voltage drop (or am I totally wrong on that one?)

Fans not gonna cause that . Could be aux fan going on and off to compensate for clutch fan being tired.

With regard to cooling system maintenance, how long has it been and what was done? That red mark is about 220F.....that's really toasty for driving in 20F ambient.

I will need to check the folder of records I got when I bought it, however I've only done a coolant flush since I bought it about a month ago.
And it dropped slightly when I was driving, only hovered around 210-220 when I was sitting in traffic.

1st thing to do is verify the dash gauge reading......point-n-shoot infrared temp gun pointed at the t-stat cover. Presuming the dash gauge is not lying and u actually r running 220F in 20F ambient, it'll never make it late spring/early summer. <$250 buys a complete new cooling system including a new rad.

Some good suggestions here. I'd also add that a cooling system pressure check could be done to ensure there aren't any leaks causing the system to lose pressure.

Is the belt tight and in good condition? Pulleys and idlers OK?
I'd remove the belt and turn each accessory by hand- the fan, water pump, alternator, etc...see if anything is loose or feels rough.
Could be as simple as a bad fan clutch assembly.

Thanks for the tips everyone! My mechanic took a look at it today - fan clutch was fine, but the e-fan was ready to disintegrate. He replaced that and let her idle for 30 minutes in his lot with the needle holding steady just under 210 where it should be.

Do you run ac/heat during travel time ? E fan should not be running untill temps hit 220plus in stop and go traffic . And idleing is not the same as stop and go traffic. Just throwing this out there .

Sounds like ya got two separate issues e fan will kick on and off when heats on . Was the noise and voltage drop.

I'm curious how it was determined the "fan clutch was fine". Did he say whether or not he heard the new efan during that 30 minutes? Idling in 20* ambient is not much of a cooling system test. This time of year, u should never hear from the efan (compressor off) IF ALL of the cooling system is in top notch condition. The main rad fan is all that's needed in 20* ambient, IF ALL else is good. Late Spring/early Summer will tell. Again, what cooling system maintenance has/has not been done. The XJ cooling system is not an area to be taken lightly.