Hi all... My 1999 Jeep Cherokee Limited runs fine and the operating temp when on the road seems to be a steady 210 or slightly lower. As soon as I engage the A/C things are still the same but if I stop to idle with the A/C still running the temp will rise to over 260 degrees. The last time it happened the water boiled out of the radiator and it took about 15 minuted to cool down. What could be causing this or is it better to not run the A/C while idling still? Any body else have this happen?

Thanks in advance!

OK, this is a wide-open question but I'll throw out some ideas.

First of all, nothing is harder on your cooling system than sitting still and running the AC on a hot summer day. However, if your cooling system is working properly, you should be able to do this without hitting 260.

If you don't have a repair manual (Haynes or Chilton), I would strongly suggest you get one. And here's a few things to check, starting with the easiest stuff:
1) Check your coolant level. If you're low on coolant, look around for leaks. Also check the quality of your coolant. Should be a nice emerald green color. Any other color could be an issue.
2) Could be a clogged radiator. When's the last time you flushed your cooling system?
2b) Check your radiator cap. If it's corroded where it seals with radiator neck, it may need replacing.
3) Belt driven cooling fan. When the XJ is completely cooled down, it should spin fairly freely. As the engine warms up the clutch engages, causing the fan to push more air. Once you get to operating temperature, the fan should be pushing a good amount of air over the engine. PLEASE don't stick you hand in the fan?
4) Thermostat may not be opening fully, or at the right temperature. You can remove this and boil it with a thermometer to see if it's working right.
5) Water pump is a possibility, but not likely. When a water pump goes bad, it usually makes some noise and leaks from a hole below the pulley called a weep hole.

There's lots of components in the cooling system. A repair manual can be a big help. Or search for posts here. Lots of people with cooling problems this time of year.

I'll check those items! ..it's got a new water pump and the coolant was full and green and the cap looks fine. It has had a recent triple core radiator installed too. The "check guages" light comes on when the temp starts to rise, that's my only warning besides the temp guage climbing steadily. Seems like an awfully high normal operating temp to me. Only 12 degrees away from boiling?

Quick question: With the AC on, is the electric fan kicking on as well? Whenever the AC is on the electric radiator fan should be on.

mine was doing the same thing even after i put in a flow cooler water pump and an 195 degree thermostat, so i put in a radiator now it moves about 5 degrees not 30 to 40 degrees like it used to

This would be where I'd start. If that electric fan does not start immediately when you turn the switch to A/C that's a big part of your problem.

Hi..the electric fan comes on just fine. It's a puzzler! I'll check the fan clutch and flush out the radiator this weekend too and let you know if there's any improvement.

I put in a new thermostat and I'm currently flushing out the radiator, so I should know something soon. Fan clutch seems to be fine. I know it's low on refridgerant. Could that be dragging the compressor and putting an extra strain on the engine?

My electric fan doesn't kick on when the a/c is turned on.

If it runs at a normal temp when driving, around 207 but heats up when sitting still its probably the fan clutch. Been there done that twice before. Once on my daughters Volvo and once on my old Corvette. My 99 does that in this 90 degree temp but only to about 215 so it almost time to change the clutch or I would like to go with a form of non-clutched fan.

Hi Guys,

When my 1998 Jeep Cherokee is idling for a good while, the Check Gauges light comes on and the Temp Gauge moves over to the right as thought the car is running hot.

However the engine’s NOT RUNNING HOT. I’m VERY CERTAIN of that fact.

Once I drive off, within a few seconds, the gauges go back to normal. I’ve also taken the precaution of replacing the Temp Sensor, thermostat, made sure both fans were operating correctly, checked coolant levels including freon, thinking perhaps these might be an issue which by the way none of these mentioned were.

I’ve had this problem with this Jeep for a while I just haven’t to this date, figured it out.

Does anyone reading this know as to why this takes place?

Has anyone out there reading this ever had this kind of issue before?

I’d appreciate some feed back.

Thanks.

I'll look into the fan and clutch further. Thanks!