Originally Posted by Geo Jeep
Thank you all for for your replies.
I have been driving around the WA coast for several weeks with quite a few days in the mid 40 deg range and the temp gauge has been getting pretty high so I suspect the expansion tank has boiled over a little from time to time. There is evidence of this in the engine bay so that would account for the missing coolant.
I'll top it up this morning and continue on!
Try to top up the overflow bottle with distilled water if you can, otherwise normal water is better than nothing. Just make sure you get the coolant flushed when you can/get home.
Some JK CRD specific advice:
Are you monitoring your temps via a OBD port reader? The gauge in the dash doesn't move past halfway until coolant temps are 107+ degrees, which is too high (unless for a few seconds only).
If your JK is auto, then if you are seeing high coolant temps then your auto trans fluid is likely going to be very hot as well.
Assuming yours is auto, keep an eye on the temps and try to keep them as low as possible, on long trips at hwy speeds JK CRD's love to get hot and can cook the trans, and/or do damage to the engine.
Manual's very rarely suffer from overheating. This is because the already cramped grill/radiator area is not shared with a auto trans cooler, which is inadequate from the factory, which then transmits heat to the other coolers around it (i.e. radiator and intercooler).
Also the factory Mopar red coolant is junk, it actually eats away at the plastics in the cooling system (overflow bottle and radiator end tanks) over time. If you still have this coolant, then flush your cooling system and run some decent coolant and you will find your average temps will drop 2-3 degrees as well.