jpluvr4life

My 1998 XJ 4.0 i6 runs at about 220 when its 95 degrees or hotter out. Never actually overheats until last night after pulling in to my driveway. Having the a/c on or off doesn't change anything and it mostly happens when pulling hills on my drive home or after driving for about an hour in regular city traffic or the freeway. I was just out wheeling (easy stuff) with it last weekend and it ran fine doing that. But that's up in the mountains and it wasn't over 85 degrees out. In the fall/winter it runs at 190 ish. Also, for a while when running the heater or a/c you could smell a little antifreeze when initially turned on. I haven't noticed this for a couple months now though. You can smell how musty the heater core and a/c thing (forget its name, its early in the day) and was planning on changing them late August.
Maintenance historty: 9 months ago had the head pulled to change the ****ty valve springs. Head looked good and they also hardened my valve seats at that time.
in the last 9 months the radiator was replaced with a copper core (I dont know if it was a 3 core) a friend did it bc the stock one cracked when he was borrowing it
new stock water pump, fan clutch, t-stat, hoses, (all stock) head gasket by default.
it does need a transmission service and oil change right now too. Both fluids are dark and smell a little burnt. Going to be doing that this weekend. It also has a stupid k&n air filter that's mighty dirty atm.
Any help or insight would be greatly appreciated!

PatHenry

Do a pressure test and see if you can find any leak.

Also don't forget the radiator cap - it's a critical part of the system. Replace it if it's old.

220 is only slightly off, I think that if you have a bad cap or very minor leak that would explain the slightly high temps. 210 is normal operating temp.

jpluvr4life

I'll go ahead and change the cap. It's around 2 years old I believe. It ran like it usually does on the drive home today, didn't bubble over in the driveway like yesterday and its was 102 out. It sure isn't consistent! And as far as pressure testing I will probably have to take it in to a shop as I don't have the tools for that. I'll keep people posted as i see I'm not the only one to have this issue on the forum

PatHenry

You don't have to go to a shop for a pressure test. Just hit your local Autozone (or other parts retailer) and you can get it as a loaner tool. You leave a deposit but get it all back when you return the tool.

I had a mystery leak years ago and spent a day (wasted, to be correct) trying to find where I was leaking. It was running just like yours, slightly hot. I borrowed the tool from Autozone and found the leak in half a second (it sprayed right out of the poorly sealed t-stat housing when I put pressure on it).