I was afraid someone was going to tell me that, after looking at these posts. Jeep has 169000 miles on it, so most of my car funds and concerns are on the engine.

 

Don't get ahead of yourself. You don't mention overheating, just around 210 for a temp. That in and by itself is not one bit unusual and is no indication of a head issue.

Just don't LET it overheat. Preventive maintenance 101.

And with the 00-01, your new hobby is checking the level of coolant in the coolant reservoir every time you open the hood. The #1 symptom of a cracked 0331 head is "unexplained coolant loss".

 

Not exactly, a '99 is OBD-II and according to the FSM, a warm-up cycle is counted when the ECT sensor has crossed 160F. It's been posted that Chrysler/Jeep dealers offered a 180 t-stat at the parts counter....surely they wouldn't do that if it affected mpg or emissions. Air/fuel is monitored/controlled by the O2 sensor(s).

I've never seen any reference, in the FSM, that 210 is the "designed/optimal/normal operating temp" of the 4.0L.

What if the Jeep gauge was like most other factory gauges....just a C and H at each end with the needle pointing to the middle?????? What is designed/optimal/normal operating temp on those vehicles?

 

Mine always runs between 203 and 206.

I wish it would run at 210, better heat! lol

 

Maybe ur heater core is plugged or heater door is not functioning correctly. At 203-206 u should be sweating on max heat.

 

Agreed. The difference in cab heat with engine coolant temp at 205 or 210 isn't going to be noticeable.

 

I have a 2000 also, with 160,000 kms (about 100,000 miles).
It suffered the dreaded cracked head problem. Previous owner put in a 180 thermostat to try to solve his problems. Oil built up into a 3/4" thick sludge inside the engine, typical if it doesn't get up to temperature. 210 is perfect for oil and engine. Water boils at 212, so oil needs to get this hot to boil off condensation. 230 is starting to get a bit hot.

I am impressed with how quick this engine gets warmed up, compared to my previous vehicles. Within a mile in -10c temps the gauge is starting to move and up to temp with heat on the windshield in about 3-4 miles at 50mph. Had to flush my system to get good heat. This engine does not seem to carry a lot of coolant, which probably helps speed up warm up.

The dealer may carry 180 thermostats, but this is no guarantee of quality.
They carry what they can sell and what customers ask for. Once it is off warrantee, they don't care what you do to it.

Steve

 

Old topic but very true. I replaced I t-stat that came out in three pieces this past fall. The kid sold me a 185 stant super stat. Didn't even realize it was supposed to be a 195 until I joined forum. None the less I ran it all winter with the 185 and ironically my engine temp would run 185-187 in any driving condition and at the tops 190 after sitting 10-15 minutes. My heat was nice and toasty even in single digit weather.

Now that its been 80 that last few days its been running 195-210 and warmer in bumper to bumper traffic like the 215-220 range. I use torque app to confirm temps but I'd assume it gets reading from same sensor as gauge.

Only bought the xj last fall so this is the warmest weather I've had it in yet. Going to do a flush and replace cap and see how it goes. It's got 206k and its a 2000 so I'm trying to keep it in normal temp range . Oil pressure has been lower also by about 5psi at 2k and 10-15 at idle after driving 30 minutes or more. I just want to get 50k more before rebuild.

 

As engine temp rises, oil pressure will drop. Normal.

You need 13 PSI at hot idle and 10 PSI for every 1000 engine RPM when fully warmed up.

 

I have been worried about my 99 xj, its been running at 210 and when im in traffic stop and go it can go to the nextline past the half 210 mark. I read the a 180 t-stat is not recommended so I will be getting a regular 195 temp and reinstalling. Everything else is new except for the radiator and belt. Since im already pretty much all in should I also have the radiator checked out and install a new belt?

 

+/-$110 buys a new rad locally. The cooling system is not an area to ignore or guess at. FWIW, we've been using a 180 stat for 3+ years now.....good heater and will stay a little cooler most of the time. No ill effects here.

 

Heres my story. Bought a 96 XJ Country with 200k plus on the 4 liter and the AW4. It has a new head, valve train, oem radiator and water pump with 15k on them. The motrr was worked on and maintained by a father/son combo that run a reputable performance shop (mostly 5.0 mustang drag cars). They purchased it from a teen that managed to crack the head. The motor runs fine. No leaks. The temp needle stayed at 210 on the road and 220 plus in a drive thru. The water pump started to weep so I decide to replace it and the fan clutch with oem equipment from NAPA. Now with a 70/30 coolant/distilled water mix and no A/C running it stays between the 210 mark in the middle and the mark to the left which is 180 I guess. This is far from the norm according to all the other posts I've read. I don't have an IR gun to check the temp. I did unplug the sending unit and spray it out with NAPA electronics cleaner. I know it works because when I was burping the system it climed to 240 for about a minute then came back to 210 or lower. The coolant bottle is not overflowing at anytime either. The day I bought it, I changed the oil. I used and oversized NAPA gold filter and some Rotella 15w-40. I live in SW Fla. Everyday has been in the mid 90s with 100% humidity. ANY speculation is welcome!!! No, due to time restraints I did not change the thermostat. Also, in the 3 days between the time I discoverd the weeping and the time I changed the water pump, I ran 2 bottles of Prestone coolant flush anticipating changing the pump. Yes, prior to the change, it always ran well over 210. Regularly in the 220s plus.

 

Should I be concerned with it running at 240?

 

Yes. But verify it with a laser thermometer pointed directly at the thermostat housing. Gauges and sending unit issues can give you incorrect temps.

And I would recommend that you start a new thread; this one is ancient. A new thread will give you more accurate responses pertinent to your exact problem.

And provide a history of cooling system maintenance when you do that...

 

Mine 1999 runs at 160 with thermosat made by sait garage