I'm going to list some behaviors and ask a question at the end, this is all considering the typical San Diego day (75-80 deg F):

• 4.0, 1996 Country, 3.73's, 31" ATs, +400lbs bumpers/winch.
• Start it up, after a couple minutes engine temp is at 210, continues to creep past 210 up to ~225 then drops quickly to 210. (sticky thermostat?)
• Flat highway: It will hang all day long at 210.
• Idling: Will climb slightly and slowly to ~220 if idling a long time, drops when e-fan kicks in (or AC turned on).
• Off road: will get up to maybe ~225 if doing really slow 4x4 offroad on a hot day (90+). E-fan helps bring it down some if I turn on the AC.
• On road: will get up to ~225 if climbing a grade for a long time, drops to 210 as soon as the road flattens.
• Has factory trans cooler out front. Trans fluid looks good, shifts fine.
• When moving slow, turning on AC helps it cool down due to e-fan. E-fan doesn't lower temps below 210 on highway.
• 210 is as low as it ever goes once warm (never driven it in temps below 60F though).
• The fan clutch is "new", maybe 3k miles old and feels okay. No clue as to age of water pump, thermostat, radiator or coolant. Given that, I plan to do the typical drain/flush/fill.
• Hoses look good, no leaks.
• No noticeable coolant loss, clean oil, clean coolant with minor red sediment staining in the overflow reservoir, no build up under radiator cap.

Given the initial temp creep and slow offroad temps, is there something in particular I should replace or check when the fluid is drained that may be causing these symptoms? Or does this all sound like normal behavior for these hot running motors on warm days?

Thanks

 

Sound pretty typical, the more notice warmup will go hotter and then drop ad the thermostat opens up, that's supposed to happen.
The motors are designed to run at approx 210 from the factory for better emissions and fuel economy.
The efan will kick in on its own at 218 or so. The Guage is nowhere close to accurate so take it with a grain of salt.
I have a 180 thermostat in mine and she still runs at 210 on hot summer days in traffic, above 2500rpm's on the highway and on the trail. And that's with 100% new cooling system.
Nothing wrong just the way the cooling system is designed. As daytime Temps drop she runs closer to 180, thermostats only dictate minimum running Temps, that's all.

 

No clue as to the age of the water pump, t-stat, radiator?????......that might be your clue......and a 100% efficient (as in new) fan clutch is an absolute must at slow speeds. The water pump, t-stat, and fan clutch can almost be replaced blindfolded when the old rad is out, prior to installing the new rad.

 

The source that validates that statement please?

 

it was a rough estimation of actual operating temps based off the operating parameters in the Factory Service manual ... as there is no actual true temp specified for the 4.0 in the FSM's
A. The factory thermostat for all models and engines is 195F, this directly specifies minimum operating temps.
B. The factory efan is set to turn on at 223F and remain on until 217F


So by simple deduction we arrive at an operating temperature range of 195-217F as ideal conditions ... per the parameters set within the FSM.


So, sitting in the middle ... we arrive at 206F, rounded to a less than accurate 210F ... given slightly higher air temps reducing cooling efficiency this time of year, and coinciding with pretty commonly stated average operating temps for the 4.0L AMC derived Chrysler motor.


I retract my previously stated 218F efan kick on temp as that is actually for the 2.5L, my apologies.


there, enough fact for you? get we get back to helping the OP with understanding his issues?

 

Seems that I've mostly heard from the forum that the e-fan turn on temp for the 4.0 is ~218*?

 

my information came straight from the FSM (Factory Service Manual) ... in which it states the temps above.

 

"fan on" temp seems to vary slightly depending on what year FSM ('98 FSM says 218*). I don't believe any year FSM references 210* for anything. FSM does say a engine warm-up cycle is counted by the ECM when coolant temp reaches 160*.

 

You will notice I did say approximately 210F... As I stated it was an approximation based on a factory minimum operating temp (195 set by the thermostat) and the temp at which the efan comes on (which appears to vary a few degrees depending on year).

Do we really wish to argue over a couple degrees?
In any event the normal operating temp is in the same general vicinity of my original statement. Especially given that I have yet to see an XJ/MJ FSM that references an actual specific temperature at all other than minimum and efan turn on as far as the cooling system goes. I did not state it runs at exactly that temp, I said approximately ... Meaning in the neighbourhood of ... Or close to ....

Would you care to offer a more expert offering then ... I'm just a resident shade tree type.

 

Factory minimum is 160, not 195.

 

You may wish to reread the FSM as the thermostat provided from the factory is 195F which is open at 195F and closes below that to maintain an average minimum of 195F ... that's what thermostats do.
If he were to replace the stock thermo with a 160F then yes, the low point would be roughly 160F.
The factory thermostat would be closed at 160F and just starting to open at 190F ish.

To the OP ... Your XJ is running normally based on what you posted ...

I'm finished feeding the troll.

 

U r correct saying a 195* stat was installed at the factory.....that's what the FSM says. Your statement saying "factory minimum operating temp (195* set by the thermostat)" is incorrect. Factory minimum coolant temp stated in the FSM is 160*, the temp at which the ECM counts/records a successful warm-up cycle with-in a given amount of time. Again, nowhere is 210* referenced nor is 195* referenced in regard to "minimum operating temp".....junior.

 

All I can add is that my 99 with almost same equipment and weight runs at about the same temps maybe a little cooler, depends on outdoor temps and AC use.

 

You guys arguing about minimum temperatures are wasting your time. No matter the minimum, 195 degree stat is the factory stat, and even so, if you have cooling system problems it won't matter much. The 4.0 is still going to run 210 or hotter if you have issues.

I've done a lot of work to my rig and it is running around 200 most of the time now. If I'm hauling a bunch of stuff and cruising on the highway, it might creep to 220. I've done a cooling system acid flush, new water pump, new rad & cap, hood vents, e-fan switch, ZJ fan clutch, and removed the transmission from the radiator loop & installed an external cooler & temp gauge for it. All of these things together have helped tremendously and resolved my running-hot problems. Also noteworthy is that I'm on 33x12.50's with stock gearing.

OP, one of the best things you can do off the bat is to wire a switch to your fan. Use a relay so that the computer can still activate the fan as normal. Do that, and turn the fan on when you get up to 200 or so. Helped a lot. You shouldn't do this before doing a cooling system flush and at least replacing the radiator cap (cheap insurance). I bet after doing these things you'll see an improvement.

 

The world is full of incorrect statements/bad info......no harm in trying to correct/eliminate some of the bad stuff, no?.....like cold tranny fluid causing issues, for example.

When off roading, a/c is most likely not used so it's quick and easy to remove the a/c clutch fuse in the PDC, then select a/c on the dash switch. Doing this allows on/off control of the efan with the dash selector switch, granted no a/c while off roading, but u don't need another switch either......u just use the dash selector switch to control efan on/off.