I have been battling this situation for a while. I need to collect some wisdom from you guys.

-- 1999 Sport Classic
-- newly installed:
* 3 row radiator
* stock thermostat
* new stock waterpump
* new radiator top/bottom hose
* flushed system
* heater core checked - ok
* mechanical and electric fan seem to be OK

I am running 197-209 when driving around town.

HOWEVER, when I start climbing a hill in 90 degree weather, AC off, the water temp on my ScanGauge starts to climb, often hits 225, and will go up and down from 220-224.

Is this normal operation, or do I still have a problem to fix? I have already spent a bunch of money ...

PLEASE comment.

RICK
TNX

 

Have you replaced the fan clutch? This can make a huge difference. Other than that seems like you've covered your butt. Unfortunately 4.0's just run hot.

 

My 92 runs hot when climbing on or off road once i crest a hill and start down it cools as fast as it went up. on the road about 70 or about it runs pretty warm but under 67 runs around 195 to 210 depending on temp outside. i am thinking its the tranny running hot but dont have a gauge on it yet.
my 2 cents

 

Clutch not replaced, but two mechanics seem to think it is ok ... ???

 

i notice that my dash temp gauge runs about 6+ degrees cooler than my digital scangauge. I lean towards digital off of the ECU ... and that is what I am reporting.

 

Sounds like the exact same problem that I had a while ago.

Firstly - yes, the 4.0 will run hotter on hotter summer days. But no, it should not be near 220.

Here is what I suggest you do.

Take it to highway - speed it up to 65 mph and drive for a while. Is the engine overheating? If yes, it's has nothing to do with fan clutch (this is because wind speed at 65 mph will be more than enough than two fans).

When the engine overheats, turn the heater on full. I know it's summer, but you gotta suck it up for a few mins. When you turn heat on, is the temperature decreasing? If so, I think I can narrow it down to either radiator blockage or the serpentine belt.

1. You said you replaced the radiator with 3 rack. So I am assuming that it's not radiator blockage.

2. The only thing left that comes to my mind is... perhaps the serpentine belt is not tight. When belt is not tight to factory specifications, it can cause overheating due to incorrect speed of water pump turning.

3. Find the mid point of the belt between two pulleys. Push it very hard with your fingers. If you can press the belt more than 1/4 of an inch, it needs to be tightened.

I hope this helps

 

great ideas - TNX!

However, does not overheat on fwy.

new radiator

serpentine belt ok.

I wonder how everyone is watching water temp?

My digital gauge runs 6++ degrees hotter than my dashboard analog gauge ...

 

U've spent good money wisely on your cooling system......spend another $40 and get a NEW fan clutch and rad cap and quit guessing/thinking it's ok....just git 'er done. The new rad may have 3 rows but it's still only 11" tall.....what a joke for radiator design (Chrysler/Jeep).....however, it does seem adequate 8-10 months of the year. We've seen those temps momentarily on the ScanGauge under extreme driving conditions, but have never seen the idiot light even flicker so guess those temps are cool enough for short periods of time.

 

The FSM says to torque the belt adjustment to 150 for old belts and 180-200 for new belts. It's insanely high and just seems wrong, but, once I did like the good book told me I haven't had any belt issues.

 

I never thought about the belt, i have been having issues with mine since i bought it.

I put in a new thermostat, new belt, new clutch, flushed what i could of the system, new hoses, new cap, new temp sender, new coolant temp sensor, trying to figure out why mine runs hot in summer time.

whats funny with mine and maybe someone can chime in here... is that if im sitting in the drive thru, or let it idle, it will get hot and the fan will kick on, the electric one. When i take or off leave, you can watch the temp needle drop down super fast.

the other day, running AC on a hour drive, it did ok, it was up around 225ish at 70MPH. I was carrying my trailer too, about a 1000 pounds, but it does the temp thing reguardless. when I picked up these tires and got on the way home, it kept getting up near the red, til I shut the air off and after about 10 minutes it dropped back to about halfway, 210.

whats bothering me is that when it gets hot while sitting, taking off you can hear the fan roar a bit and its funny to watch the needle drop back to normal real quick.

any ideas would be great, dont mean to hijack the thread..

 

If the belt was slipping, it would be squealing to high heaven, I would think.

 

.....new water pump and radiator?

 

^^^X2

 

I've been battling high heat in my trail XJ for YEARs...'96.... GDI 3 core, high flow water pump, flexalite electronic fan to replace mechanical one,various thermostats, even an aluminium core rad. (plastic caps) to no avail.
It's crazy that the exact same engine on the same trail in a TJ can stay at 210 all day AND sit and idle.
I'll keep trying new stuff... hood vents are next for me. Or no hood on the trail.
Thanks for the post, I'm waiting for the magic fix.

 

I did replace the fan clutch today, and that helped a little. Going up my steep uphill test trail, it did not stay above 220 as long, and seemed a bit cooler.

Better, but not good. I am going to try a high-flow thermostat and housing next.

You mention that the same engine is OK in a TJ. I'll wager that it is not really the same cooling system. I bet the radiator is bigger, or there is more total fluid circulating through the system resulting in the ability to dump more heat, fans push more air, etc. etc.

Physics ... it's the law!!