Cooling Puzzle

99XJ 4.0 170K

I bought it with 110K on the odometer. It looks like it had been in an accident and as a consequence it had a brand new radiator installed.

Last year at 160k, I did some major work and in the process I installed a Flowkooler water pump and a Hesco balanced thermostat as described in a write up on GOJEEP's website. Here:

http://www.go.jeep-xj.info/HowtoWaterpump.htm

Prior to the work, the temperature was stable, no matter how hot it was and if I was in traffic or on the trail. It always stayed about 3mm (or two widths of the gauge hand for those not familiar with metric) to the left of the 210 mark.

Now this depends on the temperature of the air. Under normal conditions the gauge shows a range from the first mark to the left of 210 during the winter, to about the same as before the switch on a really really hot days.

Where it gets even more interesting...things change if I am in traffic or on the trail. Then the hand passes slightly the 210 mark, which I am not happy about, because the engine runs hotter than before.

One thing to note is that once I get in traffic or on the trail, the temperature does not climb to pass 210 mark immediately. It takes approximately 15 minutes to get there. Once it gets there it fluctuates between 210 and about a mm (one hand with) pass that point. When I get going at faster speeds, it usually takes about three to five minutes to go down to whatever is normal depending on the season...

I dont see how I could have reversed the thermostat within the housing. What went wrong with this setup?

Here is the list of things I did that weekend a year ago:

Thermostat
Water pump
Belt
Pulley
Harmonic balancer
Timing chain
Fan clutch
Prestone 50/50 coolant

Thanks for reading

Best

Boris

I just installed a 195 deg thermostat in my 99, 4.0.
Normaly temp is ~210 or slightly below.
I have run with a 180 deg thermostat and temp was
always just below 210. That became a problem durring winter months
when it wouldn't get close to 190.

I run a Hesco water pump and 3 row copper radiator.

Change your coolant mix. Run 30 ethylene glycol to 70 distilled water late Spring through early Fall--the non-freezing weather. When temperatures start changing switch over to 50/50 or whatever mix is correct for winter driving in your area.

Ethylene glycol is a really good antifreeze, it has corrosion inhibitors, but SUCKS as a cooling agent. 50/50 is a year round compromise, don't be suckered by it.

Your OBD II doesn't have a "direct" reading temperature gauge. The data from the CTS on the thermostat housing is taken into the PCM, and it provides it's interpretation of the temperature to the gauge for your viewing pleasure. Pull the CTS, use some steel wool to clean it where it sticks into the coolant, see what that does.

What fan clutch did you install? A quality one, I hope.

Good luck.

joe_peters said:

Change your coolant mix. Run 30 ethylene glycol to 70 distilled water late Spring through early Fall--the non-freezing weather. When temperatures start changing switch over to 50/50 or whatever mix is correct for winter driving in your area.

Ethylene glycol is a really good antifreeze, it has corrosion inhibitors, but SUCKS as a cooling agent. 50/50 is a year round compromise, don't be suckered by it.

Your OBD II doesn't have a "direct" reading temperature gauge. The data from the CTS on the thermostat housing is taken into the PCM, and it provides it's interpretation of the temperature to the gauge for your viewing pleasure. Pull the CTS, use some steel wool to clean it where it sticks into the coolant, see what that does.

What fan clutch did you install? A quality one, I hope.

Good luck.

Click to expand...

Thanks, I will follow your guidelines and report it here.

I got the same HD fan clutch from NAPA you got...