98 XJ Overheating after Flush 'n' Fill?

98 4.0 5spd 198k... Getting ready for a cross country trip I drained and flushed the coolant system (peak flush kit). Reddish brown sludge and coolant ... nasty stuff. The rad cap was caked in it. After cleaning and filling the system back up with 50/50 i took it for a spin... overheating at idle. Prior to this everything ran fine... 210 steady. I had replaced the waterpump, thermostat upper and lower hoses after chasing a leak a few months back. I have noticed erratic electric fan behavior... It ran this morning w/ the A/C but not this afternoon. I have disconnected the sensor on the thermostat housing, but only the check engine light comes on.. nothing else. I just recently removed a shim from the A/C compressor to get the clutch to engage and it seems to be working thus far... but as far as the overheat im stumpped. Any suggestions?... on my way to AA to pick up the actual chem-cleaner and going to try and flush it again to remove any clogs...

By no means am I an expert but I just went through an overheating problem and it was the electric motor for the A/C fan. I also have a 98 4.0 but its an auto with only 103K...my fan would turn on at first when I engaged the A/C but as it warmed up it would turn off. I got everything warmed up checked for electric signal which was good, so I then unclipped the fan and hot wired the fan, nothing, so I new it was the electric motor. Unfortunately they don't build these to be rebuilt, so I would try a junk yard or look to buy just the electrical motor and swap out with the old one. Hope this helps it's worth a shot.

i thought the electric fan maybe suspect... hasnt been running from what i can tell... but it hasent been running hot either. just seems crazy for it to get hot after a drain and tap water flush. this may be the next step... thanks

UPDATE: or lack of... I drained the new coolant and set it aside for later, flushed with tap water, drained once more, added peak super cleaner and filled system with water. Now the directions say 3-6 hours; however i do not have that luxury at this time. Ran for about 5min to just under 210... looked like it was going to hold. Running at 2200 RPM The temp gauge held at 210 for about 5min then started to slowly increase back at idle. Let it run for another 5 and temp gauge read one mark past 210. I then decided to take it for a lap, get some air on it. At higher speeds more air I got the temp back to just above 210 then took it in. Let it run for another 5, temp back up... no overheat this time, just hot... still in no shape for a NJ to CO road trip. Throwin in the towel for tonight. Ill drain the water/cleaner in the morning. Could the Tstat be gunked up?... or should i try and replace my e-Fan?... headscratcher

Change your coolant mix from 50/50 to 30 ethylene glycol and 70 distilled water for late Spring through early Fall, it will cool better.

sounds like a bubble in the system. these are known for it happening after a coolant flush.

CumminsJeep said:

sounds like a bubble in the system. these are known for it happening after a coolant flush.

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This is what I was thinking.

I ordered this last night
http://www.amazon.com/Lisle-24610-Spill-Free-Funnel/dp/B001A4EAV0/ref=pd_sbs_auto_1
should be able to purge any air with my next drain/fill cycle

ChedderBob said:

I ordered this last night
http://www.amazon.com/Lisle-24610-Spill-Free-Funnel/dp/B001A4EAV0/ref=pd_sbs_auto_1
should be able to purge any air with my next drain/fill cycle

Click to expand...

Well, you can usually park a vehicle equipped with an "Open" cooling system nose up and at an angle to put the radiator cap higher than any other element of the cooling system, make sure the recovery bottle is filled to the "cold" mark, then run the engine so the thermostat gets fully opened, shut the engine off and let it cool down. That will usually "purge" even the most stubborn system. In theory, and mostly in practical application, a few heat/cool cycles will "purge" all of the air. On some of the worst designed systems we have had to put the front wheels on the lift and raise the vehicle quite high to get stubborn bubbles out.

Might take a look at the water pump, the one on my 98 Limited with less than 140k had the blades dissolve and by the time it became an obvious problem, there was only a blade or two left of the 5 blades that it was supposed to have

Here's a pic of the replacement Mopar pump in front of the factory pump.

When filling with the nose up a bit top off the rad, start the engine and let it warm up, keep the dog leg neck full, it will look like fizzy green soda, that is the air coming out. Once it stops fizzing I blip the throttle so it sucks more coolant down, quick top it off and get the 18 POUND pressure cap on.

Well i believe using the spill free funnel i was able to purge the system pretty good. Ran it untill the tStat opened then filled it untill it stopped bubbling. Running just below 210 at idle ... w/o A/C... took it out on the road. Stop 'n' Go w/ max AC the temp creeps above 210... At cruising speeds, max AC, temp normal... I havent seen or heard my AC electic fan kick on for sometime... going to pick up the e-fan at a junk yard... 75$... Fan shroud ... 35$ (busted my old one replacing the water pump few months back). Got them to knock of 10 bucks for both... oh well... we'll see what happens

joe_peters said:

Change your coolant mix from 50/50 to 30 ethylene glycol and 70 distilled water for late Spring through early Fall, it will cool better.

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Agreed that water is better for dissipating heat, but doesn't the 50/50 mixture help by raising the boiling point of the coolant?

ChedderBob said:

I ordered this last night
http://www.amazon.com/Lisle-24610-Spill-Free-Funnel/dp/B001A4EAV0/ref=pd_sbs_auto_1
should be able to purge any air with my next drain/fill cycle

Click to expand...

Those are very handy. We use them in the shop.

Must, must, must verify efan operation.

If the temperature creeps up at idle or at a light, suspect the fan clutch. Very common failure and often ignored.

Did you ever replace that crudded up radiator cap? They are $5.00 new.

Andy Steiner said:

Agreed that water is better for dissipating heat, but doesn't the 50/50 mixture help by raising the boiling point of the coolant?

Click to expand...

If plain water or a lower mix ratio of eth-gly to water .... absorbs heat from the engine better ... and sheds heat in the radiator better ..... The higher boiling point of eth-gly becomes a moot point .........


The liquid mix inappropiately called "coolant" is

Ethyglene-Glycol,
A product to help prevent the radiator freezing up in cold climates.

Water,
Because Eth-Gly alone - is not suitable for cooling purposes,

Other Additives.
Because Eth-Gly alone - doesnt provide all the corrosion protection, etc., required in a lot of new hi-tech engine designs. In fact, the XJ FSM specifies that the mix contains an additional product called ALUGARD 340-2.


Part of the reason XJs are believed to "like" running hot ... is because the 50/50 mix doesnt unload heat in the radiator as well as it should.

Combine that with a wrong radiator type, choice - that is inefficient for the vehicles use and operating location, and the late opening, factory thermostat - and you have a vehicle that just runs hot .... but not nescessarily "liking" it.

.... And thats before faulty or worn out cooling components and neglected maintenance come into the equation.