The problems keep coming. Overheating

New radiator put in the day I bought it. Flushed the system. New waterpump. New 190 tstat. Flushed again. Electric fan works. New radiator cap. Deleted heater valve. Lower radiator hose doesnt look like its collapsing when I give it throttle. No major leaks that I can see.

Ok when I drive on the highway this thing gets pretty hot. I was going around 65 for 15 minutes or so and looked down to almost being pegged on the temp gauge. I pull over and I can hear the coolant bubbling near the radiator cap. Manage to get her home and checked the oil. Good levels. Checked the stuff mentioned above and everything seemed alright. In the driveway when I give it gas the temp stays around normal but soon as I let go it shoots up. Any ideas?

So while the motor was hot I cut it off. The fan kept spinning for a second or two which seemed odd to me. So I tried turning it by hand and it was pretty easy. Thats not right right?

Right, it's not right.

The mechanical fan should not turn freely when the engine is hot...

The e-fan will continue to go if the ignition is on, even if the engine is off. It sounds like you need a new mech. fan clutch...but...that does not explain why you're overheating at speed. Symptom of a bad fan clutch is temp creep at idle, or in traffic or slow n' go.

ParadiseXJ said:

Right, it's not right.

The mechanical fan should not turn freely when the engine is hot...

The e-fan will continue to go if the ignition is on, even if the engine is off. It sounds like you need a new mech. fan clutch...but...that does not explain why you're overheating at speed. Symptom of a bad fan clutch is temp creep at idle, or in traffic or slow n' go.

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I agree with ParadiseXJ.

Odd that it is overheating at highway speeds--the fan clutch is only operating at about 30 percent of shaft speed when it is not engaged and airflow should be sufficient to keep the engine cool.

I would consider replacing the lower radiator hose with one that is "ribbed"--a universal fit hose has a spring molded in and they won't collapse.

BY THE WAY: which vehicle? Open or closed system? On the closed systems the small hoses at the pressure bottle can become plugged and cause issues, but I see you deleted the heater valve.

You're right the fan clutch didnt help. I'm really not sure what else it could be. I've pretty much replaced the entire system. There's no water in the oil and its not showing any signs of a blown head gasket. Cat converter is newish and the only exhaust leak is a small one coming from the o2 sensor port

It's an open system. Ill look into the hose. Hopefully the auto stores carry it here.

SBpunk said:

It's an open system. Ill look into the hose. Hopefully the auto stores carry it here.

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They will have universal fit hoses.

You need to take your current hose in with you to get the right ID for both ends--different if I remember right--and the right length.

SBpunk said:

It's an open system. Ill look into the hose. Hopefully the auto stores carry it here.

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They will have universal fit hoses.

You need to take your current hose in with you to get the right ID for both ends--different if I remember right--and the right length.

Stock 1990 with 4.0 hose:

Centerline Length (in) : 20.8"
Hose I.D. (in) : 1.46" x 1.78"
Hose Steel Coil : No
I.D. 1 (in) : 1.46"
I.D. 2 (in) : 1.78"
Includes Spring : No
Length (Inches) : 20.8"
Type : Molded Coolant Hose
Centerline Length (mm) : 528 mm
I.D. 1 (mm) : 37 mm
I.D. 2 (mm) : 45 mm

Thanks Joe I'll take that info down and see what they can pull up for me. NAPA should have it hopefully. Checker's is about useless when it comes to anything they can't see in the computer. I tried to get fuel injector rings from them and they asked for a part number. Then asked what my vehicle info was. Then told me they didnt carry them since they didnt come up in the computer under my vehicle info.....

Another suggestion I could be way off the mark here cause there are better guys out there on cooling systems than I am but it may need a new temp sending unit. They are only around 15$ or so. Its a cheap easy fix that may solve it without having to spend hours and hundreds of dollars chasing something as simple as that. I know I'm there right now with my 98. Just a thought.

Would that cause it to over heat because it was running hot just driving around town today

My first guess would be you have trapped air in the system. Or you may have a tiny leak someplace, that sucks air into the system during cool down periods. During cool down the radiator normally sucks coolant back into the system from the recovery bottle, coolant is around 800 times denser than air, you have a tiny leak, there is a good chance it will suck some air during a cool down period. A tiny leak can also screw with your high boiling point, typically around 260F with 16 PSI in the system. As the pressure goes down so does the boiling point. The hottest spot in the motor isn't where the sender is, it is likely right next to the combustion chamber. Steam can mess with coolant flow just like air does. A tiny head gasket leak can do the same thing, exhaust finds it's way to a high spot and acts just like an air block.

You get air trapped in a high spot and it can take awhile for the air to move much, it just gets in the way of coolant flow.

I just redid my cooling system, radiator, thermostat, new coolant etc. I burped it well and it still took a week for all the air to work it's way out of there.

One thing I always do when I service the cooling system, is mark the hot (max) level in the coolant recovery bottle and the cold minimum level. Just a little mark with an broad tip ink marker. I check it before driving and again when the engine is hot and watch to make sure the level changes. It typically sucks down the minimum (and max) level over a period of days as the air purges out of the system. It is a good habit, the last radiator I put in there had a plugged up nipple, on the radiator filler neck, for the hose running to the recovery bottle. I may not have noticed (soon enough) if I hadn't been watching closely and something may have popped.

Ok swapped lower hose, refilled the 50/50, changed the temp sensor and its still not helping much. I can get this thing to overheat in the driveway pretty easy. It keeps sucking coolant from the overflow bottle. So I keep dumping more into it. Guessing its burping itself. I'm starting to worry its a cracked head or blown head gasket. Blown head gasket is just an extreme pain but a cracked head I might as well part it out. Joe need you to tell me I'm over reacting lol

Another thing I noticed is the eFan only comes on if I click on the A/C. It'll stay on until the engine cool even after I turn off the A/C but wont come on by itself.

Sounds a lot like my trapped air experience. Mine is closed system, so might not apply.

Look up EcoMike's trapped air posts for more details.

I parked mine level, pulled the temp sensor, then slowly filled through the water pump and top radiator using a cut old upper hose.

When my head gasket went, it would blow white smoke (steam) first thing in the morning. Not something that freaked me out in the beginning, the humidity is often around a hundred percent here. Noticed a drip, drip drip of condensation out the exhaust right after start up, also fairly routine. I dabbed at the drip with a white paper towel and noticed the condensation dripping out the exhaust had a blue tint, the same color as my coolant. Wasn't much doubt after that my head gasket was leaking.

I'd also get bubbles at the filler neck when I revved the motor with the radiator cap off. After it spewed the excess out the filler cap the first time I revved it, I could see the bubbles coming to the top.

I was hardly using any coolant at all, I'd maybe use a pint every couple of weeks.

If you appear to be losing much coolant and it isn't just purging air, it is likely to show up first thing in the morning as condensation out your exhaust pipe.

Just an update on this. My little jeep has been doing pretty well. Im hoping the worse has passed. Im still getting a coolant smell when it gets warm but shes staying between 190 and 220. Least thats what the gauge says. Trying to touch anywhere around the hood after shes been running for awhile is a whole nother story. Feels like its 300 damn degrees.

Not sure what might have fixed it. Probably just letting the air work itself out but the temp sensor was replaced last. Im going to try and put in a ZJ clutch fan. Hopefully itll lower my heat a little more and the noise isnt as bad as everyone says. Im half deaf anyway from my deployments so itll be my wifes problem when I leave for work at 0500 hahahaha joke joke

Go to a website called Offroad Passport and search for a bunch of posts called Clifford. Which is what they call their xj, that guy tried everything to fix his overheating and he finally solved it.Good Luck

SBpunk said:

You're right the fan clutch didnt help. I'm really not sure what else it could be. I've pretty much replaced the entire system. There's no water in the oil and its not showing any signs of a blown head gasket. Cat converter is newish and the only exhaust leak is a small one coming from the o2 sensor port

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That leak can fool the sensor and throw off the computer, making it run lean and hot. Are you sure there is not a small leak blowing on the block? I did not find mine (bad donute) even at a muffler shop inspection until I swapped the transmission and founf the remains of worthless sealing donut at the flange that had to be leaking on the block at high rpms, but passed the idle test on the rack at a muffler shop. New donut stopped the high temps on that one.

This would normally be a bad temperature sensor, or fan relay where the e-fan is not coming on.
Have you confirmed dash gauge temp readings with an IR tester? Dash gauges on jeeps or good liars!!!
What year is this beast?

If it keeps sucking coolant and never stops you have a coolant leak.

Try and find some BarsLeaks fiber pellets, for coolant system leaks and add them.

http://barsproducts.com/catalog/view/6-radiator-stop-leak-tablets-hdc

SBpunk said:

changed the temp sensor and its still not helping much. I can get this thing to overheat in the driveway pretty easy. It keeps sucking coolant from the overflow bottle. So I keep dumping more into it. Guessing its burping itself. I'm starting to worry its a cracked head or blown head gasket. Blown head gasket is just an extreme pain but a cracked head I might as well part it out. Joe need you to tell me I'm over reacting lol

Another thing I noticed is the eFan only comes on if I click on the A/C. It'll stay on until the engine cool even after I turn off the A/C but wont come on by itself.

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The efan should come on. Anyone recall offhand if the 91 model year had a separate fan switch, or if it was computer controlled? My 98 has a single sender to the computer, but I don't know about the 91s... In any case, your fan should come on at 220 or so and turn off again at 205. That's definitely a problem - maybe not the only one.