CherokeeOutlaw

Ok so I have another thread or two related to this already but I felt a new one would help keep the issue clear. The PO apparently installed dual electric fans. I was out four wheeling and stopped on a small hill facing uphill and the temp gauge jumped from 210 to red. The instant I turned around and faced downhill at a stop, it dropped back to 210 or less. Air pocket right? So I burped and burped and burped the system and had no issues for a month or two. Went through the mountains to San Diego from AZ and it overheated about half way there. Got to a service station, refilled the radiator, burped it, turned AC off and heater on and it never overheated the rest of the week in San Diego. Replaced the rad cap, thermostat, t-stat housing, water pump, and hoses. Radiator is functioning properly, compression is good, no signs of head gasket issues, fan exceeds cfm rating of stock set up and is functioning properly. The jeep doesn't have to be driving on a hill and the hill doesn't have to be very steep to cause the gauge to jump. The gauge is working properly too because when it does show hot, the reservoir boils over. The mechanic doesn't seem to have any major ideas. He re wired the fans to the stock relay but that was just a preferential issue. Any ideas what else can be causing the gauge to just JUMP from half to full? And why only in an incline?

djb383

I'd suspect the fans.....the OE efan pulls some good cfm numbers and the OE clutch fan will pull way more cfm than the OE efan at just off idle, presuming the fan clutch is functioning correctly.

I'd suspect the radiator as well. How does one know a radiator is functioning properly yet the motor overheats?

BigBear

Make sure you have 12.5 quarts* of coolant mix in there or it will overheat.

ZINGGG

I just read through the thread you started 2 and a half months ago... so you replaced the water pump and rad cap since then? What else have you done? And same question as djb, how do you know the radiator is working properly?

How do your 2 fans work? One on at all times and the other once the temp gets to 212 and sets it off? orrrr?

CherokeeOutlaw

Well here's why I don't think it's the fans....I can run the crap out of the motor and idle at flat bottom or facing downhill an it won't get hot ever but I I idle at an incline sometimes it will get hot. I dont have to be driving on an incline. The radiator is holding proper pressure and it is circulating so I should have said its functioning properly in that sense. Oh and it was flushed and back flushed through the block too.

CherokeeOutlaw

Oh and I think it was djb who originally said my fans are NOT OEM and I swore they were but you were right. I saw here they were wired to a separate relay not in the fuse box.

offroadordnance

Is the hot air exiting underneath rising on the incline and getting sucked back into the rad?

CowboyXJ

If that was the case all xjs would over heat on a hill.

CowboyXJ

Im thinking you might have a slow air pocket build up. Just an idea.

djb383

Check the rad when the motor is cold....coolant level should be at the top of the neck, motor cold. Only way to determine internal condition of the rad is to have a rad shop separate the tanks from the core and rod it out. The XJ rad is about as dinky small as they come. If only a few tubes are clogged, efficiency is reduced. No amount of flushing will unplug a tube filled with solid scale....rodding it out is the only way to unplug it. At +/-$100, a new rad is well worth it. If that doesn't cure overheat, the aftermarket fans are definitely suspect.

CherokeeOutlaw

Yes the radiator is full to the neck when cold. if it were the fans why would it only happen randomly on an incline but cool off the instant I turn around and stop facing down hill?

CherokeeOutlaw

that's what I thought too, like even after I burb it there is air getting in somewhere causing a pocket. I'm not losing fluid though.

CowboyXJ

If your not losing fluid then its a cap. Or maybe a pin hole in the heater core, line, or even in the rad its self.

djb383

Does it or does it not loose coolant? Does it overheat while or after driving uphill? What info do u have that says the fan exceeds the cfm rating of the stock set-up?

If the rad is full when the motor is cold, don't see how an air pocket can form when the motor is hot and disappear when cold.

Again, the only thing u haven't replaced is the rad......so I'm still guessing the rad and aftermarket fans.

CherokeeOutlaw

So to start, I had the mechanic wire the fans to the stock relay and get rid of the aftermarket thermostat trigger....works properly now for sure. I am ordering a bit better radiator. Until then, here's a new almost unrelated issue...since it came back from the mechanic it sputters for a second or two AFTER I shut the motor off and it has NEVER done this before (*except once) so it's a safe bet that its something he disconnect or along that line. *When I did my headers I left a hose dis-connected on the top of the intake and the same thing happened, but as soon as I connected it, it was fine. That hose is connected so its not that. I plan on taking it back tomorrow but maybe I won't have to if you have any ideas...