99 XJ overheated. Aux fan connector? - JeepForum.com
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Unread 06-11-2015, 07:34 AM   #1
gvthnks
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1998 ZJ 
 
Join Date: Feb 2014
Location: Jacksonville, NC
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99 XJ overheated. Aux fan connector?

Daughters XJ overheated yesterday and I'm trying to figure out why. Not sure if AUX fan is the problem or if thermostat stuck. Not leaning toward thermostat cause if it was stuck closed, I would think it would've run hot before she got to me.

Here's my questions:
If the AC is on, and the aux fan isn't running, is that enough to make it overheat while stopped in traffic for 10-15 minutes?

To 250 Degrees?


Back story below if needed.

99 2WD XJ with 178k on it, 4.0 and automatic.

Two months ago, replaced with radiator with a new one because the old one split down one side of the right hand tank dumping all the coolant.
When I replaced the radiator, I also replaced the water pump with a new one and thermostat as well. Old one wasn't leaking and flowed well, but the mounting tab for the power steering pump was broken off by PO and since I was in there already seemed an easy fix. I flushed the system and backflushed the heater core and the system seemed pretty clean. With the tank broken open on old radiator I could see into the core pretty well and they were surprisingly clean. Good sign. Refilled with appropriate coolant and drove on.

No issues for past two months. Yesterday as daughter was coming to see me at work, (35 miles of mixed highway and city) she got stuck in traffic and temps hit 250. When she got to me, it wasn't boiling over but when she stopped it did and started and pushing coolant out of overflow. AC was running. I used water to cool it down by pouring it over the radiator until it started sucking coolant back in from the overflow. Once cooled down a little, I pulled the cap and topped the radiator off again.

I reached down and grabbed the aux fan wiring harness connector (located below radiator fill cap on left side of jeep) and the fan kicked on for a few seconds, then stopped. (AC still on) grabbed it again and fan started and ran continuously the rest of the time. Poor connection maybe?

I'm thinking lack of airflow... probably caused by faulty fan connection.

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Unread 06-11-2015, 09:35 AM   #2
Tru2Chevy
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Yea, sounds like the first place to start. I would check the connector and see if anything is loose / dirty. Clean up / fix / replace as necessary, and have her listen for the electric fan when the AC kicks on.

- Justin
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Unread 06-11-2015, 11:35 AM   #3
CJ7-Tim
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I would replace the mechanical fan clutch also.
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Unread 06-12-2015, 08:13 AM   #4
bluejunior
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I didn't get my AUX fan's connector reseated properly after removing it for better access once. Combined with my worn (but partially functional) mechanical clutch I experienced pretty much the exact same thing you're describing. Replace the Mech clutch (they're cheap and easy) then start it, turn on the AC and pop the hood. If the Aux fan isn't blowing good an strong when the AC is set to on then you've got a problem with the aux fan or its wiring.
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Unread 06-13-2015, 07:14 PM   #5
gvthnks
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Yeah, I was thinking about the fan clutch. Already have one on the shelf at work (part time at AutoZone) so will probably put it on Monday.

Also noticed that sometimes when I cut it off, the aux fan runs for 10-15 minutes or longer.

Is that normal or is the relay sticking?
If that's the case the relay could also be preventing it from turning on when it's supposed to.
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Unread 06-13-2015, 09:22 PM   #6
bluejunior
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Quote:
Originally Posted by gvthnks View Post
Yeah, I was thinking about the fan clutch. Already have one on the shelf at work (part time at AutoZone) so will probably put it on Monday.

Also noticed that sometimes when I cut it off, the aux fan runs for 10-15 minutes or longer.

Is that normal or is the relay sticking?
If that's the case the relay could also be preventing it from turning on when it's supposed to.
I've never heard of one running while the engine is off. Sounds fishy to me, you may be onto something there
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Unread 06-14-2015, 05:03 AM   #7
CJ7-Tim
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Relays are cheap, I would install a fresh one. A previous owner may have installed an e-fan timer.
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