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Thread: 1990 XJ Overheating

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    Default 1990 XJ Overheating



    I took the Cherokee out Sat. to do the Moody Hill/Ballard Rd. run with the group. It was about 55 miles to the meeting spot, Jeep ran great on the Hwy and had no issues. Actually did really well on MPG at 21 MPG. This was my maiden voyage with the XJ. After we left the meeting place and got in the hills, the Temp started to increase. I let it cool down when we stopped to air down, but when going up to the trail head, it started to heat up again. I decided not to proceed and turned around. My question is, is it worth changing out to an open system? My pressure tank seems to hold pressure, but the Elec. fan (I found) is not switching on. I am going to replace the elec. fan/switch, remove the AC condenser (AC pump converted to air pump), and do a flush the system (possible thermostat). I am wondering if I should change it to an open system, since I am going to have it apart, or is it not worth the effort or money? I am hoping the elec. fan will cure the issue, but I am wondering if I have something else going on.

    I know this group has a lot of XJ's , so looking for insite on how to cure the problem.

    Thank you

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    Default Re: 1990 XJ Overheating



    I don'thave an XJ but I do have a 4.0 and they're not known for overheating. I had an open system in my YJ 4.2 when I moved here from FL, works terrible in the winter, no advantage in the summer, IMO.

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    carpenle (July 15th, 2013)

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    Default Re: 1990 XJ Overheating



    ***

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    Default Re: 1990 XJ Overheating



    It is the 4.0 and never heats up in town. It was when I was pulling the hills that it heated up. I am thinking that I need some hood vents, because it holds all of that hot air in the engine bay.

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    Default Re: 1990 XJ Overheating



    my one Q is how hot did you get it ?? like just a little higher or run it very close to the red on the gauge then shut it off............the fan is big as your motor is so long it has a lot of surface area and if no air flow (slow speeds and wheeling) then I know they hold a lot of heat under the hood

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    Default Re: 1990 XJ Overheating



    I was almost to the red, then I shut it down to cool. When I turned arround, and was coasting down the hill, it cooled down to below half way on the gauge. Also did not heat up on the hwy driving 75-80 home.

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    Default Re: 1990 XJ Overheating



    Sounds like an airflow problem. If you are lucky, you can find the newer style fan from a '96, it plugs right in. If not, swap the old connector onto a newer fan.

    The cooling system works, the same set-up is used in newer vehicles. No need to reinvent the wheel.
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    Default Re: 1990 XJ Overheating



    I'll agree with Mike. It sounds like lack of airflow.

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    Default Re: 1990 XJ Overheating



    I am hoping that fixing the aux fan will help with the air flow.

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    Default Re: 1990 XJ Overheating



    Aux fan is very important. Should also consider a trans cooler. New aux fan from performance radiator is only like $100 and moves more air if you ask me(plugs right in too). While you have fan off take a hose and spray water from inside out (reverse direction of airflow). You can also use a toggle switch and run aux fan constantly while wheeling, I do.
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    Default Re: 1990 XJ Overheating



    0.02 airflow.

    I see you're mentioning elec fan, so this might not apply, but I'll recant it for kicks...

    I had just purchased a 1968 Ford Ranch Wagon in San Jose California (from a nice couple on Husted Avenue). Driving down to San Diego I saw a NICE (similar vintage) hot rod car sitting on the shoulder of the slow moving, traffic clogged freeway. I stopped to ask the driver / kid what was up and he said it always works great "around home" (country - no traffic) but whenever he goes to San Diego and hits slow moving traffic it overheats. Looking under the hood I spied one missing piece of plastic and said "quite likely" your problem is the missing fan shroud (mechanical fan).

    The fan shroud helps focus / force, at slow fan speeds, air THROUGH the radiator instead of curling in from between the fan blade tips and the side of the radiator.


    I said he should install a shroud but in the meantime, when things get hot, kick the car into neutral and bring the RPM's up a bit. That would help force more air THROUGH the rad vs. curling in at the blade tips.

    Now, you say Elec Fan (and that it wasn't turning on). Was it turning on at all?? If not, an issue to address. Second, when it does run, how air tight is the seal between the fan's shroud and the rad? If the gap is large enough to allow air to leak in from the blade tip ends instead of through the rad - a problem.

    Rad fans, on my 68 (5L v8) Ranch Wagon and my 79 CJ-5 (5L v8), can be removed so long as the vehicle "generally" travels over 25/30 MPH. There will be enough ram air through the rad to keep things cool. Long stop lights - I'd just shut down the motor to not overheat. What I mean by this paragraph, is that your highway travels likely have enough ram air to keep temps down and you're relying on the fan only at slow vehicle speeds for cooling.

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    Default Re: 1990 XJ Overheating



    xaza previously posted:
    "Should also consider a trans cooler"

    Thanks Cliff, I do have a trans cooler. I will clean out the radiator, thanks for the suggestion. That is a good point, if I use a toggle switch, I can use the fan when needed.

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    Default Re: 1990 XJ Overheating



    Hi Jim,

    The Cherokee has a mech. fan, which has a shroud, and a aux. elec. fan that is turned on by a temp switch. The elec. fan is not turning on at all, so I am thinking (hoping) that is my issue. Right now as is, the mech. fan is on only half of the radiator, and other half has no fan.

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    Default Re: 1990 XJ Overheating



    If you are not sure it is the fan you can wire it straight to battery to be sure. The temp switch that controls fan on/off is right bat top front of engine
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    Default Re: 1990 XJ Overheating



    xaza previously posted:
    "The temp switch that controls fan on/off is right bat top front of engine"

    Actually, the RENIX temp switch is in the radiator tank, on the driver's side, above the radiator hose.

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    Default Re: 1990 XJ Overheating



    oops, completely forgot it was the old sealed system, thanks mike
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    Default Re: 1990 XJ Overheating



    i thought the aux fan only came on when the a/c was on for the renix models. i had a base model renix mj and it didn't have the elec fan. don't think it even had the wiring for it. however i did add one on there with a swith

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    Default Re: 1990 XJ Overheating



    I'm a 'fan' of twins myself you can get dual fan assemblies at the junk yard cheap or you can step up for about $200 and up there are lots of options and most dual fan sets flow more than your clutch fan/ aux fan set up the trick to it all is research there are fans out there that'll flow 5000cfm but draw 50+ amps of current not ideal the wiring can be tricky if you want to run the fans independently recommend, but not terribly so not to mention the horsepower gains 10-20 hp! major considerations in this project are current rating and flow rating you can even hide the extra relays in your stock relay panel if you like the clean look if you're thinking aftermarket summit racing is an awesome place to shop

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    Default Re: 1990 XJ Overheating



    redneck23ms previously posted:
    "i thought the aux fan only came on when the a/c was on for the renix models."

    The fan will come on when the thermal switch makes, or the AC pump clutch is powered up.

    Good reminder! In the dead of winter, with the defroster on, the fan will run. Last time I had trouble with mine, I turned on the AC to see if the fan worked at all.
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    Default Re: 1990 XJ Overheating



    I have a twin fan set up for a VW golf, but it looks like it will not fit. The xj has a pretty narrow radiator, so I am thinking of going to the JY and trying to find a working OEM part. I am also thinking that the toggle is a great idea.

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