4 Wheel Drive/SUVs/electric fan

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Expert: - 7/5/2004


Question
'88 Cherokee 4.0L.
I was driving a rough forest road in 4wd at slow speed. When I parked and shut down, my it started overheating, blowing coolant out of the relief thing on the reservoir bottle.  The temp gauge was near the red arc.  It stayed at normal operating temp when driving home with good airflow across radiator.  I replaced the thermostat, but it didn't help: I left it idling, the temp gauge slowly continued to creep up towards the red.  This is when I noticed the electric fan wasn't coming on.  I hooked the fan directly to power off the battery, and it didn't work, so I got a new fan motor.  It still won't come on.  There also appears to be a crack in the top of the plastic reservoir bottle.
Thanks,
Ross Douglas


Answer
Ross,

Well, the first thing to do, is to replace the reservoir bottle, and the radiator cap.  This will insure that you have the right pressure in the radiator.  Without the proper pressure, usually 13 to15 psi, the radiator will over heat.  As far as the fan goes, you should pick up a repair manual for the Jeep, as it will have the wiring diagrams in it for the fan.  You may have a bad thermostat that is not allowing the fan to function. These manuals can be purchased at most auto parts stores for, around $20.  It sounds like the original fan shorted out, and more than likely blew a fuse somewhere.  A cheap multimeter, or a 12 volt test light can be used to trace out the wiring.  Also, make sure that the new fan has a good ground.  While your at it, it wouldn't hurt to run a good radiator flush through the radiator system to clean out any possible plugged lines.  

Carl

4 Wheel Drive/SUVs

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Carl Brandt

Expertise

Will discuss suspensions, lifts, lockers along with tire suggestions. Trail ratings and possible requirements needed for specific type of trails. Safety equipment and what you should carry with you. Certified off-road instructor. I am not a mechanic, and 4-Wheeling is a hobby, so if I can't answer a technical question it is due to my mechanical knowledge being related to vehicles that I have owned, or have worked on. I do not have manuals on all vehicles.

Experience

40 plus years of 4 wheeling in a variety of vehicles. At the present time, my major off-road rig is a 94 Jeep Wrangler with a spring over and a 1 1/2" suspension lift. This gives me a total lift of 7" or so. I have lockers front and rear. I have removed the track bars, and sway bar for maximum articulation. I am running a stock 2.5 ltr 4 cylinder with a Jacobs ignition along with a cold air high flow filter. It has 4.56:1 gears with a Dodge NV4500 transmission along with a 3.8:1 Atlas II transfer case. This gives me a final ratio of 105:1 in low gear/low range. Other vehicles I own, are a 96 Ford F-250 with a 6" lift, posi rear end, 36" Hummer tires, 5 speed with a fuel injected 460 ci engine, an 87 Samurai with an 8" lift, Ford 9" rear end with a spool, Chevy Dana 44 front end with an electric locker, 5.88 gears, 16% reduction in high range and a 6.5:1 low range with 35" Baja Claws, and a stock 2003 Grand Cherokee Overland. Trails I have run are the Rubicon (10 times), Dusey Ershim, Fordyce Creek trail, McGrew trail, several trails in Moab, Utah along with local monthly runs.

Organizations
Lost Coast 4x4's Cal 4-Wheel Corva UFWDA Blue Ribbon Coalition

Education/Credentials
Certified off-road instructor - Certificates in engineering/electronics

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