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View Full Version : 1990 Cherokee over heating Inline 6



brianwy77
04-17-2010, 02:54 PM
I just bought a 1990 XJ with 4.0L, and it's over heating. It has two electic fans but. Still over heats and blows out of the resivor. Does any one have any ideas what might be the problem.

93gc40
04-17-2010, 04:44 PM
is the T-stat working, are the fan turning on when they should.

93gc40
04-17-2010, 04:46 PM
Is it closed system or open?

BlueXJ
04-17-2010, 06:41 PM
Check the lower hose to see that it is not collapsing. Many ppl leave the spring out of them when replacing and then they don't stay open. The t-stat is the second culprit to check. WP is the least likely but it can go bad too.
Blue

brianwy77
04-18-2010, 11:08 AM
It is a closed system, I was told that it has a new thermostat, I didn't check the lower hose. The two fans that are installed are on a manual switch, I think I am going to replace that setup.

W.O.R.P.Offroad
04-18-2010, 11:47 AM
just get a generic fan t-stat switch from autozone or sim place. as for evheating i never could get the factory system to keep cool. once i changed to the open system i havet had a prob since.

4.3LXJ
04-19-2010, 08:38 PM
I see you have a 305 Chevy so I can speak to a few issues there. First off, the radiator is designed for a 250 cu in engine and that is a little marginal in some cases. You will need a bigger radiator. Second, how much air does those fans pull. Many efans are kind of weak. I put some big ones on a custom shroud for mine. Third, the XJ was never designed for a V block. The air just doesn't get out and heat gets trapped under the hood and back of the engine over heats when the front is at proper temp. Vent your hood so the heat can escape.

brianwy77
04-20-2010, 07:38 AM
I don't have the V8 in this jeep that is my other jeep. This is one that I just bought, it has the 4.0 L I6.

alwaysxj
04-20-2010, 08:48 AM
welcome to the prone over heating xj. i would look at changing it out to a open system that seems to help out a lot.

ParadiseXJ
04-21-2010, 03:16 PM
I just bought a 1990 XJ with 4.0L, and it's over heating. It has two electic fans but. Still over heats and blows out of the resivor. Does any one have any ideas what might be the problem.

1. If it's blowing out the reservoir, the reservoir is probably cracked or the reservoir CAP is no good.

2. If you have two electric fans and YOU have to turn them on...why? At least one should always be running, the other should come on if you're getting too warm. I've seen the 3 fan set-up but those are thermostatically controlled and don't rely on "the driver" to remember to turn the fan on.

3. X2 on the fans being too weak. A properly working mechanical fan with a good fan clutch can stir up a hurricane of moving air and should keep you cool except in extreme conditions (wheeling, long grades, traffic, hot hot weather) all by itself.

4. How well has the cooling system been maintained (doh, you just bought it) but a good flush, a new t-stat (195 OEM or SuperStant), new 50/50 coolant mix and going over the whole system works wonders. Which takes us back to number one.

It's still my opinion that the closed system sucks. I've converted both my XJ and MJ to openand have had no overheating issues (although my AUX fan IS on a switch that "the drive" has to remember.:driving:

W.O.R.P.Offroad
04-21-2010, 03:55 PM
It's still my opinion that the closed system sucks. I've converted both my XJ and MJ to openand have had no overheating issues (although my AUX fan IS on a switch that "the drive" has to remember.:driving:


i deff agree mine is set up the same way. one elec fan always on the other on toggle. i havent ever heated since i swaped to this with the open system. im also just runnin a factory 98 radiator and bottle.

xj4life2
04-21-2010, 05:02 PM
Wow alot of good advise out here, but lets go back a minute. How is it running? do we any white smoke comming out the tailpipe? Does the oil look like chocolate milk and overfull ? I hope all the answers here are no if you have a yes we need to investigate more. Be sure to check the bottom hose as Blue said. If its a 1990 its a renix closed system Jeep. Simple things first remove the t stat and replace the fact. 192* with a 180* stat. Wire the Aux elec fans to one constant and the other your choice. Its very easy to convert the closed to an open system If need be , I still run the closed on mine and after a few minor mods have had no issues overheating even on the hottest days. Coolant mixture is very important also the cooling bottle must be in perfect cond. No cracks of any kind. I change mine once every six months without question. Hope something here helps.

W.O.R.P.Offroad
04-21-2010, 05:35 PM
i have a brand new coolant tank you can have. no lid. the lid was junk. i used it for a week before i swapped to the open system.

i couldnt ever get my closed system to run cool unless i was runnin down the free way. even after i cut vents in the hood. it help but wasnt fixin the prob.

brianwy77
04-22-2010, 06:47 PM
What all does it take to covert a closed system to a open system? Parts?

xj4life2
04-22-2010, 07:26 PM
the easiest way is to use the Moroso inline radiator "cap" that goes in the top rad hose $45.00 a heater ctl valve from a newer XJ, junk yard $5.00 new heater hose (both) $10.00 and a radiator overflow bottle from your local parts store $10.00 and about two hours . Thats it your done