Extra Cooling Power

Hey I have a 90 xj 4.0 with the 5 speed. I'm curious what I can do to keep my jeep running cooler. I only have the stock clutch fan and am curious about adding some or atleast a electric fan to keep the engine temp down. Right now it runs hair higher than the middle mark I believe is 100C. Is it worth it? What else can I do to keep the temp down? What should I do to go about this and where should i start? Thx


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That's what they run at.....

cruiser54 said:

That's what they run at.....

Click to expand...

Oh really just seems a bit hot for the 45 minutes I ran it but ok cheers


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worry if it starts creeping up beyond that, when it'll happen is e.g. sitting in a long line at a drive through or something.

So around that blue line is okay? That is where it sits after a decent drive.


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If you don't know the history, you should do a flush on it and make sure your coolant mix is correct. Some folks still believe straight coolant is correct and that couldn't be farther from the truth.

I bought is from a guy who works at a shop with a good reputation around here but i guess it wouldn't hurt!


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The motor needs to be at 210 to operate correctly. Don't try and lower the temp as it will actually impair performance and drivability. If you are looking for ways to keep temps at the 210 mark when your crawling or sitting in traffic you have a few options.

-Upgrade to a 97+ electric fan as it has 12 blades instead of 7. You can also wire in an override switch to have manual control of the fan as it will only kick on when AC is engages or temp hits 220. There is write up in the FAQ section, super easy.

-Use a WJ HD fan clutch, not a great choice but people do it. It's loud and not really the best option but can help.

-Add hood spacers or hood vents. I used these
https://www.westmarine.com/buy/west-marine--stainless-louvered-vent--386559?recordNum=10

Bunch of options for it, a lot of guys use Lebaron vents but they can pull a premium.

Otherwise make sure the rest of the cooling system is operating correctly. Water pump radiator, good fluid, etc.

Enjoy!

100* celsius = 212* Fahrenheit. My '91 temp gauge generally runs just touching the left side of the 210 marker. I think your rig would be running better at the 100 mark.

The line you drew in blue is significantly past the 100 mark. If it creeps up there *only* during idle in hot traffic, then you should be fine. Just check to make sure your fan clutch is working properly.

But if you are up there all the time, including highway, then I would flush and refill with green anti-freeze mixed 50/50.

If that doesn't lower your temps, then consider adding a "wetting" agent to your coolant:

Royal Purple Wetting Agent

I agree with Smokeyyank that the WJ fan clutch isn't a great idea, because it will run the fan, even when the radiator is at lower temps, which we don't want. We want our system to warm up ASAP to the proper operating temps, and not go above that. A stock, Mopar XJ fan clutch does that job very well if it is in good condition. I installed a Hayes fan clutch, only to have it die about a year later. Replaced it with Mopar, and it's been great ... better than the Hayes ever was.

Verify that the temperature gauge is accurate by measuring the temperature of the sender, with an infrared thermometer, and comparing the reading to that of the gauge.
Senders can have wide variances, from one to another.

Does yours have an auxiliary fan? Single row or double row radiator? Air conditioning?

Usually higher temps. at or near idle indicate a marginal fan clutch.

Most of the air is force fed at normal road or highway speeds. More fan often doesn't help much, if at all, at highway speeds.

Check and see if you can squeeze the inlet radiator hose partially closed at 2000 RPM on a warm motor. If you have flow resistance in the system after the thermostat, the inlet hose will get really hard from the pressure if the radiator is partially plugged and may even visibly swell as the RPM's go up.

The thermal switch that turns on the Aux fan is in the lower left of the radiator. They don't often go bad, but they can get lazy. Check the plug on your aux fan. Like I said though, the fans don't actually do much at highway speeds. On my 88 the fan clutch took a dump, I removed it and drove without it for a couple of weeks, no problem as long as I kept driving, slow speed and idle is where it is really needed.

Flushing an older radiator can be iffy, the copper rots from the outside, acid from decomposing pollen and other biological junk. And the copper leeches on the inside as the coolant changes PH from age. In other words the copper gets thin and a flush may cause leaks or seeps on an older radiator.

The coolant system has to be leak free, anywhere that lets the coolant out can suck air in during a cool down cycle. Air inside the system can inhibit coolant flow. And any pressure loss lowers the boiling point of the coolant, if the coolant boils it can also inhibit coolant flow. Tiny coolant seeps can cause large problems.