Other ideas on cooling...

I just bought a 95 XJ 4.0l, and it too runs "warm". I've read many of the forums and ideas and fixed a pile of issues on the vehicle, but the needle still sits higher than the 210 number, most of the time the needle covers the "0" in "210" on the guage and it hovers above and below that... If I turn on the heat full blast it will drop the temperature and hover on 210, so it's close... And I haven't towed my 1500lb boat yet...

A couple questions:

1) The A/C is discharged, and to be honest I don't need it. would it help if I disconnected the A/C cooler and removed it from the vehicle? It significantly blocks the radiator, and I would think it would help to have max exposure of the radiator directly to the cooling airflow...

2) Under the engine there is a rubber mat tied in with zip ties all over - is this for directing airflow or limiting dust? Would it help cool the engine to remove this?

Thanks in advance...

1 - The cooler is blocking airflow to the radiator; if it's been purged it can be removed to increase that, but have you looked through it yet? Put a light begind it at night and see how much debris is between the fans; you might be surprised how well those Jeeps catch and hold bugs.

On a '95 if it's the original radiator I'd recommend a replacement. There've been countless posts dealing with 'what to use' so I'll leave that choice up to you, but refill it with distilled water and coolant instead of mineral-laden house water.

2 - It does both. It keeps splash and stuff out of your alternator, and it's supposed to help direct airflow but most of us seem to have lost all or part of ours years ago. Even without it, a properly functioning cooling system should hover right around the 210 mark summer or winter.

It sounds like you might have a cooling overhaul in your near future. Fan clutch, replacement radiator, thermostat (with check valve or hole), upper and lower radiator hoses because the lower one can collapse under suction from the water pump if it doesn't have an integral spring. The water pump itself could be an isue, but you won't know the condition of the impeller vanes unless you pull it. Once you do that, you may as well replace it anyway. There are two rotations available so make sure you get the same one (this early, pre-coffee I can't remember we use CW or CCW).

What tranny do you have? If it's an automatic, slippage will build up heat as well and dump that into the cooler...that dumps into the radiator. Make sure that's in good shape as well.

The rubber mat is a factory splash shield. Don't know if it helps cooling but it doesn't hurt it. It helps protect the alternator. I'd leave it in place.

A '95? Have you replaced the radiator? If not, do so. 10 years is about the maximum you can expect, especially if it hasn't always been run with distilled water and the coolant changed religiously every two years.

I was trying to spare you the details, but 1 yr ago the radiator was replaced and system backflushed due to overheating problems at that time. Just prior to that the water pump had been replaced (previous owner gave me all repair receipts). I've had the XJ 1 month and I'm just getting it dialed in.

I've replaced the sender for the temp guage.
Last weekend I replaced the heater core (what joy).
Hoses are in good shape and lower hose has the spring...

Today I was going to pick up a OEM thermostat and replace that this weekend.

Fan Clutch: There is the mechanical belt driven fan, and also an electric cooling fan. I don't recall seeing or hearing the electric ever work... From what I've read the fan clutch is part of the mechanical fan?
thanks-

Yes, the fan clutch is on the mech fan. The eectric should come on when the a/c is on, when the defrost runs, or when the engine temp hits somewhere right about where your temps are.

I'll check the fans this weekend and debug them, I think that is the problem...

I'm gonna ignore the tranny questions for now... yikes, don't wanna go there...

...especially after just spending $500 on ball joints, alignment, rotation and balance to solve a serious shimmy between 55 and 65mph. That's another thread...

thanks for the guidance!

Fishbum

Welcome to the world of the XJ. If you plan on towing add a tranny cooler. An aftermarket cooler is relatively inexpensive and easy to install. Do a search here for tranny cooler info. There's plenty.

Is the tranny oil currently cooled on a stock XJ? Do I need the cooler even if I'm towing only 1500Lbs? I know it won't hurt, but just one more thing to deal with...

By the way - with the engine hot the mech fan spins <1 revolution, but I bought a fan clutch anyway... at room temp the new fan clutch seems much stiffer than the existing one.
Thanks

Auto trannies run through a cooling tank in the radiator, but an auxiliary cooler isn't a bad idea, especially for towing use.

Swap the fan clutch...sounds like it's toast.

Ok, I've replaced the fan clutch while I had the front end apart removing the A/C cooler.

Now I'm operating 5 degrees cooler, but I'm thinking that this is due solely to removing the A/C cooler and exposing the radiator to full airflow. Wish I had the luxury of testing one thing at a time, but I did have the front end apart already...

The electric fan works when direct wired but not otherwise, so I need to work on that more.

I bought the tranny cooler, I'll report if that has any effect after installed.

When warm the engine runs steadily around 5/8 of the gauge. If 50% is 210 deg and 3/4 guage is 235 - I'm running at 222 deg... but it does range up to just under 3/4 of the gauge, or 235 at times.

This all ASSumes the gauge is accurate.

This problem may get to the point where I know all major systems are working, including the electric aux fan, and I just have to assume the guage is off.......

I also have two new OEM thermostats (what is currently installed is unknown). I don't think this is the culprit, but I thought it wouldn't hurt to swap it...

more tomorrow....

The 4.0 is also very sensitive to air in the system, it generally takes about 30-45 min to get most of the air out after draining and refilling it. Also the tstat OEM one has a bleeder hole in the flange, this needs to be at the 12 O'Clock position and aids in air evacuation, none of the aftermarket ones have them. Also did you use a gauge to check belt tension ?? A new belt is defined as one used for less than 15 min and should be set at around 190lbs, used belt, 15 min or more is supposed to be set at 160lbs. NAPA sells a krikitt II for around $14 for this, fits in your shirt pocket but very handy.

There might be something to the trapped air idea...

I drained the system to replace the heater core, so there could still be some air. That may be the best advantage of the OEM thermostat, the small vent...

I'll replace the thermo tomorrow and we'll see.

I have a new serpentine belt, but I didn't install it... The place that did my inspection (and they were very easy on me) installed the belt (I threw them a bone)... I'll pick up the krikitt tomorrow too.

Whats the best way to test the water pump?
thanks.

Well, as far as the water pump goes, I've always gone by 'it works or doesn't'.
When burping the system on my 98 I park it nose uphill in my driveway, remove the coolant over flow bottle and clean it out then put it back, fill to the hot mark. Then I fill the cooling system with a mix of 50/50 Mopar coolant and distilled water. I first dump in a full gallon of pure anti-freeze, then take and dump half a gallon of distilled water in the empty anti-freeze gallon then top it off with the other gallon of anti-freeze then dump the remaining half gallon of distilled water in the now half empty container, you end up with two 50/50 mixed gallons that way. Then I start the engine and top off the coolant thru the filler bung and wait for the Tstat to open, as the coolant drops I add more coolant into the rad keeping it pretty much topped off. It will look like fizzy green soda, thats the air, then I just let it run, topping it off as needed till all the fizzys are gone. At that point I blip the throttle a bit so it sucks more coolant down and quickly top it off and slap the pressure cap on. Any remaining air will bubble up into the overflow bottle and escape. When it pulls the displaced air back in it will pull it from the overlfow with no air in it.

On yours you can also fill it from the back of the head where the temp sender is, never done it that way but others here who have pre 97's talk about it. I've watched/helped rad/water pump replacments on 3 or 4 pre-97's XJ cooling systems at my friends shop and always use the machine.


The last time I did it I used my buddys Sun machine that pulls the old coolant out with vacumn and puts new coolant in with pressure and vacum. That machine spoiled me, I want one for my ownself Did not spill a drop, it has two adapters that go on the top hose after you disconnect it from the rad and another adapter that attaches to the top bung on rad then uses snap fittings to attach the two hoses to the machine which is about the size of big hoover floor vac that has two tanks in it, very slick....

Ok, OEM thermostat did the trick. This morning I stared the xj and kept feeling the hoses and watching the gauge, it got over 230 before the thermostat opened and the top hose started getting hot. So the thermo was opening late and was causing lots of fluctuation while driving.
I replaced the thermostat and now it runs consistently at 210-215. Close enough for me. No trouble with trapped air on refilling the coolant either (got lucky).

Still can't debug the electric fan... and I need this to work to prevent overheating later while towing (cooling boost). If I disconnect the sensor plug with the engine running, the fan will kick on! Which suggests the ECU and Relay circuit are working fine. But I can't get it to run any other way. I've swapped relays with other systems and no change. I swapped coolant temp sensors in the thermostat housing and no change (fan won't work).
Do I need to starty prying into the wiring harnesses to check other voltages?

Anyone know what relay terminal is what?
thanks-

Fishbum, I just redid my cooling system as well (new radiator, water pump, flex fan, thermostat & housing, hoses and aux. tranny cooler). The aux. tranny cooler was the single biggest improvement. I had previously installed a tranny temp gage and was getting between 180 and 200 degrees at the radiator connection. On one hot day (~80 degrees) I pegged the needle at 250 degrees on flat and level ground with no load. I can only imagine how hot the tranny really was and dumping that hot fluid into the radiator was not helping cool down the engine. After installing the aux cooler the tranny temp stays right around 100 degrees and hasn’t broken 180 yet. The engine runs much cooler as well. If you plan on doing any towing at all I’d say that an aux cooler is mandatory. I added some Water Wetter to the radiator and that cooled the engine down about 8 degrees. Its not a huge improvement, but it only cost $10 and took about 2 minutes to put into my radiator. I’m happy with it.

I wired my stock aux fan to run off battery power (relay, 10 ga wire, 30amp fuse) and hung a toggle on the dash. You can test yours with some 12V at the plug to see if it works...If it does, either fix up the stock circuit or make your own.

On my trail rig, I took the ATF completely out of the radiator...ran it through the unused AC condenser as a cooler and then through a remote filter (mounted where the stock airbox was) and while things were apart, I cleaned both the condenser & rad fins with hi-pressure water...There was years of mud & bugs packed up in there. I used a bottle of Water Wetter in the coolant & we'll see how that all helps...I'm sure it won't hurt.

My DD is suffering hotness off & on for the year I've had it... open system...weekly burpings have always made it happy again, but it's a PITA. I think I will have to go through the whole setup...at 16 years & 210, it's overdue. (Rad, Bottle, pump, hoses, belt, Tstat) and I'll probably go with a bigger aux cooler & remote filter in this one as well.

One thing you will get on this forum is lots of great advice. All previous posts on this subject are accurate, and could very well be the cause. Had the same problem with my 91 MJ 4.0 closed system and replaced the water pump (slight leak around the shaft), the thermostat (used the factory recommended 195 degree Mopar), mechanical fan clutch (seemed too easy to turn when hot), aux electric fan (noisy bearings), and finally a new GDI 3-row radiator. All helped slightly, but I was still running a bit higher than the 215 degree norm on a hot 'Bama day with the A/C running. When installing headers and a new exhaust system, I eyeballed the catalytic converter input, and it was gummed up with crud so badly I don't see how my engine ran at all. This turned out to be the primary reason for my running hot, and now all is well even sitting in traffic in 95 degree weather w. the A/C running or climbing a mountain (such as they are here). If you have over 100K, check the cat.

Don

I do believe that your auxiliary fan doesn't work because your AC is discharged. I have the same problem, AC discharged, auxiliary won't come on, but the relay is fine, and the switch(it's a switch on the 90 and earlier 4.0's) in the radiator works, and the fan works. If the AC is discharged, the low pressure switch disables the clutch on the compressor, and I think it also stops the fan from starting. The schematics aren't real clear for me, but the two circuits are connected.

On the cooling question, I just installed a new dual core, closed system radiator in my 88 4.0 MJ along with a rebuilt water pump, hoses, factory thermostat, etc. It's an all copper radiator from Performance Radiator. It's nice and heavy and thick. So far, the temperature has not risen above 195 F even while idleing in 80 degree weather without a working auxiliary fan. The 3 core open GDI radiator with flowkooler water pump in my XJ does not work that well. I've only the performance radiator a couple of days, so it's far from conclusive, but I've been impressed so far.

Fred

Fred said:

The schematics aren't real clear for me, but the two circuits are connected.

Click to expand...

Yes, they are connected by a diode block which creates an "OR" condition - fan should come on if the A/C is on - OR - if the temp switch signals it needs to... either condition will power to the relay.

Where is that confounded diode block????