Sudden Overheating Problem

Hi, I aquired a 90 XJ with the 4.0 and Five Speed and 163,000 miles in May. I recently drove it to Denver (I live in NW Kansas) everything went well the temperature guage was in the between the third a nd fourth mark on the guage. On the way home I was riding the edge of the red mark all the way home. I turned off the a/c and took it out of overdrive, and it still wouldnt cool off. I replaced the thermostat and I noticed I could control the temperature a little more, It would get hot at a red light and cool off as soon as I got moving again. I know that the water pump is good because the shaft doesnt wiggle and it doesnt leak. I also do not think it is a radiator issue because they dont just go bad like this. The clutch on the mechanical fan is good, (im a little concerned about this because it doesnt make noise most of the time. like the other 4.0's do) and the electric fan powers on when it should. perhaps I need to replace the seal on the overflow container cap? Any answers would be appriciated.


Ethanc

How do you know the clutch on the mechanical fan is good? The symptom of heating up when stopped and then cooling down as soon as you start rolling is THE classic symptom of a defective fan clutch.

Assuming you still have the plastic bottle on the passenger firewall, yes that cap is a pressure cap and, yes, they are known to go bad regularly. Quadratec sells a complete bottle and cap for about 20 clams -- the dealer will probably soak you close to that just for the cap, and then it won't seal to the old bottle. I'd suggest replacing your fan clutch first, then replacing the bottle.

That sounds like an idea. Can I get just the clutch or do I have to replace the whole fan? I dont think its bad, because it doesnt wobble, and it stops quickly when I turn it by hand. But I just dont hear that fan noise when I am driving around.

Thanks Eagle

I'm with Eagle on this one. Symptoms indicate bad fan clutch. Contrary to what some say, I don't think you can accurately test the fan clutch using the spin test. Consider also that the radiator might be partially blocked.

You don't need to buy a fan, just the clutch, and then bolt the old fan to it. And I suggest the OEM clutch.

Tom

I think the radiator is ok, I was driving around tonight with the A/C on and it got a little hot. So I shut the A/C off and I got on the highway and she cooled right off, so I think the radiator is ok, but I am thinking about going to a three core anyways. What all is envlolved in going to an "open" cooling system? All suggestions are welcome, Im thinking the radiator has a limited lifespan left anyways.

I'll go grab a clutch in the morning.

Thanks

Ethan

Sometimes I think the 3-core is overrated. A good 2-core Modine rad should work every bit as good. I heard the passages are larger in the 2-cores, but I don't know for sure. I've always run 2-cores and never had an overheating issue. If you replace the radiator, just make sure the one you get has metal tanks, not plastic.

Tom

Do all Xj's have overheating problems. I have an 89 xj I've had overheating problems. I've replaced tremo-st,rad,hoses,tremo-st houseing,water pump,bottel and cap and fan clutch. The oldest parts are the tremo-st 3 months and the bottel 6 months. I have gotten it really hot and I've gone thru 7 cap for some reason they wont hold pressure. Could the tremo-st be stuck or the bottel's thread be stripped.

Everything I know about Cherokee closed systems I learned from Craig Houghtaling. Here's his write-up including links at the bottom for converting to an open system.
Care and Feeding of the Early 4.0L "Closed Cooling System"

If you absolutely feel you MUST convert a non-HO XJ to an open cooling system, by all means have at it. Then you get to spend the next three months trying to find a way to control the aux fan. None of that is necessary. There is nothing wrong with the "closed" system that a replacement radiator and getting rid of the crappy plastic bottle won't solve.

If you have a non-HO with the original radiator, you can be pretty certain it is on it's last legs. May even be on artificial life support. I take pretty good care of mine, and the OEM radiator on the '88 sprung a leak in the autumn of 1999. At that time, I replaced with a GDI 3-core and I also got rid of the plastic bottle and replaced with a Moroso aluminum surge tank.

It happens that today I had to drive from Connecticut to JFK airport. There's construction on the Whitestone bridge, and more between the bridge and JFK, so we were in slow crawl mode for a good two hours. Never got past 2nd gear, and most was in 1st gear. Bright sun, ambient temperature about 95, moderate humidity. Temperature on the highway itself had to be about 100+.

The temperature needle never got UP to the 210 mark, and I didn't hear the aux fan come on once.

Okay, on the idea of conversion...

First of all, Eagle is right, the open system doesn't out perform the closed system. I feel the only real reason to change from closed to open is personal preference / comfort level. Myself, I am more comfortable with the open system (I feel I understand it better) so about eight months ago I converted (I had massive cooling system failure going on, so had to do most of the parts anyway).

So here's what you have to do, the items in bold are for the conversion, the other items are suggestions of parts to change anyway.

Radiator: For obvious reasons.
Thermostat Housing: The Aux Fan switch on the HO's is on top of the thermostat housing, not the radiator.
Thermostat: Since you've overheated it I would change the thermostat just to be safe.
Heater Control Valve: Again, the design differs between open and closed.
Water Pump: If it's never been changed I would go ahead and eat the cost and change it out, it just makes sense.
Flush The Cooling System: No sense in changing the radiator without getting all the crud out of the engine and the heater core, do not forget the core!
Fan Clutch: Again, it's about time, you're in there, and it's quite possibly bad.
Auxiliary Fan Control Switch: That mounts on top of the thermostat.
Serpintine Belt: Again, while you're in there you might as well change it.
Idler Pully: Just get your hands dirty once.
Coolant Recovery Bottle: Again, for obvious reasons. Here you can either use a newer XJ one or just pick up a cheap one at AutoZone (or even the bone yard). Personally I went for that "stock look" and bought a newer XJ bottle.
Heater Hoses: These boys also differ. Do yourself a favor and buy the OEM ones from the dealer, they're pre-bent and make the job much easier.

For my conversion I told all parts guys that I had a 1995 XJ.

Now, on control of the aux fan, you should just be able to use the new switch on teh thermostat housing, you will have to splice in longer wires to the aux fan switch and a different style connector (it's common on GM cars).

As you can see, it's an involved process to do the conversion. If I were you I would just change that clutch out and see what happens. I'd also get a new bottle (it's cheap, so it won't hurt too much if you end up changing over to open down the road) and put it in. If you end up deciding that you have to change the radiator I'd revisit this topic and decide if you want to go though the time and expense of the change. You will have to do some very minor fabrication work to do this. The top radiator brackets between closed and open will not work, but it's easily fixed with just a little bit of metal 1" stock, cut it to length, and drill two holes. Also, you will have to come up with a way to hold the new coolant recovery bottle down.

Sequoia

GSequoia said:

Now, on control of the aux fan, you should just be able to use the new switch on teh thermostat housing, you will have to splice in longer wires to the aux fan switch and a different style connector (it's common on GM cars).

Click to expand...

Okay, but what new "switch" are you talking about? The stock unit for a '95 XJ is not a switch, it's a temperature sender that feeds data to the PCM, which in turn decides when to activate the aux fan. It's a totally different setup than the non-HO, on which the aux fan is controlled directly by an off/on switch (thru a relay). The stock '95 XJ sender, from what I understand, will not operate the aux fan in a non-HO.

What did you use, and how well does it work (or have you even verified that it does work)?

One last bit of an input here. And I'm not prone to pontificating or pedistalizing but.....Eagle knows his @#$@#. Period. One of these days I may meet him (if indeed he is a human and not one of those new super puters') Take his advice when given...

Oh yeah he knows it. I stand corrected then. Aparently either it was more complicated than I remember or the site that I saw the mod was on was wrong. I haven't done it yet because I never quite got around to getting the connector that will fit (yeah, I can be lazy!), for now I'm running with a manual override for my fan.

I'll look into it (I might still have the link on the home computer) and post what my findings are.

Sequoia

Edit: You could get the thermostat housing for an open system and just get a generic switch with the right threads and toss it in there I'd think...Any thoughts?

Well thats what I needed to know. I ordered my clutch today, I think that will hold me over until I can afford a new radiator. Anyone know who makes headers for these for a reasonable price? Mine is cracked badly and it sounds like crap.


Thanks

Thank all of you for your input.It really helps me on my problem. I think it is the bottle and cap it's not holding pressure.

Tony G said:

Thank all of you for your input.It really helps me on my problem. I think it is the bottle and cap it's not holding pressure.

Click to expand...

Quadratec (www.quadratec.com) sells the bottle w/ cap for $20. That's less than half of dealer price.

Summit Racing either stocks or can get the Moroso aluminum tanks. Those ise a standard radiator cap.

I was going to ask if someone els makes a better bottle and cap.

I see the Moroso tanks but witch one. The catch can or the overflow tank ?

One thing about the clutch. I was just informed that a lot of the clutches sold by the usual auto parts stores have an issue. There are tabs taht extend forward from the clutch that are too long, they can eat your radiator. So look around and get the one with the most clearance you can find. Alternatively (if you're feeling like dropping some money) you can get one from the dealer and it will drop right in. Another alternative is to modify the new fan clutch's tabs by grinding them a bit.

bottle and cap?

When you guys are talking about the plastic bottle and cap, are you talking about the one you put the coolant in- with the markings? I've never replaced my cap ever, but I dont see how it could ever hold pressure since it has a a litte vent in the side right below the cap? whats up with the aluminum bottle?