XJ temperature problem - is this typical?

In searching this and other jeep forums, I get the feeling that the stock XJ cooling system is inadequate for the most part.

My girlfriend's XJ, on it's first long trip under her ownership, started exhibiting some overheating behavior, I just want to know if this is the typical behavior for an XJ before tearing into it:

truck will cruise at 55-65mph all day long with a/c on around 220 degrees. about 215 with a/c off.

Cruising at 75 with the a/c on, causes truck to creep well above comfortable, prompting us to slow down and turn on the heater.
(speed limit is 75 on I-10 in AZ)

Engine sits below 2500 RPM at 75mph (i'm used to 3100 in my truck!) and transmission doesn't feel like it's slipping, doesn't shift erratically. Flat ground.

1987 XJ wagoneer 4.0L automatic / NP242 (in 2wd) and 3.55 gears on 205/75-15 street tires.

Is this how the cooling issues usually look?

Possibilities

I am assuming that the cooling system is the closed system.This system is known for it's "trapping air" in the system.There,are a couple of things you can do.
1.Make sure all hoses are tight and not cracked at all connections.
2.Backflush the system,and change the thermostat.using a 180 or 195 deg thermostst.The thermostats from the dealer supposedly have a 1/8"hole in them that permits the air in the system to escape.
3.Swap out the closed system to the newer open system.
There should be a write up some where on there forumns.
You can also try this site:Cherokee [email protected],there is an excellant writeup on the the swapout procedure.
If the site doesn't work,lemmee know I may have typed the addy wrong,but I do have a copy of the write up so I can PM you the addy.

Eagle and others here would argue that the open system is not inherently better than the closed system, and a closed system in good shape will cool adequately. It is a little more touchy than the open system, though, and among other things, the tank cap is a weak spot, liable to lose pressure and cause overheating. The open system is easier to service and maintain. If it's taking a long time to overheat, I doubt trapped air is the problem. But at that age, it's pretty likely that your radiator is sick. I don't know where you're from, and whether corrosion is a big deal there, but your symptoms sound very much like those I've had with both types of system when the radiator itself began to lose its cooling fins to corrosion (a common thing in the northeast) . This doesn't affect the integrity of the system - it won't leak, it will warm up normally, run fine while cruising, etc. but it just won't carry off enough heat when the going gets tough. At the very least, you should get it well flushed, but also check carefully for fin deterioration.

The closed XJ system is a pain, until you learn the ins and outs, like burping the system. Any kind of tiny leak (some evaporate before you can see them) will eventually suck some air. I squeeze the top radiator hose with two hands repeatedly, to be repeated on consecutive days or until the fluid level stops falling in the canister (surge tank). Never let the surge tank get empty.
Your post says Arizona, one thing often overlooked, is the radiator being plugged in between the fins, between the layers. Pollen, dust, dirt, mud get in there and somewhat wash off the outside front, but still partialy plug things up between the rows. Washing it out, with a hose from back to front, sometimes helps (probably have to remove the electric fan). Take it easy with the pressure, so you don´t bend the fins flat.
When I lived in Arizona, washing the radiator outside (amazing how much pollen and dust comes out from between the fins), a yearly flush and a good coolant mix (antifreeze also helps get rid of heat), where a must.
Another overlooked cooling problem, is the gasket by the thermostat, the OEM gasket has a cutout for a partial bypass of the thermo (universal gaskets don´t), which keeps actual engine temp coolant, by the thermo. It often opens slower without the bypass. Have also seen many paritally crushed thermostats, the OEM is a little shorter than many thermos, some parts stores sell a universal thermoatat, that won´t fit in the elbow, without crushing. Even the OEM thermo can be crushed, if the "TOP" marking isn´t at the top. Don´t remeber seeing it in a Jeep, but over the years have seen more than a few thermostats installed backwords.
I cruise all day long at 80-90 MPH, only time it heats up, is traffic (idle) or long periods at low speeds.

The XJ's cooling system is not "inadequate," but it is essentially just "adequate." Both because of space limitations and because in these times no manufacturer engages in over-engineering, the system works when new and when properly maintained, but it can't last forever.

The radiator on my '88 started overheating in '98, and late in '99 it spring a leak. When I removed it, I found that the fins were all brittle, and the cores were significantly occluded with corrosion. If the GF's XJ is an '87 and still has the original raditor, I think that's the problem. The internal corrosion, even if the fins aren't falling off, both impedes the flow of coolant AND impedes the transfer of heat from the coolant to the metal of the tubes.

I generally am pretty good on maintenance, but after seeing the inside of that radiator I have revised my approach to cooling system maintenance. I now use only Zerex 5-year coolant, and I change it every two years. And I use only distilled water. My well water has a high mineral content, which can't be good. City water has chlorine, which also can't be good. Distilled water is 69 cents/gallon at any Wal-Mart, so IMHO that's the only way to go.

Thanks for the great responses guys!

We're in Arizona and it's an AZ truck (so says Carfax) - so no external rust whatsoever. We've also rinsed out the radiator and I have peeked at it wherever possible to look for dust or other obstructions, it's clean enough to eat off.

I think you might be right about either a thermostat related problem, or an air bubble problem.

It does take quite a while to heat up, which would indicate that it is a cooling system problem not a mechanical problem creating excess heat. Also the cooling issue is only at high speeds, (never in city traffic) which indicates that it's not a fan problem. The previous owner's records, plus the presence of orange gasket sealer where expected, indicate that the water pump was replaced ~10k miles ago.

When we first noticed the cooling issue Saturday on the way to mom's house, we stopped by a Walmart and picked up antifreeze, then at mom's I opened the drainc0ck on the radiator (after bleeding off pressure) and thoroughly flushed the system by repeated drains and refills (with a brief startup inbetween to push out the coolant in the block) , then refilled with water only and a half-cup of liquid laundry detergent, took a drive, drained and refilled a couple more times, then refilled with distilled water and coolant in a 66/33 mix. (based on manual's stated 12 qt specification) -

This flush dramatically improved the color of the coolant, from sick brown with a slight green tinge, to the vibrant green we're used to. It did not, however, affect the cooling issue at all.


So, this week I'm going to pull the thermostat out and inspect it, and pick up a new one from the dealer. If it doesn't happen to have a little burp hole at the "top" I will drill one, and I'll follow your suggestions for burping the system. I'll post back with the results.

We may end up replacing the radiator shortly, if that's what is needed. I think for the sake of easier maintainance we might convert to open system at the same time. What's the recommended radiator for that?

Thanks again!

:cheers:

The recommended replacement radiator until recently was the GDI 3-core, but more and more people have been reporting problems with their quality control. The consensus seems to be moving toward Modine. Both GDI and Modine have models for the old style and new style XJ system. If you feel you must convert, get a radiator for a '91 or newer XJ -- that's the conversion.

Just be certain that you're going to be prepared to deal with the side issues if you convert. The new style does not have a bung in the driver's side tank for the auxiliary fan control switch. You will have to find another way to control the fan. A simple toggle switch will work, but that requires that the driver wtach the temperature and remember to flip the switch. While I might accept that for myself, I would not impose that on a wife or GF.

While the radiator is probably the main problem, I noticed on my 90 XJ the reason for the overheating problems was the coolant bottle. It used to take a really long time to warm up, even in the summer. I found that the cap on the bottle wasnt holding pressure. I changed it (actually changed it with another bottle from a grand am) and it started holding pressure and warmed up like it was supposed to. I dont lose coolant any more and havent overheated since. It takes a few mod.s to change to a bottle from a Grand Am, but very simple. I changed to that bottle because it has an actual metal radiator cap. And I had just replaced the radiator so I didnt want to buy another "Open" system radiator when I had a perfectly good "Closed" system radiator. This is the link I used on how to change out the bottles if you are interested.
http://www.cheapxj.com/pontiac.html

I found my bottle on late 80's grand am's. There are other pontiac's that have the same bottle, just cant remember.

90red

The only way I´ve found to check for obsruction between the layers is a flashlight, shine it from the inside out (have to take the grill off and the electric fan). Have also used a dental mirror to get a look inside the closed type radiator. I use rain water (have a rain barrel), filtered through a coffeee filter (good enough).
Does the early XJ have left and right water pumps for various belt routings and accessory packages? I don´t remeber seeing it before on Jeeps, but on other makes. Contrary to logic, a left pump on a right turn, won´t pump backwords, but forwards poorly.
Like Eagle mentioned, I´ve seen radiators deteriorate to the point I could crush them between two fingers.

I was just thinking: would an obstructed fuel filter, or weak, or plugged injectors cause this high speed overheating condition by causing the engine to run lean?

thanks

Should be enough advice here to fix your problem. Main problem I had with my overheat was the stupid little O-ring on the pressure bottle wasn't holding pressure. Pressure raises the boiling point of the coolant. No pressure or less pressure means boiling coolant or decreased cooling ability (3 degrees per psi I think). 5 bucks for a new pressure bottle cap and my troubles were over.

Check that o-ring and where the hoses connect to make sure you don't have a leak. I went with the GDI radiator and havn't had any problems at all- a HD radiator is a good idea for the xj if you plan on doing any kind of wheeling in it or spend any time in heavy traffic.

Lean is pretty easy to check, but a little misleading in a computer controled vehicle, they run (should run) pretty lean anyway. Yank a few plugs after a moderate speed drive and have a look while they are still warm. Very light grey is optimum, white is the norm, white with peeling/blisters usually means a bit too lean. Can also have a look in a few cylinders if, you get just the right angle (probably need a mirror and flashlight), you can see some of the top of the piston, at the top of the stroke. If there is any kind of pit in there, get a set of colder plugs, quick (check for manifold leak).
A lean motor will heat you up at high RPM´s, as will a slight exhaust leak (usually at the head gasket) into the cooling system. The coolant will usually foam up pretty good or you can see some air (exhaust) bubbles in the coolant. Usually have a slight but steady loss of coolant, that becomes noticeable. But head gasket problems, are rare in the inline six (fairly common in the V-8´s).

1. The caps on the 'closed' systems are very susceptible to damage from OVERTIGHTENING. There is no 'stop' and no torque specification.
Tighten by hand to what an average woman can achieve; do not play body-builder and crank it down, or it will crush/twist/cut the gasket.

2. The mineral deposits from Phoenix-area water are among the worst in the nation.
* Use ONLY anti-freeze and bottled purified water (not drinking water which has tasty minerals added).
* To remove the mineral scale from the inside of the radiator tubes:
** Take radiator to reputable radiator shop and have it cleaned/rodded.
** Or, use a MILD acidic solution like Prestone Flush according to label directions.
Detergent may remove dirt and oily substances, but it cannot dissolve hard mineral deposits.

3. The radiator must transfer heat to flowing air.
* At low speed/city driving, the fan(s) moves the air.
* At highway speeds, it is the vehicle speed thru the air that forces air thru the radiator.
** A winch or lights in front of the grill will significantly reduce air flow thru radiator.
** The fluid clutch in the mechanical fan must STOP rotating at highway speeds, since the spinning blades act like an 'air brake' (actually, like 'reverse pitch' on an airplane propeller) and restrict airflow.
** Many XJer's state that removing the rubber splash shield under the radiator allows MORE air to exit the back of the radiator and thus improve the air flow. The shield is there to reduce water splash up onto the alternator.
** Some XJer's have removed the plastic air dam below the bumper. It's my personal belief that this dam creates a low-pressure area behind it, which assists good air flow thru the radiator. I believe removing this dam adversely affects good flow of cooling air.
** Some XJer's have added hood louvers to allow better flow of hot air out of the engine bay.

4. If you have an auto tranny, it could be slipping at the higher highway speeds and putting more heat into the radiator tank.
* Consider a regular tranny service (fluid + filter) or even a complete fluid flush/replacement.
* Consider having the bands/clutches adjusted (tho I don't know what this consists of on your model).
* Consider adding an aftermarket AT cooler, separate form the radiator.

5. I assume you have AC, so what you see as clean and clear when you look thru the grill is the AC condensor, not the radiator. The rad could still be significantly blocked with bugs or baked mud.

Good luck.
-Rick

Barely..

I know I'm a little late in giving you useful feedback, but I'll tell you anyways. My 93, open system, overheated quite a bit when I got the Jeep. It would run relatively normally on the highway, ect, but if you were to stop or idle for a bit, it'd shoot up to like 230/240...waaaayy too hot. But, i flushed the system thoroughly, and I replaced the thermostat with a 180. The problem has gone away and the system is just strong enough to keep it below 220, and usually at like 200. Also, is your auxiliary fan working? It should go on to help the system out.

Good Luck,

Christian

I just found this thread again while searching for alternator info and figured I would post a follow-up.

As was speculated by several of you, the radiator itself was just plain bad.

We got a replacement radiator made by GDI, 3-row core, for a 1991+ cherokee and converted to open system. The aux. fan is controlled by a Summit Racing thermal controller I had left over from my old 4x4. The truck hasn't been hot enough yet to turn it on, i've been considering obstructing the radiator (in the driveway) to force a hot condition under controlled circumstances, to test the operation of the temperature switch.

We are using an aftermarket catch can for overflow retention.

The good news is, this has more than fixed the overheating problem. Her old radiator was clogged and the fins were separating from the tubes... in addition to several "weeping" spots on the tanks and fittings. Now it takes several minutes for the engine to heat up at all, and it never gets above what I assume is about 180 degrees on the temp gauge under any conditions. (granted, it's winter.. )

Re: Barely..

csmadore said:

...Also, is your auxiliary fan working? It should go on to help the system out.
Christian

Click to expand...

About what temperature should the aux fan kick on?

8700XJS

Thanks for posting the follow-up. I wish more people would take the trouble to do that, because knowing what worked for one person helps the next time someone experiences similar symptoms.

A quick check for a rotten core is to run your fingernail across the fins using the backside of your fingernail with light to medium pressure,you are not trying to bend the fins only deflect them. If the fins are still good they will depess a bit and then spring back, if they are 'rotten' they will stay bent over. The copper fins do deteriorate after a few years, here in the NE where there is heavy road salting they last generally about 8 years or so.

Mine is always around 190 200 , i put a diff. thermostat in and that helped.