Overheating while towing

[Leica99XJ]

On the way to a campground today my 99 XJ overheated leaving me and my family stranded on the interstate. My camper is a small pop up that weighs less than 2k pounds. However the camper and XJ were fully loaded with gear for two adults and two children. This was our first trip in the new camper, the XJ didn't overheat when we picked up the camper, but we weren't loaded up.

Luckily it happened close to home and we were able to have someone come get the wife and kids, then the wife came back with our minivan and I put all the gear in the van. The XJ did fine on the way home with all the gear out of it.

Any guesses on what it could be? I recently have replaced the thermostat and flushed the cooling system for reference. Could it be the water pump is crapping out?

 

[jneary]

possibly the fan clutch

 

[j99xj]

Try running higher octane gas and downshift to a gear lower than what the transmission wants at the given speed/throttle position. (i.e. "D" to "3" or "3" to "1-2")

Higher rpms will turn your water pump and fan faster, but it will lower your gas mileage.

 

[Tim_MN]

Follow the towing instruction in your Owners Manual. It says do not tow in OverDrive (OD), tow in (3). Expand that to include no OD on long hills or steep mountain passes either. If you are towing anything, you should have a transmission cooler to help dissipate heat.


The cooling system is just that, a system, which depends on proper function from a number of component parts to keep the engine cool. Service the cooling system and replace any under performing or suspected weak parts. Any component part of the cooling system that is not fully doing its job will stress the others and your cooling system will overheat.



-Use a flushing/cleaning solution and then drain and fill the radiator with a fresh 50/50 coolant and water mix.
-Inspect the radiator for mud/bugs/grass clogging the outside and mineral deposits clogging the inside.
-Replace the thermostat with a STANT brand 195*.
-Replace the radiator cap. An old worn out cap will allow boil overs as the coolant flashes to steam. (Remember your High School Physics ?) You will see the coolant temps suddenly jump from 210* to the Red Zone if your radiator cap is weak.
-Inspect or replace the mechanical fan clutch. A worn clutch will allow temperature creep at stoplights and in heavy traffic. Looking OK and working OK is not the same thing.
-Inspect the electric cooling fan and the fan relay. Apply 12 volts and make sure the fan runs. Exchange the cooling fan relay with one of the others similar relays. Confirm that the e-fan starts when engine temps reach 215-218*. Repair or replace the fan or relay as needed.
-Inspect or replace the coolant temperature sensor that activates the e-fan.
-Replace the water pump. The pumping fins can deteriorate over time and the pump will not flow enough coolant to keep the temps under control.
-Inspect/replace the radiator hoses. Make sure the coiled wire is installed in the lower hose.


Read more about cooling systems here - http://www.offroaders.com/tech/engine-overheating.htm

 

[Leica99XJ]

What sucks about it is that it's an SE so I only have an idiot light to go by. It has the towing package though, and already has a trans cooler.

I've read on this forum about towing and the consensus was that towing in OD was fine (with trans cooler) unless you're towing up a hill, then to shift in 3. And I don't see how that would cause overheating of the cooling system.......Trans fluid yeah.

Overall I'm really disappointed with the towing performance. Before it overheated it seemed to have a really hard time, I doubt I had 3k lbs total, I don't see how people can tow with the 5klb max.

 

[Tim_MN]

I've read on this forum about towing and the consensus was that towing in OD was fine (with trans cooler) unless you're towing up a hill, then to shift in 3. And I don't see how that would cause overheating of the cooling system.......Trans fluid yeah..

What you read on some Forum someplace may differ slightly from what you discover while coasting to the side of the road with steam blowing from your engine compartment. The dash cluster with full instruments is a simple swap for any Cherokee, or just install a mechanical temp gauge.

(OD) causes additional heat to be generated in your transmission. Repeated shifting of the transmission into and out of (OD) generates additional heat as well. The auxiliary air to air transmission cooler on all models operates in conjunction with the internal radiator mounted main transmission cooler. The transmission oil is routed through the main cooler first, then the auxiliary air to air cooler, before returning to the transmission. That transmission heat is of course, is transfered to your coolant.

 

[Leica99XJ]

Ok, that makes sense, but at no time did it feel like the trans was hunting in and out of OD. If it were I would have downshifted into 3.

It just seemed like it had a really hard time getting up to speed, apparently that's where I screwed up, maybe I should be starting off in 3 working my way up to OD, or just stay out of OD completely? Like I said, it's not like I'm towing a 40 ft boat here, I own one of the smallest pop ups made, and for the Jeep to be struggling like it is just doesn't seem right. Maybe I need to buy something with a V8, I love my XJ, I just don't want to feel like I'm pulling an elephant with a hamster.

 

[Leica99XJ]

Also just remembered I was running the A/C too, probably didn't help things.......I guess the thread title should be changed to "How do I properly tow with an XJ"

 

[CharlesS]

Also just remembered I was running the A/C too, probably didn't help things.......I guess the thread title should be changed to "How do I properly tow with an XJ"

Well it looks as though you have zeroed in on the problem...
Even the best operating XJ cooling system couldnt handle a fully loaded vehicle, towing a trailer, running transmission in OD going up hills along with the A/C on....
As for the idiot gauges in a SE model; you can swap the cluster out as others have posted.... The item is easily purchased on Ebay.... for $25-70.
I swapped out mine about 10 years ago.... and have done several others since then.... The 97+ XJ doesnot require changing any sensors or connecting any wires.... Its just a plug and play item....

 

[RCP Phx]

Well it looks as though you have zeroed in on the problem...
Even the best operating XJ cooling system couldnt handle a fully loaded vehicle, towing a trailer, running transmission in OD going up hills along with the A/C on........

I do it all the time with my 3000# pop-up,A/C on and only shift when really needed.I do have a good tranny cooler though!

 

[kastein]

Have you checked to see if your radiator is badly corroded? I had barely any fins left intact on mine when I bought it, a new radiator and a coolant flush brought my temps from randomly overheating at 75mph on highway grades (no trailer or load) to never, ever overheating at 85mph with a heavy load.

When you look, look through the fan... otherwise you might be looking at the AC condensor by accident.

 

[mnoeltne]

When towing anything over about 2000 lbs I stay out of OD completely. I leave it in 3 and keep my speed under 65mph and have never had a problem. I tow a car on a flat bed trailer occasionally, and that weighs about 4000 lbs.

That said, your cooling system has to be in good shape to begin with. If the fan clutch is starting to go, or something else isn't working up to spec you will have problems.

 

[rocknxj]

Camping is my second greatest passion.

Last year, I towed my 3000 lb pop-up trailer with my '99 Sport and overheated on the way to the campsite. I anticipated this and had my wife drive my second vehicle with most of the gear in that. I was very disappointed, but I expected it to happen.

Last week, I towed the same trailer with my '99 Classic and it also overheated. That Jeep has a tranny cooler and the ambient temperture was cooler than the first event.

I am now convinced that the XJ is not the best tow vehicle I have ever had and have been contemplating selling it for a Grand Cherokee with the 5.7L motor. A cheaper route for me would bet to upgrade the intake and exhaust to a higher flowing system.

Until then, I have to lighten the load as much as possible, which is a real PITA, but it is necessary if I don't want to overheat.

 

[robert2008]

Camping is my second greatest passion.

Last year, I towed my 3000 lb pop-up trailer with my '99 Sport and overheated on the way to the campsite. I anticipated this and had my wife drive my second vehicle with most of the gear in that. I was very disappointed, but I expected it to happen.

Last week, I towed the same trailer with my '99 Classic and it also overheated. That Jeep has a tranny cooler and the ambient temperture was cooler than the first event.

I am now convinced that the XJ is not the best tow vehicle I have ever had and have been contemplating selling it for a Grand Cherokee with the 5.7L motor. A cheaper route for me would bet to upgrade the intake and exhaust to a higher flowing system.

Until then, I have to lighten the load as much as possible, which is a real PITA, but it is necessary if I don't want to overheat.

Or, you could find out what's wrong with your cooling system and fix it.

 

[RoyalXJ]

try running a seperate trans cooler. having hot trans fluid running through your radiator isnt helping it stay cool

 

[Jess]

I am now convinced that the XJ is not the best tow vehicle I have ever had and have been contemplating selling it for a Grand Cherokee with the 5.7L motor.

When was the grand offered with a 350?

 

[Leica99XJ]

Well I went ahead with the trip the next day, but took our Crown Vic along to lighten the load on the Cherokee and it still overheated. This time I kept in 3 the whole time, left the A/C off and even had the heater blasting with the windows open.

I'm pretty sure my trans cooler is external, I can see it in front of the a/c condenser unless it's an oil cooler, maybe someone can confirm.

On the way back it didn't over heat although it was all down hill so I attribute it to that. I'm also having the battery light come on now......Could I have been overloading the alternator?

I'm really starting to wonder if a Cherokee is a decent towing vehicle, cooling issues aside, it still seems to struggle with a very light load. An XJ might be alright for occasional towing, but for regular camping and road trips it might just be the wrong tool for the job.

[edit] And I'll be moving back to FL and camping during the summer, so not using the A/C will not be an option, and the high ambient temps (90+) won't help either. It was barely 70 degrees when it overheated this time.

Anything that's visible looks fine. The radiator looks new. The coolant is green and not dirty (last flush was a year ago), nothing is leaking and I replaced the t-stat when I flushed it. The only thing I can think of is a weak waterpump, or faulty fan clutch although it seems to be ok spinning it by hand and there is no visible fluid leaking from it. If anyone knows how to diagnose a water pump that would be great.

 

[Tim_MN]

... Service the cooling system and replace any under performing or suspected weak parts.....

It's a family vehicle and you are not 17 y.o. anymore, spend a few dollars and fix the problem. It is called Preventative Maintenance for a good reason.

I can tow my CJ-7 any summer day with my XJ and my temps stay under 220*.

 

[Leica99XJ]

It's a family vehicle and you are not 17 y.o. anymore, spend a few dollars and fix the problem. It is called Preventative Maintenance for a good reason.

I can tow my CJ-7 any summer day with my XJ and my temps stay under 220*.

Um, where did I imply that I'm not going to fix the problem?

Your theory about the transmission fluid causing the motor to overheat was wrong by the way.

 

[SuzysJ]

You also need to weigh the XJ and trailer, together and separately; empty and full. A genuine set of scale tickets to see where you are. That 5,000 lb rating diminishes radically on most 4wd XJs. Tall tires also ruin its abilities to tow. A weight distribution hitch is an EXCELLENT idea if tongue weight gets above 300-lbs (REESE Strait Line, "Dual Cam", is the one to have; accept no less); a vehicle equally loaded on both axles strains a bit less (and the safety factor is increased greatly).

I'd start from scratch on the cooling system. All new components. Remove freeze plugs and block drain to get crud out of bottom of cylinder jackets. Be sure to use de-ionized water and proper coolant. Fan shroud should be new or undamaged, same with fan clutch. Etc.

I shimmed the rear of the hood on mine with washers. Removed weatherstrip except in front of HVAC intake. This keeps the air moving.

I've towed a number of times with the XJ's we've had (up to 3000-lbs, scaled) at about 60 mph in 105F Texas/OK/MO heat. No problems, but cooling system was kept perfect from new. Added big downstream stack-plate cooler for ATF.

Avoid the mistakes I made as a younger man and re-do the whole system from the get go. (I prefer the ROBERSTSHAW "Balanced" design thermostat; none better). Also, check engine compression per cylinder as well as blowby; also check for exhaust restriction.

Have the axle aligned on the trailer, check for brake drag; service bearings if one year since last.

Good luck.