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overheating only when i tow???

J

jokerjosh1

NAXJA Forum User
Location
tennessee
99 xj with a new thermo, waterpump, and thermo housing. my jeep always is a few degrees past 210. everytime i tow my small 1200 lb camper ( 6.6 wide 10ft long ), it overheats. i have flushed it 3 times and it still does it. i have just ordered a new 2 core, 1 in line all aluminum radiator ( should be here this week ). will this be enough or should i convert to having all electric fans too? thanks for any info
 
An external transmission cooler will help. When towing, you are using 3 instead of D, right ? The overdrive generates excessive heat when towing.
 
Most of the heat when towing comes from the transmission, follow Tim_MN advice and get a transcooler if you plan on do a lot of towing.
 
Not sure I would do it in TN because of the winters but in AZ I bypassed the radiator when I added my tranny cooler. Maybe rig a couple ball valves so you can go back to the radiator in the winter.
 
You can still run the transmission cooler for the colder weather, just plumb it in so that fluid flows from transmission to cooler to radiator instead of trans to radiator to cooler. That will prevent the transmission from heating up the radiator, but still keep fluid heated up during the winter.
 
Tim_MN said:
An external transmission cooler will help. When towing, you are using 3 instead of D, right ? The overdrive generates excessive heat when towing.
Click to expand...

Is it necessary to use 3 instead of D if I have a B&M supercooler on the return line? I overheated twice so far, once with so much weight and once recently while towing a trailer. I ordered the supercooler and gonna install it on the return line after the radiator. I just want to take the proper precautions to prevent it from overheating again. I did have the transmission flushed today to get the old fluid out before the install of the cooler.

(overheated: transmission overheated, spitting fluid out of the dipstick and creating a smoke show behind me)
 
Last edited:
overdrive generates excessive heat when towing
 
/\ the 'blank area' on most XJs above the cigarette lighter makes a good place to mount it. If you're lucky you have one of those neat (and kind of goofy) 'monitors everything' idiot light array. I'm not a fan of idiot lights, but those things are pretty neat.

Change your trans fluid+filter ASAP after overheating the transmission.
 
hubs97xj said:
Might want to throw a trans temp gauge on it, too. For $60, it's cheap piece of mind, at least compared to repair/replacement.
Click to expand...

Gonna....but not at this time. I'm tight on $$ cuz I'm moving so all I can do right now is install the supercooler so I can haul this load of trash to the waste management site.

I plan on using the B&M trans temp gauge.
 
hubs97xj said:
Might want to throw a trans temp gauge on it, too. For $60, it's cheap piece of mind, at least compared to repair/replacement.
Click to expand...

Sorry to disagree but a trans temp gauge is a waste of money. I do not believe It will give an indication that is actually useful. The OP should have noticed that before he started burping fluid, he was overheating. Overheating is a sure sign extra heat is being dumped into the radiator and they system is unable to normalize it.

One should tow in 3rd, not OD, and not tow anything with a total weight of 5K lbs (assuming he has a class 3 hitch). Also the tongue weight can not exceed the rating of the hitch. And seeing as Muddeprived baked his transmission fluid, he should change it.

Though I have occasionally pulled an XJ behind me, the XJ was never intended as a tow vehicle, but to occasionally tow the family boat around.

Adding a transmission cooler can extend the life of the transmission by keeping things a bit cooler, but if you are torturing the machine by towing in the wrong gear, insisting on doing 75 with a full load, or jack rabbit starts, you will fry your transmission regardless of what the tranny temp gauge says.

Just my 2C FWIW. Proper operation of your vehicle is the key, and in the time of the internet, failing to research your tow ratings and tow operation before setting off on an adventure is... well, there is no excuse for it.

-Ron
 
WB9YZU said:
Sorry to disagree but a trans temp gauge is a waste of money. I do not believe It will give an indication that is actually useful. The OP should have noticed that before he started burping fluid, he was overheating. Overheating is a sure sign extra heat is being dumped into the radiator and they system is unable to normalize it.

One should tow in 3rd, not OD, and not tow anything with a total weight of 5K lbs (assuming he has a class 3 hitch). Also the tongue weight can not exceed the rating of the hitch. And seeing as Muddeprived baked his transmission fluid, he should change it.

Though I have occasionally pulled an XJ behind me, the XJ was never intended as a tow vehicle, but to occasionally tow the family boat around.

Adding a transmission cooler can extend the life of the transmission by keeping things a bit cooler, but if you are torturing the machine by towing in the wrong gear, insisting on doing 75 with a full load, or jack rabbit starts, you will fry your transmission regardless of what the tranny temp gauge says.

Just my 2C FWIW. Proper operation of your vehicle is the key, and in the time of the internet, failing to research your tow ratings and tow operation before setting off on an adventure is... well, there is no excuse for it.

-Ron
Click to expand...

I agree with you. I did research how much the jeep can tow but never knew about using only 3rd gear. I never towed before so it was new to me. I was towing a half full trailer that only had maybe 200-300 lbs of junk in it and drove slow the entire way until I got on the freeway at 55 mph. It was just the damn hills around here are so long that you have to keep shifting to maintain speed.

(this is what i was towing. It was only 1/4 full, not as shown in the pix)
PIC-0499.jpg


I did have the transmission flushed yesterday so it's all good with new fresh fluid. No signs of any strange shifting or anything.......for now. I'm gonna install the cooler 2nite.

I do prefer to install a temp gauge. I believe it can be useful by telling me if the transmission is getting too hot (if it ever does again) and then I would know to pull over and let it cool down than keep on driving and overheat it.

By the way, one question I have is which is the best side to mount the cooler on? The mechanical fan side or electric fan side? I have a fan switch that allows me to turn on the e-fan anytime i need to. Not sure if that would be of any benefit.
 
Mine has the factory cooler (tow package, or whatever) and it's on the efan side, lower half of the radiator.

I have a nearly new GM truck trans cooler scored from a 'man sale' for $5 waiting to go in my XJ, but I'd rather just swap in a manual gearbox :). Almost scored one locally, but was too late. :(
 
Do not bypass the tranny cooler on rad, go from rad cooler to external cooler then back to tranny. You will not over cool in the winter due to the fluid in the torque convertor begin even hotter than the fluid in the pan.(temps you want are 100-170 degree's).
 
Sorry to state the obvious but OF COURSE...if it's going to overheat it'll do it when towing. Try this test ~ walk up a hill on a hot day, you'll sweat.
Now, put on a 50 pound backpack and walk up the same hill. Do you sweat more? Yeah, I thought so...so you overheat when you have more of a load...I think they call that physics. Your personal cooling system HAS to work harder.

ChevelleSSLS6 said:
the 'blank area' on most XJs above the cigarette lighter makes a good place to mount it.
Click to expand...

You mean like so?

trans003.jpg


WB9YZU said:
Sorry to disagree but a trans temp gauge is a waste of money... One should tow in 3rd, not OD, and not tow anything with a total weight of 5K lbs (assuming he has a class 3 hitch).
Click to expand...

Well seeing as how the trans gets hot when you least expect it too, it's a pretty decent tool, especially for about $25. The OP says he's towing a 1200 lb. load...not a 5th wheel. My tranny gets hottest going up a dirt road, loaded with gear at about 35 mph. Hauling butt up a 6% grade in OD it runs around 150.

maxwedge said:
Do not bypass the tranny cooler on rad, go from rad cooler to external cooler then back to tranny. You will not over cool in the winter due to the fluid in the torque convertor begin even hotter than the fluid in the pan.(temps you want are 100-170 degree's).
Click to expand...

If you live in MN or the UP of Michigan or Buffalo or North Dakota...do not bypass the radiator. If you live in AZ, CA or TN it won't hurt a thing. If there is a cold snap you can add 1 18" piece of 3/8" hose and include the rad loop at will. MY XJ has been set up this way for years and never had a single problem.

How hot is your tranny?? Why does it matter??

TransLifeChartfromHECATInc.jpg
 
Right back into the 1960's, the factory -- on tow packages and police cars plus other HD -- plumbed the auxiliary cooler downstream of the main cooler in the radiator tank. You are unlikely to "overcool" ever even if:

- The cooler is mounted in the flow of the mechanical engine fan (but not attached to radiator or A/C condenser);

- And a stack-plate cooler with integral bypass is used (B&M RACING) that won't try to cool "cold" fluid.

I would also add a filter downstream of this (such as MAGNEFINE), as

- The factory pan "filter" is really only a screen
- And it's a pain to access, so only the auxiliary filter needs to be changed in the future when changing ATF.

With a temp probe installed in the pan at this time, it's the last for dropping the pan.

On the other hand, bypassing the radiator tank means the ATF is slow to come up to operating temperature, an overall bad idea.

.
 
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