• NAXJA is having its 18th annual March Membership Drive!!!
    Everyone who joins or renews during March will be entered into a drawing!
    More Information - Join/Renew
  • Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

XJ Cooling System Deficiencies & Solutions

I spent a lot of time with the local radiator shop trying to pick out the best radiator for my XJ. We concluded that since the old radiator was clogged and it was a 19 year old jeep, I should find one with larger diameter tubes. A 2 row has larger tubes than a 3 row and tend to clog sooner according to them. The shop recommended that if I was to rebuild the motor and clean all of the passages, then a 3 row would be the best.
 
Was I the only one who saw 125 mph at first, THEN saw the decimal point? I was thinking, 'holy s#!t, those guys wheel HARD!'

:)


haha. Its funny you should say that, since terminal velocity on that rig with the stroker seems to be 62.5 mph (exactly half of that).

spinning 40's aint easy.
 
Well, Cal, it isn't totally stock, it does have an aftermarket radiator. But everything else is stock including the closed cooling system with the stock plastic expansion tank, on a well built stoker motor. And besides running flat out for miles of desert with soft 40" tires, it's finished 2 King of the Hammers races which is arguably the most grueling one day offroad endurance race on the planet. The car developed such extreme heat from the exhaust that we've melted things and had to put extra heat shields, and the exhuast still melted the rear locker air lines when we thought (like 5 times) that we had enough heat protection. You can NEVER generate the amount of heat in even hard regular wheeling that you do when racing. Yet, the engine temps stay fine all the time.
 
Mr Barfly, I know you're trying to be constructive, and I know you're speaking from experience. As the other readers of this thread will do, the experience of others also needs to be included when drawing conclusions.

We all know that XJ's will eventually overheat when the cooling system has a problem. The systems need to be kept in good condition, including flushing the motor. We also know that they eventually need a larger than stock aftermarket radiator, especially when we load them up with heavy parts and gear. However, the rest of the parts in the system, like the clutch fan, electric fan, thermostat housing, etc, work just fine stock. Tons of examples of peoples experience to confirm this.

Personally, I've had 2 built XJ's with stroker motors that I've run hard, with 37" and bigger tires, on the highway and offroad, with no overheating issues and completely stock cooling systems other than a better radiator. Before putting the stroker in the XJ, I drove it on many trips from central CA to Utah and Colorado, and with the 170k motor and the weight of the rig, it seemed like the pedal was to the floor for half the trip going up and down all the hills on the interstate......and no overheating. Everything stock except the radiator. I've wheeled as much or more than anyone I know (other than AZRick) and never had cooling issues on the trail, unless the cap on the expansion tank was bad or I forgot to turn on the aux fan.

The "for profit" engineering argument is so outdated and overused it's become silly to read. The market demands good products. Sure, costs are cut where needed, but that doesn't automatically mean that everything we buy is underengineered because the company making the product is trying to make a profit. C'mon man, EVERYTHING we buy was made so a profit can be made, so based on your logic every product made is marginalized for profit. That's just not true. Sure, there are inexpensive products that compete with higher priced better quality products, but we as consumers have the choice of which we want to buy. There are surveys and reviews very readily available and people do research, it is good business to engineer a good product.

My '96 F250 with a gas 460 motor had an engine oil to water cooler. Very few people even knew they had that. The engineers didn't include that to save costs, they added it to let the engine work harder for longer.....even though most wouldn't even know it was there.
 
I have had my share of problems with my cooling system also. It all started after I stroked my engine and pulled my AX15 out and replaced it with an AW4.

I now have a 3 row aluminum rad, high flow H2O pump, good T stat, Ford Taurus elec fan, removed mech fan, hood vents, hood spacer etc. I did everything I could think of and still did not have the capacity I needed when wheeling slow on hot days in hot weather going up long nasty hills. I am talking about gaining elevation for an hour at 5 Mph.

I finally pulled the A/C condenser out so it could no longer block air flow through the rad. Removing the condensor made the largest improvement of all mods. I thought I had done all I could do. Then spending 3 days on the hiway in 95 deg F heat I found my coolant bottle was down, almost empty. This told me I had a air bubble trapped in the system which had been causing me trouble all of this time (for years). I topped up the coolant bottle and the system has worked better than ever. My main problem now is how the hell do I get the air bubble out next time? I have read all of the posts on how to do this but it doesn't work on mine.

By the way I would still highly recommend doing the Ford Taurus fan upgrade. It is nice to flip the fan to high speed when you see the temps climbing. It gives you flexibility when there was none before.

For the people who say the cooling system is adequate I say you are lucky! Because if you have one of the many jeeps out there with cooling problems they can be very very hard to fix.

I have since mounted my transmission cooler on the roof inside my safari rack. I ran stainless lines up the passenger side piller to the roof. Its definantly outside the box but I had to prevent that thing from dumping more hot air into the engine compartment.

I will have to see how the cooling system works this summer after all of this.
 
True. The most efficient heat transfer will occur with the largest temp delta though, I guess it's not so much "wasted" as... not as efficient as the hot end of the tubes. Good point on the tanks, though I tend to think with plastic end tanks it wouldn't be as much of an issue at least - taking up that much more frontal area obviously is still a problem...
The closer the fluid temp gets to ambient temp, the slower the heat is transfered therefore the less efficient the radiator is.
 
................................. My mechanic points out that for starters an XJ is significantly larger and heavier than a Wrangler so that alone puts added stress on the cooling system.
dn



I would find a new mechanic. Xjs weight less than a tj........all day long, everyday.:wave1:
 
I would find a new mechanic. Xjs weight less than a tj........all day long, everyday.:wave1:

According to cars.com. I'll compare my '98 4dr sport 4x4 to a '98 TJ 4x4 Sahara.

XJ
Curb weight - - - 3,181 lbs
GVWR - - - - - - 4,901

TJ
Curb weight - - - 3,073
GVWR - - - - - - 4,360

So, I guess my XJ can haul more people & cargo (makes sense) but it does weigh less sitting at the curb. Interesting, thanks for posting that fact up Turf since I was obviously mis-informed. :anon:
 
You need to do better research. ;)

1998 TJ.

Dimensions and more specifications
•Wheelbase: 93.4 (2373)
•Track: 58.0 (1473), front and rear
•Length: 147.7 (3756) to bumper, 151.8 (3856) to spare tire
•Width: 66.7 (1693)
•Height: 68.9 (1750) with hardtop, 70.2 (1783) with soft top, 68.2 (1732) with no top
•Ground Clearance at curb weight:
◦Front Axle
: 8.0 (204) min.; 9.6 (243) max.
◦Rear Axle: 7.9 (202) min.; 9.5 (24) max.
◦Running: 9.7 (246) min.; 11.2 (2847) max.
•Approach Angle, Min.: 42.5°
•Ramp Breakover Angle, Min.: 25.5°
•Departure Angle, Min.: 30.5°
•Payload Capacity (Includes All Occupants & Cargo): 800 lb ( 363 kg)
•Frontal Area: 28.2 sq ft (2.62 sq m) hard top; 28.3 sq ft (2.63 sq m) soft top
•Drag Coefficient: 0.55 hard top; 0.58 soft top
•Gas tank: 15.0 gallons (57 liters) standard, 19 gallons (72 liters) optional
•Cargo Volume:
◦Rear Seat Up: 10.9 cu ft (309 L) hardtop; 11.3 cu ft ( 320 L) soft top
◦Rear Seat Folded: 35.7 cu ft (1011 L) hard top; 36.9 cu ft (1045 L) soft top
◦Rear Seat Removed: 53.5 cu ft ( 1515 L) hard top; 55.7 cu ft (1577 L) soft top
•Curb weight: 3,092 lb (1,403) with four-cylinder, 3,229 lb (1,465 kg) with I-6
•Gross vehicle weight rating: 4,360 lb (1978 kg) with I-4, 4,380 lb (1,987 kg) with I-6
•Weight distribution: 49/51 with four, 51/49 with six
 
Jeeper John -

Absolutely true... however after it has flowed through the engine it is practically impossible to have coolant entering the radiator that is even close to the ambient air temperature.

The exception are:
A) when the engine is cold - the thermostat is closed & the water pump is circulating coolant.
B) in a freezing climate when it may take a long time for the engine to warm up. The thermostat stays closed until the coolant in the block up to the thermostat's temperature. An engine block heater is a great way to get the engine up to operating temperature.

Conversely, the colder you can return the coolant to the engine block, the greater the heat transfer to the coolant. The thermostat modulates this exchange & keeps the temperature of the coolant within the acceptable range.
 
Sorry to hear of the blown freeze plug heater. Check out the Kat's 10611 engine block heater. It has a SS wingnut/bar inside of the block that prevents the press-in heater plug from blowing out. It's 600 watts. The one in my block works great.

I wired a battery heater & engine block heater cord together into a waterproof plug just outside the grill. The mated end is on a 100' 10GA extension cord. You can pickup a "waterproof" cord end set at any contractor's electrical supply (circuit panel, breakers, etc. not diodes, transistors, etc.). They are used for a service disconnect for sump pumps, underwater lights, feed trough heater, etc.

When I was learning to rebuild Chevy strokers as a kid, one of the first things that I was taught, was to thread the block & install threaded brass (or even better stainless steel) plugs.

Contrary to the "street mechanics," freeze plugs will not save your block in the event of a "deep freeze". They are really there to allow the foundry plant to remove the debris from the inside of the block & passageways. Re-builders find them helpful when cleaning out a block.

To prevent them from "blowing" try threading the block with a pipe thread tap. Install a threaded pipe plug with a recessed hole for an allen's head wrench. The larger one's will have a raised lug to grab with a wrench. Plus the thicker "plug" will be more resistant to corrosion, damage, and it is almost impossible to set one into place crooked (end therefore susceptible to leaking, coming loose or blowing out).

To keep my engine warm when in the Sierra's or Rockies, I have installed the following:
Kat's Battery Heater 22200 ($25) (GM has one for about $22 PN:10954544)
Kat's 10611 freeze plug heater - 600 watts

When the need arises to rebuild my engine, I'm going to try to use a threaded SS/Brass reducer bushing, to reduce one of the 2" freeze plugs holes down to 3/4" and use a threaded heater (like Kat's 11409). I just don't know if I'll get enough clearance inside the block to clear the heater element.

The engine is ready to go on those Arctic mornings. And the interior heater can contribute to my heat sooner!
 
Last edited:
Contrary to the "street mechanics," freeze plugs will not save your block in the event of a "deep freeze". They are really there to allow the foundry plant to remove the debris from the inside of the block & passageways. Re-builders find them helpful when cleaning out a block.

I am a marine (boat) mechanic, and you have no idea how often I have to have this conversation with customers, usually after finding out that they have a cracked block.
 
I am a marine (boat) mechanic, and you have no idea how often I have to have this conversation with customers, usually after finding out that they have a cracked block.
The best protection against a cracked block from freezing is a proper mix of antifreeze in a street vehicle or making sure the engine block is dry for a boat.
 
The best protection against a cracked block from freezing is a proper mix of antifreeze in a street vehicle or making sure the engine block is dry for a boat.

True, but when we winterize, we run them through an environmentally safe marine anti-freeze for added freeze and corrosion protection.
 
has anyone experimented with one of those lightweight flex fans and a solid coupling? they move a whole lotta air at idle, just don't drop any tools in there, they become projectiles :eek:
 
Back
Top