Cooling Question

[Bald Eagle]

I have owned my 1992 Jeep Comanche for the past 24 years.  It has the 4.0L with the AW-4 automatic transmission.  4.11 gears front and rear with 31-inch tires.  Two years ago, I replaced the idiot light panel with a panel with gauges.  All through my history of driving this truck and towing a 1,000 lb. teardrop camper the lights never came on or did the vehicle overheat.  This past year I installed a new CSF heavy duty radiator and cap, new OEM clutch fan and electric fan, high flow water pump and thermostat housing, 195 thermostat and temperature sensors.  Plus flushed the system.  And did I mentioned I replaced the hoses and tried both a standard water pump and the high flow pump, and checked the temp at the sensor with a heat sensor and it matched the gauge pretty close.

The temp gauge will normally read 210 to 212.   I live at 7,200 feet and when climbing up mountain roads with just me in the vehicle and not towing anything, the temp will hit the red line.  I tested this on a local road that is about two miles long with an elevation change of about 800 feet.  I don't believe this should be normal, and I can understand if I was towing my trailer.  I also own a 1992 Jeep Cherokee that I have owned for the past 29 years, it has the 5-speed standard, and it has no problems and normally runs about 200 degrees with all stock components.

Any thoughts on the overheating Comanche?

Thanks!

[motownXJdad]

i flush my XJ every spring and fall. these 4.0 XJs and MJs cooling systems seem to run dirty from what ive seen. i live in the Detroit area, in the summer we get in the 90's often with very high humidity like Florida, or south texas. my 2000 XJ with a new motor, water pump, and stock style radiator would run way too hot with my AC on to the point of nearly over heating. i had to turn the AC off and stop a few times.  so i incorporated alot of the tricks from naxja.org etc. i started with a ZJ fan clutch, then a 180° Stant Tstat with a 1\8" weep hole drilled at the top, my pump and radiator were good, less than 2000 miles on them, so i moved on to adding a switch inline on my factory Efan. i used my factory rear wiper switch, becuase ive never used a rear wiper in my life. i run a 70% water 30% anti freeze mix in the summer, 50\50 in winter, swapping out and reverse flushing the heater core every fall, and spring. I also use Waterwetter coolant additive in summer, it really does work. now in  the heat and humidity my XJ never sees 200° with my AC on full blast. And the coldest days its 185-190, plenty of heat in the winter, i have zero ill effects from not running too hot, milage and power are the same as before the changes. hope this helps and good luck.

[motownXJdad]

almost forgot the newer style curved blade Efan is an upgrade if you don't already have one, it moves more air than the older straight blade style.

[AZJeff]

Let me ask a question--have you actually seen symptoms of overheating (radiator boil-off)?   Have you confirmed that tne temperature is as indicated on the instrument cluster?  

 

I ask this because in my MJ (which has a late model XJ dash), the gauge reads about 10* higher than the actual temperature of the coolant.

 

I use an infra-red laser thermometer aimed at the thermostat housing to verify what my guage says, and perhaps your guage (or sender) are not giving you real temperature readings.

[Eagle]

Your hi-flow water pump may be pushing the water through the radiator faster than it can shed the heat.

 

[cruiser54]

8 hours ago, AZJeff said:

Let me ask a question--have you actually seen symptoms of overheating (radiator boil-off)?   Have you confirmed that tne temperature is as indicated on the instrument cluster?  

 

I ask this because in my MJ (which has a late model XJ dash), the gauge reads about 10* higher than the actual temperature of the coolant.

 

I use an infra-red laser thermometer aimed at the thermostat housing to verify what my guage says, and perhaps your guage (or sender) are not giving you real temperature readings.

This^^. VERIFY. 

[Eagle]

You have a switch for the aux fan but have you verified that the aux fan actually works? The one in my late-wife's 2000 XJ locked up for unknown reasons, and blew the fuse. Without the aux fan, the engine would get up to the red zone in light traffic on warm days. A new fan (and a new fuse) fixed it right up.

 

[Bald Eagle]

I have tried both the OEM water pump and the High flow water pump with the same results.   I also checked the temp with an infra-red thermometer and it was within 5 degrees.  Fans are working fine and I have a remote switch to turn the electric fan on as desired.  Also, I have a separate transmission cooler that by-passes the radiator.  

I did notice that at slow speeds the temp stays around 210, but going down the highway at 55 the temp with go up and down from 210-220.  I suspected the thermostat was not working properly, so I installed a new one this morning.  Also, maybe there is still air in the system.  I will road test in the morning to see if the new thermostat fixed the problem. 

Thanks for everyone's input.

[cruiser54]

FWIW, I only use the Mopar thermostats. I learned my lesson the hard way.

[Bald Eagle]

The reason I suspect overheating is when the gauge was at the red line, I could smell coolant.  There are no leaks or signs of a blown head gasket.

[Bald Eagle]

I have read that the High Flow water pump is fine for normal RPM range, but not for running abnormal high RPM's.  Frankly, I don't know if it makes a difference or not.  When I compare my Cherokee with my Comanche, the Cherokee is all stock and does fine(standard transmission).  The Comanche always seems needy and temperamental. 

[75sv1]

Auto, towing, do you have a trans cooler? Also, did you replace the radiator cap in the past 5 years? I'd take it that the CFS is new and came with a radiator cap. My 2000 XJ runs 205 to 210 regularly. 

[Bald Eagle]

All cooling components are new.  I have a True Cool transmission cooler which by-passes the radiator.  Also, I have hood vents.  Test drove the truck this morning with the new thermostat.  Temp stayed around 210+.  Drove the high hill climb mentioned in my previous comments with an outside temp at 75 degrees and the engine temp went up to about 225 degrees.  Once I reached the top, temp came back down to 210.  When I got home, checked the temp with the engine running at the thermostat housing with a heat sensor and it was 195+ degrees (the electric fan was on), and the temp at the gauge sending unit at the rear of the engine was 220+ degrees.   So, maybe the following theories contribute to the higher temps.  First, I am operating at higher elevations 7200-9000 feet, which is +20% less oxygen and power.  Secondly, the automatic transmission creates more heat than the standard transmission.  And finally, the sensor at the rear of the engine does get hotter where there is less air flow and where all the heat comes up from below.  These engines do run hot, and if I am adding weight or pulling a trailer, that engine has got to work harder. 

I have seen the Youtube videos and forums where every option is discussed and tried and praised and ridiculed.  For example; Aluminum radiator, Ford Taurus Fan, Grand Cherokee fan, three fan arrangement, 180 vs. 195 degree thermostat, high flow vs. OEM water pump and thermostat housing and the list goes on. 

So, maybe we are expecting too much out of these engines.  I am curious about the 4.0L stroker engine and how it copes with more power and heat.

[motownXJdad]

On 7/5/2022 at 1:14 PM, Bald Eagle said:

All cooling components are new.  I have a True Cool transmission cooler which by-passes the radiator.  Also, I have hood vents.  Test drove the truck this morning with the new thermostat.  Temp stayed around 210+.  Drove the high hill climb mentioned in my previous comments with an outside temp at 75 degrees and the engine temp went up to about 225 degrees.  Once I reached the top, temp came back down to 210.  When I got home, checked the temp with the engine running at the thermostat housing with a heat sensor and it was 195+ degrees (the electric fan was on), and the temp at the gauge sending unit at the rear of the engine was 220+ degrees.   So, maybe the following theories contribute to the higher temps.  First, I am operating at higher elevations 7200-9000 feet, which is +20% less oxygen and power.  Secondly, the automatic transmission creates more heat than the standard transmission.  And finally, the sensor at the rear of the engine does get hotter where there is less air flow and where all the heat comes up from below.  These engines do run hot, and if I am adding weight or pulling a trailer, that engine has got to work harder. 

I have seen the Youtube videos and forums where every option is discussed and tried and praised and ridiculed.  For example; Aluminum radiator, Ford Taurus Fan, Grand Cherokee fan, three fan arrangement, 180 vs. 195 degree thermostat, high flow vs. OEM water pump and thermostat housing and the list goes on. 

So, maybe we are expecting too much out of these engines.  I am curious about the 4.0L stroker engine and how it copes with more power and heat.

ive heard that the stroker motors tend to run hotter, but thats internet chatter, i have no proof of that yet😁. ive also heard that the high flow water pumps are great for off road crawling\low RPMs. I'm an old school street racer, i don't like my motors running on the ragged edge of overheating, just for cleaner emissions at the tailpipe. when your getting to 215-220+ your fluids are at thier limits, oil, trans fluid, even the coolant. this chassis wasnt designed for the 4.0 and it shows with so many owners having issues with running hot\overheating. I'm happy with my cooling system as it is now with the mods ive done, it has given me the confidence to be able to drive my 4.0 anywhere in any weather and not worry.

[Bald Eagle]

MotownXdad,

Which Efan did you use?  Thanks for your input.

[Bald Eagle]

If the Jeep ZJ has the 4.0L engine with a larger clutch fan, is it not just as loud in the ZJ as in the XJ or MJ?  Is the ZJ fan blade the same diameter and bolt pattern as the XJ/MJ?

[Bald Eagle]

Tried to install the ZJ clutch fan.  There was zero clearance between the clutch and radiator.  Returned the clutch and got my money back.

[cruiser54]

Your ears will thank you.

[Bald Eagle]

Update on what I have done regarding my cooling issue.  I installed a new clutch fan from Crown Automotive, which is a direct fit and highly superior to other clutch fans.  This clutch is a little larger in diameter and depth and fits perfectly with no clearance problems.  Secondly, I installed a later model XJ fan, also from Crown and it has ten blades and works great.  So far, it is working better.  My last change will be swapping out the transmission cooler that sits in front of the radiator & condenser and installing a Derale 2-fan trans. cooler below the radiator.  This will provide better airflow through the radiator.

[Andy in Pa]

You may be on to something with the trans cooler.  These trans can run quite warm, and if the converter is not going into "Lockup" mode at speed, it will create more heat.  Also, if you eliminated the trans cooling in the radiator, you'll definitely need a decently sized one for in front of the radiator.  Best place for it is in front of the electric fan, with the fan on a switch and turned on. 

 

Do a quick test the next time you drive it, and at a steady state of cruising at 45mph or so, step very lightly on the brake pedal.  You should see the rpms jump slightly on the tach.  This means the TC is unlocking, and it should lock again once your off the brake and at that steady speed again.  This will at least tell you that the trans shouldn't be making any excessive heat.

[75sv1]

     I do wonder if the high temps are if the trans is locking and unlocking in OD. I did get that driving in WV grades. A lot of times, I had to downshift into 3rd or even lower. A bored TB, headers, 2.5 Catback did help in two XJs. 

     Recently, I installed a 3 electric  fans. I used the 'frame' from Dirt Bound. Also, SPAL 10" fans. I've only driven on flat ground. Seems to run a touch cooler. Still, haven't driven at lower speeds. I did with out any fans. A bit into 215F. So, not very conclusive. 

     I did just change out the trans. From one with 275K to one I have rebuilt about 5 years back. Also, I see not real change. I also run a 195F thermostat. Its not MOPAR though. I did have two High Flow ones malfunctions. The engine didn't heat up in wintertime. Both were probably Mr. Gasket. I will be trying a Stewart in a stoker I have assembled.

      I will be setting up a two trans cooler setup. Just looking at installing them. I have two from  ZJ's. Trying to use the U hoops brackets. I'll need to extent them. 

   Also, to Andy's post, I'd wonder if the brakelight switch might need replaced. It does some control over the trans. Still, some of the passes in CO, are really steep.

[Bald Eagle]

So, I was in Moab yesterday and drove the Sand Flats Road.  Not difficult but in some areas slow driving and pulling some good grades.  The outside temperature was 79 degrees in the morning, but after lunch it got up to almost 100 degrees.  When pulling the grades, the engine temp. stayed around 217, but the transmission temp jumped to 225 degrees (I was not running the air conditioner).  In my previous post, I stated that I wanted to remove the transmission cooler that is in front of the radiator/cooling condenser and install the Derale two-fan cooler away from the radiator.  I have not done this yet, as I am waiting for a fitting.  Novak conversions also recommends not having the trans cooler in front of the radiator and I agree as it further restricts air flow.  So, once I make the switch I will test and post the results.  

I will test my transmission as suggested by Andy.  Also, when the outside air temperature gets up to 90 to 100 degrees, it hard to keep anything cool.  

[pizzaman09]

On 7/14/2022 at 6:50 PM, cruiser54 said:

Your ears will thank you.

My parent's ZJ definitely had a noisy fan.  

[AZJeff]

Something is awry with what you have said about your MJ and its' cooling system performance.   I have PLENTY of experience with MJ's and XJ's being operated under FAR more strenuous conditions that yours.   (I live in the PHX metro area, and temperatures above 105* is a daily occurence here, and I run my AC all the time.)

 

An MJ/XJ with the 4.0 is going to run what might seem to be hot, but it's within the design limits, assuming that all components of your vehicle are up to OEM standard.   (That means radiator, fans/shrouds, hoses, radiator pressure cap, 50/50 coolant mix, and thermostat.)

 

WIth all of these things up to snuff, it's normal to see (in my climate, at least) the engine run right about 205*, with a tolerance of =/- 10 degrees.   If you think this is too hot, your expectations are incorrect.  (I assume you have confirmed your temperatures by using an infrared thermometer measuring the temperature of the thermostat elbow on the engine.)

 

The transmission in your vehicle should never exceed 200* for any more than a minute or two at most.  If it's seeing more than that, an aftermarket fluid-to-air heat exchanger is needed.  (And the trans may need investigating)

 

There is no doubt that altitude WILL reduce the effect of cooling across the radiator, as (for example) the air is only 81% as dense at 7000 feet as it is a sea level.   However, this is offset by the fact that you are probably NOT running air conditioning in your MJ at 7000 feet, so the temperature of air entering the radiator is not being increased by heat being shed from the condenser.

[Bald Eagle]

I installed the Derale 2-fan transmission cooler on Saturday below the radiator.  Also, I did the RPM check and everything seems normal with the transmission.  So, the next check will either be an offroad trip or towing my 1200 lb. Teardrop camper.