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  #1  
Old July 5th, 2018, 13:36
XJ_NorCal XJ_NorCal is offline
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Overheating/running hot...

1998 Cherokee Sport
4.0 Litre with 115K miles
AW4 Automatic Transmission
NP231 Transfer Case

On my way to Tahoe my rig began to overheat on an uphill climb. Normally temp gauge reads slightly to the left of 210 deg. F on open road and slightly to the right of 210 deg. F on uphill climbs and out on the trail. I noticed it was running hotter than normal (225ish deg. F) on a flat road prior to the climb. I was driving with the AC on so I figured that was the culprit.

A few miles into my climb my "check gauges" light came on and the temp. gauge shot up into the red (250-ish deg. F). I immediately turned my Heater on full blast and within 10 seconds my temperature dropped back to just above 210 deg. F. 10 minutes later the exact same thing happened. I pulled over at the next gas station to check my coolant reservoir and it had plenty in it. The jeep cooled down to 210 while idling in the parking lot. It continued to run hotter than normal until I reached Tahoe and on the way home on flat ground.

I've never had any issues running hot prior to this and that includes multiple 3+ hour drives to trails, trail riding and driving 3+ hours back home. I flushed the radiator and installed a new thermostat in November. I'm thinking it was related to my AC running so I'm considering cleaning out my AC condenser. Any suggestions for what else I should check/service?
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  #2  
Old July 5th, 2018, 14:58
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Tim_MN Tim_MN is offline
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Re: Overheating/running hot...

Service the cooling system. Consider installing an auxiliary transmission cooler.

I always install a new genuine Jeep or Stant radiator cap with every new thermostat. An old worn out radiator cap will allow not hold system pressure which can cause boil overs and/or allow the coolant flash over into to steam. You will likely see the coolant temps suddenly jump from 210* to the Red Zone and back to 210* if your radiator cap is weak.


The cooling system is a group of related parts that depend on proper function from each of its 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 engine will overheat. Temperature creep on the 4x4 trails, at idle, or in stop-n-go traffic, points to a weak or failing mechanical fan clutch or worn out water pump fins.

Overheating can be caused by anything that decreases the cooling system’s ability to absorb, transport, and dissipate heat, such as a low coolant level, loss of coolant (through internal or external leaks), poor heat conductivity inside the engine because of accumulated mineral deposits in the water jackets or radiator, a defective thermostat that doesn’t open, poor airflow through the radiator, a slipping mechanical fan clutch, an inoperative electric cooling fan, a collapsed lower radiator hose, an eroded or loose water pump impeller, leaky frost plugs, or even a defective radiator cap.

The most important maintenance item is to flush and refill the coolant periodically. Coolant should be replaced every 36,000 miles, or every two to three years. Anti-freeze has a number of additives that are designed to prevent corrosion in the cooling system, but they have a limited life span. The corrosion causes scale that eventually builds up and begins to clog the thin flat tubes in the radiator and heater core, causing the engine to eventually overheat.

-Inspect/test or replace the mechanical fan clutch. A worn fan clutch will allow temperature creep at stoplights, in heavy traffic, and on the 4x4 trails. A fan clutch that “looks” OK is not the same as working OK.
-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/test 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.
-Inspect all of the freeze plugs in the block and the ones on the backside of the head for rust holes and coolant leakage.
-Use a chemical flushing/cleaning solution to remove mineral buildup or rust, flush with clean water, and then drain and fill the radiator with a fresh 50/50 coolant and water mix. With neglected cooling system you may have to flush several times.
-Inspect the radiator for mud/bugs/grass clogging the outside and mineral deposits clogging the inside. Clean or replace as needed.
-Replace the thermostat with a genuine Jeep 195* thermostat. Cheap thermostats are cheap for a reason.
-Replace the radiator cap if your Jeep has one. An old worn out radiator cap will allow not hold system pressure which can cause boil overs and/or allow the coolant flash over into to steam. You will likely see the coolant temps suddenly jump from 210* to the Red Zone and back to 210* if your radiator cap is weak.


If you have covered all the points listed above and still have overheating issues, inspect and test the head for cracks and head gasket for leaks. Exhaust gasses entering the coolant can raise the temperature of the coolant or cause steam pockets in the coolant that will temporarily block the flow of coolant.

Read more about cooling systems here –
www.offroaders.com/tech/engine-overheating.htm
www.carparts.com/classroom/coolingsystem.htm
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Originally Posted by bimmerjeeper

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Last edited by Tim_MN; July 6th, 2018 at 03:55.
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  #3  
Old July 6th, 2018, 09:31
XJ_NorCal XJ_NorCal is offline
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Re: Overheating/running hot...

Thanks for the thorough response, those links were great.

Quote:
Originally Posted by Tim_MN View Post
Service the cooling system. Consider installing an auxiliary transmission cooler.
I've been strongly considering an Aux. tranny cooler and had plans to mount one on the front passenger side of the radiator. I decided not to order one after I had this overheating incident. What is the best mount location so as to minimize the obstruction of air flow to the AC condenser/Radiator?

Quote:
Originally Posted by Tim_MN View Post
I always install a new genuine Jeep or Stant radiator cap with every new thermostat.
Ordered both new this morning for less than $20, this was a no brainer.

Quote:
Originally Posted by Tim_MN View Post
-Inspect/test or replace the mechanical fan clutch. A worn fan clutch will allow temperature creep at stoplights, in heavy traffic, and on the 4x4 trails. A fan clutch that “looks” OK is not the same as working OK.

-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/test 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.

-Inspect all of the freeze plugs in the block and the ones on the backside of the head for rust holes and coolant leakage.

-Inspect the radiator for mud/bugs/grass clogging the outside and mineral deposits clogging the inside. Clean or replace as needed.
-Fan clutch will be inspected this weekend. If replacement is required, which brands should I look at?

-E fan is fine, I inspected in Tahoe before making my way back home.

-Coolant temp. sensor seems to be fine.

-radiator hoses are fine.

- Freeze plugs show no signs of leaks.

- I'll likely wait on water pump and fan clutch as these are more involved repairs. Easy, cheap stuff will be done first.

- What's the best/easiest way to clean radiator/AC condenser fins?!?
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  #4  
Old July 6th, 2018, 10:24
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Tim_MN Tim_MN is offline
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Re: Overheating/running hot...

Cherokees don't need a huge trans cooler, the stock cooler mounted at the bottom of the grille opening works for me.

Last time I bought the premium fan clutch from NAPA. Cheap parts are cheap for a reason, I always buy brand name parts, and nothing that has a "Lifetime Warranty".

The coolant temperature sensor can and be should be tested.
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I'm starting to realize people on the Jeep forums are highly expert mechanics .....
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  #5  
Old July 9th, 2018, 10:35
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Greenspan Greenspan is offline
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Re: Overheating/running hot...

Is this really a problem with the Jeep cooling system? I mean you were driving uphill, at altitude, with the A/C on. That's pretty much the worst conditions possible. I'm guessing it was a hot day too, and were you loaded up with stuff and do you have a lift with big tires?

I'm 1/2 asking for myself, I had almost the exact same situation happen to me the other day (driving hard uphill, super hot day, blasting A/C), but just took it as a lesson to be more judicious about my use of A/C. I have been okay in every other situation as long as I turn off the A/C when things get rough. I guess the question is do you think there is a problem that needs fixing, or are you looking for upgrades to increase the capability of the base system (i.e. so you can blast A/C while driving hard)? Again, 1/2 asking for myself because I am in a similar situation and looking to see how other XJ'ers feel.
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Old July 9th, 2018, 12:47
XJ_NorCal XJ_NorCal is offline
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Re: Overheating/running hot...

Quote:
Originally Posted by Greenspan View Post
Is this really a problem with the Jeep cooling system? I mean you were driving uphill, at altitude, with the A/C on. That's pretty much the worst conditions possible. I'm guessing it was a hot day too, and were you loaded up with stuff and do you have a lift with big tires?

I'm 1/2 asking for myself, I had almost the exact same situation happen to me the other day (driving hard uphill, super hot day, blasting A/C), but just took it as a lesson to be more judicious about my use of A/C. I have been okay in every other situation as long as I turn off the A/C when things get rough. I guess the question is do you think there is a problem that needs fixing, or are you looking for upgrades to increase the capability of the base system (i.e. so you can blast A/C while driving hard)? Again, 1/2 asking for myself because I am in a similar situation and looking to see how other XJ'ers feel.
I have a lift, skid plates, aftermarket bumpers, a winch and large tires. I had maybe 100 pounds of extra gear (including spare tire). My concern is that I have driven in these exact conditions before with no issue (uphill, fully loaded with A/C use) and that I had been running hotter than usual before I started the uphill climb and on my way home on flat highway driving.

To answer your questions

1) My initial feeling is that something is not right with my cooling system as I had not had issues before in similar conditions. I started the thread to check if anyone has had a similar issue and what their fix was. New radiator cap, temp coolant sensor and thermostat are easy, cheap things I can replace that might have contributed to my issue.

2) I was open to folks giving me advice on improving my cooling system as well. I had been considering an Aux tranny cooler and will likely purchase one since an added benefit (aside from cooling my transmission oil) is it may reduce the heat load on my coolant system.
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Old July 9th, 2018, 13:02
RCP Phx RCP Phx is offline
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Re: Overheating/running hot...

Trans coolers are your friend! Get the biggest/best that you can fit. Avoid tube/fin coolers while checking into plate/fin coolers. Here's my additional PS cooler beside my trans cooler.
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Old July 9th, 2018, 13:48
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#S194 #S194 is offline
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Re: Overheating/running hot...

Quote:
Originally Posted by Tim_MN View Post
Cherokees don't need a huge trans cooler, the stock cooler mounted at the bottom of the grille opening works for me.

Last time I bought the premium fan clutch from NAPA. Cheap parts are cheap for a reason, I always buy brand name parts, and nothing that has a "Lifetime Warranty".

The coolant temperature sensor can and be should be tested.

NAPA fan clutches aren't what they used to be. I just had two fail, one with around 2.500 mile on it, the second with around 250 miles.
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  #9  
Old July 9th, 2018, 15:29
XJ_NorCal XJ_NorCal is offline
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Re: Overheating/running hot...

Quote:
Originally Posted by #S194 View Post
NAPA fan clutches aren't what they used to be. I just had two fail, one with around 2.500 mile on it, the second with around 250 miles.
I looked into Napa fan clutches and I couldn't find a Premium option.
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  #10  
Old July 9th, 2018, 15:39
XJ_NorCal XJ_NorCal is offline
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Re: Overheating/running hot...

Quote:
Originally Posted by RCP Phx View Post
Trans coolers are your friend! Get the biggest/best that you can fit. Avoid tube/fin coolers while checking into plate/fin coolers. Here's my additional PS cooler beside my trans cooler.
I'm looking at this Hayden Aux cooler.

https://www.amazon.com/Hayden-Automo.../dp/B000C3DDKO

What do you have installed?
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Old July 9th, 2018, 15:39
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Tim_MN Tim_MN is offline
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Re: Overheating/running hot...

Quote:
Originally Posted by #S194 View Post
NAPA fan clutches aren't what they used to be. I just had two fail, one with around 2.500 mile on it, the second with around 250 miles.
The last one I bought was a while back.

I do know that NAPA OBD engine sensors are not what they used to be and can no longer recommend them as better quality than the Chinese crap sensors from IdiotZone.
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Quote:
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I'm starting to realize people on the Jeep forums are highly expert mechanics .....
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  #12  
Old July 9th, 2018, 15:57
RCP Phx RCP Phx is offline
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Re: Overheating/running hot...

Quote:
Originally Posted by XJ_NorCal View Post
I'm looking at this Hayden Aux cooler.

https://www.amazon.com/Hayden-Automo.../dp/B000C3DDKO

What do you have installed?
I was running that one, I just switched to the AN fitting one's.
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Old July 9th, 2018, 16:17
XJ_NorCal XJ_NorCal is offline
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Re: Overheating/running hot...

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Originally Posted by RCP Phx View Post
I was running that one, I just switched to the AN fitting one's.
details on the AN fittings...?
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  #14  
Old July 9th, 2018, 19:02
RCP Phx RCP Phx is offline
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Re: Overheating/running hot...

Just braided stainless instead of rubber hose!
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  #15  
Old July 9th, 2018, 19:18
XJ_NorCal XJ_NorCal is offline
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Re: Overheating/running hot...

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Originally Posted by RCP Phx View Post
Just braided stainless instead of rubber hose!
did you mount with zip ties or brackets?
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