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2001 Jeep TJ Wrangler Overheating Since New!


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WOW!  Overheating since it was new?  Yes, my friends TJ with 4.0l, and  automatic transmission overheats predictably when used off road on the family ranch.  When newer the owner made repeated trips to the dealer and since those early years he has sought out local mechanics to help repair his overheating problems.  I know that the only reason he keeps the vehicle is because he is the kind of man that could not sell a vehicle that is not in good shape, so he keeps it and tries to work around the Jeeps shortcomings.  I offered to help and as usual Moses I need your expertise.  

 

I will be on his ranch Monday evening and will be able to witness the overheating engine and gather all of the pertinent information that can assist you in advising me of a possible course of action.  Also before I go visit I wanted to have some options that he could consider assuming that the cooling system problem is related to design and tough off road use, and the mechanics who previously worked on the Jeep were right in their analysis of the total cooling system.  For instance I know of a TSB that would allow a 7 blade fan and a heavy duty fan clutch to be used to allow more air flow across the radiator at low speeds.  Are you aware of this?  Does it help?  I personally like the Griffin replacement radiator with possibly an electric fan. 

 

Do you feel confident that with bulldog tenacity we can solve his problem?  I'm up for the challenge but I will need your help!  Please have a list of questions you would like answered.  I'm sure the transmission will need some service work too, I think I remember a video that addresses that procedure.

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Hi, Forman!...Always up for a challenge...

 

Cooling begins with basics.  The engine produces horsepower, which equals BTUs, approximately 45 BTUs per horsepower.  The radiator must be able to disperse this heat, and to do so, the radiator requires 1) adequate gallon-per-hour flow, 2) sufficient surface area and 3) a fan system that will help dissipate heat.  Lower speed or crawling temperatures are often the most difficult to control, especially with an automatic transmission. 

 

The coolant must circulate properly, and this involves the water pump and proper hose routing.  I prefer a mechanical/engine driven fan system with sufficient air draw through the radiator.  More blades on the fan would increase CFM flow at an idle and low speeds, especially with a heavy-duty aftermarket fan clutch.  A thermostatically (temperature) controlled fan coupler is advisable.  Hayden and others offer this type of fan clutch, they can get noisy when they come on at highway speeds, but at least you know the fan is working!

 

You need to know whether the Jeep's hoses are intact and routed properly, including the heater hoses.  Also, since the engine will overheat, bring along an infrared test gun, and spot check all over the radiator, at several cylinder head and block points, plus other heat sources.  Accurate surface temp readings at hoses are virtually impossible, so focus on metal, plastic and hard surfaces.  Take readings when the engine is hot and running.  You're looking for localized overheating or obstructions noted by hot or even cooler areas.  Write down your findings.

 

I'll cut to the chase here.  The engine cooling can be improved by a high performance water pump, fan and fan clutch.  A heavier duty (higher flow rate with more surface area) radiator will always help.  My suspicion, however, is that the problem is transmission heat.  The factory radiator cooler is wholly inadequate and will actually raise engine coolant temperatures while trying to cool the automatic transmission.  I would definitely install a quality aftermarket transmission cooler, preferably with a deep oil pan and a temperature gauge system to monitor the transmission temps.  The aim is to cool the transmission without taxing the engine cooling.

 

Note: A big liability on the '01 TJ is the 32RH transmission, its last year in action.  A reasonably stout transmission, this is only three speeds, and the vehicle has the conventional NV231 transfer case with a 2.72:1 low range ratio.  The taller gearing of the transmission, especially in first gear, makes this transmission work hard—and get hot!  If the vehicle has oversized tires with stock axle gear ratios, the trouble worsens.

 

You can take infrared readings of the transmission oil pan (don't scorch yourself!), the transmission cooling lines (before and after the radiator cooler to read the temp drop or effectiveness of the cooler), and the radiator tank that holds the cooler.  I would focus on these transmission related temperatures, as they tax the engine's cooling system.

 

I'm assuming that "overheating" is running really hot.  Note the temperature range and whether the coolant pushes out of the radiator and into the recovery tank before shut-off.  (Overflow is normal after engine shut-off when hot.)  Is there actual boil-over?  If so, infrared the coolant recovery tank and the fluid in that tank for actual temperature after a boil-over.  Read temps near the radiator filler neck with the cap in place.

 

Keep in mind that coolant must not be too concentrated.  If more than 60/40 mix, there's the prospect of overflow at lower temperatures.  Coolant mixture must be able to expand within itself, and if not, there will definitely be overflow or what appears to be a boil-over.  When the engine is cold, before starting or driving, test the anti-freeze/coolant with a common coolant hydrometer or test paper strip.  Test at the radiator and the coolant recovery tank if there is suspicion of recent coolant adding.  Be aware that overheat and overflow can result from too much coolant/anti-freeze.  An engine can boil over from either too little or too much anti-freeze.  The radiator cap pressure is also part of this equation, and the cap must meet normal pressure ratings.

 

This is a place to start...Don't spend money buying trick parts until you isolate the cause of trouble.

 

Moses

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When I was first approached to look at this Jeep I thought I would go through the 9 or 10 steps to explore all of the overheating problems.  Moses you added a few more, once more your experience opens possibilities for consideration.  I made a list and set out yesterday late afternoon to evaluate the cooling system in question with a copy of your last post in my hand.

When I got there I saw this:

 

post-140-0-38930700-1440556972_thumb.jpg

 

 

A huge winch blocking air flow!  Upon further investigation I was able to see a great deal of debris in the fins of the radiator.   I cleaned the radiator using a water hose.  I noted that the coolant was clean, and the tubes visible while looking through the open radiator cap did not have a build up of hard water type deposits, there also was nothing floating on top of the coolant.  However the coolant was orange, I expected green and I didn't have a hydrometer to check the concentration percentage.  I saw that the fan was an original 5 blade design and was turning in the right direction pulling air through the radiator, the fan continued to turn after the engine was shut off for just about a couple of seconds.  I located the transmission coolant lines and was surprised to see that the lines were simple rubber hoses connected with hose clamps.  The engine compartment was a tight fit compared to my CJ.

 

We left for a test drive that would hopefully  duplicate the overheating scenario that has plagued the Jeep for several years.  The weather cooperated by being hot (94 degrees) and still with low humidity.  The drive would be a slow 5 mile trek through several deep draws and back up long steady uphill elevation changes, the same kind of climbs that overheat the transmission that you spoke of.  Three hours later we were back where we started and I took out the infared thermometer.

 

The transmission oil pan temp was 220 degrees F, I didn't feel like I was getting accurate temp readings on the transmission cooling lines.

The engine oil pan was the same temp as the transmission oil pan.

 

The temp at the top of the radiator was 226 and at the bottom of the radiator was 220.

 

I looked all over the engine for hot and cold spots but found all temperatures very consistent, as were the temps across the radiator core.

 

There was no movement of fluid from the radiator to the recovery tank, but I did hear bubbling and spewing noises inside the radiator the first few minutes after the engine was shutdown.

 

The overheating issues that I was anticipating did not occur as severely as were relayed to me by my friend.  My cleaning the core before we started may have helped.  For the most part the temperature gauge climbed slightly all night long, always at least just past the 210 degree mark.  I mentioned relocating the winch and spoke of the upgrades you mentioned to the owner and I feel like that is the approach he would like to take.  I just need some specific aftermarket recommendations from you.

 

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Forman...Assuming the thermostat is accurate and functioning properly, the coolant temp is high.  I would expect temps within 5 degrees F of the thermostat setting.  If a 205 thermostat, 210 would be the maximum.  If a 195 F, which will work with the PCM, 200 should be tops.  A 195-200 F thermostat would be advisable.  This allows some margin for hot days and driving conditions.

 

The gurgling raises suspicions about the water pump.  Ask the owner whether the water pump has been replaced or not.  Pumps are directional and must match the rotation of belts and pulleys.

 

As for replacement parts, see the Summit Racing catalog.  Derale and Hayden make good pieces.  FlowKooler makes a water pump, Edelbrock may have an offering, too.  There may be a "paired" fan and fan clutch available.  I would be conservative, begin with the transmission add-on cooler, and consider the water pump and thermostat.  Make sure the transmission add-on cooler mounts and locates properly in the system.  There should be detailed instructions if the system is model-specific.

 

I still want a concentration reading on the anti-freeze/coolant.  That radiator gurgling and the overheat could be simply too much anti-freeze/coolant concentration, which cannot expand normally.  Check the owner's handbook for the Mopar anti-freeze/coolant used in a 2001 TJ.  Determine whether this was green or orange.  Mopar did change to orange around that period.  Aftermarket orange or green anti-freeze/coolant often does not mix and can raise havoc with the cooling system.  Narrow this down.

 

Moses

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This repair is somewhat difficult because I can't pull this jeep into my shop, I'll have to travel about 35 miles to see the jeep and answer your questions.  The vehicle does not leave the ranch as of right now.  

 

I like your trans cooler/water pump/thermostat/fan and clutch approach.  With that I have some questions about the new cooler if I can't find one model specific.  I think it should mount in front of the radiator, right?  Preferably bolting somewhere to a radiator mount/frame.  Do I bypass the old coolant lines in the radiator by just leaving them open?  

 

If the TSB recommended 7 blade fan and clutch are still available should I buy them or a more affordable aftermarket fan and clutch. 

 

It may be a few days before I can get back out to the ranch to answer your questions.

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Forman...One of the best model-specific systems on the market is the thermostatically controlled, 500 CFM electric fan cooled Derale.  Engineered and thoroughly fitted to the Jeep Wrangler, good for a 30-40 degree F drop in transmission temperature, this one's got to help:

 

http://derale.com/products/fluid-coolers/transmission/direct-fit/dodge-dakota-cooling-line-radiator-adaptor-fitting-kit-detail

 

Here's everything you need to know about the installation and use of the OE cooler, which Derale keeps in place:

 

http://derale.com/images/stories/virtuemart/product/pdfs/20561.pdf

 

Derale also offers thermal fan clutches that include Jeep applications.  I'd start with a thermal fan clutch, they produce enough noise by themselves when the engine or radiator is hot.  Adding a 7-blade fan would be a guaranteed noise source!

 

Still want to know the anti-freeze/coolant mixture...

 

Moses

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