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Hi, I've been dealing with an overheating behavior in my YJ 1989 Wrangler (4.2L with all emissions control hooked up except pulse air system, Carter BBD, Auto Trans).

Long time ago I've replaced cooling fluid, It was 100% tap water that is the worst choice due to corrosion; so I decided to replace it by an ethylene glycol mix as you can find them ready to pour into your cooling system. I don't know if the coolant was poor quality but immediately after replacing the fluid I was getting the engine overheated. Perhaps it was air trapped in the system as the guy replacing the coolant did all the procedure really quick with the engine still warm... Well I had to go back to water again and the issue was solved. No more overheating during next days.

Then I went wheeling several months after, when stopped the vehicle heared something like a pressurized air leak, it was the hose from the thermostat housing to the intake manifold, was cracked and ended up blown after I pulled it. So I shortened the hose and reinstall it again. Got home with overheating issues again. 

Bought all new hoses, including upper and lower radiator hoses. Heater was disabled so former owner plug the nipple coming from the water pump and the one on the back of the intake manifold as well, I didn't enable the heater yet but I have connected a hose between those two points to keep coolant flow through the manifold and cylinder head.

 Found that there was no thermostat installed, so installed one. Inspected water pump, a little bit of corrosion but the rotor and impeller was good, no play at the shaft.

Refilled all the system with 50/50 mix and have to add some distilled water as I got short of coolant to top up the radiator. Fan clutch was replaced as well. 

 

I've been having random overheating, it is worst when A/C is turned on, obviously because the condenser is in front of the radiator. But sometimes runs good and the needle does not go above 210. I do not know where the needle it is supposed to be when the cooling system is working as it should. There are sometimes that random misfiring is happening, not too critical but I'm sure I'm not getting a perfect tuned engine.

I've replaced the radiator cap just to discard this is the troublemaker. (13lb new one installed)

Does the water to coolant swap have something to do with making debris and metal corrosion to become loose and start building a sediment inside the engine's block?

 

 

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Hi, Alberto_YJ...A very thorough analysis and description of your 4.2L engine cooling troubles—great pictures, too!  From all you share, the engine may have "block mud" and severe corrosion.  Hard water, as you say, can do this kind of damage.

I would either borrow or purchase an infrared surface temperature tester.  With the engine coolant full, "burped" of any air, and filled to the best level you can reach, run the engine to full warm-up with a 195-degree F thermostat installed.  From a safe distance, shine the infrared tester on every exposed surface of the cylinder head, the engine block, the thermostat housing and other engine castings.  Although you will not get accurate readings from rubber hose surfaces, take those readings anyway.

Try to estimate where the cylinder cooling jackets run.  Check around the water pump.  Follow the areas where coolant circulates.  Try to find areas that are excessively hot or cool.  You will be comparing the temperature readings.

The scale and corrosion looks very serious.  Block mud is rust, minerals and solids that accumulate and line the bottom and walls of cooling jackets.  Block mud clogs passageways.  First determine whether you have that kind of problem.  Look for signs that there is blockage that prevents coolant from circulating.  

Once you get these results, we can discuss whether you can remedy the problem with a chemical and pressure flushing or not.  I purchased a heater core/reverse flushing tool last year that did a remarkable job on the XJ Cherokee heater core...You may be able to reverse flush the engine's cooling system and heater core.  The biggest concern is the extent of corrosion and scale.  You do not want to damage gaskets (the head gasket in particular), seals, hoses or freeze/soft plugs.

Use the surface temperature tool across the radiator core with the engine fully warm and running.  Avoid the fan and moving parts!  See if there are blockages in the radiator core, I am certain you will find them with the infrared gun.  A clear sign is that the engine gets hotter and hotter the faster you drive.  With all of the rust and scale in the engine, the repeated draining and refilling of the system has likely clogged the radiator core's tubes.

At the least, your radiator needs "rodding" and cleaning.  This is more than just flushing.  The radiator can be sublet to a radiator shop for tank removal, rodding and cleaning.  If the core is too corroded, you will need a new core or a complete radiator.  Clean and repair the radiator after flushing the engine block, cylinder head and heater core!  You do not want to clog a freshly serviced radiator with loose engine debris and heater core debris!  Flush the engine and heater core thoroughly before draining the system and removing the radiator for service.  

Start with the surface temperature tests.  Share your findings...

Moses 

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Hi Moses, over two months and finally got a borrowed thermograph meter. I've tried to get the best angles but there were too many things around the engine so not all the block surfaces were that easy to take a picture of. Please let me know if you can diagnose something from the pictures attached.

 

Regards.

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Hi, Alberto!  Fascinating thermograph photos.  I've not had an opportunity to use this technique.  The common tool I use is a non-contact infrared thermometer.  This is a device available in the automotive tool world.  (I bought mine at a NAPA retail store years ago.)  Not expensive, here is a photo example of an infrared non-contact thermometer.  Some of these devices are less than $20, high end non-contact thermometers are less than $100:

https://www.amazon.com/gp/product/B008EW837S/ref=pd_lpo_sbs_dp_ss_3?pf_rd_p=1944687622&pf_rd_s=lpo-top-stripe-1&pf_rd_t=201&pf_rd_i=B0017L9Q9C&pf_rd_m=ATVPDKIKX0DER&pf_rd_r=H1G6JG0RBAQ207C314H3

I looked carefully at your thermograph images.  If I interpret them correctly, especially the image reading 104C/108, the coolant gets progressively hotter from the rear of the engine to the front, and that is normal for an inline six combustion engine.  This in itself does not say anything.  What is curious, though, is the high heat at the lower front end of the engine.

The high heat along the lower engine, below the piston stroke section of the cylinder, says a lot.  Given our knowledge of this vehicle's history and cooling system treatment, I suspect "block mud".  This engine and cooling system have been run on straight water, maybe with poor coolant care in the past, a quick way to mineralize the iron block and head.  If this happened, the block and cylinder head internal surfaces could be rust coated with mineral buildup and clumps of contaminants.  Machine shops call these clogging contaminants "block mud".  The heater core and other areas are often affected.

Some questions:  1)  Did you compare the temperature at the top (input) end of the radiator versus the lower radiator tank temperature?  2)  With the engine warmed and running, are there hot and cool spots in the radiator core?  If the radiator is clogged, there will be hot and cooler spots in the core, and the exiting (lower) tank will not be substantially cooler than the top of the core.  The upper radiator hose should be very hot, the lower hose considerably cooler.

Block mud and rust scale are difficult to purge.  Often, the "mud" will line the block/cylinders' lower cooling jackets until the engine is disassembled and hot tank cleaned.  For this reason, I would first deal with the radiator and possible clogging.  Begin with a caustic cooling system flush;  flush the entire cooling system.  After neutralizing the system and flushing it thoroughly, remove the radiator and take it to a quality radiator shop for disassembly and "rodding out". 

If done thoroughly, the radiator gets hot chemical dipped, and the tanks get removed.  Tubes are rodded and the core flushed before reassembly with fresh solder.  If the core is damaged or badly corroded, replace the core.

Moses

    

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Thank you for your input Moses. 

A friend of mine is suggesting to use Caterpillar cooling fluid mixed with water and run the vehicle for a week and then flush out all the removed particles.

I've been reading different techniques for flushing the cooling system, finding that there is one that uses a pump to make the flushing fluid to circulate during several hours and all the particulated material to be trapped in a bucket.

Is there any home product that can be added to the system to start the mud removal process? Or any base chemical? I will look around the city to see what kind of product I can get.

What do you think about the CAT coolant to clean the system? Considering that it is intended for big diesel engines on earth movement machines.

Now to answer your questions:

1. The pictures shows the temp for the in and out hoses at the radiator. The difference shown is less than 5 celsius. Really poor efficiency if the readings are ok.

2. I was not able to "see" the radiator core as from the front I have the A/C condenser and from the back there is the radiator fan and multiple things that blocked the line of sight.

I will try a chemical to start removing all that come off with that method, then will do the radiator core rodding and at the same time get the water pump removed to see if there is still mud inside the block.

All the symptoms are very similar to a fan clutch failure as it is overheating only at long time idling.

A final question to you:

Considering this vehicle is running with A/C on, transmission is automatic, so the fluid is going through the radiator as well, and the weather here is hot (32 celsius, about 42*C heat sensation) which would be a "normal" range for the temp needle in the dash to be at? Which would be the maximum temp for the needle to reach?

 

Thank you, regards.

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40 minutes ago, Alberto_YJ said:

Thank you for your input Moses. 

A friend of mine is suggesting to use Caterpillar cooling fluid mixed with water and run the vehicle for a week and then flush out all the removed particles.

Is this a cleaning fluid or a coolant, Alberto...?  If specifically for cleaning the system, it could work.  The lighter cleaners are intended for simple surface debris, not block mud.  Historically, a caustic (lye) product was used.  The issue here is that corroded parts like freeze plugs can leak after such a caustic cleaning.  Stick with a product designed specifically for heavy duty cleaning of an automotive/truck cooling system.  The Cat product may work.  Post a link to the product description and MSDS. 

I've been reading different techniques for flushing the cooling system, finding that there es one that uses a pump to make the flushing fluid to circulate during several hours and all the particulated material to be trapped in a bucket.

This sounds very effective but involved. Do you have a link to this equipment?   

Is there any home product that can be added to the system to start the mud removal process? Or any base chemical? I will look around the city to see what kind of product I can get.

Must be caustic and require neutralizing.  Be careful and watch for freeze plug leaks!

What do you think about the CAT coolant to clean the system? Considerin that it is intended for big diesel engines on earth movement machines.

Sounds promising...I'd like to see more details.

Now to answer your questions:

1. The pictures shows the temp for the in and out hoses at the radiator. The difference shown is less than 5 celsius. Really poor efficiency if the readings are ok.

Sounds like either poor coolant flow through the radiator or a defective fan clutch.  Or both.

2. I was not able to "see" the radiator core as from the front I have the A/C condenser and from the back there is the radiator fan and multiple things that blocked the line of sight.

I will try a chemical to start removing all that come off with that method, then will do the radiator core rodding and at the same time get the water pump removed to see if there is still mud inside the block.

Good idea...

All the symptoms are very similar to a fan clutch failure as it is overheating only at long idling.

Yes, this could be fan related.

A final question to you:

Considering this vehicle is running with A/C on, transmission is automatic, so the fluid is going trough the radiator as well, and the weather here is hot (32 celsius, abou 42*C heat sensation) which would be a "normal" range for the temp needle in the dash to be at? Which would be the maximum temp for the needle to reach?

Humidity is a "worst case scenario" and challenge to engine cooling.  Overheating at an idle is usually inadequate fan capacity or operation.  Overheating at higher speeds is inadequate cooling capacity or inadequate flow rate at the radiator.

 

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Well, actually the CAT product is not a cleaner, it is a coolant but what my friend says is that it is more aggressive as it is intended for heavy duty engines. I know they have cleaners but he's suggesting a coolant the will remove the mud slowly, from what I'm understanding.

Not sure which part number is my friend suggesting from CAT but I could say is something like this one: https://parts.cat.com/wcs-static/pdfs/PEHJ0067-02.pdf

Here is the link to the site describing different types of flushing procedures. http://www.sancarlosradiator.com/VoltageDrop/flush.htm Regarding the equipment I think there is not an special equipment designed for this use, it is more a description of what to use when performing what they call "3 Day power flush".

The fan clutch have been replaced and the behavior has been the same. I'm getting higher temps when the A/C is on, as soon as I turn it off the needle slowly start to go down, but it will need some cruising speed to get the needle to the middle of the gauge.

 

Do you know what is the normal operating temp for this particular engine? I mean when we can consider an overheat condition? above what number of celsius degrees? Is the last picture of the temp gauge an overheating condition for you?

 

Thank you again. 

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Alberto, I like to see an engine run within 10 degrees Fahrenheit of the thermostat setting.  If you're running a 195-degree F thermostat (which is likely), 205 degrees F would be plenty at an unloaded idle.  You're running around 220-225 if the temp gauge is accurate.  (An infrared non-contact thermometer could confirm the actual temperature if you focus at the thermostat housing with the engine running hot as shown in your photo.) 

I would not run a thermostat hotter than 195-degrees F.  On your carbureted 4.2L engine, 180 F-190 F would work well as long as the engine will meet emissions testing requirements.  A cooler setting would provide more of a cushion for the A/C at idle.  180 F should be tolerated, as this is well past the CTO opening point.

The idea of running a premium Cat coolant/anti-freeze is questionable.  This might be a great coolant and protectant, but would it dissolve block mud?  Unless Cat engineers this coolant to dissolve mud and also keep the system free of mud, I would consider this to be an expensive experiment.  The Cat coolant may be a superior coolant to use once the cooling system has been cleaned and restored.

The fan clutch is new, and if the engine is overheating at idle only, and only with the A/C on, you likely have a radiator problem(To rule out equipment requirements, confirm that you have the correct factory fan, the right fan clutch, and a radiator specifically for an A/C model.)  If the radiator and/or fan are non-A/C types, you need to upgrade.  If the radiator is the right one but it has blockage, improvement is possible with either rodding/hot tanking or a new core.

Is this the OEM radiator and fan?  Did the YJ come with A/C originally?  Sometimes A/C is aftermarket installed.  If the radiator and fan are not upgraded at the same time, the system is marginal.

Moses

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