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I have read the cooling system section of my FSM multiple times in the last five months and nowhere have I seen it say the engine should normally run above 195°. I’ve even used the search feature of the ebook. Do you have a page number or section to reference? Perhaps it’s different for your 1996.
sorry, its a bit late for me here, but look where it talks about the system going "closed loop"
Perhaps my memory is duff, but I think it talks about the system not operating optimally until 195F is reached, which is where the factory thermostat opens
In addition, consider the logic of engineer design...why would they program the electric fan to come on at 210F ?
imo, that is because they want the coolant temp to be between 195 and 210F
The XJ has a few other design oddities, like the restricted factory exhaust, that are also reputedly designed to save fuel and reduce pollution
As I mentioned my XJ, in our mild winter, is mainly running at around 180F, with a completely stock ( but new) cooling system, the thermostat must probably be an 82C one
(It does still reach 210F if allowed to idle long enough)
Overheating is a real issue where I live in Australia, and as I mentioned, it does use more fuel running at these lower temps
I would presume that if you have a 4.6 stroker, the enhine came out and you removed the welch plugs, and cleaned out the block, dipping them is best
I work mainly on older motors, and I have seen the cooling passages literally half full of sediment
As a last resort you could pull one easily accesible plug and see if you have a buildup
modern engines run higher pressures and coolant temps to reduce fuel consumption and CO2
THERMOSTAT
A pellet-type thermostat controls the operating temperature of the engine by controlling the amount of coolant flow to the radiator. On all engines the thermostat is closed below 195ºF (90ºC). Above this temperature, coolant is allowed to flow to the radiator. This provides quick engine warm-up and overall temperature control.
An arrow plus the word UP is stamped on the front flange next to the air bleed. The words TO RAD are stamped on one arm of the thermostat. They indicate the proper installed position.
The same thermostat is used for winter and summer seasons. An engine should not be operated without a thermostat, except for servicing or testing. Operating without a thermostat causes other problems. These are: longer engine warm-up time, unreliable warm-up performance, increased exhaust emissions and crankcase condensation. This condensation can result in sludge formation.
My FSM doesn't explicitly state the normal operating temperature is 210º like you've suggested. My electric fan comes on at 218ºF and turns off at 215ºF. If it takes about 20º for the thermostat to be fully open, then this tells me the engineers wanted the fan to come on to help the cooling system get down to temperatures where the thermostat can open/close. Based on this thread's discussion and research, I am beginning to think 195-215º is the normal operating temperature range for these engines. Anything outside of this range is not correct. For me, I still want my normal operating temperature to be 195º (within a few degrees) so that there is room for the 20º increase when there's extra load on the engine (mountain passes, towing, etc.). I've also found when the temperatures get above 220º they are much harder to bring back down.
My block was cleaned before it was built and shipped to me.
Cooler temperatures are here so I'll return to this thread around May 2023 with more tests provided the Lord tarries and the creek don't rise.
Have you guys heard this conversation with Rick Mudge? He was an engineer for Chrysler in the 80's-90's who's department was cylinder head development for the 4.0 straight 6. They ran extensive thermodynamic tests on this platform. Rick associates cooling issues with dead water flow in the engine block between cylinders 4-5 and 5-6. This is a common sense answer from Rick. This same issue plagues pretty much all inline 6 engines. Ask 2J guys about their water temp. Same issue we have.
Rick built a pretty rowdy 4.0L for drag racing. He was running mid 8's and had the crank spinning over 9000 RPM. On this engine, he made a custom core plug for the rear most bore and tapped NPT threads into the center of it. This allowed him to run a line from a tee in the lower radiator hose to the custom core plug. He mentions that between those cylinders, a little more turbulence/movement is all you need to keep the temp down. He mentions that the water in most of the engine is ripping through pretty rapidly, even behind cylinder 6. Though the water between 4-5 and 5-6 just swirls around like a toilet flushing. I know some others have simply used the NPT coolant port in that area of the block to achieve the same effect. On my current turbo build, I'm actually working on this at the moment. I'm using a steel core plug for the rear most bore, and I'm welding a -8 ORB bung into it. Then I'll just thread in a -8 ORB to 3/8" barb fitting into it and run a line from a radiator hose tee adapter. I'll probably do the same with the NPT port as well.
Rick associates cooling issues with dead water flow in the engine block between cylinders 4-5 and 5-6. This is a common sense answer from Rick. This same issue plagues pretty much all inline 6 engines. Ask 2J guys about their water temp. Same issue we have.
the same issue plagues the famous Jaguar I6 built between 1948-1992, starting as a 3.4, but by 1965 was a 4.2, and the cooling system wasnt as quite as effective then, big increase in torque, so heat is directly proportional, and that engine cants backward about 4 degrees, which I think a lot of I6 engines do and they fill up with casting sand, rust, scale and sediment, I have seen then more than half full
Those engines dont last as many miles as Jeep engines, and have that same issue in cooling the back cylinders, an alloy head to add to the cooling and longevity issues
We had a Jeep XJ owner, bought his new and from day one it over-heated on low-range uphills, others towed caravans, so they are not all the same from the factory
As I have said before, if the temp stays between 195F and 225F, everything is fine, if not, only then do you have a problem
Have you guys heard this conversation with Rick Mudge? He was an engineer for Chrysler in the 80's-90's who's department was cylinder head development for the 4.0 straight 6. They ran extensive thermodynamic tests on this platform. Rick associates cooling issues with dead water flow in the engine block between cylinders 4-5 and 5-6. This is a common sense answer from Rick. This same issue plagues pretty much all inline 6 engines. Ask 2J guys about their water temp. Same issue we have.
Rick built a pretty rowdy 4.0L for drag racing. He was running mid 8's and had the crank spinning over 9000 RPM. On this engine, he made a custom core plug for the rear most bore and tapped NPT threads into the center of it. This allowed him to run a line from a tee in the lower radiator hose to the custom core plug. He mentions that between those cylinders, a little more turbulence/movement is all you need to keep the temp down. He mentions that the water in most of the engine is ripping through pretty rapidly, even behind cylinder 6. Though the water between 4-5 and 5-6 just swirls around like a toilet flushing. I know some others have simply used the NPT coolant port in that area of the block to achieve the same effect. On my current turbo build, I'm actually working on this at the moment. I'm using a steel core plug for the rear most bore, and I'm welding a -8 ORB bung into it. Then I'll just thread in a -8 ORB to 3/8" barb fitting into it and run a line from a radiator hose tee adapter. I'll probably do the same with the NPT port as well.
Randy, thanks for posting the phone call. It’s very interesting and holds some weight given the source. I’m curious how your solution will look and function when you complete it.
Randy, thanks for posting the phone call. It’s very interesting and holds some weight given the source. I’m curious how your solution will look and function when you complete it.
You can see the LJ come together at JeepStrokers.com
Winter was nice as the cold air kept the water temperatures below 200ºF. With Spring upon us, I went for my usual test drive with a recent mod.
Turn e-fan on at 200º and off at 196º
65mph cruise
OAT 60°F
Partly cloudy
Water temps
200-208° with efan on northbound
Air temps
94° IAT northbound
109° engine bay northbound
While it's no 80º day, I was disappointed in that the water temps were still breaching 200º when the OAT is only 60º and the fan was kicking on at a lower temperature with the idea it would help keep temperatures from running away.
So, it was time to heed the input I've received from this thread and other places and replace the Mopar tow radiator. Unfortunately, Mopar is discontinuing more parts for our vehicles each year and the radiator is no exception which left me to choose from the aftermarket selection. After a bunch of research and discussions, I decided to give the newer Champion Radiators BC1193 a try. After all, they claim it's good for off-road applications and can cool a 600HP engine.
I ran through a flush and rinse prior to swapping radiators in case there was any dirt whirling around in the block. The coolant was quite clean when it initially came out. First tests in 40-50º temperatures showed some promise as the water temperature would occasionally dip below 195º. Today we had a warm Spring day perfect for the test drive.
Champion BC1193 radiator w/o water wetter
65mph cruise
OAT 84-86°F
Clear and sunny
Water temps
204-206° with AC on northbound (no efan override)
212-213° with AC on southbound (no efan override)
206° idle no AC, 197° idle no AC and efan override on
Air temps
131° IAT northbound, 132° southbound, 160° idle
144° engine bay northbound, 152° southbound, 162° idle
I finally have the results I was after and the data proves the radiator was indeed insufficient even though it took me a while to believe it. Thanks for all of the discussions to help get me there. If the Summer heat proves to still be too much then I will continue to update this thread with additional mods/tests.
Hopefully this exercise and data can help others who might be in similar situations or want to know how effective a certain "cooling mod" might be that comes up often on the forums.
A note for anyone who might want to install a BC1193 from Champion -- the HD fan clutch will be too large (not that it helped in my case anyways). I have 1/2-inch spacing between the stock fan clutch and radiator.
Hey folks, new here but was following this thread for a while. I also have a golen 4.6 + alot of extra weight and lift. Above GVWR without towing for sure.
Temp reading results, each taking the same 8% grade for several miles at 65mph. The hill is about 8 miles from my house with some rolling grades leading up to it. Ambient temp was about 75 degrees.
Temp measured at crest of big hill. I also tested with a 1/2" restrictor in the upper hose to see if the flow was too high, and interestingly it did help in a couple scenarios.
No flow restrictor:
Mishimoto + 160 tstat = hit 220' before I even got to the hill, aborted
Mishimoto + 195 tstat = 215' Stock + 195 tstat = 197' <----!!!
Still getting hot (up to 225) in 95 degree ambient desert sand. I am still running the heisco t-stat housing and pump, and a ZJ clutch...so not completely stock. May try OEM versions and report back at some point.
No flow restrictor:
Mishimoto + 160 tstat = hit 220' before I even got to the hill, aborted
Mishimoto + 195 tstat = 215' Stock + 195 tstat = 197' <----!!!
Here it is, folks...in plain English.
A properly maintained OEM cooling system straight outperforms all the "upgrades", some of us have been screaming it for years. This guy did the math. Awesome job my brother.
I have also been running a stroker for years, on a highly modded rig with lots of extra weight as well. My stock cooling system has never had a problem keeping up with demand. And, FWIW, I lived in the Mojave desert for years with it before leaving Kommiefornia.
A properly maintained OEM cooling system straight outperforms all the "upgrades", some of us have been screaming it for years. This guy did the math. Awesome job my brother.
I have also been running a stroker for years, on a highly modded rig with lots of extra weight as well. My stock cooling system has never had a problem keeping up with demand. And, FWIW, I lived in the Mojave desert for years with it before leaving Kommiefornia.
Thanks man, I was clued in by Mr. Golen himself.. he said most stroker cooling issues are solved by returning everything to stock, many confirmed cases if mishimoto radiators being the root cause. I don't know how others perform, but it would seem that at least with the mishi there is a restriction in the airflow compounded by the coolant moving too fast through it. Whatever the case, it is not a good choice for our platform.
The stock Radiator is 1 row of and others are 2 row Radiators so if you think about it the coolant in a 1 row radiator will pass though faster then a 2 row because there are 2 times more tubes for the coolant to go though and yes the 2nd row of tubes will get hotter air because the 1st row heats it up , so you do need good air flow so hood vents will help the air flow . so there is a lot to look at when looking at how hot your engine runs and when it runs hot .
Thanks man, I was clued in by Mr. Golen himself.. he said most stroker cooling issues are solved by returning everything to stock, many confirmed cases if mishimoto radiators being the root cause. I don't know how others perform, but it would seem that at least with the mishi there is a restriction in the airflow compounded by the coolant moving too fast through it. Whatever the case, it is not a good choice for our platform.
