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New engine/cooling problem

Rod Knee

NAXJA Forum User
Location
Grand Jct., CO
Less than a month ago, I had a remanufactured 4L, I6 engine installed in my XJ. A new thermostat and water pump were installed with the engine. I have a 3 row CSF radiator which I installed new about 6 months ago.

I’m back from vacation consisting of a few days at Black Hills Jeep Camp and a week in Utah rafting the Green as part of a family reunion. Had overheating problems beginning on the way out to the Black Hills consisting of my temp running up to about 230-235 degrees. Mitigated this problem by running the heater and fan. The problem persisted in the Black Hills while wheeling so I found a mechanic in Rapid City who checked out the thermostat and fan clutch on the belt driven fan and thought they were OK. The aux. elec. fan is kicking in at about 215. So I proceded on to Utah with my heat on for much of the way and eventually went to a shop there and had the thermostat and fan clutch replaced resulting in much improved performance on-road including use of the air conditioner without a heating problem. Going up a continuous uphill stretch of dirt road, however, my temp gauge quickly rose to the 240 degree threshold of the red area on my temp gauge, at which time I stopped, turned around, and let the engine cool. The mechanic that had replaced the fan clutch and t-stat concluded that some internal problem in the engine must exist on the basis of these observations. I have no reason to doubt the integrity and ability of this mechanic, and would recommend his services.

I know there are measures I could take to rectify this problem from use of Redline water wetter to placing a manual switch on the relay driven rad. fan., but they would address symptoms rather than cause. What I am wondering as a non-mechanic is:
1.what internal condition(s) in the engine could be quickly resulting in excessive temps while going steeplt uphill at slow speeds in the absence of cooling problems under other driving conditions, and
2. What testing could be performed to identify this/these conditions.
 
When moving slowly your temperature will rise due to reduced air flow through the heat exchanger--radiator.

If the flow of air through the radiator is reduced due to: mud/leaves/bugs (alive or dead)/accessories (trans cooler, power steering cooler, a/c condenser)/missing parts (fan shroud) and slow moving, while the engine is working harder, then your temp is going to rise.

Things you could do: Upgrade to a ZJ HD fan clutch, NAPA 272310, $44 and that will increase your airflow. Put in a command switch for the efan, less effective than the fan clutch upgrade, just remember to use it. Change the temp sensor for the efan so it comes on at 200 degrees. Upgrade the efan (I would still change the sensor to 200 degrees). You could also raise the boilover point by running 60/40 coolant and putting a higher pressure rad cap on--easy to do with an open system.
 
From what I've read the suggestion for the HD fan clutch is a good one. Since the engine is "new", I want to know if I indeed have an internal engine problem. From doing some reading, the head gasket could be a culprit, although that's not what I expected in a remanufactured motor. I also understand the heater core is something that could be a problem.
 
--how many miles have you put on the "new" engine? I have seen reman. engines with REAL tight clearances that will generate a lot of heat for the first couple thousand miles.

--the quick spike in temp after the thermostat change sounds like air trapped in the system that made it's way to the pocket around the sending unit and showed as a "super-hot" spot.
 
From what I've read the suggestion for the HD fan clutch is a good one. Since the engine is "new", I want to know if I indeed have an internal engine problem. From doing some reading, the head gasket could be a culprit, although that's not what I expected in a remanufactured motor. I also understand the heater core is something that could be a problem.

I think the slow moving/load more than a head gasket, but you can test for combustion gasses in the cooling system.

The heater core being plugged could give problems, more so on the later open systems than the closed systems, but from your description it sounds as if the coolant is flowing Ok as you were using that to reduce the temp.
 
The engine has about 4k miles on it now, but prob had about 3K miles on it when it overheated going up the steep grade at about 20 mph after replacing t-stat and fan clutch.

I know the stock cooling system is no great shakes, which is why I got the 3 core CSF. I suppose the cat converter could be bad....
 
The engine has about 4k miles on it now, but prob had about 3K miles on it when it overheated going up the steep grade at about 20 mph after replacing t-stat and fan clutch.

I know the stock cooling system is no great shakes, which is why I got the 3 core CSF. I suppose the cat converter could be bad....

Transmissions generate a lot of added heat on steep grades and low speed. Do you have a separate tranny cooler? If so, where is it located, and how is it plumbed? At 20 mph the torque converter will not lock, adding to the heat, slippage. You might consider a toggle switch over ride to lock the torque converter on a steep climb.
 
Hi :wave1:
Interesting post.

I just also installed a reman 4,0L engine. What oil did you put in?. I did use the 10-W30 mineral(multigrade). Not similar problem, but discovered some white smoke from exhaust, so I'm a kind of worried, but no water usage, nor grey oil on oil stick(yet..well, maybe im soon facing :explosion.)
 
A bad A/C Compressor or A/C Clutch could also cause lots of Load on the Motor thus causing it to Over Heat and drop your Gas Mileage like a Lead Brick.

Even a Bad Power Steering Pump could do the same. IMHO
 
I think I have this problem solved. Tonight I burped the cooling system by running the engine with the rad cap off. After about 15 minutes I started getting continuous bubbling of the coolant. After about half an hour the electric fan kicked in almost simultanously with about a two inch drop in the coolant in the rad neck (coincidence?).

Ran up a continuous steep grade at the same speed as the one in Utah where my overheating problem had really manifested itself, only this time I had the AC on all the way to test under worst case scenario. The hottest temp that was sustained was about 215 degrees, although I did reach a momentary peak of about 220 degrees. Still, far better performance by the cooling system than I had been having when my temp gauge quickly ran up to the red zone. Without running the combo of slow speed, steep uphill grade, and AC, my jeep ran steadily at 210 degrees.

In summary, I had two problems contributing to the overheating of my vehicle, a bad fan clutch and air bubbles in the coolant. The new engine does not appear to have factored into the overheating other than in that the cooling system had to be drained and refilled to put in a new t-stat. I am not a mechanic, so part of the satisfaction of being a jeep hobbyist for me is solving problems like this one that beforehand seemed to have had me defeated.
 
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Hi :wave1:
Interesting post.

I just also installed a reman 4,0L engine. What oil did you put in?. I did use the 10-W30 mineral(multigrade). Not similar problem, but discovered some white smoke from exhaust, so I'm a kind of worried, but no water usage, nor grey oil on oil stick(yet..well, maybe im soon facing :explosion.)


I am using 10w-30. In retrospect, I really have had no symptoms of a bad head gasket other than overheating. But the overheating seems to have been shown to be due to other factors.

Good luck.
 
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