Engine Temperatures

[Discoman9001]

Hello everyone, the running hot comanche is back again.( 1988 4.0 automatic transmission with 102k miles) So, I flushed the coolant, changed the thermostat, water pump is pretty new, radiator is brand new, gauge sending unit is about a month old. And yet the gauge runs got. I bought a infrared thermostat gun and I aimed it at the radiator, nice and cold at 185 Fahrenheit  on the outlet, about 210 Fahrenheit on the inlet, yet the thermostat housing on the black read 230+. Houses were about 205-215 and the block on the passenger side was about 210-220 and the block near the manifold was nearly 300 degrees. Is this roughly normal. Or is this poor thing cooking. Thanks for any and all advice. 

[jpnjake]

15 hours ago, Discoman9001 said:

Hello everyone, the running hot comanche is back again.( 1988 4.0 automatic transmission with 102k miles) So, I flushed the coolant, changed the thermostat, water pump is pretty new, radiator is brand new, gauge sending unit is about a month old. And yet the gauge runs got. I bought a infrared thermostat gun and I aimed it at the radiator, nice and cold at 185 Fahrenheit  on the outlet, about 210 Fahrenheit on the inlet, yet the thermostat housing on the black read 230+. Houses were about 205-215 and the block on the passenger side was about 210-220 and the block near the manifold was nearly 300 degrees. Is this roughly normal. Or is this poor thing cooking. Thanks for any and all advice. 

I mean depending on where you are and the temperatures around you this sounds pretty normal, if your in the desert with 110 degree heat I’d say that’s cold, but if your in a 10 degree tundra then it’s extremely hot. I would check out your fan clutch and think about adding the extra fan if your concerned about the heat 

[Discoman9001]

1 hour ago, jpnjake said:

I mean depending on where you are and the temperatures around you this sounds pretty normal, if your in the desert with 110 degree heat I’d say that’s cold, but if your in a 10 degree tundra then it’s extremely hot. I would check out your fan clutch and think about adding the extra fan if your concerned about the heat 

I just moved out to Arizona, so the desert heat is definitely having some effects on the comanche. Just afraid of roasting the poor thing. The second I’m in traffic the gauge just starts creeping up and I’d really hate to blow the poor thing up. 

[jpnjake]

1 hour ago, Discoman9001 said:

I just moved out to Arizona, so the desert heat is definitely having some effects on the comanche. Just afraid of roasting the poor thing. The second I’m in traffic the gauge just starts creeping up and I’d really hate to blow the poor thing up. 

In the desert environment I’d definitely suggest the electric cooling fan for backup Cooling while idling, and worst case scenario if it’s getting hot turning your heat on acts as an additional radiator, just don’t pass out from the heat 

[Pete M]

same.  I would add an efan and swap in a new fan clutch.    I assume you have an intact fan shroud? 

[AZJeff]

There was another thread on this topic about 10 days ago where I spelled out the magic formula for how to keep an XJ or MJ operating at proper temperatures in Phoenix heat.   And that heat is about as high as you will see regularly inside the US.

 

check out that thread, and follow the suggestions as needed to have a happy Jeep in the heat

[Discoman9001]

14 hours ago, AZJeff said:

There was another thread on this topic about 10 days ago where I spelled out the magic formula for how to keep an XJ or MJ operating at proper temperatures in Phoenix heat.   And that heat is about as high as you will see regularly inside the US.

 

check out that thread, and follow the suggestions as needed to have a happy Jeep in the heat

I was the host of that thread. I’ve tried most things except an open cooling system. 

[Discoman9001]

15 hours ago, Pete M said:

same.  I would add an efan and swap in a new fan clutch.    I assume you have an intact fan shroud? 

Fan shroud is intact. Thermostat, coolant, clutch fan, and radiator all all brand new, water pump on a few months old, as off all of those repairs, it runs phenomenal until the temp of the day is about 100 degrees. Then it just keeps climbing.

[AZJeff]

If you are still seeing operating temperatures of over about 215* when ambient air is at 110* (or thereabouts), then something in your cooling system is not up to OEM specifications and performance.

 

The two things people often "think" are OK, but are not, are the radiator proper and the viscous clutch fan.  

 

The radiator might flow water just fine, but if the passages have lots of corrosion or mineral buildup, they cannot transfer the heat as required.

 

The viscous clutch fan is notoriously hard to actually confirm as working correctly.   My rule is that anytime that is over 5 years of age, it gets replaced.

 

Finally, as Pete said, if you don't have an e-fan, get one installed.  My efan comes on regularly even when my AC is not running in the hot weather, and that tells me the viscous fan alone cannot cool a 4.0 when the ambient air is 110*

[Discoman9001]

14 minutes ago, AZJeff said:

If you are still seeing operating temperatures of over about 215* when ambient air is at 110* (or thereabouts), then something in your cooling system is not up to OEM specifications and performance.

 

The two things people often "think" are OK, but are not, are the radiator proper and the viscous clutch fan.  

 

The radiator might flow water just fine, but if the passages have lots of corrosion or mineral buildup, they cannot transfer the heat as required.

 

The viscous clutch fan is notoriously hard to actually confirm as working correctly.   My rule is that anytime that is over 5 years of age, it gets replaced.

 

Finally, as Pete said, if you don't have an e-fan, get one installed.  My efan comes on regularly even when my AC is not running in the hot weather, and that tells me the viscous fan alone cannot cool a 4.0 when the ambient air is 110*

Since you and I last talked I installed a new radiator and a new clutch fan, and it does have an electric fan. Yesterday it was about 108 degrees and after 10 minutes of sitting in traffic the temperature just started climbing rapidly. 

[GrandBoost98]

A YJ buddy was going through the same issue, you can read his journey here

https://www.jeepforum.com/threads/arizona-a-c-highway-overheating.4363457/ 


And here he gives his wrap up

https://www.jeepforum.com/threads/arizona-a-c-highway-overheating.4363457/post-41550292
 

[AZJeff]

2 hours ago, Discoman9001 said:

Since you and I last talked I installed a new radiator and a new clutch fan, and it does have an electric fan. Yesterday it was about 108 degrees and after 10 minutes of sitting in traffic the temperature just started climbing rapidly. 

Temps climbing rapidly in traffic is normally a sign of lack of airflow over the rad due to fan issues.

 

when you put in the new rad, what did the old coolant look like?  The guy @GrandBoost talked about had massive crud in his cooling system, and that will plug up a radiator pretty quick.

 

have you correlated instrument gauge readings with measured temperatures out at the thermostat elbow, BTW?

[Discoman9001]

4 hours ago, AZJeff said:

Temps climbing rapidly in traffic is normally a sign of lack of airflow over the rad due to fan issues.

 

when you put in the new rad, what did the old coolant look like?  The guy @GrandBoost talked about had massive crud in his cooling system, and that will plug up a radiator pretty quick.

 

have you correlated instrument gauge readings with measured temperatures out at the thermostat elbow, BTW?

The coolant that came out looked pretty clean, and I checked the gauge sending unit with an infrared thermometer, it reads accurate, I used the infrared on the elbow on the front of the engine when the truck runs real hot, and it’s reading about 230-240. Today it was cooler and I drove around all morning with little to no issues, it wasn’t until the temp climbed over a 100 did the truck start to overheat again. 

[AZJeff]

It sounds like you are getting properly correlated temperature readings on the dash.   I am wondering why they are so high, even for this area.

 

From what you are saying, your high temperature problem is most evident in traffic, when airflow over the radiator is lessened, and the radiator cannot dump the heat generated by the engine.   That can only happen if coolant flow in the radiator is reduced by some reason, or if air flow over the radiator is not adequate.

 

1.  You have a new radiator.  I assume it is at least the OEM 2 row type, correct?

2.  Is your radiator filled with a 50/50 mix of antifreeze and clean water?

3.  Have you confirmed the electric fan is working, and coming on when engine temperatures reach about 215*?

4.  What is the condition of the thermostat in the engine?  You say it is new, but have you actually checked its' function outside the vehicle?

5.  You say you have a new clutch fan.  Does it seem to be functioning as expected?  (I wonder if it's defective.)

6.  Does your MJ have factory AC?  If so, is the condenser free of any obstructions of airflow? (dried mud, tons of dead bugs, etc.)  I am looking at ways the radiator isn't getting the airflow it needs.

7.  Are your upper and lower radiator hoses nice and firm (when cold)?  A soft lower hose can collapse under water pump suction, and restrict coolant flow.

 

One last question:  when the engine temperature begins to take off for the moon, does the engine actually begin to boil over via the pressure tank, or has the tank and it's cap contained the pressure while it's exceeding normal limits?

[Discoman9001]

1 hour ago, AZJeff said:

It sounds like you are getting properly correlated temperature readings on the dash.   I am wondering why they are so high, even for this area.

 

From what you are saying, your high temperature problem is most evident in traffic, when airflow over the radiator is lessened, and the radiator cannot dump the heat generated by the engine.   That can only happen if coolant flow in the radiator is reduced by some reason, or if air flow over the radiator is not adequate.

 

1.  You have a new radiator.  I assume it is at least the OEM 2 row type, correct?

2.  Is your radiator filled with a 50/50 mix of antifreeze and clean water?

3.  Have you confirmed the electric fan is working, and coming on when engine temperatures reach about 215*?

4.  What is the condition of the thermostat in the engine?  You say it is new, but have you actually checked its' function outside the vehicle?

5.  You say you have a new clutch fan.  Does it seem to be functioning as expected?  (I wonder if it's defective.)

6.  Does your MJ have factory AC?  If so, is the condenser free of any obstructions of airflow? (dried mud, tons of dead bugs, etc.)  I am looking at ways the radiator isn't getting the airflow it needs.

7.  Are your upper and lower radiator hoses nice and firm (when cold)?  A soft lower hose can collapse under water pump suction, and restrict coolant flow.

 

One last question:  when the engine temperature begins to take off for the moon, does the engine actually begin to boil over via the pressure tank, or has the tank and it's cap contained the pressure while it's exceeding normal limits?

1. Yes it is an OEM type radiator

2. yes it is filled with 50/50 and clean water

3. the electric fan is working, and with the A/C running it practically never shuts off

4. the thermostat is functioning properly. I tested it before installing it

5. The fan clutch does seem to be functioning properly, spins freely when cold and locks up solid when warm

6. The condenser is clean

7. The hoses are nice and firm when cold, they were replaced in December 

8. when the temperature takes off to the moon the coolant expansion tank looks swollen but doesn’t leak out. I try to shut off the jeep or get to a long stretch of highway as soon as it starts crawling up in temperature, but when I have check it when it’s hot the expansion tank is definitely swollen and when I shut the truck off it gurgles a bit. 

[AZJeff]

6 hours ago, Discoman9001 said:

1. Yes it is an OEM type radiator

2. yes it is filled with 50/50 and clean water

3. the electric fan is working, and with the A/C running it practically never shuts off

4. the thermostat is functioning properly. I tested it before installing it

5. The fan clutch does seem to be functioning properly, spins freely when cold and locks up solid when warm

6. The condenser is clean

7. The hoses are nice and firm when cold, they were replaced in December 

8. when the temperature takes off to the moon the coolant expansion tank looks swollen but doesn’t leak out. I try to shut off the jeep or get to a long stretch of highway as soon as it starts crawling up in temperature, but when I have check it when it’s hot the expansion tank is definitely swollen and when I shut the truck off it gurgles a bit. 

So if you can escape traffic, and begin cruising at a steady 40+mph, do the temperatures return to the normal range?

 

If it does that, it sure implies that not enough air is moving across the radiator when the vehicle is sitting still to dump the heat being put into the rad.   Once vehicle speed raises the air flow rate, then the radiator can do it's job correctly.

 

I am going to ask another question--do you have a OEM fan shroud around the mechanical fan?

[Discoman9001]

20 minutes ago, AZJeff said:

So if you can escape traffic, and begin cruising at a steady 40+mph, do the temperatures return to the normal range?

 

If it does that, it sure implies that not enough air is moving across the radiator when the vehicle is sitting still to dump the heat being put into the rad.   Once vehicle speed raises the air flow rate, then the radiator can do it's job correctly.

 

I am going to ask another question--do you have a OEM fan shroud around the mechanical fan?

Yes, I have the OEM fan shroud, and yeah, once I’m moving the temperature regulates, it’s basically only at a complete stop or at an under 10mpg issue. It’ll run down the highway or on normal roads all day at 195-210

[Pete M]

the 97+ rad fan is supposed to be better than the older version. 

[AZJeff]

21 hours ago, Pete M said:

the 97+ rad fan is supposed to be better than the older version. 

Yeah, but the older fan, if working as intended, should not cause total overheating like the OP is reporting.  The new fan should just give a bit more margin.

 

I am sort of stumped here.   The "plumping" of the coolant tank is to be expected, especially when it's older.  I was expecting the OP to report some sort of pressure loss at the cap, since that is a COMMON issue with older closed system tanks.

 

I keep going back to the fact that the vehicle only overheats when stationary.  That is almost ALWAYS a sign of lack of airflow over the radiator.  (I had an F150 that would do the same thing.)

 

OP---I have a question.  When your AC is running, and you come to a stop, does the interior cabin temperature start to climb noticeably?  And then once you start moving again, it cools back down to what it was before you stopped?

[ghetdjc320]

On 9/13/2023 at 5:49 AM, Discoman9001 said:

I just moved out to Arizona, so the desert heat is definitely having some effects on the comanche. Just afraid of roasting the poor thing. The second I’m in traffic the gauge just starts creeping up and I’d really hate to blow the poor thing up. 

Does the temperature eventually hit a stopping point or does it just keep creeping up until it pegs out? 

[Discoman9001]

I wanted to revise the thread, I found a solution for my problem and my jeep has been fixed and running well for about 2 weeks now. I changed the electric fan for one out of a 97 much like someone had suggested, and it’s been running cool ever since. A/C on, sun coming down. The temp no longer goes above 210. And on cooler days it stays around 200 degrees constantly. I’m not 100% sure what the difference is as far as the fans other than a different blade design but boy does it move some air. I wanted to thank everyone for the advice on here and all the help because it had me absolutely stumped. 

[Pete M]

more air = better   

[Drahcir495]

On 9/13/2023 at 12:30 AM, AZJeff said:

There was another thread on this topic about 10 days ago where I spelled out the magic formula for how to keep an XJ or MJ operating at proper temperatures in Phoenix heat.   And that heat is about as high as you will see regularly inside the US.

 

check out that thread, and follow the suggestions as needed to have a happy Jeep in the heat

Hey AZJeff, I looked for that threat you spelled everything out in? It would be a good thread to read up on. If you get a chance, could you direct me to it. Thanks in advance.

 

[AZJeff]

7 minutes ago, Drahcir495 said:

Hey AZJeff, I looked for that threat you spelled everything out in? It would be a good thread to read up on. If you get a chance, could you direct me to it. Thanks in advance.

 

Here is my list of tips from that thread, repeated for posterity:

 

I have owned multiple XJ's and now an MJ here in Phoenix, and all of them have run just fine in the heat.   The secret to that is to make sure your cooling system is operating AS DESIGNED by Jeep.   If ANYTHING has deteriorated below OEM spec, overheating is likely.

 

 Here are my thoughts:

 

1.  I don't trust the temperature gauge on the dash to be particularly accurate.  I alway confirm temperatures by using one of the infrared meters with a laser pointer on it (Harbor Freight for the win.), and I take my temps on the thermostat elbow.  By doing that, you can sort of extrapolate how far off the gauge on the dash is from reality.

2.  If your coolant is even the slightest bit cruddy, a flush is the minimum to do.   When you refill, be sure you run the correct mix of antifreeze, because it not only lowers the freezing point, but it raises the boiling point of the coolant as well.

3.  If your viscous fan clutch is more than 5 years old, replace it, regardless of if it "feels" OK.

4.  If you don't have the electric fan in your MJ, install one (An improved one was used in the 97+ XJ, and is a worthy upgrade.).

5.  If your radiator has any crud that does not come out from a good flush (an inspection mirror and flashlight is needed to see inside the end tanks to look for permanent deposits in the radiator), then  consider converting to an open cooling system while you are replacing the radiator.  It removes a bunch of weakness with the closed system pressure tank and cap.

6.  If you are redoing the system to convert to open, ditch the heater control valve while you are at it.  That plastic piece of junk is prone to breaking, especially with the heat we see out here.

7.  If your hoses are even the slightest bit soft, you can expect them to get MUCH softer very soon with the higher under-hood temperatures.  I just automatically replace mine as soon as I see or feel any squishiness at all.

8.  While you are changing the hoses and/or the radiator, put on a new belt if the one you have isn't new within the past 5 years was well.  The heat kills those things as well.

 

I know guys who run the hood louvers, but I am not convinced it really helps the actual engine cooling that much.  It might make the temperature of various components lower, but actual engine temps are not going to be improved that much.

[Drahcir495]

Thank you . lots of good info there. looking into the 97 XJ E-fan now.