Typical summer time operating temp with A/C on?

[Ken G Ford]

Wanted to see others typical operating temperatures for 4.0 Jeep TJ's during the summer time.

I have a digital after market temp gauge as I don't trust the OEM Dash gauge.

Ambient Temps here in Arizona being 114 Deg , I am seeing my Digital Gauge climb as high 119 Deg while running at 55MPH with AC running at Max.

Seems a little hot but maybe I am still "Gun Shy" after a previous over temp event that blew the head gasket and resulted in a $3K
0 Mile rebuild.

 

[DuckNut]

Here in FL I am always at 195 regardless of the outside temp. Freeway or city, always the same.

 

[User4574]

Your digital is reading your engine temps at 119 deg? You aren't even opening your thermostat. I am 205-210 all the time when circulating open.

If not a gauge, plug in an OBD dongle and run the Torque app or similar so you can monitor what the computer sees while running. Plus on your phone you should be able to screen record and review later.

 

[cpwolf]

Wanted to see others typical operating temperatures for 4.0 Jeep TJ's during the summer time.

I have a digital after market temp gauge as I don't trust the OEM Dash gauge.

Ambient Temps here in Arizona being 114 Deg , I am seeing my Digital Gauge climb as high 119 Deg while running at 55MPH with AC running at Max.

Seems a little hot but maybe I am still "Gun Shy" after a previous over temp event that blew the head gasket and resulted in a $3K
0 Mile rebuild.

I hope you meant 219.

119, that’s not normal operating temp. You’re not up to temp. Even with no thermostat I would think you’d get above 119.

In that kind of heat, run 200-208 ish with the bypass on.
I have a small leak in the heater core, I bypass it.

When it’s not bypassed in the winter, and it starts to get hot in Texas before I bypass again, it runs hotter, up to the 215 maybe 219

Just my experience, but I believe the leak lets the pressure off the system some.

Just my experience.

 

[DaveC]

AC at max doing freeway speed, I'm right about the middle of the 2 on the OEM temp gauge. At a long stop light, it may creep up to the 12 o'clock position, but eases back down as soon as I'm moving again. That's at our current temps here in the Phoenix area.

Only time it goes past 12 o'clock is if I'm trying to maintain highway speeds pulling a long, significant grade.

 

[bucky]

05 LJ 4.0 6sp. My gauge stays just past the 210 mark regardless of the outside temp. Pulling the Cajon Pass on I-15 which is a 20 mile 4-6% grade fully loaded with my teardrop trailer in 90-100+ degree ambient temp it stays the same. I run 3K rpm and 4th at the top 6% grade. I always keep an eagle eye on my gauges.

 

[Ken G Ford]

Sorry, meant 229 and not 119.

 

[JKP]

229 is not normal, but what does the dash gauge read in comparison?

Do you have an OBDII reader to read the actual temp from the PCM?

 

[cpwolf]

Sorry, meant 229 and not 119.

Yeah, that’s high.

You need to look into a cooling system refurb.
1. I’d look into the Radiator, if you don’t have Mopar see if you can find one.

2. Flush the system. Check for leaks too, I used Thermocure.

3. Check heater Core if it’s leaking. Bypass it to see if that is contributing

4. 195 mopar thermostat, or a good one, might not be any, everyone says they all suck, ha, I just used a Stant.

Zerex G05

Lots of threads on this, I’d educate myself

 

[KennethS]

Ambient Temps here in Arizona being 114 Deg , I am seeing my Digital Gauge climb as high 119 Deg while running at 55MPH with AC running at Max.

What RPM is your engine at that speed? RPM is more important than MPH. Higher engine speed generates more heat, which must be removed by the radiator.

My muscle car would run 190 with the AC on all day long if the engine was below 3000 RPM. Speed up to 70 mph / 3200 RPM and the temp started climbing to 220. Slow down to 2900 RPM and the temperature dropped back to 190.

 

[PRNDL]

I had a similar experience last summer but worse. On the freeway at speed with the AC on max, the odb reading was 239F and only dropped to 228-231 in town.

I did the whole cooling system refresh and temps are 202-215 now regardless of what speed I'm moving and the AC usage.

Post in thread 'PRNDL's Green Jeep'

Jul 17, 2023

It's 104F today and the Jeep did not like it. Coolant temps got as high as 239F on the highway on the OBDII readout and dropped to 231F on the road in town. Looks like I have more work to do.

• PRNDL

• 
• 

Post in thread 'PRNDL's Green Jeep'

Oct 3, 2023

Still dealing with cooling issues on the highway, around 235+F this past weekend cruising at 70-75mph. Temps actually come down under idle or around town driving. Still higher than ideal at 215-225F. I did the flush and thermocure treatment a few years ago when I purchased it, but it's time to replace the cooling system. Radiator, hoses, water neck all look to be factory, the pump looks like it has been replaced.

Part	Part Number	Retailer
Water Pump	Mopar 5012366AF (68382492AA)	Rock Auto

...

• PRNDL

• 

Post in thread 'PRNDL's Green Jeep'

Oct 9, 2023

Tackled this over the past several days. I was able to get the rear lower johnny joints serviced on Thursday and started draining and removing parts the following evening once I had tracking numbers and knew when I could expect deliveries.

With the rad, fan and belt removed, this is where we started. Its obvious that this is not the factory water pump. The lack of Mopar logo, the purple heater pipe and the worm clamp give it away. All of the other components appear to be factory including the thermostat.

Pump, water neck and generator bracket removed. The idler pulley looks...

• PRNDL

• 

 

[Ken G Ford]

Sorry everyone. FAT fingers. My accessory Digital Temp Sensor, tied into the top hose is showing 219.

Engine his a zero mile rebuild Top to Bottom with about 1000 Miles. Has new Aluminum Radiator single row (Can't find an OEM Mopar unit) New Flow Kooler water pump, High flow thermostat housing, Robert Shaw Thermostat, Texas Jeep Products Over Drive Water Pulley, New HD Fan Clutch, and the Heater Core was flushed before engine rebuild.

Just terrified about the temperatures now that I'm back in AZ.

Now I'm thinking about investing in the Camaro electric Fan conversion.....

 

[cpwolf]

Sorry everyone. FAT fingers. My accessory Digital Temp Sensor, tied into the top hose is showing 219.

Engine his a zero mile rebuild Top to Bottom with about 1000 Miles. Has new Aluminum Radiator single row (Can't find an OEM Mopar unit) New Flow Kooler water pump, High flow thermostat housing, Robert Shaw Thermostat, Texas Jeep Products Over Drive Water Pulley, New HD Fan Clutch, and the Heater Core was flushed before engine rebuild.

Just terrified about the temperatures now that I'm back in AZ.

Now I'm thinking about investing in the Camaro electric Fan conversion.....

I have seen folks talk about electric fans. I'm just not sure why anyone would do that, when the TJ has a system that works when setup correctly.

Sounds like you have all new equipment. Lots of high flow etc,. I'm in Central Texas, and feels like the surface of the sun most summers, ha. and the cooling system for my TJ when I set it up like it came, works.

I don't know which radiators are good, I got a Mopar and a used backup Mopar if necessary.

You're using an aftermarket temp sensor....have you plugged in an OBDII reader to see if that temp matches what the computer sensor is reading? A lot of the folks here are posting temps....ready by the engine sensor and using the OBDII port with a reader. I have a traildash and that's where I get the exact temp reading.

Just curious if that could show a difference. 219 is not that far off if you're in major heat with AC on.