Pegged the temp gauge! Huh??

KeighJeigh · **Posted:** Sat May 17, 2008 7:50 pm

Overheated the hell of the mule today. This is the 2nd time I have noticed a temp problem - but I rarely stress it very much. The first time was after a long stretch up a logging road in deep snow early last winter with the throttle pegged to the floor. It got hot enough it that it started to chime at me. This time I had the AC on and climbed from the valley floor up to my house which is about 4 miles and 1,400 vertical feet. We are having record hot temps here in Seattle for May and it is currently about 87 degs. By the time I got to my house the temp was pegged.

I took it to the stealer about the overheating the first time it happened last winter and, of course, they could not reproduce the problem so sent me on my way insinuating I had imagined the whole thing.

If there is nothing officially wrong with the vehicle, perhaps and auxiliary tranny or radiator would bring these temps down? If this thing is seriously overheating on a hot day in May on my driveway and no trailer, I hate to think what it might do on my weekly logging road & trail jaunts in Easter Washington this summer! :evil:

The threads I have found on this topic are dated and I have not yet seen a concrete answer on what to do. Some say tranny cooler - but that seems related to towing issues. Some say aux fan while others were going to try and cram a larger radiator into it. The hardier in the bunch were going to turn off the AC in 117 deg weather when going uphill. :roll:

What is the consensus of the expert CRDers? (I don't know if my wife's 06 does the same thing but she has never reported it. (Than again, she didn't report anything wrong with our old Subaru before she completely baked it and seized the motor on the hwy)

Note: In the past few days I did 3 things: ORM (I don't have the SEGR circuit board built yet so for the mean time I just yanked the sensor plug); 2) New fan belt; 3) Elephant hose mod. (last night). Since this is the second time I have noticed overheating I can't imagine any of these recent activities could have contributed to the problem. But???

- Chris

Sir Sam · **Posted:** Sat May 17, 2008 7:53 pm

if your fan belt was loose(real loose) you might not be pulling air with the fan.

Also, how many miles now and have you ever flushed the coolant?

You could also have crud built-up on your radiator(s).

Endurance · **Posted:** Sat May 17, 2008 8:02 pm

Did you get the TSB/recall done? Some CRD's have this problem, they read out the wrong temperature, too hot.

warp2diesel · **Posted:** Sat May 17, 2008 8:16 pm

..and wiring.
The head temp sensor is just a Thermistor stuck in a Mopar threaded adapter.
Unplug it and see if your gauge stays on cold.
Check the FSM and see if there is a chart with values for specific temps.
A wire going to the sensor grounded out will show a pegged guage!!
Check wiring for pinched wires.

Good luck

ATXKJ · **Posted:** Sat May 17, 2008 9:08 pm

FYI - I've been in 100+ temps - traffic jam with the AC on and barely gotten above midpoint - so start troubleshooting.

nursecosmo · **Posted:** Sat May 17, 2008 10:06 pm

Was it high engine temp or the transmission that was chiming? They both have similar idiot lights. I have had the tranny chime at me when driving fast in deep sand. and in the case you describe the transmission should have overheated before the engine. The capacity of the CRD radiators is so high that they should never ever overheat in 87 degree weather.

Jim Friese · **Posted:** Sun May 18, 2008 12:03 am

How many feet above sea level are you when you boiled over? Remember warter will boil at a lower temp. the higher you go. Have to
remember that half of you coolant is water the other half is antifreeze. The atmospheric pressure is less at the higher elevations allowing
water to boil at a lot lower temp. that could be the cause of your problem.

Jim

Turbo Tim · **Posted:** Sun May 18, 2008 12:05 am

Yes you can overheat the CRD in 80* weather. I have done it a few times now. I can only do it when I’m towing a 3500 LB trailer and trying to go 75+ MPH up a 6% grade. After about 5 miles or so it will not only have the temp gauge pegged, but will start chiming at me. Only when I slow down to some stupid speed of like 50 MPH everything works Ok.
If you don’t have your foot in it, you shouldn’t have any overheating problems. If it does overheat, take your foot off the go-pedal. It will cool right down.

Sir Sam · **Posted:** Sun May 18, 2008 3:12 am

Jim Friese wrote:

How many feet above sea level are you when you boiled over? Remember warter will boil at a lower temp. the higher you go. Have to
remember that half of you coolant is water the other half is antifreeze. The atmospheric pressure is less at the higher elevations allowing
water to boil at a lot lower temp. that could be the cause of your problem.

Jim

Except the pressures the cooling system is under should negate this effect entirely.

KeighJeigh · **Posted:** Sun May 18, 2008 4:36 am

Thanks guys!
Some more specifics:

1) It did not boil over or chime at me this time - I caught it as I was pulling into my driveway but it was nearly pegged. I let it idle and it cooled down quickly. The first time it overheated was last fall when I was pushing it hard up a logging road in deep snow. On that occasion, it did chime at me so I pulled over, turned off the engine and then thought better of it and turned it back on so it could circulate coolant - after 2 minutes it had cooled down again. I went to the dealer after that incident because I thought something must be terribly wrong: The air temp was below freezing, the heater was on and I made the assumption that a relatively new car had a properly designed cooling system. The dealer, as usual, drove it around the block, could not replicate the problem and refused to do further investigation. I know there was a problem with some of them with regard to the temp gauge but the dealer claimed it was not associated with my VIN number.

2) The gauge normally does not budge. It stays one tick to the left just like most everyone else's. It is precisely because the temp has been so unwavering under varying conditions that this came across as a major failure the 2 times I noticed it.

3) The car just turned 30K and the coolant looks like clean Koolaide. I seen no signs of corrosion or contamination or sludge. I've considered flushing and putting in a new thermostat just in case - and perhaps I should take the time to do so as a good maintenance move - but I hate chasing the wrong problem.

4) Last winter I took it into the dealer and asked them to do every TSB published. I then took them a list I got from this forum and made them do even more. :twisted:

They claimed my VIN was not associated with any gauge problems. Perhaps they are wrong (as they are with MANY things regarding this car) but I don't have specifics to prove any case even if it were the problem....

5) Warp2diesel, I'll pull the thermistor & see what happens.....but the gauge goes down when I stop and let it idle. The car does cool down fast.

6) I gain 1,400 ft from sea level to get to my house from town - which is too low for any major differences in coolant performance. However, the last 1/2 mi is gravel and gains 600 ft straight up (which is why we have 2 CRDs) so the engine see a lot of stress on that last stretch - especially during hot weather and the AC on. However, I assumed they had been designed to tolerate far more harsh heat conditions than my driveway.. :roll:

Uffe · **Posted:** Sun May 18, 2008 5:28 am

KeighJeigh wrote:

Thanks guys!
Some more specifics:

3) The car just turned 30K and the coolant looks like clean Koolaide. I seen no signs of corrosion or contamination or sludge. I've considered flushing and putting in a new thermostat just in case - and perhaps I should take the time to do so as a good maintenance move - but I hate chasing the wrong problem.

My experience with clogged radiators is that they can be completely buggered up with crud and you won't tell it by staring at the coolant. You will only by sheer luck be able to tell it from looking into the radiator cap or the overflow tank if a new particle has just formed and it on its way to the radiator to get stuck. If it passes through the radiator once you're in luck, it will at all probability stick the next time. The radiator acts like a filter for the buggers, and as such you won't be able to catch it by visual inspection because they are trapped in your radiator.

I would do what I could to perform a radiator flush, if problem then persists I would either do another more thourough flush or change the radiator.

BEFORE you do that check if your temp gauge is correct. There is no reason to believe all sensors are perfect and will remain so for several years after production. Some are meant to go wrong at some point, and that point can get closer to production time as probability falls near to zero.

nursecosmo · **Posted:** Sun May 18, 2008 5:47 am

Turbo Tim wrote:

Yes you can overheat the CRD in 80* weather. I have done it a few times now. I can only do it when I’m towing a 3500 LB trailer and trying to go 75+ MPH up a 6% grade. After about 5 miles or so it will not only have the temp gauge pegged, but will start chiming at me. Only when I slow down to some stupid speed of like 50 MPH everything works Ok.
If you don’t have your foot in it, you shouldn’t have any overheating problems. If it does overheat, take your foot off the go-pedal. It will cool right down.

Well sure, most vehicles except heavy duty trucks will get hot towing almost two tons up 6% at 75+mph. The point is that an unloaded vechicle should never overheat under those conditions. I'd bet that the problem is simply a faulty sending unit.

Chris, Autozone sells a raditor cap with a thermometer in it for 12 bucks, which will tell you if it's faulty sensors/gauges or if it is truely overheating.

Fulltimer · **Posted:** Sun May 18, 2008 7:36 am

I started a thread in the General Section on the same topic. Very different situation, but still a over heating problem. I have the 3.7L, I wonder if a CRD radiator would fit mine. I take it that it is bigger in some way.

Terry

Sir Sam · **Posted:** Sun May 18, 2008 12:21 pm

Uffe wrote:

KeighJeigh wrote:

Thanks guys!
Some more specifics:

3) The car just turned 30K and the coolant looks like clean Koolaide. I seen no signs of corrosion or contamination or sludge. I've considered flushing and putting in a new thermostat just in case - and perhaps I should take the time to do so as a good maintenance move - but I hate chasing the wrong problem.

My experience with clogged radiators is that they can be completely buggered up with crud and you won't tell it by staring at the coolant. You will only by sheer luck be able to tell it from looking into the radiator cap or the overflow tank if a new particle has just formed and it on its way to the radiator to get stuck. If it passes through the radiator once you're in luck, it will at all probability stick the next time. The radiator acts like a filter for the buggers, and as such you won't be able to catch it by visual inspection because they are trapped in your radiator.

I would do what I could to perform a radiator flush, if problem then persists I would either do another more thourough flush or change the radiator.

BEFORE you do that check if your temp gauge is correct. There is no reason to believe all sensors are perfect and will remain so for several years after production. Some are meant to go wrong at some point, and that point can get closer to production time as probability falls near to zero.

I was referring to clogged on the outside, dirt, feathers, leaves, bugs, etc.

Depending on where you drive it can really get bad quickly.

KeighJeigh · **Posted:** Sun May 18, 2008 12:57 pm

Quote:

.and wiring.
The head temp sensor is just a Thermistor stuck in a Mopar threaded adapter.
Unplug it and see if your gauge stays on cold.
Check the FSM and see if there is a chart with values for specific temps.
A wire going to the sensor grounded out will show a pegged guage!!
Check wiring for pinched wires.

Good luck

Warp2, where is the thermistor located? I have been looking for a manual on this thing so I don't have to ask such basic questions of this forum but thus far none of the parts stores carries one. (off to the dealer for it?).

So, your suggestion is to wait until it is cold, unplug it and see if it stays on cold?....What specifically does that check? Wouldn't it just stay on cold?

KeighJeigh · **Posted:** Sun May 18, 2008 12:59 pm

Quote:

Chris, Autozone sells a raditor cap with a thermometer in it for 12 bucks, which will tell you if it's faulty sensors/gauges or if it is truely overheating.

Excellent! I will get one today!
Of course, now I am going to go out and beat the sh#! out of it all day and see if I can get this problem to occur again.
Hmmm To wife: "I've got some testing to do, be back this evening"

Sir Sam · **Posted:** Sun May 18, 2008 1:06 pm

KeighJeigh wrote:

Quote:

Chris, Autozone sells a raditor cap with a thermometer in it for 12 bucks, which will tell you if it's faulty sensors/gauges or if it is truely overheating.

Excellent! I will get one today!
Of course, now I am going to go out and beat the sh#! out of it all day and see if I can get this problem to occur again.
Hmmm To wife: "I've got some testing to do, be back this evening"

We are out of orange juice, I'll be back tonight.

warp2diesel · **Posted:** Sun May 18, 2008 4:40 pm

The head temp sensor (Thermister) is called a Sensor Temperature Sending Unit, item #18 on page 102 of the 06KJ_moparpartsamerica.com.pdf manual . Sorry about all the confusing names for the same part, but they do this to keep their technicians on the edge and parts people just number finders. The sensor you want to unplug is located on the left side of the cylinder head up front behind the alternator almost directly below the oil filler. I unplugged mine went for a drive, the gauge never moved, I plugged it back in and the gauge worked again. I looks like all of the other Mopar temp sensors I have seen for years and may be the same as the old slant 6, just for the sake of parts commonalty.

Now the old test; reach down on the plug with an extra long pair of long nose pliers and pull the plug off the temp sensor and secure it so it will not get tangled up somewhere. Now drive the CRD and see if the gauge stays cold. If the gauge stays cold, the temp sensor is junk (most likely). If the gauge pegs with the temp sensor unplugged, either the gauge is junk (50-50), the wiring is shorted to ground (50-50), or some other device tied into the bus is sending a bad signal to the gauge (rare). Check every inch of the harness for cuts through the wiring, firewall area is the most suspect for this type of damage to the harness.

I will try to post a pic of the page, out of the parts book and the location on the head, but it will take some time.

Sir Sam may know where you can download the Parts Manual and Service Manual to help :idea:

Good Luck,

Steve

scrambledKJ · **Posted:** Mon May 19, 2008 9:57 am

I have gotten mine to go way up a few times too. They all involved keeping it on the mat while pulling long grades with my camper. The temp will start to climb fast when the EGTs hit 1050. I let out of it at 1100 degrees and the temp guage was just over 3/4. It took some rolling downhill to cool it back off. EGT seemed to take as long to go back down. The little motor is just trying to hard.

Travis

KeighJeigh · **Posted:** Tue May 20, 2008 1:20 am

Try as I may, I could not get the mule to pant again. I even drove over the mountains to the hot side of the state to run the dusty, hot green dot trails looking for rattlesnakes and fossils with my son. Found both - especially lots of snakes to his delight. (Do they taste like chicken daddy?) Still no overheating!
Not sure what the heck to do now! As long as there is some governing function so I don't fry the motor, should I just ignore it?
- Chris

Note: Very strange, but I got 29 mpg for the whole trip which included the mountain passes and an hour driving the trails. I'm up to 350 miles on this tank and still have plenty left. Not sure what the heck is going on with the mileage but even into work and back today - which includes stretches of heavy traffic in downtown Seattle - I managed 26.5 mpg. The mileage thread on this forum may have something to do with it. I aired up tires to 50 psi, I idle in neutral rather than drive, I coast down hills (engine running for tranny pump) and the number #1 thing: I keep the speed down to 60-65. I also have most of the popular mods. Amazing difference compared to my wife's consistent, seemingly impenetrable, 19-22 mpg with her 06.
Found this guy on the trail:

Dusty fun:

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Pegged the temp gauge! Huh??

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