This may be a dumb question, but it causes me enough concern to ask it.

When towing my trailer (hauling Jeep CJ) (gross 12,750 lbs.) up a steep section of mountain (explained below), my temperature gauge comes up between the last normal mark and HOT. It has never gone higher, never boiled over, or caused me any problems. I noticed this last July-August during the hottest months. Naturally it runs a bit cooler during the winter months, but still nears that temperature. I haven't had the truck long enough to really know and would like to hear what you folks have to say about it.

Is this normal? Do I have a problem in the making? I need "peace of mind."

Those familiar with NC Hwy 421 N between Wilkesboro and Boone will know exactly where I am referring to. For those who aren't, this section of highway has a 4 mile stretch that is an 8 percent grade. It's steep!!!

 

That seems high to me. I'd replace the thermostat with a genuine Cummins part. Check the radiator as well, if it's original it's probably pretty well scaled inside, which makes it less effective.

 

My set up runs the same temp when floors puling hills. it comes right back to normal*first mark* when i let off. the inside of my rad is rather scale. right before it hits the 2/3 rds mark*thats the hottest it ran* the clutch fan comes on. Before this summer/spring i plan to flush coolant and see if that makes a difference. someone on here said that 2/3rds mark is 225F is this true? jiMMy

 

I wont go into the ugly details regarding temps like that in my 93 350 4x4. From the 3 trucks Ive had you should be running empty at 1/4 way up or a little past. You have a problem, be it the guage, radiator, thermostst, fan clutch which should be roarin at those temps. i was shooting it with a infared sensor and at 2/3- 3/4 it was reading 230+- at the thermostat housing.

 

5 Spd or auto?

 

OK... I need to do this again. My description was not exactly right regarding the gauge. Since I can't post a pic, I will try to describe it better.

The gauge has a COLD mark and a HOT mark. Between those two marks is what I will call the normal operating range. It is an arc drawn between the HOT & COLD marks with 4 graduations on the arc (one on each end and two more in the middle, equally spaced).

My temperature climbs close to the upper end of the operating range arc, but has never gone out of it. I hope that makes better sense. I just went out to look at the gauge to make sure I am telling it right this time.

Per jiMMyCTD's post, it looks as if we are running the same with the exception that my gauge stays about the middle most of the time when running normally.

 

Automatic w/OD (I do not use the OD when towing)

Transmission oil is pretty, red/pink, and has a nice clean smell. No burning.

 

i tow in OD all day long even pulling those hills too. You described the gauge to a T.
ill go ahead and call it the 3/4 mark . just before it my fan comes on and robs me of power thus i back off a bit fan cools it down to half*no mark at half*. Once i crest the hill or resume flat ground throtle i will cruise just a bit above the 1/4 tick mark on the gauge. jiMMy

 

I think the cooling system is scavenging heat from the tranny. You can get a gauge and measure between the output and tranny cooler to see how hard the tranny is being worked. When I put the new tranny in I bi-passed the heat exchanger and put in a big cooler. I'm sure the cooling system is keeping things from cooking. I just don't like the idea of the fluid getting re-heated after having gone through the cooler. Might be better than nothing having the heat exchanger save the tranny, but the gauge would catch any trouble sooner. JMHO< Don

 

I was going to post and ask a similar question about the temps. My temps seem to cycle where I can actually see the thermostat open and close. It's either that or the fan clutch engaging.

When I bought the truck everything was flushed and I put a new fan clutch on it.

I live in FL and summer temps are around 93-94. Truck runs nice and cool empty. Haven't really loaded it up that much.

Below is a pic and the cycle point in the current weather (60 - high 70's).


Might help with other peoples descriptions too


Den

 

If it gets that hot only while working the truck hard in hot weather, that's OK per my '93 FSM. If it runs that hot all the time, something's wrong. Where Den marked his pic is exactly where you want to see it running around empty or on flat ground.

 

he he, i was too lazy to get a pic. the red marked on dens pic is my normal cruising warmed up spot. the hash to the riht of that is the max i see working it hard up a hill. thanks for the pic Den. jiMMy

 

Have you tried a coolant additive called "Water Wetter"?
I think it is made by Red Line. I've used in my Chevy V8
during the summer months. When the air was on and during slow speeds the
coolant temp would get up to and over 215 deg even though I had a 180 deg thermostat.
After the treatment the coolant temp stayed around 185 deg.

 

Does anybody see it cycle back and forth in that range constantly while crusing empty?



Den

 

'Does anybody see it cycle back and forth in that range constantly while crusing empty?'


yes