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GDGorsuch · 08-10-2022, 07:03 AM

First trip on a really hot day (97) in our newer to us 07 Diplomat 40 w/ISL 400, towing the Jeep. Rear radiator. Assuming the Aladdin sys is accurate, I was surprised by the engine temp variance.

Five hour trip, mostly flat, all kinds of roads fm interstate to stop/go. Max speed 65, mostly less. After warmup, Max temp reading 208, lowest 178. Most of the trip was 195-205. Seemed higher speeds = higher temps.

No performance problems, I was just surprised by the temp variation, that stop/go = lower temps and how quickly the temp reading would change, esp getting cooler sometimes. I’m used to vehicles that the temp remains fairly constant. Thank You for your input!

Hpozzuoli · 08-10-2022, 07:05 AM

205 is still cool. Most diesels will run 210-215 before the cooling fan comes on. They can reach temps of 220 without causing damage.

YC1 · 08-10-2022, 07:36 AM

Very normal temp ranges.

IF you have the rear engine factory fan it is immensely overkill and there is an aftermarket one that is much quieter and uses a lot less hp.

Watch transmission temps in stop-and-go traffic on hot days. I mean the type where the is an accident holding up traffic. If it is obvious it is going to be stopped for several minutes, set the parking brake and put it in neutral for best cooling.

windsorbill · 08-10-2022, 07:42 AM

I have same engine but side radiator.

I'm nearly always in the 190's, maybe low 200's, but seldom. I never see below 190's after engine is warmed up. When I did a coolant flush a couple years ago, I replaced the thermostat. Didn't notice much temp change, however.

YC1 · 08-11-2022, 12:21 PM

Even though the temps seem normal there was a thermostat change around the time of the 2007's. Mine failed and I found the new model. Have never had an issue with it in over ten years or more.

It might be a good idea to change it. It is not that difficult.

mmartin_tdc · 08-11-2022, 12:52 PM

Just an FYI - my 2012 Cummins has a stock 200 degree thermostat. My truck runs 204 normal, on hot days, not towing. Towing 9500# in 103 degree - it will hit 217 t0 219 before the fan kicks in. So your range seems to be a happy zone for a diesel.

Lowflyer1 · 08-12-2022, 06:58 AM

Quote:

Originally Posted by GDGorsuch

.....I’m used to vehicles that the temp remains fairly constant. Thank You for your input!

In most of today's vehicles, the temp gage movement is controlled with electronics. The needle points to where a manufacturer desires unless the actual temp is beyond normal operating range.

Same goes for most oil pressure gages, the pressure is either good or not.

jdw1 · 08-14-2022, 09:21 PM

Great thread!

We got home a week ago from Wyoming and pulled Powder River Pass and it was around 90* when we started up from Ten Sleep Wy east bound, my temps ran 198* - 212*, at 212* I started backing out of it, if a hose should fail you’ll be forced to pull over, you have no cool down idling. I spent 20+ years driving over the road to California from Mn in my own trucks, at 212* for me it’s time to quit making more heat, jmo.

One other thing I did on our way west the week before, while my wife was driving I went back to the wardrobe closet and opened the small engine cover and observed the engine at work, it’s interesting to listen to the engine and the fan doing it’s job. Next time I’ll have my laser temp gun to take some temps out of curiosity.

I would say your temps are normal based on my temps in my coach and my trucking experience, jmo.

One thing to keep in mind is that these coaches do not get any air passing across the radiator stack from vehicle movement, ether side or rear radiators so the fan has to do all of the air movement across the radiator stack, coolant, air to air aftercooler, ac condenser and any other cooler that might be in there, hydraulic, transmission…… that fan is doing a lot of cooling work!

Mile Marker 42 · 08-14-2022, 09:29 PM

I would change thermostat to a 180 degree. Easy to do.
Might want to look into source engineering engine fan. Gives back horsepower factory fan strals. I have it on my 2003 knight 315 isc motor. Definitely a difference. Might look into the aero turbine muffler too.

oldguy70 · 08-14-2022, 11:12 PM

The faster you go the more horsepower so more heat. I like running diesels hot so I
have a 190 degree thermostat and my fan kicks in at high speed at 210 degrees.

moisheh · 08-15-2022, 08:42 AM

Do not install a 180 stat. Today's engines are designed to run hot.

Mile Marker 42 · 08-16-2022, 02:37 AM

Have had a 180 in my rig for 5 + years now. Bought it from the Cummins parts department. Runs great. Nothing wrong with a 180. I tow a jeep and usually jet skis behind the jeep. We travel out west. It gets plenty warm.

2cyber71 · 08-16-2022, 04:27 AM

I had a great 400 ISL in my 07 Ellipse.
Temp ran 180-210 depending on weather and hills
The secondary fan kicks in at 208-210 and will get it back into the 190 range.
Also, my 2020 With a 450 ISL does exactly the same.

I’ve pulled over the Big Horns & Homestake Pass in hot summer weather. No problem it kicks in when it needs it.

Didn’t do Powder River Pass in the motorhome, but I drove up there on Crazy Lady Trail from Buffalo in my Jeep. That was a cool climb in the Jeep. It was 80f out and it got to 220f on that steep climb on a cool dirt trail. Moose and a Glacier is up there. Had Ice cream at Crazy Sally’s in Ten Sleep, Wy
It’s beautiful

YC1 · 08-16-2022, 05:35 PM

My 2008 ISL has a fixed pitch fan. Not electric though that is one option I wish I would have added. However, the Source Engineering fan replacement does an awesome job and the improvement in acceleration and mpg was amazing. The noise level dropped 5DB about ten feet away from the radiator.

Never have had a cooling issue do to the fan. Thermostat went bad early on and the new one was some sort of new style replacement.