Cummins 8.9 gets hot looking at a hill?? :-( - Page 2

Diego-Ted · 07-17-2021, 01:52 PM

I hope I didn't scare anyone off? I truly am trying to learn as I do not know, the Techniques and methods to insure the Pusher is doing it’s job as designed. I appreciate every input and comment.

thx Ted

KRedburn · 07-17-2021, 02:24 PM

I have ISL9 Cummins in my Dynamax DX3 Allison 3200 series tranny
Generally on any long grade it is best to preselect your gearing near the bottom. If you wait for the tranny to downshift it will be out of your torque curve when it shifts at 1400 rpm.
So, I shift when rpm hits around 1550 - 1600 and try to keep the engine in the 1950 rpm range. You should be hearing your fan engaging on occasion to keep your coolant in range. At this point you have to watch your temp for both water and trans oil. If water is climbing and not lowering on occasion back out of it some (you may/probably have a fan clutch issue). If your tranny just keeps going up you have a transmission filter and/or a cooler issue (which most likely will be a fan clutch issue also)

Your engine has a governor in it to limit max rpm but don't count on it. When you hit above 2100 rpm make sure you upshift. I climb manually shifting and put the tranny in Drive when nearing the top of grade so it controls the engine rpm in case I forget to upshift.

Just some suggestions.

Diego-Ted · 07-17-2021, 02:35 PM

Quote:

Originally Posted by KRedburn

I have ISL9 Cummins in my Dynamax DX3 Allison 3200 series tranny
Generally on any long grade it is best to preselect your gearing near the bottom. If you wait for the tranny to downshift it will be out of your torque curve when it shifts at 1400 rpm.
So, I shift when rpm hits around 1550 - 1600 and try to keep the engine in the 1950 rpm range. You should be hearing your fan engaging on occasion to keep your coolant in range. At this point you have to watch your temp for both water and trans oil. If water is climbing and not lowering on occasion back out of it some (you may/probably have a fan clutch issue). If your tranny just keeps going up you have a transmission filter and/or a cooler issue (which most likely will be a fan clutch issue also)

Your engine has a governor in it to limit max rpm but don't count on it. When you hit above 2100 rpm make sure you upshift. I climb manually shifting and put the tranny in Drive when nearing the top of grade so it controls the engine rpm in case I forget to upshift.

Just some suggestions.

Thx for the info. To date no Tranny warnings, hope it stays that way. So to understand you, on any deemed major grade, you are at the lowest gear you think you need to get up the grade from the beginning with no run at it? You just gear down and keep RPM around 2K all the way up? In my case I am guessing I would be in 3-3 (lowest tranny will allow to date) doing around 30 mph? And you stay cool on say a 10-15 mile pull?
thx Ted

KRedburn · 07-17-2021, 02:54 PM

Quote:

Originally Posted by Diego-Ted

Thx for the info. To date no Tranny warnings, hope it stays that way. So to understand you, on any deemed major grade, you are at the lowest gear you think you need to get up the grade from the beginning with no run at it? You just gear down and keep RPM around 2K all the way up? In my case I am guessing I would be in 3-3 (lowest tranny will allow to date) doing around 30 mph? And you stay cool on say a 10-15 mile pull?
thx Ted

Sort of, I will run at it but as I climb I do not wait for the tranny to downshift. I manually downshift as needed (shifting near 1500 - 1600) in order to keep the engine around 1950. Once the engine is no longer rapidly dropping rpm and I can maintain around 1950 rpm I have found the gear necessary for that hill. Remember, just because it is rated to pull xxxxx lbs does not mean it will do that at 70 mph nor in high gear. (ie. A semi is rated to pull 80000 lbs but on some hills it may be pulling that weight at 25 mph in second gear)

I have had my DX3 on a 9% grade. It pulls it just fine but it is not pulling that at 60 mph.
The DX3 is rated to pull 54K combined gross weight. It does the job just fine but on occasion you have to manually select the proper gear for the hill you are on and therefore your speed will be lower. Just like the semi trucks have to do.

And yes, by managing the gearing and the engine rpm I stay nice and cool even with air conditioning. Happy DW, happy pets, happy driver.

Hauler · 07-22-2021, 08:17 PM

Redburn has good advice on the downshift. You don't want to lose your RPMs on a pull as heat will build up fast. Does your Allison have an oil cooler in front of the radiator? That will block airflow and throw more heat back. You might also be able to install a big electric fan in front of the radiator with a manual switch on your dash so that you can turn on the at the bottom of the grade to help cool things down and give you more time before the fan clutch kicks in robbing you of needed power.

Bannings · 07-22-2021, 11:25 PM

We had the same problem with our Cummins 340hp. Running fine on the away but as soon as you started to climb the temperature started climbing till the overheat buzzer came on. Had the radiator redone at Cummins but it ended up being the Horton clutch fan. Freightliner replaced the clutch fan and no more problem!

ssmote · 07-23-2021, 06:21 AM

Quote:

Originally Posted by Bannings

We had the same problem with our Cummins 340hp. Running fine on the away but as soon as you started to climb the temperature started climbing till the overheat buzzer came on. Had the radiator redone at Cummins but it ended up being the Horton clutch fan. Freightliner replaced the clutch fan and no more problem!

That's the same thing I was thinking. Maybe either the fan clutch is bad or the thermostat may needed replaced.
The thermostat is an easy change on the 8.9L. Just remove to two bolts from the water outlet on top front of the engine. Thermostat is right under there.
The fan clutch may be harder to diagnose. Could be either an air or electric actuator. Probablyl need a service center to take a look at it.

Bannings · 07-23-2021, 02:20 PM

It did cost $2700 for the new clutch fan installed, and we had previously six months earlier had Cummins go through the cooling system radiator flush, new thermostat, new EGR valve, new turbo sensor and none of that I had fixed the problem. If only Cummins would have checked the clutch fan while they were in there it probably would have saved a lot!

Frankiejay · 07-23-2021, 04:42 PM

The fan clutch makes a loud roar when it kicks in, listen for it when accending your next grade. Almost sounds like a downshift. Safe & Happy travels

dave-g · 10-29-2021, 04:20 AM

Did you ever get to the bottom of your problem- I'm thinking fan clutch?

Also some thing I do while towing my Raptor- (6000 lbs) I set the dash display to show trans temp and engine temp- so much more accurate. On a long climb my engine temp with go to 212-215 then the fan starts and it will drop to 185-190 ish then the fan shuts off and heads back to 212-215. In 100+ weather it hangs around 205.

Dodge Guy · 11-06-2021, 08:02 AM

As you found out engine RPM makes a big difference! My gasser, a 2012 V-10 with the 5 speed) I drive hard! Going up I70 out of Denver I keep it would up, never overheated and I’m towing a 13 Explorer (approx 4600lbs). Seen many newer gassers at the side of the road cooling down. My buddy was 3 days ahead of me and said he had to pull over to let his 17 V-10 with the 6 speed cool down. Well he didn’t like the high rpms and tried to keep the RPMs low, that’s why his ran hot. More rpm means more coolant movemet and heat transfer. If it still runs on the warmer side it may be time to invest in a radiator flush (a real flush) and a T-stat and new fan clutch.
Good luck.

Diego-Ted · 01-27-2022, 05:44 PM

Hello all, I thank everyone for the help. Here is a bit more info. Took to reputable local shop. They found a code"1969" (aftertreatment exhaust temp 2 data above normal range, operating range most severe.) they replaced a exhaust gas temp sensor? They confirmed a bad diagnosis on my part. They told me my analog temp gauge was way off getting into the RED at 212* Further, they noted the fan clutch engaging at around the same time. It is their opinion and now mine, that I was not getting HOT, there was no way. The Coach started and I was on my way in less than 30 minutes? No way could an overheated motor cool down that fast. I did have the shut down problem, which they attribute to this sensor? What do you guys think? Also what is the particulate recycle and could it be part of my problem? I appreciate all the help I can get, I am leaving for Havasu on Tuesday.

thx TEd

**Lincman983** · 01-28-2022, 01:41 PM

the DPF (diesel particulate filter) does get pretty warm and when in regen mode it may elevate the EGT (exhaust gas temp) and trigger a shut down mode. Glad i have the DPF delete on my Powerstroke.

Diego-Ted · 04-03-2022, 12:14 PM

OK, just returned from Lake Havasu and had to Pull the Laguna Summit, which would be the best test if the sensor was the issue. I decided to downshift at the stall to find the best gear that triggered the clutch fan for the pull. The Cummings performed perfectly. I down shifted as described the RPMs stayed between 2200 and 2500, temp went from 205* to 216* and back down.

I am confident I can run the country now :-) Thanks everyone for the help.

Diego

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