450 HP overheating on 2018 bus

[mike369]

Thanks for all the input. I'm going to try several different things and see if I can figure out what's going on. I don't think that this is normal for a coach with only 8100 miles. I do start it regularly and everything looks clean. I did mention that on the last trip the check engine and temperature light came on just as we reached the top of the mountain but went off almost immediately on the way down. I believe it reached 230 degrees at the top and that's when the lights came on. It's been climbing to 220 on long inclines since it was new. Again, thanks for all the input.
Mike 369

[mike369]

Update, I contacted Gary at Tiffin and was informed that I had a Kendrion clutch. He sent me instructions on How to lock the clutch down and told me to drive the coach and see if it still overheated. Two bolts to lock it down and then I drove it with the toad attached on the same roads that it overheated on. Results: The temperature never exceeded 195, and actually went down a little climbing the same hill. I also found out that Tiffin will repair under the 3 year chassis warranty. Right now I'm waiting for the part as Tiffin has no parts at the factory and they have coaches sitting waiting for parts.
Maybe someday things will return to normal ( whatever that is )
Thanks to everyone for the support. I'll let you know how things turn out.
Mike 369
2018 Bus 40SP

[DRM901]

Glad to hear Gary came through, again. He is so knowledgeable on all the models over a lot of years.

[CDougherty]

Mike 369

We have a 2018 Tiffin 40 AP with the exact same problem. We bought it in 2019 with 11,000 miles on it. Due to Covid, we didn't make our first trip until May 2020. We first experienced the problem on an Oregon mountain pass. It overheated and I witnessed the exact same temperatures as you. We limped into Sparks (Reno) and made it into the Freightliner Dealer late Thursday night. The next morning the Service Tech determined the belt tensioner wasn't providing sufficient tension. Working directly with Tiffin Chassis, the parts were overnighted and arrived Saturday. Tiffin was outstanding in everyway. They shipped a new tensioner, belt and tensioner mounting bracket. Which I was told cracks at the mount. Sure enough ours was cracked and rust made it easily visible. The new bracket is reinforced so it will be on an inspection watch. Also welded a brace on the old bracket for a spare, bought a new tensioner and kept the old belt to back up my new spare.
Thought the problem was solved, came back to Washington via California Siskyou Pass on I-5, one mile before the pass we overheated and had to pull over and let it cool down...again. We made it home without overheating but watched the temps rise and fall.
I researched the problem but only came up with better driving techniques, using the alternate transmission mode and taking inclines at higher RPM and lower gears. On two short, flat terrain trips, the temps would rise but no over heating.
Then our September 2021 trip to Eastern Washington with a 6200 pound car and enclosed trailer brought the problem front and center, again. Crossing two major mountain passes and a number of steep grades. We overheated twice and the 2nd one found us with no place to pull over. We finally pulled over and luckily didn't damage anything or go into de-rate. (Not sure that will happen when over heating, but think I have read it does).
The coach went into Cummins in October for the injector recall and I reached out to Tiffin Chassis. The Tiffin Chassis Techs told me about the manual lockup on the Kendrion Fan Clutch and they also told to test the electromagnetic clutch by applying 12V. power to verify it locks up. It doesn't lock up.
They referred me to Gary Harris, also who has been terrific to work with. Gary agreed to have Cummins verify the ECM is sending a signal to activate the clutch. They said it was functioning and they noted a change in the fan/engine when it did. Two Cummins Techs have proposed a Fan Switch to provide a more controlled function of the Fan Clutch. I had to leave town so the issue is still pending. Cummins was going to followup with Tiffin and we are going to regroup on the issue.
I would sure like to follow your situation and final resolution. And will be eager to share anything further.
I still suspect the clutch and haven't been able to perform the manual lockup. Besides the fact the mountain passes will be covered with snow and have low temps. I'm not sure I can recreate the same Summer condition, even with the added load.
I also have not witnessed what many owners have referred to as the distinct sound of the fan in full lockup. When I was limping into Sparks, a friend that has been with Cummins for years as an Engine Representative told me, you will know when the fan is in full lockup.
Does anyone else have input? I am interested in any additional thoughts and feed back.

[harbottle]

When our almost new Bus overheated on the freeway, many red lights on the dash lit up and I think there was some kind of an audio alarm also. I believe we had a message stating to turn off engine. The temperature gauge was pegged.

Are these the messages you are getting when you are over heating or is it the temperature gauge going too high?

Our fan clutch had no oil in it and that's why it failed. Lots of smoke too.

Just trying to determine if there are different issues here or if they are all related.

[jkorn]

Originally Posted by mike369

Has anyone had problems with their Allegro bus overheating when they are climbing steep grades. My coach ( 2018 40SP with 450 engine ) seems to climb up to around 220 to 225 degrees when climbing long hills while towing our car
( 5000 pounds ). I've checked fluid level and check the radiator. It's been doing this since we purchased it new. I've tried downshifting, doesn't seem to help. On our last trip to have the recall done by Cummins on the way home it got so hot the check engine light went on right before we got to the top of the hill. On the way down it went back to normal ( 190 - 195 ) Because of the pandemic our coach only has 8100 miles on it. Any thoughts?

According to Tiffin that’s normal. Have you called them? Jeff

[CDougherty]

Harbottle

Yes, I received all dash warnings and audible alarm. Yellow and Red MIL's. Along with the Engine Temp Gauge confirming the warnings.

Interesting, you found that the clutch was without oil. I have been unable to obtain very little technical information on the Clutch. I wasnt aware the Clutch contains oil. I liked the clutch to the electro-magnetic clutch on an AC compressor. Do you have any specifics on it?

Thank You

[mike369]

CDougherty
Sorry to hear that you're having the same problem with overheating on your rig. I'm waiting on the new fan clutch to arrive from Tifffin. I would try locking down the Kendrion clutch and taking it out on a test drive. This eliminated the thermostat and told me that the radiator was not clogged or dirty. I'm still not 100% convinced that the temperature sender is functioning properly, but the new clutch should tell the story.
It only takes about five minutes to lock down the clutch and my temperatures on the coach were completely different after doing this. Good luck.
I will do an update when the new clutch is installed.

Mike369
2018 Allegro Bus 40SP

[CDougherty]

Mike 369

Thank you for the reply. I'll be watching for your update. I do plan to lock up the clutch, but am concerned winter temps won't create the same overheating condition.

[DRM901]

It is my understanding the clutch is electronically locked like an AC compressor clutch. However, I think there is oil inside for when it is disengaged.

A tech installed a solenoid as a work-around for our AC condenser freezing up. There is a module in the PS rear compartment that controls the fan & compressor. (Top, left of compartment.) There is a light that shows when it is kicked on. If you started it, looked at which lights are on, then put it on the fast idle, the light that goes out should be the wire for the clutch (assuming engine isn't too hot). If engine is somewhere over 200, the module will demand the fan, so the light won't go out.

[Larrikin]

No mention here of the % grade involved, distance (time) of the grade, nor of the Outside Air Temp. May not be that far off. As others have said check fan operation and clean the radiator.

[DreTom77]

Had overheating on hill 2 years ago during the summer. Turned out that the solenoid was bad and was not causing the fan to come on at 220 degrees. Had it replaced, problem solved.

[Idleup]

Originally Posted by mike369

Has anyone had problems with their Allegro bus overheating when they are climbing steep grades. My coach ( 2018 40SP with 450 engine ) seems to climb up to around 220 to 225 degrees when climbing long hills while towing our car
( 5000 pounds ). I've checked fluid level and check the radiator. It's been doing this since we purchased it new. I've tried downshifting, doesn't seem to help. On our last trip to have the recall done by Cummins on the way home it got so hot the check engine light went on right before we got to the top of the hill. On the way down it went back to normal ( 190 - 195 ) Because of the pandemic our coach only has 8100 miles on it. Any thoughts?

\


220-225 is totally normal on an incline especially when towing. Generally when it reaches that temperature, the fan will be fully engaged and depending on the grade either hold that temperature or lower it depending on you load. Nothing to worry about!


Drive Safe - Mike

[YLBlues]

Originally Posted by mike369

Has anyone had problems with their Allegro bus overheating when they are climbing steep grades. My coach ( 2018 40SP with 450 engine ) seems to climb up to around 220 to 225 degrees when climbing long hills while towing our car
( 5000 pounds ). I've checked fluid level and check the radiator. It's been doing this since we purchased it new. I've tried downshifting, doesn't seem to help. On our last trip to have the recall done by Cummins on the way home it got so hot the check engine light went on right before we got to the top of the hill. On the way down it went back to normal ( 190 - 195 ) Because of the pandemic our coach only has 8100 miles on it. Any thoughts?

At the recent Casa Grande rally, there was a seminar delivered by Cummins. We were basically told to not be concerned about temps up to around 225 degrees. I see 200-205 regularly when climbing long grades, but that always drops quickly to around 185-195….assuming it’s either the thermostat opening, fan kicking on, or both.