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Old 01-25-2011, 08:29 PM   #1
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Join Date: May 2006
Location: Washington State
Posts: 866
Fan Mount Bearing Failure

We started out from Tucson today on our way to Texas. After a lunch stop at the rest area in Las Cruces, I listened to the engine on my walkaround after engine start, and heard a strange noise that sounded like a bad bearing in a water pump, or similar.

Stopped at Cummins Rocky Mountain in El Paso and they determined the bearing in the fan mount pulley was shot, producing the rattle noise. The fan mount pulley is located on the rear of the engine, directly in front of you when you open the rear hatch on ISL 400 engines. The drive belt and the air conditioning belt roll over this pulley. In most Cummins engines this is an add-on part, not provided by Cummins, but on our ISL 400s with side mount radiators, it's a Cummins-provided part. Don't remember seeing this issue posted here before.

The good news for me is that the part is being overnighted and it should get repaired tomorrow, and is still under the Cummins 5 year warranty so it's only $100 deductible. One thing I did not check out along the way is to shake this pulley a little periodically and make sure it did not feel loose. It definitely was loose as we checked it today.

Making you aware of this in case you get the rattle-noise in that area and wonder what it might be. We have almost 45,000 miles on the coach. We did drive it 70 miles to get to the facility, and it might have been gong out for 150 miles before that.

One of those memorable days when things just go wrong -- started out with everything going well this morning (other than the low air suspension issue again at 40 degrees, but my temporary fix of not reapplying the parking brake, solved that). Then we got the fan mount bearing issue. After I stopped at the Cummins facility, scheduled the repair, disconnected the car to hook up to power and stay for the night at the Cummins facility, the Remco lube pump monitor for the toad went out and wouldn't shut off in the coach. Works when hooked up but won't shut off when disconnected. Solved that problem temporarily by disconnecting it until I can get a new monitor.

Then I leveled the coach, pushed the slides out and forgot I had one bay door open with the latch not latched and the slide pushed against the cargo bay latch and broke it. Never did that before. Searched the threads on this forum and ordered a new one to be delivered to our temporary address in Texas on Friday and tied the door shut with a rope through the bay to the other side of the coach for the next three days

Then the door step wouldn't come out. Recycled the battery disconnect switch in the battery compartment and solved that. Then my rear TV wouldn't work, again. Gave up and decided I had enough for today, and drank a beer and had couple glasses of wine to look forward to a better day tomorrow! Ever have one of those kind of days?

Former Owner, 2006 36MDDS
2010 Arctic Fox 22GK Travel Trailer
2007 Toyota Tundra
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Old 01-25-2011, 08:38 PM   #2
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I Agree! That is a Bad Day. At least you made it through the day without getting hurt.

You deserve another beer! Hope tomorrow goes better!

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Old 01-25-2011, 11:20 PM   #3
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Location: Long Beach, CA
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Criminently! Well at least you've used up your bad luck (hopefully!). I hope the rest of your trip is a breeze....
2003 Alpine 40FDTS (400HP)
Long Beach, CA
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Old 01-27-2011, 07:55 PM   #4
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Beer won't solve that. Need gin.
Baja-tested '08 2-slide 36'
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Old 01-27-2011, 08:12 PM   #5
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Started with beer. Next night was a Beefeater's chilled martini. It helped and your advice was as usual, spot on.

I am impressed with the response we got from Cummins Rocky Mountain at El Paso. They ordered the fan pulley (called the Accessory Drive) and its bearing. It was overnighted in and it arrived about 10:30 the next morning, and they got on it at 1:00, right after lunch, and they were swamped. They jumped the schedule so we could get fixed and out of there.

Took about an hour for the technician to remove the fan mount, remove the old bearing with a press, press in a new bearing, and reinstall the mount, plus the belt drive and A/C drive pulleys. Runs great, noise problem solved, old bearing was shot.

For those of you that want it, here's the Cummins part number for the replacement bearing (which was the culprit, not the accessory drive pulley): 3910739. The tech said he had been working there 15 years and had only seen one other pulley bearing go out like this, and it was on a Dodge diesel pickup. So it's a rare occurrence, but sort of like a number of the issues on Alpines, right?

Cummins El Paso has 3 outside hookups with 50 amp power, a dump station, and a place to add water. They are working toward becoming a full CoachCare facility. There people are very friendly, very helpful, and very straightforward. One of the cleanest and most orderly truck diesel shops I've ever seen. I've seen a number of aircraft repair facilities in my career that weren't as clean and orderly as this shop.

BTW, the "fan mount" is located at the engine where the radiator cooling fan would be if we had a radiator at the rear of the coach. It would have a fan attached to the pulleys. But since we have a side radiator, we have no fan there. It's still called a fan mount, and bolts on to the engine block. When the bearing begins failing, like ours, it makes enough noise you will have no problem hearing it. But it appears to also be very rare. Not sure I would carry an extra bearing for the problem.
Former Owner, 2006 36MDDS
2010 Arctic Fox 22GK Travel Trailer
2007 Toyota Tundra
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