Cummins 5.9 ISB 'mystery pulley'

[OwensKa1a]

My first newbie question. Please advise if I'm putting it in the wrong place.

I've recently purchased a 1999 Coachmen Catalina pusher. It runs strong at 33k miles. I have an appointment at the shop 31-Aug (soonest I could get) for having fluids/general service. In the meantime I'm doing general repairs on the vehicle...storage latches, broken mirror, upgrade backup camera...

With the engine running and bed lifted I noticed a 'new sound'. It was pretty easily traceable to a pulley at the rear of the engine. Specifically, looking at the engine, toward the rear of the coach, it is located on the left rear and sticks up above the rest of the engine. Just to the left, and slightly below the pulley is the AC compressor. There is a belt connecting the pulley/compressor and then running down to the fan.

The pulley in question is clearly 'bent' toward the rear of the engine. I say bent but...I guess worn bearing or whatever is causing it to be 'wobbly'. This is the source of the noise. I have checked about 1000 engine diagrams for this 5.9L ISB and NONE of them show this configuration, with the compressor and 'mystery pulley' located where mine is.

The pulley LOOKS like a tensioner to me (based on my many years of absolutely zero experience with such things). Since I have about 10 days before I go to the shop, I am considering tackling this repair myself. The part in question appears to be very accessible and held on by one or two bolts. Assuming I can locate/identify the part, I think I could do it, with some help.

My (random) guess is that maybe this dash AC was done by Freightliner for the RV build and that could explain why no Cummins engine diagrams show the compressor/pulley in that location. But I don't know...

If anyone has any insight/suggestions, I'd sure appreciate it.

[Tajfish]

Here is a link to another topic that might help. Reply #14 has a pulley diagram. Hope it helps

https://www.irv2.com/forums/f123/isb...-r-321230.html

[Skip426]

Yes Freightliner installed the dash A/C compressor on your 5.9 Cummins .

Big problem is that they also changed tensioner set ups about as often as most of us change socks .
Would your set up be similar to the picture below?

[OwensKa1a]

Hey Y'all. I pulled the pulley off yesterday. It's a small miracle that it was hanging on at all. The bearing was completely shot and the inside of the cylinder (where the bearing used to be...) was spinning on the mounting bracket, with enough pressure to wear a pretty deep groove into the bracket. Somehow that groove was enough to keep the pulley from falling off completely and...spin? in the groove. Crazy. Took it to a couple parts stores nearby...no luck. Then I called Freightliner and...bingo. This was my first experience calling 1-800-FTL-HELP. The guy who answered, very quickly, took the last 6 of my VIN and gave me the pulley PN and told me the nearest FL Shops. He was also able to provide me with the Cummins Engine Serial Number for my rig, something I was having a hard time locating... Unfortunately the shops were closed by the time I got the info so I'll need to check Monday to ensure that it's the right part and if, by some miracle, it's in stock. Either way, when I do get it...it's a single bolt to slap it back on. Good stuff.

Turns out that, yes, FL did do the AC Compressor install as I suspected and as SKIP426 confirmed. Apparently the part is not technically a tensioner but rather an idler pulley. I'm not entirely sure what purpose it serves other than to route/take up slack in the belt. But mine is not to question why...

[HarryStone]

A pulley that is designed to take up slack in the belt is technically a tensioner. If your design is like the one that Skip posted, then it is in fact a tensioner. Instead of a spring, it uses a sliding slot. Loosen the bolt, slide the pulley up or down until the belt tension on the non tensioned side is correct, then tighten the bolt. Usually you have to use a lever to get the pulley to the correct tension.

[Skip426]

When I called Freightliner help for the first time ( 11 years ) ago , they gave me engine , transmission and differential serial numbers . Joining Access Freightliner ( Now DTNA Connect ) got me wiring diagrams and schematics , and a long list of part numbers linked to my chassis serial number .
Your Cummins engine data plate , is hidden below the A/C compressor , so very hard to access.

Glad you have a P/N , now you just need the part .

[OwensKa1a]

Originally Posted by Skip426

When I called Freightliner help for the first time ( 11 years ) ago , they gave me engine , transmission and differential serial numbers . Joining Access Freightliner ( Now DTNA Connect ) got me wiring diagrams and schematics , and a long list of part numbers linked to my chassis serial number .
Your Cummins engine data plate , is hidden below the A/C compressor , so very hard to access.

Glad you have a P/N , now you just need the part .

Thanks for that - I will look into DTNA Connect.

P/N doesn't help...No longer available...FL pointed me to Fleetpride...nothing.

At this point I'm on the hunt for something 'close enough' that I can rig up. I'm just looking a 'v belt' style pulleys that match the dimensions. The big problem may be the bracket. When the pulley bearing was shot and hanging on for dear life it wore a sizable groove into the neck of that bracket. Nearly half way down (and into the bolt). What an irritating problem to find in my beginning stages. Trial by fire I guess.

Anybody tried/have any luck with RV salvage yards? Seems like a long shot for finding the actual bracket replacement.

[OwensKa1a]

Originally Posted by HarryStone

A pulley that is designed to take up slack in the belt is technically a tensioner. If your design is like the one that Skip posted, then it is in fact a tensioner. Instead of a spring, it uses a sliding slot. Loosen the bolt, slide the pulley up or down until the belt tension on the non tensioned side is correct, then tighten the bolt. Usually you have to use a lever to get the pulley to the correct tension.

This pulley is indeed the 'non spring' style tensioner. The belt/pulley is standalone and only connected to the AC compressor. Interestingly...there are no notches/sliding slot. The surface where the bracket connects is smooth and appears to rely solely on the torque applied to the mounting bolt.

[Skip426]

Could you post a picture of the pulley ( with a tape measure in frame , for size ) and the bracket damage .

Maybe a member can identify a replacement from an automotive application .

[OwensKa1a]

Originally Posted by Skip426

Could you post a picture of the pulley ( with a tape measure in frame , for size ) and the bracket damage .

Maybe a member can identify a replacement from an automotive application .

Hey all - In the end I was able to get a new pulley of the same dimensions and get it remounted. Due to the damage on the original bracket I was reluctant to us it but...after a couple of failed attempts to find a suitable replacement I went ahead and reused the original. The whole thing took me about a week of elapsed time which consisted of about 30 minutes of actual labor...the rest was research/trial and error for parts. Dang. A friend raised two concerns...suggested I try to identify the reason for the original failure and wondered how I determined the proper belt tension. I told her my assumption is the pulley being 22 years old is the primary reason for failure. Though now I'm a little paranoid about the rest of them. As for belt tension, I went with, tight/pretty tight/not too tight. In other words I have no idea how close I am to the 'right' tension. The AC is still not working but I'm pretty confident that has nothing to do with the belt tension. Troubleshooting that will start soon.

My generator doesn't fire. I have basic service scheduled for Tuesday. They said the had me down for generator maintenance as well ($235 I think?). I told them the generator isn't working and they said expect 2 hours of diagnosis at $171 per hour. So that's almost $600 BEFORE anything gets fixed. I've decided to tell them to leave it alone and have a go myself. Unfortunately, the way the Marquis 7000 is mounted in my coach the ONLY thing you can do without dropping it is filter/oil change. Very cramped quarters. So my nephew is going to help me pull it out next week and we're going to start troubleshooting (and change all the fluids/filters). The generator has fewer than 500 hours on it so I got to get it running. Stay tuned for specific questions as the arise.

So far all I've been able to do is check fuses/breakers and make sure the batteries are strong. Something is keeping it from being able to fire...maybe a corroded/loose connection somewhere up/back there...

[SmilingSam]

Idler pulley is to route the belt generally to miss other parts and of course like ALL of the pulleys and things has tension on it, otherwise it would fall off !

but not tension-er, as tensioners are either adjustable or spring loaded (or pneumatic/hydraulic/etc) idle pulley serve NO OTHER function than route the belt correctly or needed.

we should not confuse and obfuscate the labeling of things technical if we do not have to !

[Jakeman]

Originally Posted by OwensKa1a

Hey Y'all. I pulled the pulley off yesterday. It's a small miracle that it was hanging on at all. The bearing was completely shot and the inside of the cylinder (where the bearing used to be...) was spinning on the mounting bracket, with enough pressure to wear a pretty deep groove into the bracket. Somehow that groove was enough to keep the pulley from falling off completely and...spin? in the groove. Crazy. Took it to a couple parts stores nearby...no luck. Then I called Freightliner and...bingo. This was my first experience calling 1-800-FTL-HELP. The guy who answered, very quickly, took the last 6 of my VIN and gave me the pulley PN and told me the nearest FL Shops. He was also able to provide me with the Cummins Engine Serial Number for my rig, something I was having a hard time locating... Unfortunately the shops were closed by the time I got the info so I'll need to check Monday to ensure that it's the right part and if, by some miracle, it's in stock. Either way, when I do get it...it's a single bolt to slap it back on. Good stuff.

Turns out that, yes, FL did do the AC Compressor install as I suspected and as SKIP426 confirmed. Apparently the part is not technically a tensioner but rather an idler pulley. I'm not entirely sure what purpose it serves other than to route/take up slack in the belt. But mine is not to question why...

Do you still have the part number, I am looking for the same pulley

[153stars]

Sometimes an extra idler pulley/s to add more wrap and grip around the pulleys, serpentine belts don't grab same as V-belt.