Changing serpentine belt

[ncsteve]

Getting ready to change out my serpentine belt on rear radiator Knight. Couldn’t find the belt info on any of my books, but did manage to get numbers off the current belt. More of a preventative maintenance so I don’t have to do it on side of road. I have the belt ordered and looking for any tips or tricks to make it go as easy as possible as I know it will not be easy. 
Oh and if anyone has the belt number for the AC compressor, that would be much appreciated as I did not see any numbers on it. 
thanks, Steve
 

[Chuck B 2004 Windsor]

Take the advice of one who has been there and attempted that.  Go to your Cummins authorized distributorship dealer and let them do it for you.  Once you take the belt off and cannot put the new belt on, you are stuck dead in the water.  It's not worth the few bucks you save.  Chuck B Former Diplomat owner.  

[Guest Ray Davis]

Steve,    The 3 things I suggest are, document the routing of the belt,  save the old one,    and replace the tensioner too.

 

[Terry T]

On more thing a big cheater bar......not hard with that.

terry

[Admirial RVr]

Just changed my serpintine belt on my 2006 Diplomat 400 Cummins. Was not really that difficult especially with 2 people. One person under and one up top . Took us 1hour 15 min. I don't have a seperate belt belt for the AC.  Ray is right, Yes, do change the tensioner at the same time. That is the easy part.

[ncsteve]

Would anyone have the tensioner part number? Quick search and there are more than one out there of course. Thanks for the replies.

[6Wheels]

I have had to change the S-belt twice.  Once when the water pump bearings froze up, and once when the alternator bearings froze up.  You are lucky to be able to pick your time to replace it.  I was on the side of the road both times on a Sunday night!

[ncsteve]

Following upon this. Got the belt changed.  Not that bad of a deal, well if I have to ever change it again it shouldn’t be. The adjustment bolt on the AC compressor was stuck. Ended up removing the 2bolts that held compressor on, moved it out of the way which allowed me to get to the adjuster. I then removed the whole assembly, took it into the shop and cleaned and lubed it up. As for the belt, inserted a ratchet in the tensioner and then slide a 16” cheater bar over the handle. This gave me leverage as well as got the handle up to where it was easy to get to. Then basically release tension, remove belt and install new one in reverse order. Once belt was off, was able to get to tensioner bolt from bottom and replaced it.  Reattached the compressor and tightened adjuster. 13mm and 15mm to loosen mount bolts, 18mm for compressor adjuster and 1/2” ratchet with 16” cheater for tensioner. 

[Bob Wightman]

Did anybody take note of what the belt number was for the AC compressor belt?  I just had my serpentine belt explode on my trip this weekend (had it replaced 3 years ago so now am wondering why it blew up...of course in the middle of a blinding rain storm) that I got replaced and drove it home 3 hours without a problem.  When we had the engine compartment hatches open I saw the AC belt, figured i'd better change that too and keep spares in the coach.  Trying to order the belts but don't know what the part number for the V-drive belt.  BTW, the Gates part number for the serpentine belt is K080690 (8PK1753) 1-3/32" X 69-1/2" OC if anybody needs that info.

Knight 34PDD W/Cummins ISC 8.3L 330HP

[jacwjames]

In my owners manual there was a table that listed all the belts and filters.  You might check there.

[cbr046]

@Bob Wightman When I replaced a belt I discovered they had different levels of quality (good, better, best) and prices to match.  The other shocker was some belts had uuuu grooves while others had vvvv grooves.  Or a pulley that might have been replaced with the wrong shaped grooves in it.  Not saying it was any of these but that might explain an early demise. 

- bob

Edited August 21, 2023 by cbr046

[Happycarz]

Dayco 4470 belt for the A/C compressor.

[jmatusic]

My AC compressor froze about a mile down the road after a fuel stop in rural Alabama. Caused the AC belt to break. The AC belt turns the water pump. Engine overheated. Found it impossible to locate a new AC compressor and even if I had, would need to replace more AC components due to potential damaging crap in the dryer and condenser and hoses, big job. Had to bypass the AC compressor in order to turn the water pump with a shorter belt. Luckily the mobile diesel guy knew the part number for the bypass belt. He located one and got us back on the road to finish our trip without the dash AC. Now I carry several spare belts (AC bypass and original), a spare water pump, a spare alternator and the old tensioner so a mobile mechanic doesn’t have to source parts if I breakdown far from home. Cheap in the long run and they don’t take up much room.

[Lost Outlaw]

Just read all the replies found it to be good information about the belts.  But I have one question, was accessibility to the belts made by removing the radiators or leave it in place?

[jmatusic]

4 hours ago, Lost Outlaw said:

Just read all the replies found it to be good information about the belts.  But I have one question, was accessibility to the belts made by removing the radiators or leave it in place?

In my case, I have a side radiator

[Bob Wightman]

I left the radiators in place and changed the belts through the hatches in the floor of the bedroom in the closet.  Takes two guys though, one to position the belt and hold it there and the other to load the tensioner spring to where you can get the belt on that pulley.

 

[Lost Outlaw]

Thanks, I sure hope that could be done. 

[96 EVO]

On 8/22/2023 at 5:03 AM, jmatusic said:

My AC compressor froze about a mile down the road after a fuel stop in rural Alabama. Caused the AC belt to break. The AC belt turns the water pump. Engine overheated. Found it impossible to locate a new AC compressor and even if I had, would need to replace more AC components due to potential damaging crap in the dryer and condenser and hoses, big job. Had to bypass the AC compressor in order to turn the water pump with a shorter belt. Luckily the mobile diesel guy knew the part number for the bypass belt. He located one and got us back on the road to finish our trip without the dash AC. Now I carry several spare belts (AC bypass and original), a spare water pump, a spare alternator and the old tensioner so a mobile mechanic doesn’t have to source parts if I breakdown far from home. Cheap in the long run and they don’t take up much room.

Care to mention the length?

I've read 66", but, would be nice to hear confirmation!

[jmatusic]

20 hours ago, 96 EVO said:

Care to mention the length?

I've read 66", but, would be nice to hear confirmation!

My bypass belt lengths range from 67 1/8 (Gates K08060HD and Gates K080665HD) to 66.78 for a Continental 4080660. There are belt cross reference charts online that show various manufactures belts, for example I can also use a Cummins 3289124 or Duralast 663K8. My engine/AC compressor setup might be different from yours.

Our first motorhome was a 2000 Monaco 36 Knight with one slide. Thats what caused me to be a member of this site. Learning never stops with these things. It was our trial purchase to see if we would like this pastime. We loved it but wife wanted something larger with more space, lucky me. So now we have a 2010 Tiffin 43 foot with four slides, Cummins engine. I stay on this site as well as several others to learn from other owners. The Tiffin has many of the same issues as other manufacturers, same appliances, leveling, etc. I keep several spare belts as well as the routing diagrams available in case/when I'm needing that for the roadside repair guys. Had a frozen alternator eat a belt in my driveway. So I have a spare alternator onboard. I changed out the water pump, belt tensioner and idler pully when I got home from the incident with the frozen AC compressor on side of interstate. Have the old ones on board also as spares.

Joe

belt routing.pdf