scottknight Posted May 18 Share Posted May 18 original owner since 05 I found cracks this year in my serpentine belt after inspecting new radiator hoses install before last years trip. The manual said two belts but I have 1, 83.9 inch belt Napa measured. This generation 2004 isc was short lived in rvs and the isb hp was tuned to replace the isc 330hp The Monoco manual shows 2 belts. Looking through NAPA catalogs with parts person could not find idler pulley with the right diameter . I have a rear radiator. Anyone have info available. Would like to repair once, at home now no hurry. pics included Cummins supplied the tensioner, but engine configuration maybe decided by motor home mfg. NAPA Belt # gates 8PK230\K080839 was recommended by Napa auto parts Link to comment Share on other sites More sharing options...
jacwjames Posted May 18 Share Posted May 18 Look in your manual and it might show the belt(s) number. Towards the back of my manual there is a list of parts including the belt. Can you clean the old idler up, there is probably a part number on it that can be cross referenced. That or create an account on the Cummins Quickerve site https://quickserve.cummins.com/info/index.html Once you create an account you have to register your engine using the SN. From there you will have access to all the parts for your engine. That's what I did ~2 years ago when I replaced my idler pulley. Got the number and did a general search. Found a Cummins pulley for a good price, NOS. Link to comment Share on other sites More sharing options...
tmw188 Posted May 18 Share Posted May 18 (edited) Cummins Quickserve has always been a MAJOR PITA for me. Trying to login and or reset my password which worked now still can’t get in. I have fought this site for yrs. After :45 I’m done, throwing in the white flag. Edited May 18 by tmw188 1 Link to comment Share on other sites More sharing options...
scottknight Posted May 18 Author Share Posted May 18 yeah , unfortunately the book shows 2 belts and Cummins stops at the tensioner, the motor configuration with one belt has a larger idler pulley . NAPA parts clerk could only find the name of the bearing , stamped on the bearing . Talked about pressing a new bearing in ? this ntn 6203lax30 is stamped on the bearing I think i have read that the 330 is on combines............ but the size of the wheel is smaller by 3\8 ish . Not sure if that changes belt length much. Tensioner Pulley For John Deere 6203LAX30 Link to comment Share on other sites More sharing options...
BradHend Posted May 18 Share Posted May 18 (edited) Send me your ESN, I’d be more than happy to add it in my Quickserve account to get you a part number. I have nothing but good good luck getting proper parts or the latest supercession. Edited May 18 by BradHend Link to comment Share on other sites More sharing options...
tmw188 Posted May 18 Share Posted May 18 Well I appreciate that, not really looking for anything currently but have always had issues with their website. Now it appears they’ve made changes? Link to comment Share on other sites More sharing options...
jacwjames Posted May 18 Share Posted May 18 Back a couple months ago I had trouble getting into quickserve. I had had an account since 2011, so it was frustrating. Finally resorted to calling the help line, once I got a rep who knew what was going on they explained the Cummins had transitioned to a new login system which required users to use an email address as the login. He advised me to just go ahead and set up a new account, which I did. He stayed on the line until I was successful. Haven't had another problem getting logged in. Link to comment Share on other sites More sharing options...
jacwjames Posted May 18 Share Posted May 18 The tensioner I bought was Cummins Belt Tensioner 3936213 It was NOS OEM for $50. There is no recommended guidance on when to change, some people do it whenever they change a belt. But there is some guidance on how to check and look for that would dictate when to change. For me I was doing some work on the rig, had about 110K miles on it and I thought it was time although I could not find any problems with the old one. So I changed and kept the old one as a spare. When I change the belt I always keep the old one as a spare. Cummins Service_Repair Belt Tensioner.pdf Link to comment Share on other sites More sharing options...
scottknight Posted May 18 Author Share Posted May 18 easy esn # 46434512 ... Link to comment Share on other sites More sharing options...
BradHend Posted May 18 Share Posted May 18 (edited) Serpentine belt part number for your engine is 3972375 and appears to be in stock. Edited May 18 by BradHend Link to comment Share on other sites More sharing options...
scottknight Posted May 18 Author Share Posted May 18 the tensioner 3936213 is a exact match i have on site. A new idler pully seems to be a bit smaller but some reading indicates that the belts are tight to get on . I was able to get the belt off with a old school craftsman 1\2 ratchet and i have a repurposed floor jack handle as a breaker bar that slipped over the ratchet, access under the bed 2 trap doors . Maybe the john deer idler now being a bit smaller (3\8) inch will go on easy and still work well. thanks , can't find length specs on belt 3972375 mine measured 83.9 inches, other belts researched have come in 10 to 12 inches short and mine is unbroken . I think Monoco for whatever reason made a change on this 8.3 that clearly did not have a ac belt and a alternator belt, just one belt. I can use the old idler pully if i have to but the belt, belt tensioner and idle pully all 2004 . I am considering the john deer idler pully as a close substitute . Was looking for guidance on someone who already been down this road. the picture of the john deere idler pully with the oblong slots and number ntn 6203lax30 is stamped on the bearing My spare part bin is increasing Link to comment Share on other sites More sharing options...
BradHend Posted May 18 Share Posted May 18 (edited) Quickserve is saying your engines original belt tensioner is part# 3976831, however it is showing the latest active supersession as part# 5259022. Also, the original idler pulley according to Cummins is part# 3970945, which is still active and available. Here is the build data for that engine too: Edited May 18 by BradHend Link to comment Share on other sites More sharing options...
Ivan K Posted May 18 Share Posted May 18 Your belt number 3972375 crosses to Dayco belt 5080840 with following dimensions Rib Quantity 8 Top Width 1.10 in Effective Length 84.06 in Effective Length 2135.13 mm Outside Circumference 84.68 in Link to comment Share on other sites More sharing options...
scottknight Posted May 19 Author Share Posted May 19 thanks all copied and saved ....... went with wife to Culver for burger and custard came back to find great info. The tensioner and idler used a 13mm socket and flipped belt over each fan blade no surprises. Work on getting parts to install. Thanks again all ! Link to comment Share on other sites More sharing options...
Bykerboy Posted May 19 Share Posted May 19 (edited) I have a 2006 Knight with the ISC 330 and went through a similar exercise just about a year ago when I decided to proactively replace my serpentine belt. The Monaco maintenance manual is wrong. Mine also listed two belts and I only have a single belt. After some trial and error I ended up with NAPA 25-080830 belt and tensioner part number M-3976831 that I purchased from Interstate-McBee. The belt was tight fit to get on but with a 1/2' breaker bar it was not too bad and the belt went over the fan blades with no problem. Edited May 19 by Bykerboy Link to comment Share on other sites More sharing options...
Rikadoo Posted May 19 Share Posted May 19 Boy that tensioner issue brought back some bad times. Prior to replacing my radiator i had developed a squeek (while parked in front of my house) which started a massive search, i had tried the esn, that went no where, tried to match one up, fail, ended up calling i believe the mfg, they gave me a pn which no one had, on a lark i reached out to of all places… Wal-mart on line🤪 i had to order it an it was the right on! When i spoke with the mfg. they had told me they did upgrades that had changed the bearing/pully and assured me of a proper fit. I remember at that time thinking had that happened on the road it would have taken forever to find the right part. Main serpintine belt: Cummins 3911581, or Napa 25-080690 Belt tensioner: Orig is a Dayco PN= 3936213 / 3542230 now updated to Dayco 89481 so needless to say i recorded that info in every place i could🤦♂️ 1 Link to comment Share on other sites More sharing options...
scottknight Posted May 27 Author Share Posted May 27 05 Knight 8.3 belt replacement Installed these parts for belt replacement, rear radiator Belt went with Dayco 5080840 longer than new local purchase Gates K080839 ........... new backup belt idler pully Cummins 3970945 tensioner Cummins 3976831 all installed but not tested I did tie down ratchet\breaker bar on frame right at full de tensioning then last sliding belt over a beveled pully, water pump ? from under the rv Hope these part numbers become useful thanks again 1 Link to comment Share on other sites More sharing options...
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