On my 10K6516 D6C, is twisting fan belts, then eventually they break which is logical. Going back a few weeks ago we replaced the alternator, found that pully on it somewhat worn, so replaced the pulley for a new one. It seems to fit fine. Only a few hrs on the new set of belts after the alternator & alt pulley change & today it twisted another belt. Alignment seems ok. Changed them out again & am keeping a close eye on them again. Neither the crank our fan pulleys seem to be worn bad as the belts are still a ways up from riding on the bottom as they should be. We are starting to think that the crank & fan pullies are the culprits from limited wear maybe? Any ideas on what makes the belts twist like that?
Is an edge of a pulley warped and causing the twist or the pulleys out of alignment?
Not that we can see. TBH its really hard to get a clear line of site because of how the machine is configured.
Use a brazing rod, or straight edge to be sure everything is in alignment. A harmonic ballancer can slip. Are the belts put on too tight? or forced on over the pulley instead of loosening the adjustment? was it twisting belts before the new alternator?
Are they a matched set of belts?
The belts should be riding up on the flanges just like the RH one in your photo. The only time I saw a belt twist, the pulleys were out of alignment. Get a hold of a fan bade and see if you can shake the pulley. Check the profile of the new belts for an exact match to the angle of the pulley flanges.
They were not forced over the pulley, rather loosened. Yes, the twisting problem surfaced after the alternator was replaced, but the alt is an exact replacement. I am beginning to suspect an alignment issue that we need to get to the bottom of. As mentioned earlier, it is hard to get a line of site to check alignment. Belts are a match set BLS. Fan blade is tight & does not wobble at all.
I would put the old pulley back on till you can replace them all .
Belts should ride slightly above the pulley groove. Check v-groove for u-shape wear pattern. For some reason the D6C's seem especially sensitive to pulley wear.
Suspect the pulley on fan &/or crank have erosion wear causing the belt to try to climb out of the groove which is typical of older machines, could be the new Alt pulley is narrower or wider by a slight amount pulling to one side the belt noted and that starts that climbing sequence much as a car on a road rutted by a larger machine. Reinstalling the old alternator pulley may help in the short term, replacing or refacing the other two pulleys may become necessary.
I had a lot of trouble with mid '90s CH Macks doing that. I finally found that the A/C compressor mounts were flexing.
The snip below is an enlargement from the photo attached to your OP. To me it appears as though your fan pulley is worn. The belt ought not to sit below the top of the groove like it is in the photo. It would be interesting to see what the other belt looks like in the fan pulley groove when it is correctly orientated. You may well have an alignment problem but I'm of the opinion that the wear on the fan pulley is what's allowing the belts to twist. There's also apparently a chunk out of the back side of the pulley that while it won't affect the belts could easily cause bearing failure due to inbalance. That would probably cost you a new fan and a radiator core. Also have a look at the state of the tensioner spring while you're in there. Quite a few of them have been updated.
My western star with a 12.7 detroit loves to throw its alt. belts. Pulleys are straight, but I know the pulley's are worn/ dished. It seems like it will go for a long time and not throw them, and the next set it will throw right away- no rhyme or reason. I didn't know anyone sold "matched" belt sets any more. I can ask, but it seems like all I get is two belts that may or may not be close to each other. With worn pulley's - would it make any difference if they were toothed belts or a smooth v-belt? Most of my experience is from the ag augers/ grain moving, and I always thought a smooth one would slip quicker, but be less likely to jump than a toothed. It seems like the teeth make it more likely to climb/ twist.
Can't speak for Western Star or for that matter be sure what Cat sells is a "matched set" but they do list one part number and call it a "set of two" 2P6140 for this particular application. Not a V belt but at the quarry we had a Sterling(AKA Ford) truck for a water truck it had the Mercedes/Detroit engine in it, for get the model, might have been a MBE900. Anyhow it had one of those Poly-Vee belts for the fan drive. Short time after we got it I noticed that one of the ribs was tron off. So I replaced it with new belt which is a bit of a pain as truck had pump running off the front of crank. Short time latter noticed same thing one rib gone at the front. Again replaced and inspected very close to see if anything could be hitting it or if there was any out of line between the pulleys. Hate to admit it but never found a cause and the fact that the truck never got more than a mile from the shop and unless there was some idiot running it never got over 25 mph just decided I had more important thing to worry about. Also problem never progressed just shed that one rib and it would go for a year without any more damage. Have to wonder if there was some flexing of frame or motor mounts as the cause. Truck did have problems breaking front fender brackets that I fixed by fabricating new ones and those held up for the last years I was there. I just don't think that truck was ever designed to be run in a off-road application. Not that our roads in the quarry were that bad but some operators just think they are stunt drivers for the Duke's of Hazard T.V. show!
Some years back, Gates announced that they no longer sold matched sets, because modern manufacturing techniques resulted in All their belts being matched. Right after that, they offered an ocean-front condo in Az, cheap.
have had lots of rubbers come out on harmor balancer till you pull pan under and look will cause all sort of problem or just quite pulling belt will also make run hot
Ok......our mechanic pulled off the front belly pan this morning & here is a few shots of the crank pulley. Seems the belts ride a bit low in the groove & the report back was pulley grooves were somewhat -U shaped, so he is going to order a new bottom pulley. He says the bottom one is worn somewhat worse than the fan pulley. Plans to do the front crank seal when he is at it, as it will be in the open...…….. The report back was the alignment was good for all 3 pulleys.
MM55 I would SERIOUSLY consider doing the fan pulley while its down, and YES I know is an expense not needed but is downtime all that affordable either? A lot of abrasive(Dirt) and good hard belts make lovely lapping tools.
We would but Tony our mechanic tells me that there are availability issues with getting the top fan pulley. He also said that the top pulley changeout is an easy fix compared to the bottom one, so one step at a time I guess. Anyone know where there may be availability of good used or new top pulley?
2P-3807 was discontinued by Cat. Best bet is probably Offroad Equipment - www.offroadeq.com/ - or a similar organization in your area.
Ok...……...thanks Nige. I'll let you know how we make out!
sounds like your man has been there he is doing what i have in past. i even made a puller to do with out pulling raditor can be done just takes time.and yes on seal too.
just a random idea, but on hard to get or discontinued pulleys and sheaves, If there is enough material, i have re-machined the grooves. the only problem is that after machining, the original belts may be too long requiring the use of shorter belts. also the reduced pulley diameter can cause a slight change of shaft speed but its usually not an issue
Sounds like new pullies for top & bottom are in the works from what I have heard. Stay tuned...….
If you're going to that level of expense then an overhaul of the tensioner with new bearings and a new spring might not go amiss.
Kinda hard to do seeing how it don't have one. Bob
Good to know.
Parts book shows 1P7122 fan pulley and 5S8168 crankshaft pulley (separate from dampner) 1P7938 v-belt set (2-belts) Lots listed on Machinery trader parts
I’m abit late to this party chaps,but you’ve probably figured out by now that all your pulleys are Infact worn out. All three need replacing. I’ve found non Cat pulleys readily available and have stood the test of time. I would also insist in forking out for genuine Cat belts. Non genuine Cat pulleys are fine,but make sure you buy genuine Cat belts. Your other option is to keep messing about for the next few years getting it wrong. I’ve learned the hard way.
Ok, back on the pulleys...…..were able to get a new after market crank pulley as well as a good used Cat fan pulley & Tony & I got back at it today. We fashioned a home made puller from a scrap of steel & some puller parts he had in his arsenal…..they worked & we didn't have to pull the rad! Crank pulley came off easy! We didn't change out the crank seal however, as it was soft by the feel & Tony thought it may prove a challenge to reach in past the front mount bracket......not a huge job to get off if it does go bad....
Now would be a good time to take the alternator off and see what is the matter with it. Bob
Alternator pulley problem has been solved now we think. I have owned this machine for about 7 yrs & it had an incorrect pulley on the old alternator...….ordered the correct one & it is on now.
All back together now! Note our way around of lifting the HEAVY $%&*# of a front belly pan on!!
Belly pans a painful necessity.
I worked on my D6C fan pully a while back. It has some endplay so replaced the bearings. The grooves in my pully looked good to me, no wear in the root, had rust etc. One of the reasons I dug into that part of the machine was a belt squeak/squawk when I'd kill the engine. http://www.acmoc.org/bb/showthread.php?30333-D6C-10K-engine-squeak-when-shutting-off&highlight= Pics of my project for reference to anyone else working on this in the future: https://imgur.com/a/N2rdh7C I will say, the new belts sat lower in the grooves than the old belts. Neither set of belts were CAT belts... As you can see from the pictures in that link, the endplay wore a groove in the pully shaft support. Bearings were fine, keeper plate bolts were loose...
My fan bearings were in excellent shape yet. Changed the fan seal while it was apart though. When we were working on it we were wondering what the recommended grease intervals were for the fan. We do it about every 50 hrs or so. Anyone know? Changed the belts out again with the new pulleys going on even though there was only 40 hrs on the last ones...…..new ones set about even with the outside of the pulley.
Fan bearing service interval is 250 hrs or monthly.
Looks like a good result and fair play for getting the crank pulley off with the rad in. As for greasing it,a couple of shots every 250 hours or twice a year for an old hobby horse. They do not like being over greased