Serpentine belt issues Komatsu PC290-11

Replaced the belt and tensioner last winter, genuine Komatsu parts. Belt and tensioner was like $600. Same issue. Even without running the a/c, the belt squeals/chirps, fan slows way down, lower RPM helps. Currently, I can't run in P mode, if I run the engine at 1500-1600 it seems to kind of work. The a/c compressor runs off of a separate v-belt that drives off the fan hub. I have a picture of the belt routing, I believe it's a s hitt y design, in reality, only about a third of the fan hub is contacted by the belt. Machine only has 4000 hours, was a problem at 3400.

I had the same issue with an 8.3 Cummins. Fan pulley grooves were wore out. You could spin the fan by hand with the belt tight and I could here a whirling sound at max RPM. I put a new fan pulley on and couldn’t hardly move the plastic fan. Same deal with the A/C compressor. It’s driven same as yours. The A/C didn’t work when I bought the machine. As soon as I fixed it, I would lose the fan belt in about 30 minutes of run time.

LN Pipeline said: I had the same issue with an 8.3 Cummins. Fan pulley grooves were wore out. You could spin the fan by hand with the belt tight and I could here a whirling sound at max RPM. I put a new fan pulley on and couldn’t hardly move the plastic fan. Same deal with the A/C compressor. It’s driven same as yours. The A/C didn’t work when I bought the machine. As soon as I fixed it, I would lose the fan belt in about 30 minutes of run time. Click to expand... I REALLY don't want to have to change that fan pulley. I really don't care to be dealing with this s hit at all, a 6 year old machine with 4000 hours should not be having this sort of issue. I honestly can't believe that there isn't some sort of update or something. It's a pis s-poor design.

Like this routing?

heymccall said: Like this routing? View attachment 346895 Click to expand... I wish. Alternator is about 4" higher on mine. You have closer to half pulley of contact.

Shimmy1 said: Replaced the belt and tensioner last winter, genuine Komatsu parts. Belt and tensioner was like $600. Same issue. Even without running the a/c, the belt squeals/chirps, fan slows way down, lower RPM helps. Currently, I can't run in P mode, if I run the engine at 1500-1600 it seems to kind of work. The a/c compressor runs off of a separate v-belt that drives off the fan hub. I have a picture of the belt routing, I believe it's a s hitt y design, in reality, only about a third of the fan hub is contacted by the belt. Machine only has 4000 hours, was a problem at 3400. View attachment 346879 Click to expand... Generally, the squeaking sound is caused by the belt being loose. Try adjusting the screw on the side of the belt tensioner.

Didn’t know te tensioner was adjustable? I would be leaning twords the fan pulley being bad also. Anytime you have a serpentine belt giving you problems, it’s either an alignment issue or a worn out pulley. Even a run out issue doesn’t really affect the belt much.

HarleyHappy said: Didn’t know te tensioner was adjustable? I would be leaning twords the fan pulley being bad also. Anytime you have a serpentine belt giving you problems, it’s either an alignment issue or a worn out pulley. Even a run out issue doesn’t really affect the belt much. Click to expand... How the F can a pulley be wornout at 3400? Ran too long with a bad tensioner???

Not sure but something is causing your new belts to go south. I have replaced hundreds of sheaves, that were prematurely wearing belts. I will say operating conditions can really affect wear. In a sawmill, sheaves wear out extremely fast with the fine sawdust in the air. I imagine it’s the same with other equipment also, especially in certain dust conditions. My lawn or topsoil has a lot of beach sand in it and it dulls the blades, wears the belts and pulleys out and plays havoc on the deck bearings. I realize they are supposed to be sealed but dust and fines get everywhere. I remember parking my truck at the sawmill, with all the windows up and still getting sawdust all over the inside of the cab.

Shimmy1 said: I wish. Alternator is about 4" higher on mine. You have closer to half pulley of contact. Click to expand... This this the correct routing if u can’t get the belt on this way u need to try harder. I know u can put it on the wrong way and it will slip like a big dog.

I put the belt on this way outlined in red and it will go on and it will slip like hell on the fan.

What belt you using? 8PK1805? 6732-82-3360? I gotta ask, did the tensioner come with a shipping pin, and, if so, was it removed? Is the tensioner index pin in the hole on the timing cover? A tensioner has a stroke range. With no belt on, say it points to, say, 8:00. How close to 8:00 is it when the belt is present?

Have seen one crank pulley with so many tiny rocks stuck in the tiny v-grooves that the belt woulod not sit perfectly. They were hard to pick out with a sharp pic and did not have belt problems after. Simon C

Apparently sometime the past someone got their hand down close to a belt and probably got hurt. Now Komatsu hides that belt behind a labyrinth of guards so tight I can't see in to check the condition of the belt. When I've inspected those machines I've had say I can't see the belt and it isn't squealing when the engine starts or stops. I recently got a bore scope so I can check them. From my experience, I don't think it would be hard to miss something when you changed it.