Replacing fan belt on BX: if a 60-something nerd can do it, so can you

[diggindoc]

My BX24D developed a case of "the squealies" at 7 years / 400 hours, a loud squeal mostly on cold startups and growing gradually worse. Tightening the fan/alternator belt relieved it temporarily, but eventually I reached the end of the adjustment slot, so it was time to replace the belt. I'm a better nerd than I am a mechanic, but I did get through it, dusty but unharmed. I've appreciated help I've received on this forum, so I'm sharing my experience.

As the belt wears out, it doesn't stretch all that much, but it gets thinner and thinner, so it sits lower in the pulley grooves, which makes it looser. It may squeal like mine, but you might also see low/erratic tach readings, or overheating because the fan isn't being driven consistently. You can adjust the alternator to tighten the belt to the recommended tension, but eventually you come to the end of the slot. So here's a step-by-step procedure to replace the belt:

1. Tools you'll need: 17 mm open-end wrench for the alternator mounting bolts and nuts. 12 mm socket with a socket wrench and 4" or longer extension. Also round up a hefty 18" screwdriver or an iron bar 1/2" - 1" wide, at least 18" long. If you're working alone, you may need a C-clamp too. And finally, goggles for when you get under the tractor. And of course, you've made sure the engine has cooled off enough to work on.

2. Remove the engine enclosure (the manual describes that so I'm not going to), and find the upper alternator mounting bolt (photo below). Loosen it with the 17mm wrench. You don't have to take it completely out.



3. The lower alternator mounting bolt has 2 nuts on the end (photo below). These tend to "lock" the bolt, so you can't just loosen it by turning the head. Instead, loosen the nut on the right (which holds the dipstick brace) a few turns, then you can either loosen the second nut or loosen the bolt via the head. The alternator should now be movable.



4. Swing the alternator inward as far as it will go. You can then lift the belt off the alternator pulley.

5. Now take the belt off the fan pulley and extract it from the fan shroud. To do this you'll gently flex a fan blade and work the belt out from between the blade and the shroud. Repeat this for each fan blade and the belt will be free from the fan, but still looped around the driveshaft pulley. Here's a look at that driveshaft pulley from the left side of the engine.



6. You're going to be loosening 3 bolts that hold the driveshaft to that pulley. The problem is, when you apply torque to the bolts, the engine crankshaft may turn, making it impossible to break the bolt loose. My solution was to wedge a hefty screwdriver between the openings in the driveshaft hub. Since I was working alone, I used a clamp to secure the screwdriver to the tractor frame. (Maybe if I had a helper, they could have just held the screwdriver.) You could also clamp a piece of angle iron to the frame so it engages a tooth of the flywheel at the front of the engine.



7. Put on your goggles and lay on your back under the tractor. Look forward toward the engine and you'll see an access opening in the bottom chassis pan. The driveshaft attachment is shown in the photo below. There are three bolts with 12 mm heads holding the driveshaft coupling to the engine. (In the photo the bolts are already removed and I'm pointing to one of the three attachment holes.) Loosen and remove the first bolt you can see. Then come back up, remove the screwdriver locking the hub and rotate the engine 1/3 of a turn. I don't recommend "bumping" the starter to do this, I found it easy and safest to just rotate the flywheel by hand at the front of the engine. Relock the driveshaft hub, crawl back under, loosen second bolt, and repeat for the third one too. Then take the screwdriver/bar off because it will get in the way.



8. The driveshaft which runs backward from the hub can then be compressed by pulling on the shaft by hand (don't pull on the rubber boot or it might tear). At this point, I got help from my wife. I held the shaft compressed, and asked her to yank the belt free through the opening between the driveshaft and the pulley.

9. Here's the new belt held next to the old one. Scientific proof of the thinning phenomenon! OK, only a nerd would care. You have to replace the bugger anyway.



10. Fishing the new belt though the gap between the compressed driveshaft and the pulley required help again. Then I repositioned the driveshaft hub, got one hole matched up and inserted a bolt. I reinstalled my clamp mechanism and tightened the bolt. Then it's just unclamp, rotate, insert, tighten, and repeat for the third. I didn't use an impact wrench and I don't own a torque wrench, but about as hard as I could pull on a 10" ratchet handle felt about right. Be darn sure you then remove the screwdriver/clamp assembly because it would make starting up the engine later an unpleasant experience.

11. Now work the belt back between the fan and the shroud, again one blade at a time.

12. Finally install it on the alternator pulley. This proved one of the more difficult tasks. Even with the alternator swung fully inward, there wasn't enough slack to slip the belt over the pulley. I found a trick was to get the belt into the pulley groove where it just starts to contact the pulley, maintain inward pressure there with a gloved finger, then rotate the alternator pulley (unfortunately, you have to drag along the fan and engine too). The belt should ride up onto the pulley. This might have been easier with a helper. I sure didn't want to use a pry bar, damage the belt, and have to go through this all again soon.

12. Here's the alternator tension setting I ended up with for the new belt. No more squeals! After about 10 hours of operation I'll recheck the tension.



Now, off to mow those fields...

 

[KennyV]

Replacing a belt is often the fix... and they do wear out Exactly like you described, they get thinner, they Don't stretch.
I usually like my New belts to start out at the shortest possible setting on the adjustment, not only to give me more future adjustment, but it keeps everything more compact. My alternator piviot is directly above the oil fill on my Kubota L4200... the more the alternator leans out, the less accessible the oil fill is... so the shortest belt will keep it in and out of My way.
I get several belts from different manufactures and will find the one that with the alternator un-mounted to the engine, will allow me to angle the alternator & slip the belt into the pulley and Then bolt the alternator at its pivot.... Then attach the belt tension arm at it's shortest position... This gives me many belt length to find the correct belt tension (too much is bad for all bearings involved), have a great parts supplier that will allow me to only buy the one I find that is the shortest possible...
Just do not over tension your belts and everything will be fine for a Lot of hours.... KennyV

 

[CHDinCT]

Nice write up. Gonna save this thread for when I do mine, which may be soon given I have over 400 hours now on my BX25. I know I do need to adjust the tension some already.

 

[Cye]

From a 61 yr old nerd with plenty of will power but not a lot of knowledge/skill --- triple, (or quadruple whammy, but who's counting if I can keep my tractor running), whammy, I don't even have any Y chromosomes, I also thank you for this post.
I'll try out your method....But..Ifirst, I want to figure t if there is another way. I read in another post about A type of belt called " powertwist ", but I haven't been able to pull that post up again for some reason.
Does anyone have any experience with using these?

I have a Kubota bx24 with about 250 hours...I've been doing the maintenance , but the tractor was used hard before I got it, and I'll also be replacing the transmission fan, so maybe I can do both at same time.

If anyone has general tips, I'll be very interested to add to my knowledge and skills, so thanks for any helpful ideas.

 

[zoltanthegypsy]

I had to replace the belt on my '24 a few months ago. Wasn't squealing but the tractor was running hot. As the OP says, it had worn skinny and was slipping. Fan spinning but not at full RPM and not cooling well.

Wish I'd had the write up - but managed to figure it out on my own. Then again, I'm only 66

Z.

 

[Danner]

I know this is a few years old, but I need to do this to my BX2660 tomorrow, and this thread is definitely going to make the project go better. No question about that.

Thank you.

 

[4570Man]

This might not have been possible in your case, but when I encounter a stuck bolt on a movable object I found that striking the wrench with a hammer or block will usually break it loose. That's assuming I don't have my impact wrench or it's not possible to use it. Hitting a wrench with a hammer is the same concept as an impact wrench though.

 

[Pinecrest]

I had difficulty getting the new belt on ...at last I got my neighbor to come over and as I started the belt over the Fan Blade
pulley he turned the engine over with a 14mm socket at the front of the engine. it rolled right on . Tightened up the alternator, changed the oil & filter while I hade the cover off . ...put it all back together. A Ryobi impact made the work easy.

 

[ImaginaryTango]

I know it's been a while since there have been responses on this thread. I joined the forum so I could add a few things.

1 - I have a BX25D - but had issues and now have a 23D engine.
2 - Like so many others, I'm in my 60s. I'm a computer geek, but had to learn a lot about tractors and what I can use them for when we bought a large piece of land in 2015 and built a house on it in 2017, then renovated the old pig barn on the lot later. I still get anxious about tractor repairs when I see something like, "Disconnect the drive shaft." The process is far easier than I expected.
3 - I only found a need for 12mm wrenches, not any 17mm. That could be due to model differences. Yes, I needed open wrenches, not socket, to handle the drive shaft and the bottom pivot screw on the alternator.
4 - On the drive shaft, I found an easier method that doesn't involve using a clamp or having to move back and forth from under the tractor to reaching in from the top. First, for turning the shaft, I used the torque from the wrench to turn the shaft. I put my wrench on one of the bolts on the drive shaft connector and turned it - but instead of turning the bolt, it turned the shaft. That's what I wanted. Then I put the screwdriver in so the shaft wedged in the connector and against the edge of the opening to access the connector:

Again, in case I wasn't clear above, I put the wrench on the bolt and turned it. That turned the drive shaft until the bolt was easily accessible, then, as the rectangular metal "post" on the connector came around, I put my screwdriver in so it wedged between the edge of the access opening and the connector. That held it in place. I was able to do something similar when reconnecting the drive shaft. The wire looms there may be from my modifications for adding work lights on the back of my tractor, so they may not be on your tractor.

Before starting, as always, I re-read the first post (and, sadly, it looks like the OP is no longer active here) multiple times, examining the photos and studying it carefully before doing anything. Then I thought, "Drive shaft? Yeah, I bet I get it off there and have to wait weeks for the tech to come out and put it back together for me." So I called the service department at the dealer. First guy said, "No, just slip it over the pulley. No need to disconnect the drive shaft." So I spent a lot of time looking things over and called them back. Got another guy that time who said, "Yes, you do have to pull the shaft out a bit so you can get the belt on, but it's not a big deal and easier than it sounds."

So there really is not an easier way, but this isn't really a tough fix.