Fanbelt moved forward - why?

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Model T Ford Forum: Forum 2012: Fanbelt moved forward - why?
Top of pagePrevious messageNext messageBottom of page Link to this message  By Stephen Blancard on Wednesday, August 08, 2012 - 07:37 pm:

I was just out for another practice drive in my new-to-me '24 touring. I was slowly going up and down my street getting the feel of things. All of a sudden I start hearing this buzzzzzz sound from under the hood. So I pull it back in the garage and take a look. I see that the fan belt has slipped forward, partially off the bottom pulley. Its still on and the fan is spinning, but the fan blade is hitting the belt causing the buuzzzz sound. I shut it off pretty quick and the fan belt doesn't look frayed, so I think it is ok. The belt still feels tight. After it cools down, I'll loosen the adjusting bolt and slide the belt back into place. My question is - what causes the belt to move forward like that? Here's a pic, sorry about poor quality, I took it with my cell phone.
fan belt


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Wednesday, August 08, 2012 - 07:52 pm:

Set it as loose as it can be and still turn the fan. See if it will stay on.

Other than being too tight would be mis alignment of the pulleys. Either the fan pulley ahead of the crankshaft pulley, or the bushing worn so that the front of the fan pulley is lower than the back. The pulleys must be aligned with each other.

Another thing would be the crown in the center of the pulley worn off.

If the belt is stretched, you might need to start with a new belt.
Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Stephen Blancard on Wednesday, August 08, 2012 - 08:34 pm:

I just went out and loosened the adjustment bolt, slipped the pulley back into place and re-tightened it. The belt is snug, but not tight. I started it up and the belt immediately moved forward over the lip on the bottom pulley, but remained behind the lip on the top pulley, so the fan blade didn't hit it. Maybe its been that way for a while, and it just jumped the top pulley lip tonight and started rubbing on the fan blade. I'll try to check the alignment and bushing for slop tomorrow. There is one of those fan belt guides in the parts I got with the car, but I'd like to find the root cause and fix it rather than treat the symptom.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dan Treace, North FL on Wednesday, August 08, 2012 - 08:44 pm:

Root cause is old worn down crank pulley. The crown in the center is worn, allowing the belt to roll to the edge. Replace the pulley is the efficient fix. Or remove and try to file the outer surfaces down which can 'restore' the crown somewhat.

Have heard of others doing it with the pulley in place and holding a bastard file against the outer edges, and run the motor and file as the pulley turns....but that's not a way for me, a flying file off the hands isn't a pretty thought.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Stephen Blancard on Wednesday, August 08, 2012 - 08:55 pm:

Both pulleys have a crown. What is the best way to measure the pulley alignment? If the pulley bushings are worn, I need to remove the belt and see if there is slop between the pullies and their shafts? Sorry for all the questions, but just got my T last week so this is all new to me. I've been searching the archives on this and am finding lots of good information. Thanks - Steve


Top of pagePrevious messageNext messageBottom of page Link to this message  By Harold Schwendeman - Sumner,WA on Wednesday, August 08, 2012 - 09:01 pm:

It'd be my guess that the fan belt pulley bushings are worn to the point that even if the shaft is parallel to the axis of the crankshaft pulley (which it should be) the worn bushings allow the fan pulley to tip downward at the front enough to cause the belt to move forward, crown or no crown.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Doolittle on Wednesday, August 08, 2012 - 09:33 pm:

If the spark advance is not correctly set, then the timer rod and cotter pin will ride against the belt pushing the inner edge of the belt inward causing it to ride toward the front of the pulley. Under the right condition the pulley can ride up on the pulley.

This happened to me. As it turned out there was a problem with the timing gear which was causing the rod to travel too far.. Fixed now- belt stays on pulley.

I should have watch the signs because there was a wear mark on the belt from the head of the pin rubbing.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Glen Chaffin on Wednesday, August 08, 2012 - 09:37 pm:

Everything that has been mentioned can affect how the belt runs. But in my experience over tightening of the belt will bend the fan bolt and arm down at the front causing the belt to run forward.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Allan Richard Bennett on Wednesday, August 08, 2012 - 09:59 pm:

Stephen, you mention a lip on the front pulley. A T normally does not have a lip on the bottom pulley. It is a crowned cast iron pulley with no flange/lip. I suspect the lipped pulley was fitted to cure the belt from running off some time ago. Glen is on the money with his suggestion that the fan arm/bolt is bent downwards at the front.

To cure the problem I would re-bush the fan hub and fit a new shaft. Then you need to bend the fan arm a little towards the engine and test run it. The idea is to adjust the "bend" until the belt runs in the middle of the bottom pulley.

My woodworking bandsaw has an adjustment which allows me to angle the top pulley so the saw band runs in the centre of the pulleys. All it does is tilt the top wheel, back or forward, until the band runs correctly. Your fan belt needs the same treatment. Tension on the belt needs to be just enough for the belt to drive the fan. The usual tension on a modern V belt which drives a water pump, alternator, aircon compressor etc. is way too tight.

Hope this helps.

Allan from down under.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Joe Van Evera on Wednesday, August 08, 2012 - 11:52 pm:

Hi Stephen: I just went through this, and while there are lots of great suggestions, I'd go with Glens first. My belt came off and it was due to being almost torn through. I replaced it with a new belt and couldn't keep it on. (Had no problems with the old belt...) It was coming off the crank pulley. I never have it too tight, but in checking the arm, the mounting hole and the fan pulley hole just didn't "line up." I put bars (that fit good and snug) in the holes and kept bending the arm until the bars lined up like they should (by eyeballing...) and the belt works fine now. I didn't just bend the arm up, but to the side a little too, in order to get the correct "dynamics." Of course I took the arm off when I did this, and it bent quite easily (thanks, Henry...).


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Blancard on Thursday, August 09, 2012 - 08:09 am:

It seems clear to me that the design of the fan pulley mount is pretty weak and could be easily bent if the belt was over tightened. Tonight I'll remove the belt and first check the pullies for looseness and then try to measure them for parallel and alignment. Is the fan pulley bracket/arm a forging? I assume it is, rather than a casting. Generally speaking a forging can be safely bent a little, a casting cannot.

I see fan pullies in vendor catalogs with ball bearings rather than bushings. Is this a worthwhile upgrade if the pulley is shot?
Thanks - Steve


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ed in California on Thursday, August 09, 2012 - 08:22 am:

I just went through these issues with my T. It was diagnosed as a worn fan pulley, as well as a worn arm. I realized my arm lower mounting hole was wallowed out slightly, causing movement on the mounting bolt. I replaced the arm and mounting bolt, and replaced the fan pulley shaft and put on another fan pulley that was snug. Problem solved.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Walker, NW AR on Thursday, August 09, 2012 - 08:34 am:

Steve -- The repro pulleys you asked about have sealed bearings, so they don't sling grease all over your engine compartment. The original setup will do that if you add a bit too much grease/oil. The new ones also should last a long time before wearing out.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Scott McBrook on Thursday, August 09, 2012 - 09:47 am:

FWIW - My pulley was so loose NOS pulley was still loose as the crank had worn. From a tip from Lang's parts department I used a 4.5" cutoff wheel to cut a slot straight towards the center hole. I had to cut a bit more off the outside to allow for movement on the inside where distance is shorter. Then I put the thing in a huge vice and bent it in as much as I could. I still had slop in the other axis so I mig welded a bead front to back, then using a cylinder grinding attachment ground 95% of the bead off and this snugged things up. I then installed the pulley, welded with a couple of spot welds on the inner/outer pulley face, let those contract when cooling, then welded the rest of the face and then ground it smooth. May not be your problem but it was a bit of fun and I had to tell y'all about it. again. LOL


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry VanOoteghem on Thursday, August 09, 2012 - 01:19 pm:

Steve,

Yes, the fan arm is a forging. If you decide to "straighten" it, don't do it while it's still bolted to the engine. The ear that it's bolted to, on the engine block & timer cover, are cast iron and will most likely break off. Bigger trouble then.

Really, I sort of doubt that the arm itself is bent. More likely, the spindle that the fan pulley rides on is bent, or you have worn pulley bushings, or both. Try loosening the spindle bolt, rotating it 180 degrees, snugging it up and giving it another try. If it's bent, you will have essentially reversed the bend and should get a different result. Maybe not better, but different.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Blancard on Thursday, August 09, 2012 - 06:50 pm:

Update - I just loosened the bracket so I could get the belt off. Then I grabbed the fan pulley to see if there was any slop on the shaft - there was a little, so I figured - worn bushings. So I removed the fan/hub/bracket from the car. Then I find that the hub has ball bearings in it, at least in the rear. I haven't yet removed the fan from the hub. Should there be any slop with ball bearings? I wouldn't expect so. But then I looked close at the surface of the pulley where the belt rides. Instead of being domed slightly in the center, the domed area is toward the front more. Is this typical wear on a pulley? - see the photo. Would this kind of wear cause the belt to ride forward?

I looked at the crank pulley and it seems to still be slightly domed in the center of the belt riding surface. I also tried to wiggle the crank pulley to see if it wobbled on the crankshaft. No movement, it seems solidly mounted.

So it seems the worn fan pulley surface may be causing my trouble. Maybe worn ball bearings too. I haven't yet checked for a bent bolt, but I will. I will also check to make sure the bracket arm is not bent or twisted.

What do you think?
Pulley assembly


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Thursday, August 09, 2012 - 07:28 pm:

I think you have found your problem. The belt will ride toward the front on the fan pulley and run off the lower pulley. It has the same effect as having the top pulley forward of the bottom pulley. You might be able to put the pulley in a lathe and re-shape the crown to the center. At least it's worth a try. If that doesn't work, you will need a new pulley. As long as the ball bearing turns smoothly, the play is not likely the cause of the problem.
Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chester Leighton on Thursday, August 09, 2012 - 07:38 pm:

The highest point on the profile of the fan pulley(i.e. the crown) appears to be toward the front instead of in the middle of the pulley. It needs to be replaced or the pulley cut on a lathe so the crown is centered. I would also like to suggest that you replace the fan blade with a new one from the vendors. I lost a fan blade this year and was fortunate that I didn't loos the radiator or get injured. After I sand blasted the what was left, I discovered all the blades on my original 26 pulley had cracks at the root of the blades. I'm not certain but I think ball bearings in the pulley hub are a rare thing. Possibly some one experimenting to improve the design over bushings.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Blancard on Thursday, August 09, 2012 - 07:40 pm:

I just took apart the hub and here is what I found.
hub 1hub 2

It looks like a ball bearing at the motor end and may be a needle bearing at the fan end. There is a spacer trapped between the bearings also. On the bolt are two spacers, each goes outside of the bearing. The larger spacer at the fan end is a bit loose on the shaft. Is this some kind of hybrid/custom made hub?

Both the bolt and fan hub have Ford script on them. Does this indicate they are original parts or do the repro parts have the Ford script also? I checked the bracket and bolt for straightness, and they both seem to be good. But there is a little wear on the bolt where the bushings/bearings go.

I'm inclined to order a new bolt, hub and bushings, but I just looked in Langs, Snyders and Mac's catalogs and none carry new bushing type hubs. But they all have the new ball bearing hubs. Does no one make new original style fan hubs? Considering the amount of wear on my hub, I'm pretty sure it needs to be replaced.

I'd really appreciate your thoughts.
Thanks,
Steve


Top of pagePrevious messageNext messageBottom of page Link to this message  By Allan Richard Bennett on Thursday, August 09, 2012 - 07:44 pm:

Steve, your photo of the top pulley is revealing. The fact that the shoulders on the pulley are not worn indicates that the belt has not been running off centre for any length of time. The crown of the pulley is slightly greater at the front. This means the belt would be tighter at the front edge, causing it to migrate to the BACK of the pulley. The fact that it isn't means the arm must be tilting the pulley forward. You can safely bend the arm back, but do not do it on the motor. Gently does it. Bend, run it. Bend it a bit more, run it, until it runs correctly.

Hope this helps.

Allan from down under.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Thursday, August 09, 2012 - 09:04 pm:

The original fan pulleys had bronze bushings but many have been replaced by ball bearings. When properly done, the ball bearings will last a long time without problems. They are also sealed so you don't need to add oil or grease.
Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Blancard on Thursday, August 09, 2012 - 09:31 pm:

Thanks for your thoughts gents. I think I will order a new sealed bearing hub and bolt/shaft tomorrow. After that is installed I'll take some careful measurements to see if the bracket is bent, and make adjustments as needed. Thanks - steve


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Friday, August 10, 2012 - 10:50 am:

You might also need a new belt. If that belt is stretched it could still run off a new hub. If one side is larger in diameter than the other, it would move the belt toward the smaller side and the larger side would ride on the crown, and so it would come off even if the pulleys are aligned.
Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Blancard on Friday, August 10, 2012 - 11:04 am:

Norm - Yes, I plan to put a new belt on it. I got a couple spare Gates belts with the car. It also appears to have a pretty new powdercoated fan.


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Stroud on Friday, August 10, 2012 - 05:10 pm:

Steve, I would try a new belt before you get new parts. That may be all that is wrong. It's worth a shot. Dave


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Blancard on Friday, August 10, 2012 - 08:17 pm:

With the worn fan hub crown and visible slop on the fan hub bearing, I decided to order a new ball bearing hub and shaft. They are on their way now. I have a new belt but am reluctant to try it with the old parts as it seems likely it too will ride up on the hub lip and possibly stretch. I'll just wait for the new parts to arrive, then assemble it, check the alignment, adjust as necessary, then install a new belt and try it. Thanks for all the advice fellas, I really appreciate it.


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