Slack Fan Belt

[Wilson]

What's going on here?

Checked the fan belt a couple of days ago - tension felt fine.

Took the van out today for a 30 mile drive, dunked the dog in the sea, feed the kids ice-cream, etc - no problems with engine while out.

Van back in the garage this evening. Checked the fan belt but it now feels very slack. Using my hands to move it turns the generator pulley, but not the crankshaft pulley.

Is this just a knackered fan belt? If so, why would it have been ok a few days ago, but gone slack so quickly?

Engine is a reconditioned engine which has done around 500 miles so far - so would hope engine is ok.

Wondered if I should just change the fan belt, but worried that I might be covering up another problem.

Advice appreciated.

 

[StuF]

How tight is the nut on the top pulley?

Have you taken the top pulley to pieces to see how many shims are fitted?

Mine exploded after roughly 300 miles on the way to busfest so it is pretty easy to fix and cheap (£12 all in!)

 

[KevH]

I had a similar issue a few weeks ago: I noticed the belt fraying before it snapped. It was fine when I left home.

As StuF suggests, it might just be a case of your belt bedding in if the set up is new, especially if the nut on the alternator pulley was not tight enough, allowing the pulley to let the belt run slack.

You could try taking a shim out and see what happens.

 

[Wilson]

My nuts are tight.

Would removing a shim make that much difference?? It was 1/2 inch deflection when I checked it the other day - now i can push the two sides of the belt in the middle so they just about make contact. Will try it tomorrow.

From what you are saying, it does't look as if I should be getting worried that anything more serious is lurking.

I need to order a belt anyway - why do the ones on coolair/justkampers/etc have teeth? The one I've got is smooth.

 

[sparkywig]

Have you stacked the unused shims behind the pulley nut and washer?
They need to be mounted here to do the nut up properly or it will loosen.

If they're OK, fit another belt and shim it up, run the engine for a while and check the deflection again.

 

[Wilson]

Took washer off to remove top pulley.

All the shims were on the outside of the top pulley - there were none between the two pulleys. The rear pulley was in bits - very like the photo above of the one that went on the way to busfest.. So it looks as if the rear pulley needs replaced. How do I remove the remaining pieces of the rear pulley? The top pulley came off by sticking a screwdriver through the wee hole and then turnign with a screwdriver. The rear pulley I can grab with the screwdriver but unsure how to get purchase - the dynamo just turns with the screwdriver.

 

[Wilson]

it's ok - it slid off so waiting for new pulley to arrive before doing anything further.

 

[KevH]

Glad you found the reason for the slackness, though it looks like it may have been running very tight, what with no shims in place. Maybe that caused the rear half to disintegrate? Same happened to StuF.

 

[Foz]

Make sure you don't lose the little woodruff key! (little half moon shaped piece of metal)A small but vitally important bit of the spline!
Mine dropped down into the engine bay, took me forever to find!

My new belt has teeth, and i have no Shims in mine to get the right belt tension.
Drove to the isle of Wight and back from the midlands, also Leeds and back with no issues so far.

--------------------------------
Own a Bay?......Feel the love!

 

[sparkywig]

Make sure you don't lose the little woodruff key! (little half moon shaped piece of metal)A small but vitally important bit of the spline!
Mine dropped down into the engine bay, took me forever to find!

My new belt has teeth, and i have no Shims in mine to get the right belt tension.
Drove to the isle of Wight and back from the midlands, also Leeds and back with no issues so far.

Your fan belt is too long then.

 

[KevH]

Make sure you don't lose the little woodruff key! (little half moon shaped piece of metal)A small but vitally important bit of the spline!
Mine dropped down into the engine bay, took me forever to find!

My new belt has teeth, and i have no Shims in mine to get the right belt tension.
Drove to the isle of Wight and back from the midlands, also Leeds and back with no issues so far.

Your fan belt is too long then.

WHS. For a standard 1600 alternator set up, anything other than 11.3 x 912 will run slack or tight. If you are running without shims there is no scope for adjustment if it begins to slacken off with age. Oddly enough, it was Midlands to the IoW that did mine in.

 

[Wilson]

I've ordered a 9.5/905 for a 1600 engine with dynamo - does that sound about right?

That was the size I've just removed so presumed should be like for like, although with some of the earlier problems I've had with this refurb, I would be open-minded to advice.

 

[KevH]

I've ordered a 9.5/905 for a 1600 engine with dynamo - does that sound about right?

That was the size I've just removed so presumed should be like for like, although with some of the earlier problems I've had with this refurb, I would be open-minded to advice.

I have not got a dynamo, got an alternator, but the VWHeritage catalogue suggests you have ordered the right size. Oddly, JK disagree and suggest a slightly tighter belt, 10 x 900. Strange that.

 

[sparkywig]

9.5 x 905 is the right belt for a dynamo/generator.

 

[Wilson]

Update.

Lovely day here today.

Replacement pulley and fanbelt arrived. Managed to change pulley ok. New fanbelt had teeth - I couldn't get it to sit tight enough even when no shims in place. Used previous fan belt without teeth (condition of that belt seems to be ok) and seemed to sit much better.

With engine off I can't manually use the belt to turn the pulleys.

Engine turned on - pulleys turning without any bother. generator light flickered faintly for the first minute but went off (it's possible it always does this but I can't remember).

Fan belt looks like it's doing the job right.

Turned engine off to measure deflection - about half an inch.

Does this sound promising?

 

[crede999]

Hi if you have a new belt put 6 shims inbetween pulley halfs as a starting point and 4 on outside under nut ........ Then See what the deflection is like

When fitting and your at the stage where everything is in place .....tighten nut a little turn the pulley by hand tighten a bit more turn pulley .... Keep doing this till pulley nut is tight and
Belt sits correctly

Hope this helps..
Chris