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Discussion Starter · #1 ·
Hi,

I have 320i with the M50 engine and I put the correct fanbelt size on it as specified on realoem.com (6PK 1555). When I fitted it I thought to myself "That seems a bit loose" but it seemed to work so I thought "Well it's what BMW specify so should be alright".

Took it for a test drive and all seemed fine, then when driving back the belt started to squeal, so I pulled over and had a look, it all seemed to be on alright, so I continued driving. The squeal stopped for a bit, then just as I came to my house the battery light came on, and lost power steering, so I was thinking "It's come off or too loose to drive the pulleys". Stopped and the belt had come off some of the pulleys and was wrapped around the fan pulley and bits of it were shredded (from being wrapped around)

So clearly the belt was too long and slipped off one of the pulleys. Does anyone know why it was too big, all I can think is that either someone has changed the pulleys for smaller non standard ones in the past, or that the automatic tensioner is somehow faulty and has gone lower than it should be.

Cheers,
Matt :D
 

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Hi,

I have 320i with the M50 engine and I put the correct fanbelt size on it as specified on realoem.com (6PK 1555). When I fitted it I thought to myself "That seems a bit loose" but it seemed to work so I thought "Well it's what BMW specify so should be alright".

Took it for a test drive and all seemed fine, then when driving back the belt started to squeal, so I pulled over and had a look, it all seemed to be on alright, so I continued driving. The squeal stopped for a bit, then just as I came to my house the battery light came on, and lost power steering, so I was thinking "It's come off or too loose to drive the pulleys". Stopped and the belt had come off some of the pulleys and was wrapped around the fan pulley and bits of it were shredded (from being wrapped around)

So clearly the belt was too long and slipped off one of the pulleys. Does anyone know why it was too big, all I can think is that either someone has changed the pulleys for smaller non standard ones in the past, or that the automatic tensioner is somehow faulty and has gone lower than it should be.

Cheers,
Matt :D

You sure you routed the belt correctly?

do you have the old belt to compare the length to the new one?
 

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Discussion Starter · #4 · (Edited)
Belt definitely routed correctly.

Hydraulic belt tensioner, I'm pretty sure (from looking at realoem.com)

So when they go do they go shorter (for want of a better word!) and so the belt will be slack? Will I be able to just stick a shorter belt on there, it doesn't need to be a long term fix.

The tensioner is designed so you can put a wrench on the end of it and "untension" it (by holding the wrench in position) for the purposes of putting the belt on and off (although there is another thing above to do this, called a 'Deflection pulley' on realoem). After you take the pressure off the wrench it goes back to normal (tensions belt). This mechanism still works as it should, which would indicate that the tensioner is working to some degree?

edit: Yeah new and old belts seemed about the same length, I was expecting the old belt to have stretched, so I was a little suspicious before I put it on.

Cheers,
Matt
 

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Discussion Starter · #5 ·
Hi, It's actually a mechanical tensioner, and the pulley on the tensioner had come off, I was looping the belt around the remaining bit of it which was metal. No wonder it was loose, I fell stupid now :hihi

Ordered a new tensioner to be delivered tomorrow and all should be well!

Cheers,

Matt
 
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