Serpentine belt replacement

[1004ron]

In the case of my wife's BMW it was the tensioner doing a jiggle that drew my attention to the need to replace these components, and the reports that when the belt goes on the BMW engine it typically trashes the crank main seal.

 

The failure mode that leads to the tensioner oscillation is a worn or contaminated (oil) friction damper - not a worn spring as many suggest.

 

A previous vehicle of mine used a flat friction disc whereas the BMW use a friction drum - you can see in the attached photo of the old tensioner that I tore apart.

The tensioner's bearing felt and sounds rough while the idler felt and sounded smooth.

 

 

 

[omar302]

@Cerberus

@1004ron

 

Thanks for the input.

I asked because although I do understand the concept for replacing it as a preemptive maintenance, but then using the same concept you'd replace so many other parts. Unless a specific part is known to fail, or cause a disaster if failed (internal water pump).

 

Also, searching around for Ford tensioners, found this on Motorcraft, stating they are tested for a 10 year / 150k mile life cycle.

Edited April 10 by omar302
Double post.

[1004ron]

Thanks @omar302

 

I decided to go with Motorcraft seeing as the existing components have been trouble free for so many years and miles, although I also have a lot of confidence in Gates.

 

The tensioner in that example uses an external hydraulic damper which I believe will extend the life of the tensioner assembly compared to ours with an internal friction type damper.

 

 

[Cerberus]

2 hours ago, 1004ron said:

 

The tensioner's bearing felt and sounds rough while the idler felt and sounded smooth.

 

This is the most common reason to replace tensioner or idler, bearing noise or crunching 

[1004ron]

Took about 1.5 hours to complete this morning.

 

All the old parts were in really good condition and the only real sign of deterioration was the idler bearing, it had expelled a little lubricant and felt just a little notchy.

 

There's no room to get a socket and breaker bar on the tensioner to retract it for removal and installation of the belt so resorted to two ratchet wrenches seen in one of the photos.

 

No doubt these components were good for another few thousand miles but I cant put a number to it, so given the choice again I'd change them at the same mileage, 103,000 mi.