Serpentine Belt broke while driving - new belt won't install!

Post by **abscate** » 21 Mar 2019, 04:40

On P2s the alternator load changes as the pulley free wheels , unlike the non- bastard P80s

That will make the belt tension change and wobble the tensioner. I’ll try to record mine today.

XC70Rider · Post by **XC70Rider** » 21 Mar 2019, 07:03

What's the lifespan on our serpentine belt tensioners? Don't want my engine blown away.

Recently did a timing belt job with Contitech belts and INA tensioner & Idler for the timing belt. The OEM serpentine belt tensioner was in good shape so it wasn't changed.

Shanestrait · Post by **Shanestrait** » 21 Mar 2019, 07:22

I will take a look today and observe all the pulleys to check for issues.

Alternator is roughly 1.5 years old.

Shanestrait · Post by **Shanestrait** » 21 Mar 2019, 07:56

Also - no squealing from the belt.

I will post a video later of what's going on. Thank you all for your concern.

Shanestrait · Post by **Shanestrait** » 21 Mar 2019, 08:39

Video link:

Post by **abscate** » 21 Mar 2019, 08:46

I think that's totally normal. Your engine idle is fluctuating slightly, and I think the tensioner is responding in synch to that idle. Ill try to compare with mine before it pours rain

Well, there is a lot more motion in yours than in mine. Ill have to recant and leave that comparison open.

Shanestrait · Post by **Shanestrait** » 21 Mar 2019, 15:11

Uh oh. Thanks for checking.

I had someone step on the gas a little to bring RPMs up from idle and the movement persisted. So it doesn't appear to be from the idle.

Post by **cn90** » 21 Mar 2019, 18:56

My rule of thumb is whenever I replace the Timing Belt (and its 2 pulleys), I also replace the the Serp Belt (and its pulley) for the peace of mind.

I find it funny that people pay so much attention to the TB (b/c of the consequence should it break), yet people don't pay much attention to the Serp Belt. TB or SB and their pulleys usually break around 130K-160K miles range.

So at 110K, it is a safe time to do the preventive maintenance.

The video above (posted by the O.P.) showed the Serp Belt pulley moving a bit more than normal.
The video below showed the serp belt pulley to move very little, if any:

Shanestrait · Post by **Shanestrait** » 21 Mar 2019, 19:18

Took belt back off:

Should the alternator pulley spin freely in both directions? Any tests I can run on the pulleys to check their functionality?

Post by **cn90** » 21 Mar 2019, 20:40

The PS Pulley is loose, this explains your tensioner moving around.
How many miles on your car? You probably have around 200K miles to have loose PS Pulley.

The alternator has a clutch, it seems normal the way you did it. I posted a trick to check the alternator clutch in forum w/o the need to remove the belt.

Serpentine Belt broke while driving - new belt won't install!

Re: Serpentine Belt broke while driving - new belt won't install!