Serpentine pulleys

mar601 · Post by **mar601** » 20 May 2020, 13:27

Need to place an order for parts today and one final thing --
98 S70 with 160K and wondering if the the serpentine belt idler pulley and/or the tensioner pulley generally need to be replaced? a good idea? -- thank you

Post by **misha** » 20 May 2020, 13:35

If they don't make noise and have no play....i would leave them alone.
Mine are still original and i'm on 3rd serpentine belt replacement...from new.
I just inspect them when i'm replacing the belt.

mar601 · Post by **mar601** » 20 May 2020, 14:41

Thanks! that's the answer I was looking for.
Let me ask this, I remember at one point during the cold winter, I was getting some noise from one of them -- the one that's enclosed which I imagine is the tensioner pulley, and I very carefully sprayed a bit of WD40 inside of it through that slit. Ever since then, no noise at all.
But then again, does that make sense or not? Didn't spray much in there and it was whining pretty bad. Like I say, no problem since and that was a couple of years ago. (!) ? -- thanks for the help

Post by **misha** » 20 May 2020, 14:55

The bearing on the tensioner pulley have protective membrane(seal).Wd-40 couldn't get into it without dismantling.
If you want....you can remove tensioner arm,it is bolted with 2 bolts to the engine and then remove the pulley which is held with big torx bolt....but first release the tension and remove the belt....or just pull it off from power steering pulley.

Be carefull with that torx not to strip it and carefully pry out the protective seal from the bearing,put a lot of grease in it on both sides...one by one.Just regular lithium grease(green) for bearings.
Grease and close one side at a time.

If it have no play,re-grease it and it will last forever.

Post by **erikv11** » 20 May 2020, 15:29

Release the serp belt.

Spin the pulley by hand, if it spins freely and does not slow down quickly, it could benefit from maintenance (see misha suggestions) or replacement. Most are freewheeling by now and need service.

Post by **June** » 24 May 2020, 15:54

One thing nobody has mentioned, if the serpentine belt jumps it is highly likely to take out the timing belt. So a few bucks saved now by not just replacing a questionable tensioner may cost you a engine. Below are photos of another users engine who's belt took out the timing belt. June

Post by **misha** » 24 May 2020, 16:33

That scenario is possible but that is rare.

It usually happens when serpentine belt is old and damaged,have cracked channels,and it start to slice itself on the crankshaft and ac pulleys,then it breaks and enwraps itself around the crankshaft blocking it,which leads to timing belt failure.

There is a little protective plate under the crankshaft which protects timing belt route from this possibility.
Owners or mechanics usually remove it and throw it away when they do a timing belt job,not thinking that it's there for a good reason.

Serpentine belt must not have cracks on it and it's replacement interval is the same as for timing belt.

It never breaks without a warning(squeal,humming) and if neglected...it can lead to failures like this.

If tensioner fails it will light up a battery warning light and it will lead to immediate loss of power steering.
Serpentine belt idler pulley will also not fail unexpectedly without a loud warning of dry bearing.

Post by **June** » 24 May 2020, 16:53

misha wrote: ↑24 May 2020, 16:33 That scenario is possible but that is rare.

It usually happens when serpentine belt is damaged,have cracked channels,and it start to slice itself on the crankshaft and ac pulleys,then it breaks and enwraps itself around the crankshaft blocking it,which leads to timing belt failure.

There is a little protective plate under the crankshaft which protects timing belt route from this possibility.
Owners or mechanics usually remove it and throw it away when they do a timing belt job,not thinking that it's there for a good reason.

Serpentine belt must not have cracks on it and it's replacement interval is the same as for timing belt.

It never breaks without a warning(squeal,humming) and if neglected...it can lead to failures like this.

If tensioner fails it will light up a battery warning light and it will lead to immediate loss of power steering.
Serpentine belt idler pulley will also not fail unexpectedly without a loud warning of dry bearing.

Not rare according to Volvo as the later 2.5T get a serpentine belt tensioner suggest with the timing belt service due to common failures taking the timing belt out. I personally have overheard customers getting the bad news too many times while I was in for service for it to rarely happen.

You nor I can predict what will happen WHEN his old failing tensioner let's go. Also the tention portion can be weak at this point and allow the belt to jump. I felt the OP should be aware of the possibility of engine damage from saving a few bucks now. Assuming it's not a junker on its last leg that is.... June

p.s. that belt pictured had 12K on it. So no cracked old belt shredding, but failed tensioner did take it out.

Post by **misha** » 24 May 2020, 17:04

But OP asked about serpentine belt tensioner pulley and idler pulley...not the tensioner itself.

Pulleys are both replacable and maintenable as a regular service on proper mileage interval.

Off topic a bit...
I had brand new Gates serpentine belts failure in a 6 months on some of other cars...but NEVER with Conti or OE belts.

Idler pulleys and tensioners were not the culprits because Conti belt installed after Gates failure is still on....2 years after with no sign of wear and tear.