Belt spray on Serpentine. Yes or no?

flashnazia

My BMW e90 has started making a slight squealing noise. This started after the recent damp weather.
It was loud but seems to have lessened somewhat.
Belt seems fine - no obvious wear.

Mechanic has given me a can of belt spray.
I'm wary.
Yes or no?

Mileage is 79000.
I suspect it needs a new tensioner and a new belt just in case but wonder if the damp weather could make a car noisy?

oldagetraveller

Temporary only. With the engine running and keeping hands, clothing etc. well away from the belt or other moving parts, sprinkle some granulated sugar onto the running surface of the belt - honest, this is not a wind up. I've only ever done it with vee belts, so can't comment on it's effectiveness on a car's flat belt. However it used to work on industrial flat leather belting, the old lineshaft type arrangement seen in cotton weaving etc., rather than using belt dressing.

mikey72

I use a belt dressing spray on mine, occasioally there is a squeal in the damp, and it's either that or overtighten it.

gilbert_and_sullivan

Tried it before now, some MB's suffer similarly...only made the problem worse.

Having had numerous different belts fitted to try to cure the problem, the latest one made by Continental is by far the best for noise.

s_b

flashnazia wrote: »

My BMW e90 has started making a slight squealing noise. This started after the recent damp weather.
It was loud but seems to have lessened somewhat.
Belt seems fine - no obvious wear.

Mechanic has given me a can of belt spray.
I'm wary.
Yes or no?

Mileage is 79000.
I suspect it needs a new tensioner and a new belt just in case but wonder if the damp weather could make a car noisy?

i havent used that stuff since 1977 and then it was an american import can
i squirt a little water on the belt if squeal goes then it either needs adjusting if it can be or replacing
if you leave it squealing then it smooths the pulleys it runs on and so a belt alone may not cure the issue
i guess your mechanic doesn't want the job?

flashnazia

s_b wrote: »

i havent used that stuff since 1977 and then it was an american import can
i squirt a little water on the belt if squeal goes then it either needs adjusting if it can be or replacing
if you leave it squealing then it smooths the pulleys it runs on and so a belt alone may not cure the issue
i guess your mechanic doesn't want the job?

He is very busy.

I've read that BMWs have automatic tensioners so if the belt is loose it probably means the tensioner is knackered. The belt spray thing is controversial. Some say it works to temporarily stop slippage but others say it ruins the belt. I'm none the wiser!

flashnazia

mikey72 wrote: »

I use a belt dressing spray on mine, occasioally there is a squeal in the damp, and it's either that or overtighten it.

Do you have a bm?

I am tempted to post in the bm forums but they tend to throw money at their cars by replacing every possible component in order to rectify even inconsequential issues. Not very mse!

CrazyRed

flashnazia wrote: »

Do you have a bm?

I am tempted to post in the bm forums but they tend to throw money at their cars by replacing every possible component in order to rectify even inconsequential issues. Not very mse!

As a BM owner myself, I can confirm that mine did this a few weeks ago - despite having a new belt on it just a few months ago.

Tensioner's fine, as are the pulleys - my problem turned out to be the PAS fluid being old and full of crud, making the PAS pump stiff to turn when the weather got a bit nippy.

Don't bother with the belt dressing - it's a very, very temporary measure. It'll stop the squeal, but said squeal will come back if the root cause issue isn't identified and resolved.

Incidentally, those tensioners are very long lasting - mine's still on it's original, after a quarter of a million miles!

Continental, or OEM-quality (GSF) belts are the best - the Gates one on mine is "OK" but I've had better!

HTH

mikey72

flashnazia wrote: »

Do you have a bm?

I am tempted to post in the bm forums but they tend to throw money at their cars by replacing every possible component in order to rectify even inconsequential issues. Not very mse!

Not a bm. I've used it on a few cars over the years. It works, doesn't damage the belt, and does reduce the squeal on damp days. As sb has said, a slipping belt polishes the pulley, so even replacing the belt doesn't fix it. Roughing up the pulley will help, but I can't get in with it on the car, and taking it off to get a power drill with a wire brush on it to abrade the surface just isn't worth it. In winter it was once a month on the worse one. Belt was fine, it's probably suffering more damage when it slips and squeals.

forgotmyname

Fix it properly.

Spray is a quick fix that may last minutes/hours/days/weeks. But its not a long term fix.