'93 300 E - Temporary Squeal at Startup

My '93 300 E makes a high pitched whining noise or squeal at startup and goes away after it warms up. Sometimes it goes away after 10 seconds, sometimes it takes a minute and sometimes it doesn't squeal at
all.
Anyone have any ideas?
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I had this happen on my '90 420SEL. It turned out, in my case, to be the air pump that runs at engine startup for a minute or so to dilute the exhaust gasses for emissions purposes. At least this is my understanding of it's purpose. Anyway, if the pump is frozen, and the clutch engages, the belt will slip and thus cause the squeal. My solution was to unplug the connector going to the pump.
John S.
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Hi mate I think its just the alternator belt might be worn or your battery losing charge the alternator is under load when you first start trying to put a charge back in the battery if you go for a short runs turn the engine off and restart i bet there is no squeal,hope this help
"John Simpson" wrote
> > > My '93 300 E makes a high pitched whining noise or squeal at > startup > > and goes away after it warms up. Sometimes it goes away > after 10 > > seconds, sometimes it takes a minute and sometimes it > doesn't squeal at > > all. > > > > Anyone have any ideas? > > > > I had this happen on my '90 420SEL. It turned out, in my case, > to be the air > pump that runs at engine startup for a minute or so to dilute > the exhaust > gasses for emissions purposes. At least this is my > understanding of it's > purpose. Anyway, if the pump is frozen, and the clutch > engages, the belt > will slip and thus cause the squeal. My solution was to unplug > the connector > going to the pump. > > John S.
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You need to change the belt.
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my friend had the same proble turned out to be serpentine belt adjuster stoped adjusting rubber mounts inside unit had failed the belt slips when you start up and can squeel if you pull away hard .
Check tension on belt

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Graymatter wrote:

It may also be the bearing of one of the small pulleys (one above the alternator and one on the tensioner).
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I have a very annoying noise at startup also, but it's not a belt, or anyhting else that I can think of that would be on an average car.
It is the most annoying noise in the world and it sounds like it's coming from the glove box or under the right front speaker.
It sounds like this aeaeaeaerarrarrerereaerrghhhagreaerrarhagerhaeghrgeaehraerhagehraeaghr !!!!
Like when you were a kid and blew up balloons and then pinched the hole and let the air out to make that god awful squeal....
Well that's the noise it makes. It's just at startup, only when it's cold, and it last for 10 to 60 seconds.
Any thoughts on what That could be ??
_______________________________________________

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I would pop the hood open and have someone start up the car for you to hear where it is coming from. It can be the starter causing the noise... this is because the gear on the starter is not lined up perfectly with the cogs on the engine flex disc... check for loose starter bolts.
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I agree with Tiger - open the hood an give a listen. But I betcha' it's the air pump (left-side while looking at the engine from the front). If so, it's about USD$800 for a shop to replace with a rebuilt unit. If you have it fixed, while they're in there have them replace the belt tensioner and possibly the belt itself. Also a good time to replace the water pump if the radiator needs to be pulled for the work and you have not replaced it yet.
Josh

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