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W163 and General M Gremlin
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My 2000 E320 has started to squeal sometimes at stop lights. The squeal stops if I put it in neutral. Everything seems to be working fine. Just a squeal. Any ideas?
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DustinL,
You need to be more specific on where the squeak is emanating from - needle in the haystack.
Could be a belt under the hood, your water pump.....
 

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Discussion Starter · #3 ·
If it were a belt it wouldn't stop when I put it in neutral. It would just keep on squealing. Same with the water pump. If I knew where it was coming from exactly I'd already have my answer. My guess is it has something to do with the transmission. Since when I put it in neutral the squealing stops. My car just hit 200k miles. I'm sure there are people who have had a similar issue.
 

W163 and General M Gremlin
Joined
16,988 Posts
If it were a belt it wouldn't stop when I put it in neutral. It would just keep on squealing. Same with the water pump. If I knew where it was coming from exactly I'd already have my answer. My guess is it has something to do with the transmission. Since when I put it in neutral the squealing stops. My car just hit 200k miles. I'm sure there are people who have had a similar issue.
Not necessarily. They can squeal all the time and they squeal intermittently.

If you're sure it's related to the transmission, then full disclosure when you are posting and asking for assistance.
Don't ask members to play whack-a-mole.


If this is the case, that others have had a similar issue, please elaborate. Help us, help you.
 

W163 and General M Gremlin
Joined
16,988 Posts
I;m sorry. I figured that part was pretty obvious. Maybe wait till someone who has some good answer to chime in before you respond with criticism though.
No criticism here. :)

Just elaborating to you that if you wish to obtain assistance, then lay your cards out so all members know the background, history as well as your own presumptions on the issue; you're going to get (more) Qs and general responses, when your first post says...
My 2000 E320 has started to squeal sometimes at stop lights. The squeal stops if I put it in neutral. Everything seems to be working fine. Just a squeal. Any ideas?
You still have not elaborated on how you are sure others have had a similar issue. examples? links to read thru?
If not, I'll move on and others can certainly chime in.
 

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Discussion Starter · #7 ·
I'm sure others have had a similar issue because everything about these cars is a known quantity. It's not like my car is so original or different that it's breaking in a totally new previously undiscovered way. It's nearly exactly like every other E320. Likely produced in the millions. There are no new, unknown, issues with these cars.
 

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2005 E320 wagon
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3,021 Posts
When you drive off the squeal goes away?

Very loud squeal or possibly the whine of the auxiliary air pump? I can hear if the pump runs when the engine鈥檚 idling. I don't notice it when the car鈥檚 moving.

Sixto
98 E320 wagon 197K miles
 

W210 Section Moderator
1998 E320 base sedan @ 242 kmiles
Joined
11,146 Posts
The secondary air injection pump only runs when the engine is just started and cold, for 90 seconds. And also for a few seconds in a drive cycle, to test the air injection system. If it is running all the time, it is a major issue. You would have the CEL anyway.
 

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2005 E320 wagon
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In my usual commute, I come to a long light after 8 miles. In the 鈥98 wagon, 鈥98 sedan and 鈥02 C320 I distinctly hear a whine while idling at that stop. Not the whole time but long enough to worry about it. I don鈥檛 recall if I hear it later in my commute.

If it runs at cold start the OP would hear it with every cold start, not just later in the trip.

My next guess is tensioner or idler bearing is worn and has resonance at particular temperature and rpm.

Sixto
98 E320 wagon 197K miles
 

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Discussion Starter · #15 ·
It only squeals in stopped in drive. If I were stopped with my foot on the break and gave it some gas the squeal would stop.

The tensioner and idler bearings were replaced 6 months ago.

I don't know enough about automatic transmissions to diagnose.
 

W210 Section Moderator
1998 E320 base sedan @ 242 kmiles
Joined
11,146 Posts
In my opinion, it is one of the pulleys, power steering, alternator, water pump, or compressor. I would remove the belt and see if the squeaking goes away with gear in D. It will not harm the car to remove the belt for few minutes to test. If the squealing goes away, you can then evaluate each pulley, and the belt.
 

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Dallas, Texas
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In my usual commute, I come to a long light after 8 miles. In the 鈥98 wagon, 鈥98 sedan and 鈥02 C320 I distinctly hear a whine while idling at that stop. Not the whole time but long enough to worry about it. I don鈥檛 recall if I hear it later in my commute.


Sixto
98 E320 wagon 197K miles
What you hear is SAI test. It happens once per drive cycle after engine reached temp over 80C. If test is successful it will not happen again until engine temp drops below 35C and rises again above 80C.
 

W210 Section Moderator
1998 E320 base sedan @ 242 kmiles
Joined
11,146 Posts
It is easy to test if it is teh SAI or not.

When the engine is cold. start the engine, and with gear in P, listen to the SAI pump. If squeals, it is the SAI, and it should stop in 90 seconds. Else, it is not.
Or you can disconnect the SAI pump from its top connection (remove the engine cover, pull the connector out from the pump). If there is squealing, it is not the SAI pump.

In any case, the SAI system test is only few seconds. And if the desired result is not obtained, you would get a Check Engine Light with a code P0410.
 

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Discussion Starter · #20 ·
It doesn't squeal consistently enough for me to remove the belt and test. I have never heard this squeal sitting in my driveway. It's not a pully. It's something to do with the transmission. If it were a manual car I'd say it were something like the throwout bearing.
 
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