Author Topic: Whaling buzzing sound from dash when cold.  (Read 227 times)

OLDGOLD

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Whaling buzzing sound from dash when cold.
« on: 05 March 2019, 06:01 AM »
Hello! When it's below 25 degrees Fahrenheit, like it's been in Dallas the last couple days, and I start driving the vehicle a few miles after cold start I will get a sudden, very loud buzzing noise from the dash. The noise seems to go away once I let off the accelerator pedal and the vehicle slows down. It's super loud and sounds similar to the light switch buzzer, but more of a whaling noise combined with it. This happens after letting the vehicle warm up at idle for 15 minutes. I've also noticed that the brakes become more stiff and the engine takes a hair longer to shut off. I'm nearly certain that this has to be vacuum related, but why does this only happen on the coldest days of the year below 25 degrees? I've checked the vacuum lines near the fuse box under the hood, but I must be losing vacuum elsewhere. The sound seems to be coming from inside the dash on the right side of the instrument cluster.

I've also noticed that the heat won't work even with the engine at operating temperature, unless I cycle the ACC temp wheel to full cold, then back to heat, then it usually works. I know that these are supposed to be great winter vehicles, since they are German after all, but is this normal? I couldn't imagine living somewhere cold like Alaska, Finland, Canada etc. and having these sort of issues.

Any help would be appreciated!

Diesel 617

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Re: Whaling buzzing sound from dash when cold.
« Reply #1 on: 05 March 2019, 06:56 AM »
Sounds like the dash sound occurs while driving. Pull your instrument cluster and remove the speedocable and pour a about half a cap full of trans fluid down the cable. No more ear piercing horror sounds from the dash :)

Leaky vacuum, hoses shrink from the cold and the seal quality is wearing out at 40years of age.

You have automatic ACC? Could be a sign the servo internals are starting to leak causing corrosion, or the amp if it is original is starting to go faulty. Test the resistance on the motor would help you answer this question.
https://forum.w116.org/mechanicals/1980-300sd-climate-control-monovalve-manipulations/msg131665/#msg131665
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OLDGOLD

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Re: Whaling buzzing sound from dash when cold.
« Reply #2 on: 05 March 2019, 09:07 PM »
The servo and amp were replaced with the electronic upgrade kit.

I was asking a technician today and he though it could be from a tear in a rubber diaphragm under the dash that shrinks in the cold possibly. I’ll try the trans fluid.

OLDGOLD

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Re: Whaling buzzing sound from dash when cold.
« Reply #3 on: 20 April 2019, 03:30 PM »
So I think you were right Diesel617. The noise is coming from the cluster after all. It happened again this morning when it was 45 degrees Fahrenheit. I’ll pull the cluster and lubricate later this week. Thank you!

Harv

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Re: Whaling buzzing sound from dash when cold.
« Reply #4 on: 20 April 2019, 07:35 PM »
Does it sound like this?

https://youtu.be/XDTfbIIFibs

If so, it's the speedo cable.
1980 300SD
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OLDGOLD

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Re: Whaling buzzing sound from dash when cold.
« Reply #5 on: 23 April 2019, 07:24 PM »
Oh Lord! That's it! The sheer volume is deafening.

I didn't have any more trans fluid, so I used genuine MB synthetic power steering oil down the speedo cable over the weekend. I guess I won't know till it gets cold again if that did the trick.

One last thing, my buddy was fixing my odometer and the needle came of the resting pin, now I'm off by 5mph @ 25mph, 10 @ 50 and 15 @ 70. So if I'm going 75 mph, I'm really going over 90! Any idea on ways to fix this? All other gauges work, only my speedo is off. Thanks.