Rattling air cleaner problem - new find.

[tenknots]

When I first got Hans, two of the air cleaner mounts were broken causing the air cleaner to dance all over the place and make a racket, especially when cold. I replaced the mounts and all was well, except that I noticed the elbow that attaches to the turbo inlet was not tight and was moving all around - there was no more thread left to tighten.

Then the mounts broke again 4 months later and I replaced them.

Then last week, the bracket itself broke.

I was torn between spending about $65 for a new bracket and mounts or just going with the K&N type mod and trashing the original air box. Looking through the PO records, the bracket had been replaced 2 years ago, and maybe a total of 6 times over the years. But I know the MB engineers designed the airbox for maximum performance and flow, so I didn't really want to mess with it. And there are questions about K&N filters allowing too much dirt in.

As I watched the air cleaner as the car was idling, I noticed that it vibrated at the same frequency as the engine, but not in the same phase. In other words, the air cleaner, only being held to the engine by three flexible rubber mounts, was in effect, moving the opposite direction at each pulse as the rubber stretched and contracted. No wonder the mounts and brackets didn't last long.

Last night, I decided to try something. I took off the air cleaner assy and removed the clamp at the elbow. I then put on a stainless steel hose clamp, size 2 1/16" to 2 7/8" and snugged it. I replaced another bad mount and reassembled the air cleaner. Then I tightened the clamp around the turbo and started the car.

What a difference! Even with only two rubber mounts (the rear one can't be used since the bracket is broken) the air cleaner assy doesn't move at all.

The clamp on the elbow is needed to attach the air cleaner to the engine as much or more than the rubber mounts. A peek under my wife's 300SD showed hers was loose also. This may be a common problem and a reason the mounts/brackets don't last long.

[Pete Burton]

The rubber sleeves inside the elbow get really hard and brittle, enough so that it's hard to believe they were ever flexible. Replacing those helps to reduce the vibration, IMHO. Also, my bracket broke years ago, and when I welded it back together I added a few small gussets perpendicular to the crack underneath. I have about 60K on the bracket and it's holding fine. And no, I'm not a big fan of the air cleaner design either.

[P.E.Haiges]

tenknots,

I fabricated an air cleaner bracket out of a piece of scrap metal for my '80 300SD. It lasted about 100,000 miles then broke. So I fabricated another bracket out of steel about twice as thick as the first one. This one is still in service, and I expect it to out last me.

Too bad MB didn't do the same thing: thicker metal for the OEM bracket.

P E H

[lietuviai]

I have a cheap little arc welder that I can use to fix the bracket if it ever breaks on mine. I have 2 spare brackets I can switch between if the new one I have ever breaks.

[02HD677]

Originally Posted by tenknots

When I first got Hans, two of the air cleaner mounts were broken causing the air cleaner to dance all over the place and make a racket, especially when cold. I replaced the mounts and all was well, except that I noticed the elbow that attaches to the turbo inlet was not tight and was moving all around - there was no more thread left to tighten.

Then the mounts broke again 4 months later and I replaced them.

Then last week, the bracket itself broke.

I was torn between spending about $65 for a new bracket and mounts or just going with the K&N type mod and trashing the original air box. Looking through the PO records, the bracket had been replaced 2 years ago, and maybe a total of 6 times over the years. But I know the MB engineers designed the airbox for maximum performance and flow, so I didn't really want to mess with it. And there are questions about K&N filters allowing too much dirt in.

As I watched the air cleaner as the car was idling, I noticed that it vibrated at the same frequency as the engine, but not in the same phase. In other words, the air cleaner, only being held to the engine by three flexible rubber mounts, was in effect, moving the opposite direction at each pulse as the rubber stretched and contracted. No wonder the mounts and brackets didn't last long.

Last night, I decided to try something. I took off the air cleaner assy and removed the clamp at the elbow. I then put on a stainless steel hose clamp, size 2 1/16" to 2 7/8" and snugged it. I replaced another bad mount and reassembled the air cleaner. Then I tightened the clamp around the turbo and started the car.

What a difference! Even with only two rubber mounts (the rear one can't be used since the bracket is broken) the air cleaner assy doesn't move at all.

The clamp on the elbow is needed to attach the air cleaner to the engine as much or more than the rubber mounts. A peek under my wife's 300SD showed hers was loose also. This may be a common problem and a reason the mounts/brackets don't last long.

Got pix?