What should the inside of a diesel sound like when running? - PeachParts Mercedes-Benz Forum

WINGAS · #1 02-01-2011, 06:20 AM

I'm chasing down a new anomolous noise somewhere in the engine bay. Fropm the cabin it sounds like a power sterring pump w/o fluid, a "gerotor" type noise.

Under the bonnet, man I cant find anything. Alt bearings a little weak. Water pump a bit whiney ( likely due to the recent cooolant LEAK), but here's the weird thing:

When I pop the oil fill cap, there is a very distinct "slapping" sound eminating from the valvetrain/engine. I dont remember my first diesel making any sort of such noise. There I could only hear the chain against the follower.( but that was with B100, which is quieter)

Is this common, or do I have a second pooched motor?

I just changed oil and will inspect filter carefully for metal.

Car runs fine, starts fine, just noisy. Someone please tell me its normal.

Sounds like alot of piston slap, but the piston slap I'm used to ( big block chevs) is more of swirly sound, not literally a slapping.

vstech · #2 02-01-2011, 06:50 AM

is this on your 97?
it should be silent in the cabin nearly so anyway. did you check your powersteering fluid? does your car have SLS? did you check your sls fluid? is there any oil in your engine compartment signifying a leaking hose of some kind?
there are cams and lifters in the valve cover. you will hear slapping/clicking with the oil fill cap off... normal. how's it sound under the hood with the cap on?

WINGAS · #3 02-01-2011, 10:10 AM

It is the 97, no SLS. I assumed it was the PS pump, and it was a bit low. I sucked some fluid out and replaced to fill line. Still had the noise. ( dang it!) Also had indy check the trans with their universal dipstick ; it was a qt low. Still ahd the noise. ( never 'heard" a trans pump before, so it was a long shot)

But the gerotor type sound ( just like a PS pump thats low/dry) can still be heard in the cabin.

More importantly, good news on the valve cover noise. Its LOUD in there.

No oil leaks at all. A slight coolant leak I am chasing around.

Diesel911 · #4 02-01-2011, 11:09 AM

Have you been using a Mechanics Stethoscope or some other item (I like to use a piece of Broom Stick ear on one end other end on what I want to listen to) to probe around and pinpoint the noise?

Vacuum Pump?

babymog · #5 02-01-2011, 11:56 AM

Transmission front pump?

C Sean Watts · #6 02-01-2011, 03:59 PM

Quote:

Originally Posted by Diesel911

Have you been using a Mechanics Stethoscope or some other item (I like to use a piece of Broom Stick ear on one end other end on what I want to listen to) to probe around and pinpoint the noise?

Vacuum Pump?

X2, I have a lllooooooonnng & thin common screw driver my grandpa had for dedicated purpose, with a bronze sleeve on top of the handle. I have not bought a stethoscope.

WINGAS · #7 02-01-2011, 04:38 PM

I'm a hoser gents, I use hose.

The vaccum pump. That insidious bastid. I spend near $1000 redoing a cylinder head on the old 95, only to have the pump fail a few months later. ( I heard the bearings in their races with my HOSE, but it was subtle). That's near $1000 in parts and the machine shop bill. The labor was all mine. Damn things. I was greeted with a tablespoon of metal filings on top of the oil filter.

Tranny front pump huh? It would be my very uneducated guess as its not from the front of the motor, but you can hear it more alongside the motor near the IP ( its not the IP). And it's much more audible in the cabin at 1000 rpm than in the engine bay.

I'll stick the HOSE back there and check it out. Is this a part prone to failure?

KarTek · #8 02-01-2011, 08:52 PM

If this is in the first minutes after a cold start, the belt damper can make quite a buzz from the front of the engine.

vstech · #9 02-01-2011, 08:56 PM

Quote:

Originally Posted by Diesel911

Have you been using a Mechanics Stethoscope or some other item (I like to use a piece of Broom Stick ear on one end other end on what I want to listen to) to probe around and pinpoint the noise?

Vacuum Pump?

My mom got me one of these for my birthday a while back... very sensitive, and mine came with 3 extensions for versatility... VERY SENSITIVE!

TMAllison · #10 02-02-2011, 10:57 AM

Are you burning D1, D2 or Wingas (and what is wingas BTW)?

Could be combustion related. My 99 makes more noise when it is cold (is 40f here today, brrrr) in the morning. Running a can of DP through it quiets the engine considerably. If during the DP the whine remains, your noise is probably mechanical. If it disappears use of a better quality fuel would be in order.

A sagging left MM can also lead to vibration and odd noises.

Both are easy to rule out.

Diesel911 · #11 02-02-2011, 11:56 AM

Quote:

Originally Posted by C Sean Watts

X2, I have a lllooooooonnng & thin common screw driver my grandpa had for dedicated purpose, with a bronze sleeve on top of the handle. I have not bought a stethoscope.

I was using a Mechanics Stethoscope and because of the way it is made it required me to get too close to what I was trying to listen to and I burned my Cheek on an extremely hot Exhaust Manifold.

Since that time I have mostly relied on the piece of Broom Stick. It keeps my Face out of troubles way.
I also find the Stethoscopes to be too loud.

WINGAS · #12 02-02-2011, 07:55 PM

I've never tried a broom stick.

Right now its running on D2 with a splash of Stanadyne. Its MUCH quieter on B100. Tons.

WINGAS as the main feedstock for our bio is literally chicken wing fryers. Our bio doesn't cloud like normal bio does; the chicken fat forms little balls! ( I never push the mix when it starts getting cold, and clearly, we aint brewing now. Not in an unheated garage!)

I do beleive the MM are on their way out; the motor idles shaky only when hot. I haven't had that trouble much lately as ambients are well below 32f.

No odd metal in the filter btw. Guess they're just LOUD inside.

BTW, I DP'd it and took it around a country block. It runs much easier/quiter on DP. But that whine is everpresent . Its defintely mechanical. Its not what I'm hearing under the valve cover.