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Metallic sound from 6.9 engine front end?

Started by Jan S, 09 May 2022, 10:22 AM

Jan S

Engine is a 1977 US 6.9

I know this is a difficult one ... a verbal description of a sound. I'm giving it a try to see if this is a familiar sound to some of you.

-- The metallic sound comes from the front end of the engine
-- Only when engine is cold
-- It seems as if the sound goes through four cycles per second at 1000 rpm
-- It seems to be a combination of a scratching and rattling sound

Could it be the water pump? Since the noise disappears when warm ...?

Probably not the chain guides/tensioners?

Doesn't seem to be the alternator.

Any views/assessments is highly appreciated. A metallic sound from the engine is no good for my sleep  :'(
1975-mod W116 450 SE with 6.9 engine

daantjie

#1
As a very general guideline noises at engine speed are from the bottom end and at half engine speed from top end.
So approx 10 taps per second @ 600 rpm would be bottom end noise and 5 taps would be top end.
Would be best to try and link a clip.  Indeed noises can be a pain to pinpoint.
Try and get a mechanical stethoscope. They are pretty cheap and can help you localize the noise.
Daniel
1977 450 SEL 6.9 - Astralsilber

Jan S

Thanks,daantjie!

I follow your logic regarding bottom end and top end. In my case it should be closer to 16 and 8 taps per second (1000 rpm).

My sound is somehow continuous, with variations like a sinus curve, approx. four cycles per second. My subjective assessment.

I will try to record it tomorrow, to see if the noise can be separated from the general engine sound.

The suspect I have in mind is the water pump. Has anyone experienced that sound? Does it vary with operating temperature?

I will read me up on the use of a stethoscope. Thanks for the tip.
1975-mod W116 450 SE with 6.9 engine

Jan S

Bought this stethoscope today.

The patient was in a good mood today, i.e. the noise could be heard in part as sharp ticks, but not as distinct as normally. And only for a short period.

After a few minutes the noise disappeared. I were able to check the alternator, water pump, power steering pump, exhaust valve area on both sides, front end in general e.g. where the chain and guides sits, top of valve cover.

All seems to be fine, for an untrained ear.

But I need to remeasure later when the noise is heard clearly.
1975-mod W116 450 SE with 6.9 engine

daantjie

Also listen to the SLS pump, might be coming from here.  Unless you don't have it as I think you don't have hydro suspension?
Daniel
1977 450 SEL 6.9 - Astralsilber

Jan S

Right, I don't have hydro suspension - it's a 450 SE but with 6.9 (a previous owner replaced the original 4.5 liter. And removed the AC and washer tank, among other things  >:(  ).

I checked again today. No noise, engine runs beautifully.

I have to wait until the noise is back. Annoying.

In the meantime ...

-- Could it be the fan clutch?
-- Could it be the crankshaft pulley?

At some point I might have to remove all the belts and let the engine run for a minute, to see if the noise disappears. Should be fine for the engine, I guess?
1975-mod W116 450 SE with 6.9 engine

Jan S

The noise from the front end of the engine is till there, specially when cold. However, it varies. from day to day ... no obvious pattern.

I'm planning to take off all the belts, i.e. disconnect the water pump, alternator and the steering pump.

How long can I let the car run without the water pump? 1-2 min?

Any thoughts?

I'm trying to eliminate things.
1975-mod W116 450 SE with 6.9 engine

Randys01

 2 mins tops.....start with a cold motor.

ptashek

Maybe a sticky valve lifter? They tend to emit clicking sounds.
1993 "Pearl Blue" W124 280TE
1988 "Arctic White" W124 200T
1979 "Icon Gold" W116 450SE

Jan S

Quote from: Randys01 on 12 September 2022, 10:34 PM2 mins tops.....start with a cold motor.

Thanks, I thought so. Should be sufficient.

Quote from: ptashek on 13 September 2022, 02:24 AMMaybe a sticky valve lifter? They tend to emit clicking sounds.

Thanks for the tip, but what do you mean by "sticky valve lifter"? The hydraulic valve lifter is full of oil/dirt and not moving freely? Need replacing?
1975-mod W116 450 SE with 6.9 engine

raueda1

Quote from: Jan S on 13 September 2022, 11:13 AM
Quote from: Randys01 on 12 September 2022, 10:34 PM2 mins tops.....start with a cold motor.

Thanks, I thought so. Should be sufficient.

Quote from: ptashek on 13 September 2022, 02:24 AMMaybe a sticky valve lifter? They tend to emit clicking sounds.

Thanks for the tip, but what do you mean by "sticky valve lifter"? The hydraulic valve lifter is full of oil/dirt and not moving freely? Need replacing?
Huh, I just tried to respond to this but it apparently didn't post.  Anyway, I think I have a "sticky" lifter.  Seems similar to your description but not metallic or grinding, just a gentle, intermittent tapping that quickly goes away as engine warms up (just a minute or 2) or revs a little.  I've heard the same sound in lots of engines with hydraulic lifters.  I don't think it's dirt, maybe just some wear or clearance that disappears as engine warms up? Admittedly, I haven't tried to identify which lifter or mess with tappet clearance by swapping the spacer on top of the valve (maybe a 6.9-only thing).  It's a messy, awful job.  Cheers,
-Dave
Now:  1976 6.9 Euro, 2015 GL550
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

ptashek

Quote from: Jan S on 13 September 2022, 11:13 AMThanks for the tip, but what do you mean by "sticky valve lifter"? The hydraulic valve lifter is full of oil/dirt and not moving freely? Need replacing?

Likely the passages have clogged up and oil is not getting into the lifter. I believe they can be cleaned, but haven't done this myself.
1993 "Pearl Blue" W124 280TE
1988 "Arctic White" W124 200T
1979 "Icon Gold" W116 450SE

Jan S

Thanks to both of you.

I will start by removing the belts and take it from there.

Update coming soon.
1975-mod W116 450 SE with 6.9 engine

Randys01

The very closest valve lifter is by "stethoscope standards"  a mile away from the water pump..SLS pump alternator and other rotating hardware.

So identifying a valve lifter should be relatively easy.  Listen along the inlet manifold side of the cam box for that tick.

Jan S

Quote from: Randys01 on 13 September 2022, 10:49 PMThe very closest valve lifter is by "stethoscope standards"  a mile away from the water pump..SLS pump alternator and other rotating hardware.

So identifying a valve lifter should be relatively easy.  Listen along the inlet manifold side of the cam box for that tick.


Thanks for the tip!

Today I was able to compare the engine's stethoscope-sound with a smooth running 380 SEC. Alternator, power steering pump and water pump fairly similar (although a bit more noise from the power steering pump). Further tests without the belts will follow.

And a bit more ticking sound from the engine's exhaust side cylinder 2-4.

Later this week I will remove the air filter and measure at the inlet.

To be continued ....
1975-mod W116 450 SE with 6.9 engine