Knocking/Slapping noise - out of ideas! - PeachParts Mercedes-Benz Forum

imgolden · #1 09-20-2020, 12:27 PM

Hi guys, I am really struggling to figure out a weird slapping/tin can knocking sound in my 82' 300D.

I've spent a LOT of time poking around with a stethoscope and it really sounds like the noise coming from the top of the valve cover by the chain. Here's what it sounds like while running diesel purge:

https://youtu.be/G1TOgGyp81Q

I have done a valve adjustment, I have ran diesel purge a few times, and I have shut off each cylinder and the noise remains, so I don't think it's my injectors.

The car runs excellent. Virtually no smoke, little oil consumption, smooth idle, lots of power, average blowby.

I have pulled all the accessories off the front, inspected the vacuum pump, and the shaft that attaches to the pump, and everything there looks great.

I checked chain stretch using the 'line up' method (don't have a dial right now) and it's right at 5 degrees.

Adding to that, there's another thing I've noticed. Upon startup, it's quite clattery, but then after a few seconds it quiets down a lot, then slowly comes back. This video captures what I'm talking about:

https://youtu.be/mWvWSlQsphE

So, what do you all think? Timing chain tensioner? Oil too thick? (20w50 in San Diego) What else?

Sorry for the long post, I am really stumped.

Diesel911 · #2 09-20-2020, 01:08 PM

Did you listen to the vacuum pump especially at start up where the vacuum Pump is working to give everything vacuum.

Diseasel300 · #3 09-20-2020, 01:30 PM

Quote:

Originally Posted by Diesel911

Did you listen to the vacuum pump especially at start up where the vacuum Pump is working to give everything vacuum.

x2

I suggested the vacuum pump in the last thread the OP had several weeks ago and he soundly ignored it. I stopped making suggestions at that point.

imgolden · #4 09-20-2020, 02:03 PM

Quote:

Originally Posted by Diseasel300

x2

I suggested the vacuum pump in the last thread the OP had several weeks ago and he soundly ignored it. I stopped making suggestions at that point.

I'm sorry if I offended you. Right after you made that suggestion, I used the stethoscope to listen to the pump and heard nothing. Someone also suggested (maybe you) that I pull it out and inspect, which I did.

imgolden · #5 09-20-2020, 02:05 PM

Quote:

Originally Posted by Diesel911

Did you listen to the vacuum pump especially at start up where the vacuum Pump is working to give everything vacuum.

Upon inspection, the pump looks fine, everything is solid. Is there a way to start the car without the pump installed? I imagine it would make a mess if done wrong.

hercules · #6 09-20-2020, 09:52 PM

May be more than one thing. I would ck for cam and rocker wear.

Diesel911 · #7 09-20-2020, 10:23 PM

Quote:

Originally Posted by imgolden

Upon inspection, the pump looks fine, everything is solid. Is there a way to start the car without the pump installed? I imagine it would make a mess if done wrong.

For sure something gets oil to the Vacuum Pump. If you run without the vacuum pump it will likely be a mess but you can do it long enough to maybe find out where the noise is coming from.

I had a rattling noise coming out near the timing chain and gear as it turned out to be the upper most timing chain guide rattling. Tightening it fixed it.

Below that guide is an idler Gear but no one has ever posted issues caused by it that I have seen.

Don't know what the other timing chain guide rails can cause if there is a problem.

Way down at the bottom on the Oil Pump Chain Tensioner there is a little snap ring that people have said wears through and when that happens it can ever jam things up down there.

People have replaced timing chains with other the IWIS/jWIS Chains and had issues. Or I suppose someone could have changed the chain and not done a good job of it.
Remover the valve cover and check the make of the chain and have someone roll the engine by hand and observe the chain rivets and gear teeth for something abnormal.

Look at that camshaft and the bearing towers for something unusual.

Not sure how you would tell this but there has been at least 2 cases where people had cracked valve guides.

If you have a Federal W123 the Air Filter Housing is noted for beating on the intake manifold due to various reasons. It happened to me and I thought that something was going to fall off of the car.

imgolden · #8 09-21-2020, 10:38 AM

Quote:

Originally Posted by hercules

May be more than one thing. I would ck for cam and rocker wear.

Thanks, last time I had the valve cover off, I tried moving each rocker and they were all tight. Anything in particular I should look for?

imgolden · #9 09-21-2020, 10:40 AM

Quote:

Originally Posted by Diesel911

For sure something gets oil to the Vacuum Pump. If you run without the vacuum pump it will likely be a mess but you can do it long enough to maybe find out where the noise is coming from.

I had a rattling noise coming out near the timing chain and gear as it turned out to be the upper most timing chain guide rattling. Tightening it fixed it.

Below that guide is an idler Gear but no one has ever posted issues caused by it that I have seen.

Don't know what the other timing chain guide rails can cause if there is a problem.

Way down at the bottom on the Oil Pump Chain Tensioner there is a little snap ring that people have said wears through and when that happens it can ever jam things up down there.

People have replaced timing chains with other the IWIS/jWIS Chains and had issues. Or I suppose someone could have changed the chain and not done a good job of it.
Remover the valve cover and check the make of the chain and have someone roll the engine by hand and observe the chain rivets and gear teeth for something abnormal.

Look at that camshaft and the bearing towers for something unusual.

Not sure how you would tell this but there has been at least 2 cases where people had cracked valve guides.

If you have a Federal W123 the Air Filter Housing is noted for beating on the intake manifold due to various reasons. It happened to me and I thought that something was going to fall off of the car.

I ended up running the car without the pump. The noise is still there, so I can definitively rule out the pump. For anyone else thinking of doing that, there wasn't much mess at all - I was suprised.

Thank you, I have inspected under the valve cover, but I wasn't really sure what I was looking for. This post gives me a lot of good things to check for,
time to get the valve cover off again! Do you know which side of the chain the manufacture would be on?
Thanks again

Mike D · #10 09-21-2020, 10:48 AM

Quote:

Originally Posted by imgolden

Thanks, last time I had the valve cover off, I tried moving each rocker and they were all tight. Anything in particular I should look for?

Tight? Define "tight"? You should have "play" in most of the rocker assemblies no matter where the cam is positioned. If not, then the valves are adjusted too tight.

imgolden · #11 09-21-2020, 11:36 AM

Quote:

Originally Posted by Mike D

Tight? Define "tight"? You should have "play" in most of the rocker assemblies no matter where the cam is positioned. If not, then the valves are adjusted too tight.

I suppose the correct term is 'not loose'. I was applying pressure on the rockers around in directions they weren't meant to to move.
I've checked valve clearances twice, and they are correct.