Timing chain issue 300SD

[soothappens]

I've had a slight noise coming from my 81 300SD engine since I installed it.
The engine is from a 83 300SD.
The sound it makes is like pedaling a ten speed backwards.
The noise the chain will make going through the derailleur. Real inconsistent no pattern to it but mainly at idle.
Raise the throttle and it goes away.

Ive read the chain stretch threads and have done the one lining the marks up. (About to tackle the 2mm one.)
This gave me 5 degrees , so 3 above Mercedes break in spec.
While the valve cover was off I noticed real light marking on the valve cover above the chain.
This to me indicates the chain is lifting upwards slightly.

Now the Question: is the tensioner slacking at idle or is the chain wore out.

From what I understand the tensioner has a spring that takes up the slack.
Then the ratcheting mechanism should hold this position not relying on the spring.
This to me would prevent the chain from rising on the cam gear.
Some stretch I've read about exceeds what I'm getting without any noted problems.
Owners Adding a offset key to bring it back in specs and go on driving.

Now I need an idea on what I may have and where to take the troubleshooting from here.

Any Ideas ?

Thanks in advance.

[Diesel911]

Originally Posted by soothappens

I've had a slight noise coming from my 81 300SD engine since I installed it.
The engine is from a 83 300SD.
The sound it makes is like pedaling a ten speed backwards.
The noise the chain will make going through the derailleur. Real inconsistent no pattern to it but mainly at idle.
Raise the throttle and it goes away.

Ive read the chain stretch threads and have done the one lining the marks up. (About to tackle the 2mm one.)
This gave me 5 degrees , so 3 above Mercedes break in spec.
While the valve cover was off I noticed real light marking on the valve cover above the chain.
This to me indicates the chain is lifting upwards slightly.

Now the Question: is the tensioner slacking at idle or is the chain wore out.

From what I understand the tensioner has a spring that takes up the slack.
Then the ratcheting mechanism should hold this position not relying on the spring.
This to me would prevent the chain from rising on the cam gear.
Some stretch I've read about exceeds what I'm getting without any noted problems.
Owners Adding a offset key to bring it back in specs and go on driving.

Now I need an idea on what I may have and where to take the troubleshooting from here.

Any Ideas ?

Thanks in advance.

When I had the somewhat similar noise #89 in the diagram was loose and ratteling. If it was loose enough it is possible for the Timing Chain to rub on it.

Hunter had posted a pic of a Timing Chain in mid Failure. One of the Links was actually backing out.

You might want to slowly rotat your Engine and observe the Chain for any defects or wear marks where they should not be any.

If the Engine that you installed is from a different Vehicle that you had not previously drove before or a recent rebuild could it be that the Camshaft Gear is on in reverse?
I read of this on another Forum. With the Camshaft Gear on backwards the Chain made contact with the Cylinder Head. (It is pissible to revers the Gear because the timing mark for the Gear/Camshaft is on the Washer not the Gear.)

Use a Mechanics Stethoscope or something like a piec of Wood to listen and locate where the sound is coming from.

On your Oil Pump Drive there is also a chain with a Chain Tensioner.

Then it is also possible it is not Chain related at all but the sound is coming from the Vacuum Pump.

[soothappens]

Originally Posted by Diesel911

When I had the somewhat similar noise #89 in the diagram was loose and ratteling. If it was loose enough it is possible for the Timing Chain to rub on it.

Hunter had posted a pic of a Timing Chain in mid Failure. One of the Links was actually backing out.

You might want to slowly rotat your Engine and observe the Chain for any defects or wear marks where they should not be any.

If the Engine that you installed is from a different Vehicle that you had not previously drove before or a recent rebuild could it be that the Camshaft Gear is on in reverse?
I read of this on another Forum. With the Camshaft Gear on backwards the Chain made contact with the Cylinder Head. (It is pissible to revers the Gear because the timing mark for the Gear/Camshaft is on the Washer not the Gear.)

Use a Mechanics Stethoscope or something like a piec of Wood to listen and locate where the sound is coming from.

On your Oil Pump Drive there is also a chain with a Chain Tensioner.

Then it is also possible it is not Chain related at all but the sound is coming from the Vacuum Pump.

Thanks 911 Ive done two valve adjusts in the past year and the chain looks like its in good condition. iwis brand.
The only mark if you could call it that is on the valve cover. Its in the 11:00 position of the timing gear on the cover Just a slight rub mark.

A mechanics stethoscope doesn't pin point it. I put it on the vacuum pump and I get no noise whatsoever .
I removed all belts and still the same noise. You remove the oil cap and it becomes more pronounced.
With the stethoscope to me it seems louder near the AC compressor.
This would be in line with the oil pump chain I'm guessing?
Is there an easy way to check it and the lower tensioner?

Thanks for the diagram .
#89 is simple enough to check I will do that first.
As for the who what when and where on this motor it was a transplant into the 83SD.
PO said it only had 139,000 miles on it and from the internals it looks like a low mileage one.
All the inner surfaces are Real clean and the cam shows no wear. it still has the crosshatch on it.

I drove the 83 15 miles before pulling the engine. It ran smooth started great but even in that car it had the noise.
Is there a way to tell if the gear is on backwards? I'll check it when I look at #89

Thanks for the input.

[Diesel911]

To see if the Gear is on backwards you could compare it with the Engine you pulled out.

Or, in the account that I read the OP said the Gear Backwards caused the Chain to rub on the Head a little.

[soothappens]

Well the noise had nothing to do with the timing chain.
I checked with my stethoscope and found the noise greatest on the timing pointer.
Figured easy fix bent it upward ....still had the noise.

I bit the bullet pulled the lower oil pan and there it was.

The oil chain tensioner came undone and was hitting the front of the case.
It would bind and slack the chain and the slack and rubbing is what I was hearing.

I will start a new thread with pictures.