engine and drivetrain Oil pump chain hitting oil pump cause rod knock type noise?

[E39guy]

I pulled my M10 expecting to find bad rod bearings. I was unsure though because pulling the plug wires revealed no change in the knocking sound. After pulling my pan it's very clear my oil pump chain has enough slack to hit the pump housing. I pulled a main bearing cap and while there was some VERY minor scratching that a polish job could remove, the bearings looked good. I am going to pull all the main and rod caps now and check the bearings for evidence of damage.

 

I suspected I COULD be hearing a chain slapping around in there due to the noise it was making. Has anyone else experienced this?

 

Thanks

Edited November 14, 2015 by E39guy

[conkitchen]

^{add a shim}

Edited November 14, 2015 by conkitchen

[Anthony]

First of all is there any evidence of the chain hitting? From experience you will see scratches and marking and if the chain encounters aluminum it will eat into it fast. 

 

Also chain rattle/slap usually occurs on change of RPM, constant rpm will load the chain up on one side and it will be pretty quiet. 

 

You say you pulled a main bearing cap? Did you mean to say rod cap? You need to check all of them. 

 

Did you cut the filter open and check the media for debris?

 

Edited November 14, 2015 by Anthony

[E39guy]

No I just pulled a main real quick right before I left the house since it was easier. I will go pull the rod caps now. There are marks where the chain has touched that area. I have no clue how long its been since this motor has been run. It is worse when revved but when you hold it at just the right rpm you can hear it as well.

 

I am going to go pull the bearing caps now, the suspense is too much. BRB

[jgerock]

All (3) of the M10 engines I have dismantled had very loose oil pump chains.   The original 69 engine had very bad timing chain wear marks on the front cover (gouges).  

[E39guy]

So the rod bearings aren't in great shape but don't seem bad enough to cause a knock. They aren't down to copper or anything.

[jimk]

You can test for whether the chain is worn to differentiate from just a shimming issue by holding the chain against the oil pump sprocket at two points 180 degress apart (i.e. 3 o'clock and 9 o'clock locations) with the thumb and fingers of one hand. Then with the other hand lift the chain at midway between the points held. If the chain is worn the chain pitch will have inceased and it will lift away from the sprocket. If not worn, it will hold tight against the sprocket.

Most likely the chain is worn, but this check tells something about what is going on.

The technique can also be used on a cam drive chain with only the valve cover removed!

Edited November 14, 2015 by jimk

[E39guy]

That's a great tip Jim, Thank you.

[TobyB]

Buy some plastigauge and see what it says.  It's not perfect, but good enough for a go- no go like this.

 

There's a lot of metal on those shells- they can be worn, and not look too bad.

 

t

[E39guy]

Reasonable advice Toby, thanks. I just want to figure out why it was making this racket before I rebuild it.

[jgerock]

If your timing cover looks like this one - your engine needs some help