Odd Engine Noise

[Hans]

A friend's 1600-2 has an odd noise from the engine. He rebuilt it about 12 - 15k miles ago, but I was unavailable to assist in person. Fresh block was bored to match old pistons.

It appears at start-up and seems to ease off as engine warms. It also seems softer with revs (and thius more oil pressure). I initially thought valve train, but the clearances are all .007/.008. Can't detect any loose rockers. Cam chain is under tension from piston (I can move the tension shoe about 1/4" with big screw driver). 

I sent him a stethoscope and he reports the noise is loudest on the pan and lower block. I would have thought rod knock would be different. 

Have a listen and see what you think.

Thanks

Hans

[TobyB]

Does he have an exhaust leak?

 

Flat spot on one or more of the adjusters?

 

What's odd is that it's so loud at idle, and then goes away with revs.  Although, that could be AGC on the recording device....

It sure sounds like a collapsed hydraulic lifter- but of course, it isn't.

 

If it really is loud down low, oil pump chain?  

 

Something loose flopping around in the sump?

 

t

guessing

[Hans]

11 minutes ago, TobyB said:

Does he have an exhaust leak?

 

Flat spot on one or more of the adjusters?

 

What's odd is that it's so loud at idle, and then goes away with revs.  Although, that could be AGC on the recording device....

It sure sounds like a collapsed hydraulic lifter- but of course, it isn't.

 

If it really is loud down low, oil pump chain?  

 

Something loose flopping around in the sump?

 

t

guessing

Thanks. I can't think of what the oil pump chain would hit hard enough. Now friend reports he went from 20-50 to 10-40 and it got worse. Still puzzling as to what would be affected by that.

[TobyB]

oh, yuk- 

piston slap?

 

t

 

[Hans]

Just now, TobyB said:

oh, yuk- 

piston slap?

 

t

 

I wondered about that. If shop was accurate, shouldn't be an issue at this point. I only had that once 50 years ago with my Bavaria. I seem to recall it was a bit deeper.

[kbmb02]

29 minutes ago, Hans said:

I wondered about that. If shop was accurate, shouldn't be an issue at this point. I only had that once 50 years ago with my Bavaria. I seem to recall it was a bit deeper.

 

Did your friend check/measure the machine shop's work, prior to assembly? -KB

[Son of Marty]

Loose oil pump chain sounds just like that IMHO.

[Hans]

Hmmm.

 

[Hans]

3 hours ago, kbmb02 said:

 

Did your friend check/measure the machine shop's work, prior to assembly? -KB

He's pretty sure the pistons were numbered and put in the right hole. I was out of town so only able to assist by email..

[Son of Marty]

I hope the machinist knew to inspect the ring lands carefully, it's a known weak spot on the m10, depending on mileage, but well over half fail on medium to high mileage engines. But in the picture above, if it's the engine in question, the o/p pump chain is obviously hitting.

,

Edited August 10 by Son of Marty

[paulyg]

My 2002 makes the same noise with the same symptoms. Probably the oil pump chain or an exhaust leak but I can’t be bothered to do anything about it right now. 

[John76]

1 hour ago, Hans said:

Hmmm.

I second the Hmmm.

Oil is thicker on startup and oil pump is therefore harder to turn.

The slack side of the oil pump chain is tapping the pressure relief valve.

[Hans]

Thanks all. I had forgotten how close the chain gets to the pump body. Certainly makes sense given evidence. Off with the pan!

[John76]

42 minutes ago, Hans said:

I had forgotten how close the chain gets to the pump body.

Yes, it does. 

Let me know if you need a 0.10 mm shim. I have a spare that was sent to me by @Mark92131.

Glad to repay the favor to others in need.

John

 

 

[Einspritz]

My $.02

Sounds like a rocker arm to me.

 

Are you sure those nuts are all tight?

 

Something to re check before you get into the pan....

 

And, I was taught by a factory master mechanic the lash is 0.06 intake. 0.08 exhaust Cold.