engine and drivetrain My Engine noise....Still not gone

[PatAllen]

you would be surprised to "feel" what piston clearance should be. among at least 10 supposedely reputable shop i know, none of them would put them in that tight. hence the reason why i did try to knurl the pistons....which i did, and among other things i changed, the engine purrs like a kitten.

things i suspect in order of importance

piston slap

small end rod bush

crank axial play

hth

[PatAllen]

 

 

[roadhog0]

Sounds sorta like an IDI diesel, sure you didn't put a VW engine in it? LOL! Sorta weird, doesn't sound like piston slap to me at least. I am definitely curious now!

[arminyack]

11 hours ago, PatAllen said:

you would be surprised to "feel" what piston clearance should be. among at least 10 supposedely reputable shop i know, none of them would put them in that tight. hence the reason why i did try to knurl the pistons....which i did, and among other things i changed, the engine purrs like a kitten.

things i suspect in order of importance

piston slap

small end rod bush

crank axial play

hth

I'm not convinced I have piston slap..the machine shop I used is very reputable and knows M10's quiet well....but who knows. The motor makes the same sound whether cold or hot, and its only at idle, and engine decel...

 

Piston knurling is so old school...I don't even know a shop locally to take them to to have it done!

Edited June 5, 2016 by arminyack

[arminyack]

I pulled the head off tonight, and did preliminary inspection of things....here is piston #4 rocking @ TDC. Seem excessive?

 

https://www.youtube.com/watch?v=_Z8IpHVMWRM

[PatAllen]

no reply ?

 

unless you have long feeler guages its almost impossible to tell....but it looks "loose" to me.

my knurled ones wasnt making this for sure.

[percy]

I do not associate the video sound with piston slap or a rod knock.  However, the piston movement seems excessive.  (Before going further, a lot of movement could be normal with forged or exotic alloy (magnesium) pistons since these will expand until reaching normal operating temperatures.)

 

A long feeler gauge may or may not be helpful for a couple of reasons, the first being a tapered cylinder wall.  The second being an irregularly shaped piston.  (A third but unlikely scenario is ill fitting or broken piston ring/s.)  There may not be any irregularities other than normal wear and greater than normal piston to cylinder wall clearances.   Bear in mind that honing will not address cylinder wall taper.  It may disguise it and make it less difficult to detect. 

 

Not knowing (or remembering) the details of your rebuild, one suspects you reused the pistons.  It would be interesting to see the skirts of those pistons since removing scuff marks generally tends to remove material - making piston-to-cylinder wall clearances greater.  Knurling, as PatA suggested, is one way to address the problem.  (Pat did not disclose whether his knurled pistons were originally for a Toyota or the more usual Mahle versions.  )  Another consideration is to carefully inspect the cylinder bore - even with the piston in place.  If there are no obvious wear marks, bolt everything up and live with the sound - for possibly a very long time.  Instead of driving with a kitten, your engine may sound like an old tomcat or a puppy.  All can make good pets.

[arminyack]

I mic'ed out the bores over the weekend. Bearing in mind, measuring down to .0001" is a dicey thing, best left to those with good tools, good practices and experience...I measured bore diameters a good number of times in a number of different places, and found the bores to check out ok. The pistons were new old stock Mahle units, so i had no worries there..

What I did notice, once I got the timing chain off, was that my brand new timing chain, which was really damn tight upon install had slackened, and the tensioner would now interact with the chain as it should. I was able to bleed the tensioner properly, and obtain a solid column of oil behind the tensioner piston, which was not possible before.....when then lead me to my oil pump chain. When I first installed the new oil pump chain, I was just inside the 5mm max deflection number. Well guess what...this chain also slackened, and combined with the largish link width that I posted about above, made out for a lot of movement! So I replaced that chain with an e21 chain (which is narrower) and put in 2X shims. It's now much tighter, and none of that excessive side to side movement. (see below) I put it all back together, and the engine is now in the car...I just need to hook everything back up. 

 

The top chain is the original, the middle one is the "old" new one, and the bottom is the e21 chain that in the car now. Notice how much wider the "old" new on is.  We'll see how this plays out when I start her up later this week.

 

Edited June 13, 2016 by arminyack

[jimk]

May be just the photo, but the middle chain looks to have a larger pitch than the other two.  If it does, it's the wrong chain.

[arminyack]

I'll check it when I get home....but I did confirm the PN....it is right. Maybe Iwis screwed up.....

[Stevenc22]

The "old" new one simply does not look right. Bet the sounds goes away.

 

Im impressed you removed the engine and pulled the head. SO MUCH work to track down this problem.

[arminyack]

1 hour ago, Stevenc22 said:

The "old" new one simply does not look right. Bet the sounds goes away.

 

Im impressed you removed the engine and pulled the head. SO MUCH work to track down this problem.

Having a hydraulic car lift + a 1000 lb lift cart makes pulling the motor a piece of cake. If I didn't have these two things, I'd would have just said "screw it, let it be noisy!"

[wegweiser]

FWIW: I have one of the new (wider) IWIS oil pump chains in my own car. So far, at about 3800 miles - no noise. I *did* notice it comes quite close to the Nr 1 main bearing cap, but only if you actively deflect it with your finger - not the kind of thing that should happen during normal engine operation. And I always thought E21 M10 oil pump chains were the same size / part number as 2002 ones….I guess I learned something today. 

[KenH]

Well did you solve the noise issue ?

[arminyack]

Nope.....the noise is still there. I'm going with piston slap. I'll just deal with it. The car runs smooth and strong...it just has this annoying noise at idle...and I can kinda hear it in the background of the din of engine roar at higher RPM's.

 

It's disappointing after all this work...but I learned a lot , and had fun doing it. I'm already hatching my 2.0l ITB megasquirt motor plans....I wasn't planning on staying 1.6l forever!

 

Anyways..... I'm doing the SoCal Vintage BMW Mullholand/Malibu run tomorrow. Gonna be fun!