Subject: [s-cars] Ate a rod bearing?

[Charlie Smith]

Earlier, Bill Clancy wrote:
> 
> I'm no expert on rebuilding engines... but i have done a few.
> 
> I'm not sure how difficult it is to get the oil pan off, but once you do
> that, replacing rod and crank bearings is not that difficult.   As long as
> the crankshaft is not scored, it is a fairly easy fix.    You just have to
> get it up in the air so you can get at it... or flip the entire car upside
> down and work on it from the top.   ;-)

Don't just paste it together like that!

You have (READ:  MUST) to remove the rod and resize the big end,
probably do all the rods.  The big end of the rod is certainly
no longer round.  Just putting a bearing shell in a not-round
rod is the short route to another failure.

If metal came out of the rod bearing, and if it's rapping it certainly did,
you MUST take the whole durn thing apart to CLEAN it 100.00%  Metal dust
in oil passages will work it's way into new bearings, and *presto*, you
have another bearing failure.

A rod rapping makes a very distinctive sound.  It will make noise
when in neutral and lightly accellerating the engine from idle to
about 2000 RPM.  Run the engine in neutral back and forth from
1000 to 2000 RPM.  Up and down a few times.  It will rap when 
picking up speed and will be quiet when slowing down.  It will not
make noise under load, and usually won't make noise over 2000 RPM.

As the bearing comes apart, the layers of lead and copper/tin come apart
and pin head size pieces of material come out of the bearing surface as
it work hardens and breaks apart.  Those pieces of material will imbed in
other bearing surfaces ... and as each piece gets pushed into the bearing 
metal it work hardens a small area of *that* bearing.  Pretty soon, that
bearing will start to come apart too.

While this is happening, the big end of the rod will be deformed so
that it's not round.  If you reuse it like that, the new bearing
shell won't have the right clearance to the crank journal so it
won't retain the right oil film layer - and a failure situation starts
again.  You can resize the big ends of rods if they aren't too bad.
Be sure to use new rod bolts and nuts.

You would be better off installing a set of aftermarket forged lighter
rods anyway  :-)

If the crank journal isn't round, be very careful where you have it
reworked.  A so-so machine shop may not be real careful to maintain
the right fillet radius' on the journals when they regrind them, and
the oil passage edges into the journal need to be rounded off ( I can't 
spell champfered / chamfered / ?) exactly like it was originally.
Then there's the issue of grinding a journal that was surface hardened,
and I assume the Audi crank is hardened.  Any work on this must be
done by a shop that really knows what they are doing.

Go for Rod Haney's engine!

    - Charlie


> 
> 
> ----- Original Message ----- 
> From: "Postupack, Jeff" <Jeff.Postupack at analog.com>
> To: <s-car-list at audifans.com>
> Sent: Friday, May 21, 2004 11:27 AM
> Subject: Subject: [s-cars] Ate a rod bearing?
> 
> 
> 
> ///
> So.what is the group's collection knowledge/opinion on this?  Did I
> indeed eat a bearing?  If so what are the options?  Rebuilt the lower
> end only? Swap in a new used motor?  What's most cost effective?  It
> looks like I have a big bill ahead of me no matter what, but if one
> approach is better both cost and longevity wise I want to go that route.
> Looks like all the other work I was seriously contemplating (RS2
> goodies, suspension) may go by the wayside in view of this new issue.
> 
> 
> Ug
> 
> Mike Bess
> 
> '95S6 MTM 1+
> ///
> 
> 
> 
> Mike;
> 
> This is a tough situation. It only takes low oil an instant to damage
> tender bearing surfaces.
> There's only a few mechanics with an ear and instinct tuned well enough
> to detect a rod bearing rap.  If this mechanic is very good, trust his
> intuition. And don't run that engine!
> 
> The _only_ way you'll really be certain is to take off the oil pan, and
> analyze each rod and main bearing.
> Then there you are, initiating a motor rebuild.
> Or you buy one of a few $3K complete engines out there, like Darin N's
> or James at the Peachgroup [mailto:34p at snet.net]
> 
> I know Chris Semple at Force 5 still has the older but famous Rod Haney
> 500 HP engine. There's a story with that.
> 
> 
> Sorry to hear of your new trouble, it's a bitch indeed.  Take your time
> to think it out.
> 
> Jeff
> Es-car-go