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

Sat May 22 00:10:25 EDT 2004

Rod bearing noises are very distinct and Charlie's tests that he outlined
below are very good detectors.  I think which route you take depends on your
long term plans for the car.  Are you going to run it for another year or
two and dump it, or do you keep your cars for 10 years between changes?

I have seen these failures fixed two entirely different ways.  One way is
what Charlie suggested and one way is what Bill suggested.  Bill's "patch it
up method" does have its merits if you don't plan to hang onto the car that
long.  It's easy, cheap, and fast.  I have seen a number of engines with
this done to them last quite a long ways before the owner's sold them still
running fine.  However, Charlie is right that you do stand a chance of
getting metal shavings in your engine.  Sometimes this can kill it and
sometimes it doesn't.  I know I personally ground a cam lobe down to nothing
because of a stuck lifter and just stuck a new camshaft in because that's
all I could afford in college and never had another problem with the car.

If you do go the full route as Charlie suggested be sure to double check
everything the machine shop does, or has done.  Most machine shops don't
grind their own cranks, they send them out.  Be sure the filleting is done
properly as well as the fact that the journals are still properly indexed to
the crank when you get them back, i.e. not turned off center.  This caused
me a whale of a problem on one engine I built.  Also, be sure to clean out
the oil passages with a rifle brush or the equivalent after you get the
crank back from the machine shop.  Don't assume they are clean!  Or ask the
machine shop to do this explicitly.

Good Luck!

--Calvin

P.S. Rod's engine is awful tempting :)

-----Original Message-----
From: s-car-list-bounces at audifans.com
[mailto:s-car-list-bounces at audifans.com]On Behalf Of Charlie Smith
Sent: Friday, May 21, 2004 4:18 PM
To: Audi S Car List
Cc: Charlie Smith
Subject: Re: Subject: [s-cars] Ate a rod bearing?

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
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