CGT: Rebuild or Swap?

[ricematthews]

Huw's right - replacing a bearing SHOULD be much easier than doing a motor
swap - and really easy if your oil pan will clear the cross member with the
motor in the car.  There's a few things to keep in mind though.

First off - if it's a rod bearing, you can probably detrermine which one by
pulling each spark plug wire one at a time (be careful not to shock
yourself - you may want to shut the car off and restart it each time).  The
noise should go away when the spark plug wire is off of the cylinder with
the bad bearing.

One other thing to do might be to run a quick compression check first.  I
swore that I had a bad bearing in my Toyota Truck.  I was about to go after
the bearing and fix it (and yes - unplugging a specific spark plug DID make
the noise go away).  On a hunch, I ran a compression check and concluded
that I had a blown head gasket.  It blew between cylinders and I was getting
combustion interference between the 2 cylinders creating an awful detonation
problem - sounded like a rod knock.

The big problem is that if you have a rod knock, you may need to have the
crank turned and polished.  This would generally require removal of the
crank which will probably require removal of the engine or at least the
trans - in which case, you may just as well swap motors and be done with it.

Bearing removal and checking out the crankshaft should only take a couple of
hours to get to, I would think (based on non-Audi experience in this matter)
so that's probably a decent place to start (after the compression test).  If
you end up doing a motor swap, I would think that you could do it in a full
weekend with (again, based on non-Audi experience):
    - a mechanically inclined friend
    - a motor hoist
    - a case of beer
I'm assuming here that you wouldn't do a true "swap", as I figure that the
bad motor wouldn't exactly get installed in the bad body.
The nice thing about doing the swap is that I would think the 2 engines
would have most of the same components so things like fuel injection,
alternator, etc. can be swapped with the motors to save time.
Of course before attempting this, I would get an idea of actually how
difficult the procedure is from a manual (I would choose Haynes over Bentley
for this, as I know there is a Haynes manual for the CGT as close as your
nearest Pep Boys and they tend to write to the regular Joe as opposed to a
trained Audi tech.)

Good Luck!
-Mark Rice


> Though I've moved on to another daily driver, the fact remains that I have
> two Coupes (one for parts) sitting in the parking lot.
>
> So!  The parts car has what's proven to be a pretty reliable engine;
unknown
> mileage (but probably pushing 300K) and no terrible noises except for a
> faint lifter tick (or is that the brake vac pump rod?).  Served reliably
> with decent power for many thousands of miles; the car could go 112, which
> is just 3mph under a CGT's rated top speed.
>
> The "good" car has a bad engine, though, some sort of terrible clunking
> noise which a mechanic said was a bad rod.  The only information about rod
> knock I've been able to find indicates the bearings just need to be
> replaced, assuming the crankshaft hasn't been royally fudged.
>
> Now, bearing in mind that I have limited cash and very limited tools, is a
> rod bearing replacement going to be inexpensive or effective assuming I
can
> track down someone to help me with it?  Or should I just stick to my
> sockets, bite the bullet, and pull the parts engine?

As much of a pain that replacing that rod bearing would be, swapping
engines will make it look like child's play, unless you have a very
enthusiastic friend with an engine hoist and a weekend or two to kill.

The bearing is only so-so bad, helps if you can identify which one it
is.  Drain oil, drop pan (need new gasket), maybe remove oil pickup for
easier access (needs new gasket), undo rod bolts, separate, remove old
bearing, clean up, lube surfaces with build-lube, reassemble.  You could
do all the rods, to be sure, I suppose.

My old 5kt had this problem once, years ago.  Friend at a local shop did
it for me, somehow he knew which bearing ot replace because he only did
one.  Fixed it good.

--
Huw Powell