[T3] Engine Rattling.... Update...

[Jim Adney]

On 25 May 2012 at 22:04, Jim Adney wrote:

> On 25 May 2012 at 15:17, J. Jonik wrote:
> 
> > Re/  71 sqbk FI Std shift....with a seemingly worsening rattle in engine area.

> > Yes...(as explained here not too long ago) it's about too much play
> in the crank shaft, as seen by moving the fan pulley in and out.  
> It's largely about old age of the engine....as the bearing dowel holes
> in the case have gotten a bit elongated and are not holding the
> bearings, and the crank, snugly any more.  How four dowel holes can
> wear out is a mystery. 

Let me explain a bit more about the main bearing dowels. They do NOT 
hold the bearings in place. The main bearings are held in place by 
the grip of the case halves around them. The dowels fit snugly into 
holes in the case, but are about half the diameter of the holes in 
the bearings. The ONLY purpose of the main bearing dowels is to 
assure that the bearings are installed in their correct positions 
before the case halves are torqued together.  

If the case halves lose their grip on the bearings, the dowels will 
try to keep the bearings from moving, but they eventually fail and 
the bearings will spin in the case. This usually destroys the engine. 
If you actually have excess end play, you want to stop and fix this 
NOW, before the bearing spins.  

Once the bearing is loose, there's no telling when it will spin. It's 
not worth gambling on.

But my guess, and from this distance it's only a guess, is that you 
don't have excess crankshaft end play.

Another possibility that might cause such a noise might be a loose 
flywheel. I've never seen or heard this, but I've heard that it can 
make an odd noise. This can ruin a crank & flywheel, but it's not 
likely to destroy the engine. Once again, however, I'd expect it to 
cause an oil leak, so this "possibility" seems remote.

-- 
*******************************
Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
*******************************