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Engine Tapping Noise :(



I've personally experienced piston slap, and although it was not on a vw, it was a similar engine (Buick Skyhawk 1.8l).  The cause
was coolant mixed with oil due to a failed head gasket, which took its toll on one of the rod bearings.  It started light, more
pronounced above 3k, but started getting worse and louder.  The tap was very lightly audible at idle.  As compared to a valve train
issue, it was a considerably more "solid" tap/knock, almost as if someone was tapping the head from underneath, with a hammer.

I miss that Skyhawk.  It was the sole reason for my learning to work on cars - as every week it threw a new curveball at me.  It was
my first car, and 2 days after getting it, the starter fell out (i.e. on the ground).  That set the tone of things to come over the
next year :) .

HTH
Al

> -----Original Message-----
> From: Dan Bubb [mailto:jdbubb@verizon.net] 
> Sent: Tuesday, November 14, 2006 6:59 AM
> To: haygood@myway.com; scirocco-l@scirocco.org
> Subject: Re: Engine Tapping Noise :(
> 
> I don't believe the head will need to come off. The tapping 
> is typically a failed hydraulic lifter, so just replacing 
> that should do the trick unless its damaged a cam lobe. 
> Mostly the valve and spring aren't damaged by this unless it 
> goes on for an extended time, then the shock loads may do 
> some damage. Bentley has a procedure for testing the lifters. 
> I've never actually identified a bad lifter using the 
> procedure, but that's where I'd start.
> Course the other thing it could be would be rod knock. 
> Heavier sound but it starts out as a tapping sound and gets 
> louder. If caught early enough it might not damage the crank 
> and replacing the bearing shell. Visual inspection of the 
> crank bearing surface and plastigage check should be sufficient.
> Dan
> 
> From: "Brian Haygood" <haygood@myway.com>
> Sent: Tuesday, November 14, 2006 1:03 AM
> Subject: Engine Tapping Noise :(
> 
> 
> > 
> > So, I've got a loud tapping noise apparently coming from 
> the exhaust valve area of my number 3 cylinder.  It started 
> out as a slight tap above 3krpm but rapidly changed to a 
> constant loud tapping noise.  
> > 
> > 
> > 
> > Obviously the head has to come off.  What parts are likely 
> to have been damaged and need replacement?  Is the head 
> itself damaged by this?
> > 
> > 
> > 
> > Also, what parts would you normally replace when rebuilding 
> a head with no known problems?  I'm not asking for a list of 
> gaskets - do you replace valve springs? hydraulic lifters? 
> valve guides? 
> > 
> > 
> > 
> > I'm dealing with heads from PL and 9A 16v's.
> > 
> > 
> > 
> > Thanks.
> > 
> > 
> > 
> > Brian
> > 
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