Re: Ticking noise

[shields@tembel.org (Michael Shields)]

> Sources for ticking noises on Audi 5-cylinder engines:
> ======================================================

I've had too much experience with these.

> b) On some engines, there is a pushrod vacuum pump.  I've heard that this
>    can be removed to test if it is causing the problem.

Yes.  Two 13mm nuts hold it on.  As you loosen it the spring pressure
will push it away from the head.  Don't lose the washers.  You'll see
a cylindrical rod.  It will pull right out.  Reassemble without the rod.

Several people, myself included, have been running just like that with
no problems.  I don't think anyone has determined what causes the actual
noise; if it were known, the vacuum pump could be rebuilt to fix it.
I'm not going to bother finding out, since I now have a quiet car and
slightly firmer brakes, both of which are good things.

The vacuum pump is used on the 4k series, which have vacuum-assisted
brakes; follow the line from the brake booster to the intake manifold,
and it's in the middle.  The 5k series don't have a vacuum pump because
they have hydraulically assisted brakes, with that Pentosin setup.

> c) Lifters - either mechanical (tappets) or hydraulic.  Mechanical noise
>    can reduce a little if the engine is warm - hydraulic lifter noise is
>    likely to cease at high revs or after a drive.  If it doesn't, a 
>    lifter may have failed - this is fairly uncommon.  Hydraulic lifter
>    noise is usually louder if the engine has been standing for a while.

Hydraulic lifters are not too hard to replace as part of a timing
belt job.  Just pull the cam (careful, follow Bentley) and then the
old lifters pull right out (Robo-Grip pliers are perfect) and the
new ones drop right in (I would lube them first).  Even I can do it.
pdqship posted a procedure a few months ago.

Get a neoprene valve cover gasket, change the camshaft oil seal
(unnecessary but $6), do not do not do not bind the distributor, and
watch the torque and sequence on the bearing caps.  As usual Jim at Blau
has all the parts.

This turned out not to be the problem in my case, but I don't feel too
bad; it couldn't hurt to replace the decade-old lifters and the engine
seems a bit smoother.  This could be just cognitive dissonance.

> d) Exhaust manifold cracks.  Much more noticable when restarting an 
>    engine that has partially cooled.  Rare on on non-turbo engines.

But not so rare is broken studs.  Over the years the heat cycles on the
exhaust manifold cause it to warp, which break the studs, which causes
it to leak.  You need to pull the manifold, machine it flat, possibly
drill the old studs out of the head, and reinstall it all.

The idea of drilling hardened studs out of an aluminum head, in my
driveway, in December, with my basic set of tools, and without a backup
car, didn't seem appealing to me.  I ignored it for a while until I
suddenly had some extra cash and then had the shop take care of it.
An outrageous $700.  But at least it doesn't make that goddamn ticking.
-- 
Shields.
'86 Coupe GT, finally quiet after ten months