Date: Mon, 22 Aug 2011 19:18:55 -0700
Reply-To: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Subject: Re: Timing belt replacement and valve timing in VW gas and Diesel
engines
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Hi,
leave gas engines out of the discussion as they used a keyed camshaft
sprocket location system ..
where the diesel it is a steep taper, and the sprocket can be tightened
down anywhere..
a very nice feature.
Best cam sprocket mounting system of any engine anywhere that I have ever
seen, and I've worked on many, many types of engines and cars.
for sure ...if replacing the t-belt, one must re-do bolting down the cam
sprocket for it to come out right.
first step, put a bar through the cam sprocket to hold it from turning,
against the top of the head..
Get that bolt loosened. The engine will not be at tdc to do that ...do it
with the engine in a convenient position for holding the cam sprocket with a
bar .
nothing will move, at that point, like get loose, as the sprocket will still
be stuck firmly to the cam.
then get everything lined up and locked. ( including end of cam lock plate )
remove the old t-belt.
then get the cam sprocket off by giving it a good tap with a hammer to get
it to jump off the cam. Tap it toward the timing belt end of the engine of
course.
there is a trick........I won't mention here, but I have a nice method to
get the new belt on with tensioner, and not have the crankshaft turn at
all - or at least end up where you want it.
that is your next goal..-
new belt and tensioner on and everything stays put.
have the bolt holding the cam sprocket on to that the sprocket is in place,
but is slightly free to move to it's new correct place on the cam.
at that point ..
if nothing has moved ( like the crank marks ) ...tension the belt.
Tighten the cam sprocket bolt somewhat ...like 25 ft lbs..
like spark plug tight.
then remove all locks.
then turn engine a little clockwise until you can put your bar through the
cam sprocket to hold it firmly from turning while you tighten the cam
sprocket bolt more.
( DO NOT ... ! ...use the cam lock plate to hold the cam from turning while
you tongue down the cam sprocket bolt . I have seen even a auto shop class
teacher and writer for Haynes manuals make that mistake..
it just breaks off have of the cam where the lock plate goes. )
Then turn through 2 complete revolutions of the crankshaft ( one of the
cam ) and see if all marks are sill lined up.
then ...do final, final tightening of the cam sprocket bolt.
I make them pretty darn tight by feel. Probably 50 ft lbs. I think the spec
is 37 ft lbs.
I have read about more than one person not tightening that bolt enough,
leading to disaster.
I hope it's very apparent that holding the cam sprocket from turning with a
large bar through the sprocket,
and engine at 'whatever' position to facilitate that ..is the obvious right
way to do it.
it's a job that MUST be done 100% right. No margins at all for anything
less than fully solid and perfect.
get one bolt or nut in that entire timing belt mounting and tensioning
system not fastened down correctly..
and it can be goodbye engine, or at least head. It's happened a lot too,
ever since VW diesels started to exist. Do good solid careful work. There
are lots of ways to screw the timing belt job up. A few gothas perhaps.
Check for injection pump shaft play or slop when belt is off too. If
the injection pump sprocket moves up and down much ..that's not a good sign.
Watch it run with t-belt cover off. If the belt does not track dead center
and consistently..........that's not a good sign. It's a zero margin deal -
vw diesel timing belt. Good luck !
Scott
www.turbovans.com
----- Original Message -----
From: "Poppie Jagersand" <poppie.jagersand@YAHOO.CA>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Monday, August 22, 2011 3:05 PM
Subject: Timing belt replacement and valve timing in VW gas and Diesel
engines
When replacing the timing belt in a Diesel, the VW instructions say to
(first to lock everything up) then *loosen the camshaft nut* (Then put new
timing belt, tension, tighten camshaft nut etc). This camshaft nut
re-setting seems to be for precisely setting the camshaft angle at TDC. (or
is there another reason?)
If I remember right (and I may be wrong - it is a long time since), for the
similar 70's and 80's 4cyl gas engines instructions were basically lock up
cam, replace timing timing belt. No camshaft nut loosening and re-setting of
cam timing.
Any reason a Diesel would be more sensitive to (very small variations in)
cam timing? Anyone skipping the camshaft nut part?
Martin (and '82 Westy "Poppie")
