Date: Wed, 29 Mar 2000 12:26:43 -0500
Reply-To: "Joe L." <jliasse@TOAST.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: "Joe L." <jliasse@TOAST.NET>
Subject: Post Headgasket-Job "Chuuuuk"
Content-Type: text/plain; charset="iso-8859-1"
I just completed a left head gasket job in my 83.5, 1.9 Westy. For
reasons I wont get into the job took about 6 weeks and the engine was not
run at all for that time. After the job the engine started right off and
all seemed fine when idling. I took it for a 20 minute run to let the
lifters fill up and settle down and during this drive it seemed to be
running great but when the wife got home and helped me bleed the cool sys by
working the gas a strange new noise materialized the cause of which I have
not yet isolated.
Under no load (transmission in neutral) when the throttle is brought up
to about half way and let off smoothly all is fine, but if the throttle is
brought up half way and let off suddenly so that engine RPM falls off
quickly there is a loud grinding like "chuuuuk" sound of about a half second
duration that seems to be coming from the vicinity of the left head.
The only thing I can think of that could be causing this "chuuuuk" is
some kind of "blow-by" from a valve that is not closing quite rapidly enough
on sudden deceleration. When I adjusted the valves as per Bentley I noted
that the intake valve on #3 seemed much tighter than the others in that
during that "two turns after contact" it was much tighter due to valve
spring compression. As the pushrods were properly centered on the lifters I
figured this tightness was due to that one lifter not draining as the others
had or had drained all the way and had "bottomed out". Not wanting to risk a
burned valve by overtightning I made up for this by taking only one turn
after contact vice the two turns per the Bentley. If that one lifter was
indeed "bottomed out" when I adjusted it the lifter would not be able to
self adjust against the spring pressure that kept it "bottomed". This would
have the effect of making that hydraulic lifter a solid lifter incapable of
adjusting itself. If this occurred then the valve is still too tight, hence
the blow-by.
It also occurs to me that the tightness during the "two turns after
contact" was perfectly normal and by not taking the full two turns I have
made the valve too loose and the lifter, being fully extended, cannot take
up the slack and that "chuuuk" is from the pushrod being "dribbled" like a
ball between the lifter and the rocker during the sudden deceleration, hence
the "grinding quality" of that half second "chuuuk" sound.
The main thing that occurs to me is that as I am no mech I am only
guessing at the cause and that "chuuuk" may not have anything to do with the
valves at all. Hence this post requesting help.
Any ideas greatly appreciated.
|