Date: Mon, 6 Aug 2001 19:20:23 -0500
Reply-To: John Rodgers <jhrodgers@CHARTER.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: John Rodgers <jhrodgers@CHARTER.NET>
Subject: Re: Clakity-Clack
Content-Type: text/plain; charset=us-ascii
Dana, it is good to know the specifics. I am further enlightened.
Thanks!
John Rodgers
88 GL Driver
Dana Morphew wrote:
> A technical bit follows: Most oil filters have two valves. One of
> them, the non-return or anti-drainback valve, is usually a rubber, EPDM,
> plastic, or neoprene-like material that is a flapper valve and is
> located to block the oil's exit through the periphery entrance holes
> that surround the bigger, threaded, and central exit hole. This
> "exiting of the oil" from the filter will occur when the filter is
> mounted sufficiently beyond the vertical position. The second valve is
> generally a spring loaded bypass valve located centrally and at the
> opposite end from the larger threaded exit hole. It allows some/all of
> the oil to bypass the filter media and to flow out the large hole
> without first being filtered when the oil pressure exceeds the valves
> designed opening pressure point or the filter media is clogged. It is
> set to allow bypass at 1 bar in the Mann W 719/12 made for the
> horizontally opposed engines used in the '80-'91 Vanagons,and it opens
> at 2.5 bar in the Mann W 940/25 used in the 1.6 diesel installed in the
> '82-'83 Vanagons.
>
> -Dana-
>
> > Finally, to clarify the most common cause of clacking that occurs, there is a check valve in the oil filter that keeps pressure on the oil galleries of the engine when the engine is shut down. If you don't have the right filter(Mahle) with the right spring pressure(Mahle) on the check valve, when the engine sits a while the weaker filter spring allows the pressure to bleed down, thus allowing the lifters to bleed down with
> > the resulting rattlety-clack on the next start-up.
> >
> > It is said that it doesn't hurt for this to occur, because the lifters will pump back up. I don't agree. IMHO, over time, each cold start under those conditions is a start with components out of tolerance. I don't see how this could but increase the rate of wear. Granted, it's not much wear, but it is more than that which occurs on a start-up when everything fits properly. Metal parts banging together can't help but suffer
> > at least some damage. Won't cause immediate failure, but will shorten the life of the vale train.
> >
> > Good Luck,
> >
> > John Rodgers
> > 88 GL Driver
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