Date: Tue, 20 Jul 1999 09:46:13 -0400
Reply-To: Derek Drew <drew@INTERPORT.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Derek Drew <drew@INTERPORT.NET>
Subject: Viscous Coupling Expert Located & Interviewed
In-Reply-To: <l03130301b3b9c396aab0@[142.104.17.103]>
Content-Type: text/plain; charset="us-ascii"
I located this morning an expert who works at a manufacturer of viscous
couplings. As part of a lengthy interview, he said these things:
1. The viscous coupling fluid goes bad over time when it acquires small
metal particles from the surrounding metal and suspends these particles.
2. The process of having the fluid go bad is called "gellation" and was
caused as a reaction causes a gas to be formed.
3. You can fix a VC by replacing the fluid with fresh fluid. You should
also examine the condition of the plates.
4. The percentage of air in the viscous couling is critical, and the
percentage is almost always a low of 80% and a high of 86%. He said that if
you went above an 86% fill then you would have the VC activating on the
highway during normal driving and a dangerous situation would exist. If you
went below 80%, he said you might never achieve lockup, even when stuck. He
said all these numbers are subject to investigation and confirmation, which
he will try to give me in August after consulting with Europe to check on
our exact unit. He said the probable range for our vehicles is 84% to 86%
air--possibly closer to 86% for a vehicle intended to go off road as ours is.
5. He said a room temperature VC should *not* be under any internal
pressure, and that it might be a simple fix to partly repair a VC to simply
open up the bleeder holes and let the fluid under pressure in there out and
then put the plugs back in and keep using the unit.
6. He said that he wanted to help us in order to keep VCs from getting a
bad rap amoung OEM manufacturers. He said that even if his company did not
make the SDP units themselves, his company would have an interest in
helping us and making sure our VCs were not wearing out prematurely and
that they were being rebuilt properly.
7. He said that if Wheedle and Oregon Transaxle were refilling the VCs
without letting any air get into them (which both Wheedle and Oregon told
me!!!) then the rebuilds from Wheedle and Oregon would be faulty. The
symptoms would be early wear, intense heating of the VCs, and lots of
premature lockup.
8. I observed that this might be the reason Wheedle and Oregon both told me
they are moving to a lighter formula fluid--that they are mistakenly not
adding the required 14% air and that they are not rebuilding the units
correctly. The GKN official agreed that this is a logical possibility. He
said the idea of a VC being 100% filled with fluid was something that would
simply never be done under any circumstances. This statement tracks the
statements of the engineer Wolfgang in Tim Smith's article from VW in 1979.
9. I believe it is possible that after my guy checks with SDP that someone
will shut him up and they won't talk to us any more.
10. He said the proper refilling procedure is to apply pressure at one
little hole while applying a vacume at the other little hole .
11. He said the key to preventing the fluid going bad over time was
additives in the fluid that his company routinely uses. He said it is
possible that SDP does not use these additives.
12. He said the fluid gets hot and that this is what causes the lockup.
13. I asked him why the VC doesn't appear to have any air in it and asked
him why it seemed to be 100% fluid. I asked if perhaps this was a special
VC that required 100% fluid. He said that no, this would not be the case.
He said that in manufacturing the air is added and then the air gets mixed
up in the fluid and occupies the little holes between the plates of the VC
and you cannot see the air any more.
14. He said not to quote him on any of this. I guess that means I should
leave his name out. :-) I think what he really meant was that he wanted to
investigate and confirm what he told me.
CONCLUSIONS:
a) Anyone with a bad VC should hault any work being done by Wheedle and/or
Oregon until we resolve the issue of the % air.
b) Anyone with a bad VC might want to simply vent it, reseal it, and reuse
it, and see if that fixes the problem.
c) Derek gets this week's "VC Award."
At 11:13 PM 7/19/99 -0700, you wrote:
>
>Derek,
>
>at the risk of stating the "bleeding obvious", for the fluid to under
>pressure there must be some "airspace" in the VC. Wasn't there some
>discussion about whether the VC was completely filled with fluid or not?
>
>Alistair
>
>
_______________________________________________
Derek Drew New York, NY
CEO, ConsumerSearch
drew@interport.net
212-580-6486
917-848-6425 (cell; this phone is a reliable way to reach me fast or to
leave messages)
Alternate numbers for the industrious phone caller that wants to try every
avenue: 202-966-7907 (Work), 212-580-4459 (Home), 202-966-0938 (Home)