[Healeys] Overdrive Question

[Austin Healeys List]

Hi Roger,

The overdrive brake ring will seal fine whatever you put on it- as
long as you don't drive anywhere! The issue is that there are only
four bolts holding the back housing on and in between them at the
bottom is a cantilevered lug that takes all the reaction force of the
engine and transmission when applying the brakes. The housing just
opens up a little under braking and there you go, instant oil leak.

A solution I found successful was to grind a curved slot around both
sides of the steel sandwich plate with a Dremel about 1mm deep and
when assembling it, cover the faces and fill the slot with 3-bond 1215
silicone. When the slot opens up, the silicone in the groove stays
flexible enough to bridge the gap.Oring cord could work too but I
didn't have anything to machine the groove accurately enough.

Slightly related- the two other annoying leaks I had on the engine,
one from the rear main and one from the front crankshaft seal both
stopped completely as soon as I replaced the cork rocker cover gasket
with a silicone one. The rocker cover has a similar issue in that only
two bolts are expected to hold the entire thing on and cork simply
can't flex and comply like silicone can when the cover starts dancing
around on the various resonant frequencies produced by the engine.

Andy.


On 11/6/16, Roger Grace <roggrace at telus.net> wrote:
> Sorry to reopen this, but have this same leak in my BJ8 OD and fixing it is
> one of my Winter projects.
> Given that the black sealant stuff that was used before didn’t last (have no
> idea how long ago or what it is) and that there is no oil pressure on the
> joint, am sensitive to using what is the appropriate goo that will last and
> contain the oil.
> Have done some checking around and the Hylomar universal blue is used by
> some shops that fix OD’s.
> Overdrive Services (ex Laycock people in UK) tell me that the originals were
> sealed with a product called Wellseal.
> Nowadays they use a Wurth sealant that mentions flange mating in its website
> blurb.
> BTW they said that they could supply me with a gasket for this joint that
> seems like a good idea ?
>
> The reality is that these are 2 Al flanges that are mated without a gasket.
> I wonder why ?. Plan to do some careful flatness checking when have my hands
> on them.  Has anyone had a problem with the mating flatness ?  do they have
> a tendency to warp over the years and maybe abuse too ? given the shape not
> easy to machine flat - why do they leak ?
>
> Comments/ideas please.
> rg