TRNW-2: VW O9G mysterious leak

Wed Dec 17 04:55:33 PST 2025

   I'm not sure what the owner paid for this one, but they've been a little
hard to find,  they got one core which wasn't the same bellhousing,  then
found the one I used ,
    We took the housing to a local machine shop that is going to tig weld
the crack this morning,  I'm going to look closely at the dowel pins and
see if I can figure out whether bolting it down a certain way could have
caused the crack,  I always tap housings down flush with a rubber mallet or
similar before installing the bolts,  so I don't know ?

    Steve

On Wed, Dec 17, 2025 at 6:25 AM Fred Whitaker <ibsprag at hotmail.com> wrote:

>  How high are cores for these?  I would consider just starting over with a
> complete transmission if they aren't ridiculously expensive.
> ------------------------------
> *From:* trnw2-bounces at trnw.net <trnw2-bounces at trnw.net> on behalf of
> Steve Everett via trnw2 <trnw2 at trnw.net>
> *Sent:* Tuesday, December 16, 2025 2:31 PM
> *To:* pat schulte <zzyzxpat at gmail.com>
> *Cc:* Technical Discussion Forum <trnw2 at trnw.net>
> *Subject:* Re: TRNW-2: VW O9G mysterious leak
>
>  This one is bolted on to the top of the bellhousing , round, attaching
> bolt through the middle, two coolant hoses
>
>    Steve
>
> On Tue, Dec 16, 2025 at 3:27 PM pat schulte <zzyzxpat at gmail.com> wrote:
>
> The usual difference is whether the cooler is remote or bolted on as I
> recall.
>
> On Tue, Dec 16, 2025 at 12:12 PM Steve Everett via trnw2 <trnw2 at trnw.net>
> wrote:
>
>  We put dye in the fluid and finally verified where its leaking from, the
> crease where the arrow points,  there apparently is a crack there , can't
> see it with your naked eye, but the dye was seeping from that crack, same
> place the other bellhousing was apparently leaking from,  we're going to
> see if we can get it tig welded by a machine shop locally
>
>     there is a pressure passageway on the other side of that crease,  that
> is fed by a passageway on the pump body , I've since discovered the
> valvebody was replaced when it was originally built, there is more than one
> valvebody for these units,  I don't know if there is a difference in
> pressures or variations that might explain this ?  I know there are a
> couple of holes different between VB's relating to lube supply ?
>
>    Steve
>
> On Tue, Dec 16, 2025 at 2:48 PM Donald Day <trnsmaster at verizon.net> wrote:
>
> If bell is porous clean good then coat with epoxy
>
>
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> On Tuesday, December 16, 2025, 10:24 AM, Steve Everett via trnw2 <
> trnw2 at trnw.net> wrote:
>
>   I have an 09 Jetta with a O9G , originally built at another shop, 2
> months after being built it had a small leak from inside the bellhousing,
> small enough that sitting running after 5 minutes there will be one drop at
> the inspection hole at the bottom of the bellhousing,  when you look up
> inside that hole the fluid seems to be seeping from the right side up
> inside the bell,  we pulled the unit, and fluid appeared to be coming from
> around the uppermost bolt on the right side,  (red dot in picture
> attached)  I removed the bellhousing, cleaned everything, resealed the bell
> and used silicone on all the bolts,  reinstalled unit and still had the
> leak,  pulled again,  this time I thought maybe the case was porous in the
> are above and to the left of the bolt, as fluid appeared to be in that
> area,  I cleaned everything with brake clean, coated that area with JB
> weld, resealed the same bolt again, installed a different converter,,,
> installed unit,    same leak again,
>        took a week or so for us to find another unit,  removed bellhousing
> from core unit, cleaned and resealed everything related to the different
> bellhousing,   reinstalled,   still have same leak,
>
>   Different bellhousing, changed attaching bolts the last time around,
> using ultra grey silicone to seal everything,  plenty of silicone on all
> the bolts, changed converters once, ( fluid is not all over inside of
> bellhousing , only on right side, so I don't believe its converter related)
>
>   only explanation would be two different bellhousing being porous in same
> area ?    in the picture attached the fluid originates in the area where
> the red dot is
>
>  Anyone ever seen something like this ?
>
>    Steve
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>
>
> --
> Pat Schulte
> AAMCO Transmissions
> Temecula, Ca.
>
>
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