[TR] Spin on Oil Filter Leak

Jim Henningsen trguy75 at gmail.com
Sat Aug 23 07:47:22 MDT 2014

Mike and others.  Thanks for the replies.  I am going to drain the oil today
and recheck and test as described.  I did remove old seal from block.  Jim

Sent from my iPad

On Aug 23, 2014, at 5:18 AM, "Mike Porter" <mdporter at dfn.com> wrote:

> Here is my question.  I have a spin on oil filter unit and put in a new
> rubber seal before mounting to block.  I am getting a pretty good leak
> between the block and adapter seal.  I tightened a bit more but still
> leaking.  Is there a trick to getting this unit to not leak.  I had it on
> previous motor without a leak.  Do I need some sealant?
>> The adapters are made uniformly, but the block lands were not.  The depth
of the land was not critical to get the original filter canister to seal, so
the factory was not all that concerned about machining the land depth the same
from block to block. So, there are actually two points on the adapter that
need to seal properly--the inside land (on which a small-diameter
thick-section o-ring rides), and the outer land in which the large diameter
square o-ring is fitted.  The inner o-ring prevents oil from recirculating
through the bypass orifice.  If that leaks, the oil doesn't go through the
filter. The outer square o-ring prevents oil escaping to the outside of the
> If the inner land on the adapter stands too tall, the outer ring on the
adapter won't put enough pressure on the square o-ring to get a seal, and
further tightening of the center bolt can split the inner o-ring, or distort
it to the point that it leaks, too (although that leakage is not visible). The
only right way to stop the leakage is to match the adapter to the block.  If
the outer ring is too tall for the block, the inner o-ring does not seal.  If
the inner land on the adapter to is too tall, the inner o-ring seals, but the
outer one does not. Typically, the instructions for most adapters recommend
fitting the outer square o-ring, putting some modeling clay where the inner
o-ring sits on the adapter and then trial-fitting the adapter with the center
bolt fairly snug. If there's little or no clay left on the inner land (has
been squeezed out or squeezed very thin), the inner land is too tall and must
be machined down a bit, then another trial fitting to make sure there's
adequate compression of the outer seal and enough room for the inner o-ring to
be compressed adequately, but not so much that it's damaged.
> Sounds tedious, but it's really only an extra half-hour or so with the right
tools.  It's not the fault of the adapter manufacturer.  Given the way the
blocks were machined, there would have to be an infinite number of adapters to
fit all the variations, which isn't practical.  Sometimes, if the outer land
on the block is really deep, one can get away with using two square o-rings,
but my experience is that such an arrangement never quite seals completely.
Best to just bite the bullet and match the adapter to the block and be done
with it.
> Cheers.

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