Crankshaft Seal Conversion
Macy's Garage, Ltd.
We know all the jokes about
British cars and oil leaks, and we laugh it off as part of the charm. It's
supposed to be part of the factory rust prevention system, (obviously designed
in part by Lucas, because it didn't always work!), and there's nothing you can
do about it because they all leak.
Well maybe we can't stop it
completely, but we can seal the worst of the offenders. I'm referring to
the rear crankshaft "seal", or that pitiful excuse for one that came in our 4
Times have certainly changed from when our
charming little Triumphs were first designed. Oil was cheap and paved
driveways were rare, and if you were fortunate enough to have a carriage house
or shed to park your TR under roof, chances were that it had a dirt floor rather
than something concrete or painted with a high gloss coating. Oil leaks
were nothing to get all worked up about as long as you didn't empty the sump on
the short drive to the store! Take a look at the TR3 owner's handbook, and
you'll see that checking the oil level and "topping up" were recommended every
250 miles! Today, our TR's are pampered and kept clean, parked on concrete
driveways and fancy garage floors, and the oil leaks which were once accepted as
routine are now a much larger annoyance, and something must be done about it!
The hardest leak to stop, and probably the
biggest offender of the lot is the rear crankshaft "seal". It's not really
a seal at all, but a series of grooves in both the crankshaft and the seal
assembly, and it's supposed to guide the oil back into the sump through the
rotation of the crankshaft. The seal assembly doesn't touch the
crankshaft, so there's really no sealing action taking place, and once the
engine is stopped and the crankshaft is no longer spinning, the oil is free to
run right out the back and start marking its' territory! Some oil is
expected to get through even when the engine is running, and a drain tube is
provided behind the seal to provide a return path back to the sump.
Thankfully, a rear seal conversion kit has
been designed which will seal this problem spot with a modern neoprene seal, but
it requires the crankshaft to be removed from the engine block and some
precision work to be done by a competent machinist. It's a modification
that I highly recommend doing whenever your engine is apart for an overhaul or
whenever you have an opportunity to remove the crankshaft.
The following photos will demonstrate the
installation of these seal conversion kits, and it's not as scary as it sounds.
Follow along as we solve possibly the largest and most difficult of the TR oil
leaks, but don't worry that your TR will lose any of it's charm. There are
still plenty of places left for it to leak oil!
|Here you see the rear of a TR3 crankshaft, and the oil
"scroll" at the rear that must be removed by a machinist. You can see
the grooves in both the scroll and the original seal, which are supposed to
direct the oil back into the pan.
||In this photo, you can see that the scroll has been machined
off of the crankshaft to the dimensions supplied with the conversion kit.
Also note the new seal conversion kit, which resembles the original but is
designed to hold the modern neoprene seal in contact with the crank.
|In this photo, we see the rear main bearing cap, and the
original drain tube for the oil to run back into the sump. The Moss kit calls for two additional holes to be drilled in the cap to
relieve pressure against the seal, and to provide additional oil return
||I always drill these holes myself using a drill press, and
blocking the cap so that my drill bit is parallel to the original drain
tube. I like to start with a small drill bit and increase the size in
a couple of steps. Don't try this with a hand held drill!
|Here's the rear main cap with the two additional holes
complete. The instructions called for 3/8" holes, but that's a lot of
metal to remove so I always stop at 5/16". The kits we now use do
not call for these holes. (See note #1 below.)
||I always use a Dremel grinder and small stone to remove all
the burrs and flashing around the inside of the holes, as shown on the
center and right holes of this photo.
|After lightly filing any burrs or rough edges of the new
seal holder, apply gasket sealer to the areas indicated in the kit
instructions. I like to use non-hardening Permatex #2 here. This
is not a place to use silicone!
||With the seal holders prepped, install the neoprene seal
around the rear crankshaft journal. Apply a little light oil to the
seal and the crankshaft for lubrication, and be sure that the deep channel
in the seal points toward the front of the crankshaft as shown. The
split in the seal will be positioned later to be "UP" toward the top of the
|A small spring is installed into the deep channel seen in
the previous photo. The two ends of the spring have small hooks to
join the ends, and the spring will hold the seal against the crankshaft as
it eventually wears.
||With the main bearing shells in place, and the upper half of
the seal holder bolted loosely to the block, gently install the crankshaft
into the block. Carefully guide the seal into the seal holder, and be
sure to have the split in the seal pointing to the top of the motor (which
is down toward the floor with the block upside-down on the engine stand).
|These grooves along both sides of the rear main bearing cap
are a good place for oil to seep through, and need to be tightly sealed.
When bolting the lower half of the seal holder to the bearing cap, note that
one bolt hole on each side extends into the grooves. I leave these two
bolts loose for now, to be certain that I can press the felt seals all the
way to the bottom.
||Gasket sets usually come with only one piece of this rear
cap seal. Buy a second because one will not be enough to totally seal
these grooves. Cut both pieces into little pieces about 1" in length.
The seal conversion is complete! You've just taken a giant step toward
dispelling the British Car's reputation for leaking oil! This really
is something you'll want to do if you ever have the chance, and the
environment and your garage floor will thank you for it!
With the rear main cap torqued in place, I dip the small cap
seal pieces in Aviation Permatex an push them to the bottom of the grooves
with a long thin screwdriver. Pack the pieces in tightly one after
another until the entire groove is completely filled. Note the loose
bolt below the tweezers in this photo. This is the one that I left
loose until after the groove has been filled with the seal pieces.
Don't forget to tap the two seal holders together and tighten all the bolts
when you're done.
We're now using seal
conversion kits exclusively from Revington TR in the UK after difficulties
with a couple of kits from USA suppliers. You'll have to order these
from England if you want to be assured of using the best possible parts.
We have recently
discovered (the hard way) that the new aluminum seal holders are slightly
thicker than the original scroll seal. Normally this isn't a problem,
but we did have one instance where the flywheel bolts had stretched
slightly, and they extended fully through the rear of the crankshaft hub and
dug into the seal holder, just enough to keep the engine from turning over.
Either use new flywheel bolts or try to rotate your crankshaft immediately
after installing the flywheel to check this!