Yes it was leaking on the non JB Weld side. Big mistake
using that high temp epoxy I bought. I should have asked
Mazdatrix what they used for p-ports and they would have
told me JB Weld as they did later.
OK it worked great. It is like working on someones teeth however.
You need a small inspection mirror and a small pencil flash light
that will lie in the bottom of the tube. I glued a small
section of 1/4 inch dowel about 3/16 long to a small wood tongue
depressor to apply the small gob of JB Weld to the leaking
area. The vac pump pulled in the JB Weld.
If you want belt and suspenders on
this Burns stainless has 321 SS 1.875" OD tubing with
a .035" wall. Cut the SS tubing just long enough to go
up to where trochoid wear surface starts but not beyond.
Coat it with a very thin layer of JB Weld and insert it into the
aluminum tube. I have some inquires out for even thinner
wall SS tube. On the order of .015" to .020". I think I will
do this with Marks engine.
Best to just pressurize these tubes to 50 psi before you assemble
the engine to check for pin hole leaks.
BTW one advantage of the P-port is you can visually inspect
the trochoid wear surface with a flashlight and a small inspection
mirror in the compression chamber area.
Paul Lamar
Well, one of my concerns over this approach is definitely longevity of
the repair. I have no doubt that the current leak is fixed by the
JBWeld sucked into the crack(s). I have more concern over what will
happen given future heating / cooling cycles.
One of the assumptions we've been operating under is that the first
failure was caused by residual water in the water jacket freezing over
winter, expanding the tension bolts, & failing one of the combustion
o-rings. Yet, on tear down we saw no evidence of this -- in fact I still
have all the original combustion o-rings & they are pristine. I submit
what actually happened is that the "bad" epoxy was coolant-soaked during
the dyno runs. This then froze, failing the epoxy in a big way such
that when I went to refill the engine with coolant, splish-splash it
ended up in a puddle on the floor.
So - given this scenario I worry about both the heat/cool cycles from
running the engine, as well as freeze/thaw cycles from the upcoming
winter. Because the existing repair technique can only fix fully failed
cracks (such that the vacuum can draw in JBWeld) there still seems to be
a big risk for future failures -- areas where the old epoxy has not
*yet* failed. The scenario above is still very much in play, and thus I
would expect future failures due to heating / cooling.
I suppose a sleeve inside the existing P Port could in some ways address
this. But this scenario counts on a very small (and perfect) ring of
JBWeld holding regardless of the leaks which may or may not develop
behind it. It also counts on the JBWeld to prevent the sleeve from
being ingested into the rotor - not a pretty thought!
Mark
That is a possible scenario.
Not to worry about the sleeve moving Mark. The sleeve is so long the
epoxy will keep it in place. Also there is no force applied
to the sleeve.
The next thing to do to ease every bodies mind on this subject
it to make a sample. Boil it in anti freeze solution and place it
in the freezer and do it repeatedly.
Many P-port engines have been built over the past 30 years with
different epoxies and different methods of installing the tubes.
I have never heard of a seal failure but then most people don't store
them in an unheated place with pure water in them either. I think
the guys at Mazdatrix would have mentioned it as well.
What ever you want to do. We will take the engine apart and
replace the white epoxy with JB Weld if you wish. I think
the thin SS sleeve is still a good idea as it is easy to do
unlike a press fit.
Paul Lamar ...No rotor no motor.
I ran across the following on the Tailwind list. Don't forget ZAP A
GAP. Personal testimonial to follow.
I know this doesn't have much to do with off road stuff but I thought
this might spark some ingenuity in some folks for future reference.
A few days ago I was flying my airplane back from Santa Maria to Rialto
when I encountered a slight inflight problem. As I was level at 9500' I
started to see little specks of something on the windshield that soon
became streaks of oil. As most can guess, oil on the windshield of an
airplane is NOT a good sign and usually generates a pucker factor that
exceeds the normal scale. A quick PAN call to SoCal controllers gave me
vectors to several nearby airports but the GPS said I was only 17
minutes from home so I elected to continue to Rialto based on the (flow
rate ;-) and landed safely.
After landing and pushing the airplane back into the hangar I removed
the cowling to try to find the source of the oil leak. I sprayed the
engine down with AVGAS and rolled it outside and ran the engine up to
try and see where the oil was coming from. Low and behold it was coming
from the centerline case seam near the back accessory cover. Now, for
those that are not familiar with a Lycoming O-360 engine it is almost
just like a Volkswagen engine. Flat pancake style four cylinger air
cooled motor.
On an aircraft engine like mine the case halves are sealed together with
a single silk thread between the case halves. This thread had apparently
broken and the only remedy was to split the case halves and reseal it.
Well, that costs about $12K with an overhaul and homey wasn't about to
part with that kind of money so I enlisted the help of a really good A&P
mechanic who said he could fix it for a lot less.
The end result was that we connected a vacuum pump to the engine and
plugged the breather line to generate a vacuum enviroment in the engine
case. This caused the the leaking case split line to leak from the
outside in. While it was sucking air we applied a small line of super
glue ( Zap-A Gap to be exact..) to the case split line and the vacuum
sucked it into the case halves sealing them. We then applied a thin film
of fuel tank sealer over it for good measure.
AND IT WORKED!!
Just goes to show that a little ingenuity and experience goes a long way
in solving a problem that is not as bad as you think it is.
Just thought I'd share that kind of a fix......
---------------------------------------------
I also have some goo (2 part urathane) that we use to repair horse's
hooves. It would stand up to the 50 psi pressure test.. Take my word for
it. Jerry
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