crank-nose repair brace?

[simple]

My poor wee car has suffered the dreaded early-MX5
crank-nose failure. Fletcher & I are going to give it the
tender loving loctite-fix next weekend (well, I'll be tender
with the car, Fletch will be tender & loving with his
tools).

Part of the fix involves using a brace/jig to hold things in
place while the loctite sets overnight - has anyone in
Auckland made one of these jigs and could lend it to us? If
not, I'll just make my own, but it's not the sort of thing
which gets used much after doing the repair (maybe useful as
a paperweight).


For people who are interested, details of the repair procedure are here:
http://www.miata.net/garage/hsue/LoctiteCrank1.html

Plans for the jig are here:
http://www.miata.net/garage/hsue/Techtool.htm

Info about the crank-nose problem is here:
http://miata.net/garage/crankshaft.html


One semi-useful thing I have discovered so far is that a
good place to buy loctite is at bearing places (like SKF
Bearings) - they stock the specialist grades of loctite as
well as the common stuff - no problem getting the 243 and
660 loctites, as well as a primer to help with setting.


thanks,
Karl.

[poison]

I keep hearing about this, but how can you tell if there is a problem (I have
an 89 model).

Gazza
"PO1SON"

[Tiddy Family]

a wobbly front pulley isnt neccesarily a crank failure
mine was merely the rubber packing between the pulley sections giving up the
ghost
new pulley cost around $250 from mazda, second hand one about $80 from mx5
mart
h

[patrick malone]

--- Gazza wrote:

I keep hearing about this, but how can you tell if
there is a problem (I have an 89 model).

from what l have read its the early 89-90 models

they redseigned the crank to make it longer.

mine is 90 model . l dont think it affects all cars

and alot is to do with when u get the cam belt changed
that the bolts on the pullie ar tightned to the
correct
toque settings .

but apprenty the 89-90 models are the most popular
l think might rev a little quicker with the lighter
crank.

so not all bad news . l think long u get the cam blet
changed to service limits and get done by compentent
mechianic it should be fine

hope this helps , slso your find info on the internet
do a search on this subject line

hope this helps

[simple]

Gazza said:

I keep hearing about this, but how can you tell if there

is a

problem (I have an 89 model).

The single most informative article I've seen on the subject
is this: http://miata.net/garage/crankshaft.html (note that
the VIN numbers they refer to are not applicable to the cars
in NZ)


The first tangible thing I noticed was that the fuel economy
turned to crap about 184,000 - 185,000km. Also somewhere
around this time I drove another car (a very rare experience
for me) and noticed that it seemed to have more pull at low
revs. At the time I largely put it down to that car being
an ordinary old Corolla which is a lower-revving engine, but
I also started getting paranoid (about the car - other
paranoias remained nominally stable).

About 185,300km I moved into new housesitting - a place with
a steep driveway which the car couldn't manage when cold.
Was fine when hot, so I assumed it was something to do with
being cold or damp, and started looking into those sorts of
things. At various times I checked these things:

- checked ECU error codes (were all clear)
- removed & tested the air-valve from the ISC (seemed
possibly faulty, but turned out to be fine once I was able
to compare it with a good one)
- used some injector cleaner
- checked spark-plug leads connected OK
- checked for oil/water in the sparkplug wells (found a
little residual oil - cleaning it out didn't help).
- checked voltages at assorted ECU inputs (all nominal)
- checked sparkplugs & spark timing

For a while, upon leaving work late in the cold of night
(10pm), the car would be gutless and then die at the end of
the first straight - the first time I put my foot on the
clutch. Revs would drop to about 700, stumble briefly, then
die altogether. Attempting to restart resulted in fierce
cranking (new battery recently) but no signs of life for
about 10s or so. Then it would barely start & stumble into
life. Keeping revs up prevented further problems. Once it
was warm everything was apparently normal (apart from being
a little low on power). This behaviour has now stopped, for
no reason obvious to me. Still gutless when cold, but no
stumbles. Stone-cold start has always been fine - it starts
straight away.

We eventually got around to the definitive test one evening
(186,700km) when I was visiting Fletcher - he took the
sparkplugs out, stuck the dipstick in cylinder #1, rotated
the crank until the dipstick was highest (ie. at Top Dead
Centre), and observed that the TDC mark on the pulley was
far from where it should have been. We also found at this
point that the crank-nose bolt was loose. Thus it was
concluded that I have the dreaded crank-nose failure.

Since then (2.5wks ago) I've been assembling the parts
required to do the loctite repair. I've got the 2 different
sorts of loctite specified, as well as a primer to aid in
quick setting of the loctite 660 (but not to be used on the
loctite 243 since it degrades the strength of that one).
Tomorrow I get the replacement pulley, crank-nose bolt, and
woodruff key from Mazda. Also getting new crankshaft front
oil seal and camshaft oil seals, since they're easy to
replace while we're in there. Parts cost from Mazda is
about $100 incl GST, while the loctites and primer came to
about $50.

We're planning to do the repair this Saturday, leaving it
overnight for the loctite to set before reattaching belts
etc. I'm then going to give it a further day before I start
the engine, since the loctite curing takes longer in cooler
weather.

My fuel economy is currently about 20% worse than it used to
be. I've had to re-tighten the bolt again once since doing
the TDC test (that was only 300km ago) - not certain that it
was loose - difficult to tell when the crank is only being
held still by handbrake + 5th gear, but it seemed like the
bolt moved. Fortunately, the wheel-nut lug wrench fits the
crank-nose bolt, so it's not too inconvenient to tighten the
bolt. I'm avoiding using the car where possible, until
fixed. The pulley doesn't wobble as far as I can tell.

We've decided not to use the re-assembly jig described along
with the loctite fix, since it appears not to do anything
constructive. As far as I can see, it risks holding the
pulley in place while the crankshaft gets twisted (by the
bolt) - this is twisting the pulley in the 'unfavourable'
direction and potentially worsens the alignment. Without
the brace, the pulley gets twisted in the 'favourable'
direction if anything. If anyone has constructive views on
this and can offer a good explanation of how the brace can
help then I'd be interested to hear it - I'm just an
electronics engineer - nothing at all like a mechanic



tiddy@maxnet.co.nz said this:

a wobbly front pulley isnt neccesarily a crank failure
mine was merely the rubber packing between the pulley sections giving up
the ghost
new pulley cost around $250 from mazda, second hand one about $80 from
mx5 mart

I assume this is a later design revision from what I have -
mine has no rubber packing between pulley sections that I'm
aware of. The price I have been quoted for the pulley for
my car is $30 incl GST (which sounds very cheap for a Mazda
part) - I'll find out tomorrow whether they're selling me
the right item...


Karl.

[simple]

Just in case anyone cares, there were a couple of other things I
forgot to mention regarding the crank-nose failure...

Since having the loss of power, I've also gained a bit of backfiring.
Whilst I recognise this as a symptom of the bad things in my engine,
I do quite enjoy the odd little backfire sometimes

There is also a strange surging feeling when driving on the motorway,
at nominally constant revs (100kph or so, 4th or 5th gear) - it's
subtle, but there's some sort of variation going on which never used
to happen.

When cold, the sound of the engine reminds me of an old VW.


(note: I have a history of imagining 'extra' anomalies in my car when
something is not going right - the only thing you can really trust
about my observations is that the engine is gutless when cold and/or
low revs)


Today I visited North Shore Mazda and bought the new pulley, bolt,
oil seals, and woodruff key. Price with club discount was $92.77
(without discount was about $102). Part numbers as specified in the
loctite-fix docs
(http://www.miata.net/garage/hsue/LoctiteCrank1.html) are correct,
even though the salesperson reckoned that the American part numbers
would be meaningless here. Not all parts were immediately available
from stock at North Shore, but they had them the day after ordering.

Prices: ($NZ, excl GST, incl discount)

$16.74 "BOLT LOCK CSHAFT"
$6.65 "KEY, WOODRUFF"
$16.60 "SEAL, OIL" (front crankshaft oilseal)
$16.20 "SEAL, OIL" (camshaft oilseals, $8.10 each)
$26.28 "PULLEY, TIMING BELT"

My guess is that the pulley is so cheap because Mazda feels guilty
about their crap crank-nose design... but I have been known to leap
to baseless conclusions before


If you've got this far in reading, then you may care that the repair
could be postponed from this weekend, due to technical difficulties
with my Chief Engineer's health


Karl.

[Mikkels]

Karl

Good luck. Are you in Auckland? Do you mind if I came
around for a look? I have put a 1.8 in my 1990 and have
checked out a few crank nose problems.

Email me if you are OK for some extra advice/assistance.

Don
[...]

[David & Judy Kerr]

Now you have got every MX-5 owner paranoid!
Don't forget that this happened to a small % of cars only. If you have had
your cam belt changed take your car into your favourite mechanic and have
him check that it has been torqued up correctly. Good piece of mind for
$20.00.

Dave.

[simple]

Dave said:

Now you have got every MX-5 owner paranoid!

Not me - paranoia is provided by the paranoiac. I've just described
my experience of my car, and provided links to more information for
those who feel it is worth investigating.

Don't forget that this happened to a small % of cars only.

Good point - according to the article I referenced, about 1% are
affected, and it is known only to occur with 1990 and early 1991 cars
(after that they changed the design). I (in my paranoid/unqualified
opinion) think that as the cars get older, that percentage/risk will
rise enough to be worth doing something about it.

If you have had your cam belt changed take your car into your
favourite mechanic and have him check that it has been torqued up
correctly. Good piece of mind for $20.00.

Bearing in mind that I'm not a mechanic, and therefore my opinion is
even more highly suspect (at least I'm not trying to make money out
of you), I suggest that this is an incomplete plan.

If you're going to bother touching the bolt at all, it is apparently
possible to remove the bolt & check the state of the woodruff key
without doing anything much more difficult than removing the bolt
(removing the plastic tube carrying air from the filter to the
throttle body will make things easier to work on). Whilst we didn't
bother taking the bolt out (since we'd already found it was loose),
Fletcher & I got this far in under 10 minutes, parked on the road
outside his house under a streetlight - it's pretty easy.

Having removed the bolt, it is apparently possible to pull the key
out, and check its condition. Then you know if you have a problem or
not. The important thing now is to put in a new bolt (mine was
$16.74+GST, Mazda NZ part number B630-11406C, "BOLT LOCK CSHAFT")
since your old one has probably stretched during the last 150,000km
or so.

The bolt costs less than your mechanic, and I reckon it could all be
done in half an hour pretty easily. Do it even if you haven't
changed your cambelt, as the problem has been known to occur on some
cars where the bolt has never ever been messed with.


Doing a better job would involve loctiting the bolt in (Loctite 243,
$15.09+GST, from SKF NZ Ltd, in locations throughout NZ) and then
repeating the procedure with a new bolt every year. You're also
supposed to use a new woodruff key (mine was $6.65+GST, Mazda NZ part
number B630-11317A, "KEY, WOODRUFF"). If you're really going to be
thorough, I reckon loctiting the pulley to the shaft can't be a bad
idea - the loctite is designed to be removable if need be, with hand
tools.


A lesser quality test (since it only shows anything *after* you've
already got the problem) is to check that TDC of cylinder #1 matches
the TDC mark on the pulley. Whilst I saw Fletcher do this, I can't
describe the markings on the pulley accurately enough to tell anyone
else exactly what they're looking for - I just know I saw a dot, and
Fletch said it wasn't in the right place


Having said all that, I deny everything but my own observations, and
I may change my mind about them too. I am offering no advice except
that you should read the information (eg.
http://miata.net/garage/crankshaft.html) and make your own decision.


Karl.