Shortnose crank problem help please!!

[ger]

Well, had a bit of a depressing evening of internet diagnosis.

I have been getting a rattling from the crankshaft alternator pulley for a while now, I thought it was water on the belt, when I sprayed wd40 on the belt it went away for a while but always came back.

Then yesterday I was setting the timing and noticed the pulley was wobbling and the timing mark on the pulley was moving back and forward slightly (bout 1 degree worth).

Is this a worn keyway on the crank?

Found these options if it is

Replace the crankshaft. A robust fix. Probably a $3000 bill comes with that.

Replace with a used engine. Also a robust fix . $600-2500, depending on who does the labour

Weld the crankshaft to repair the gap. Perhaps weld the gear in place. Some risk of failure. $ 100-700, depending on who does the labour.

Try the Loctite Fix described in this web site. Some risk of failure. $ 50-700, depending on who does the labour.
No one guarantees this Loctite Fix will work on your car. That's why there is a risk of wasting time and energy. If you are a do-it-yourselfer though, it may be worth your effort.

Anyone tried the welding or the loctite fix?

Should i try to re torque the crank bolt ( afraid of doing more damage if the keyway is damaged)

Here is the loctite fiz
http://www.miata.net/garage/hsue/crank/loctite_1.htm

Really appreciate some help for the more mechanically experienced members.

ger

[ger]

forgot to mention I have also had a gradual loss of power, slightly wobbly tick over (but not to bad).

Thought my timing had go out yesterday, the car just hasn't been pulling as hard recently, I was just about able to keep up with a 1.9 TDI on the m50, before he would have been getting smaller in my rear view mirror.

Set up is 1990 1.6 with greddy @ 6psi - Bipes - o2 clamp (190K Km on clock) what a pisser in the post FMIC & stainless cat back from moss. :

[leamyj]

Sorry to hear you're in a spot of bother Ger.
Just wondering if your problem is a result of having the engine turbo-charged or would this problem have arisen eitherway. Anyone??

John

[ger]

no this problem is with pre 91 cars, that have a short nose crank.
Its easy to identify.

I did the timing belt a while back with geese, but AFAIK we did not have to remove the crank bolt.

One of the causes is the crank bolt coming loose.

Thought i'd gotten away with it though as their is 120k on the clock.

[Geese]

Ger just tried to call you there. I guess you're worried about the crank.

We didn't touch the main crank pulley bolt since it's wasn't necessary.

Don't jump to the conclusion that the key is failing could be something else. A loss of power and rough idle could be a number of things. Could even be a slipped belt!

[NickD]

The short nose crank engine does have known problems and if your bottom pulley is wabling then it's a very good indicator. You can tell the engine as it only has 4 slots in the pulley / engine damper as the long nose have 8.
I'm not sure what afflicted the designers because the engagement of the pulley over the crank really is minimal.

It's my understanding that the loctite fix does work, provided it is not in too bad a state.

If you know about engines then it really is not a difficult thing to strip the parts off to get this done, the main thing being you generally do need a good long breaker bar to undo the crank bolt.

I don't know the actual clean up procedure for the crank, but I would have thought you are only looking at 4 hours labour tops plus coolant replacement

[Steve]

I'd go for the loctite fix, nothing to loose really... it seems to have worked for lots of people.. http://www.miata.net/garage/hsue/LoctiteCrank1.html

To undo the crank bolt, brace your socket wrench up against the body work like in the 2nd pic here : http://www.mx5ireland.com/gallery/tech_5.htm
Or stick some scaffold over it and wedge it against the ground, then put the car in neutral and "pop" the starter with the key to shock the bolt loose. Make sure everyone has stood clear first!

[ger]

Thanks for the advice.

The first thing i need to do later is torque the 4 bolts on the timing pulley,
gave them a pinch last night then started the car and the chattering from the belt is much less than before. I believe there is also a harmonic balancer somewhere, anyone know anything about this?

Just trying to eliminate the simpler stuff first.

I will meet up with geese later to give him a look.

[Steve]

Yeah, the balancer is "in" the pulley.

Good info here :
http://list.miata.net/pipermail/miata/2 ... 60573.html

[ger]

Thats interesting,

Anyone got a good secondhand pulley for sale?

Going to check the timing mark is correct with no1 at TDC.

ger

[ger]

Well, called up to geese last night and did a few runs with his gps and the power is well down 50-80 and 0-60 were abysmal.

Timing was out by 10-12 degrees when checked against TDC on cylinder 1

So when I thought I had 16 base I actually had 4-6 and then the bipes was pulling 8 degrees at boost.

We re torqued the crank bolt and the pulley stopped wobbling, timing advanced 10-12 degrees, took it for a spin home and the power was back, boost gauge reading 22 Hg at tick over.

Went out today and within 15 miles the crank pulley had slipped. Back to crappy running, wobbling pulley, 16Hg at tick over & loss of power.

Going to go for the loctite fix ordered the parts today, hoping for the best.

On the up side we did a compression test and all cylinders showed up well 160-166psi or 11-11.5 bar.

Hope i can save the bottom end.

Ger

[Steve]

so... is it the crank bolt thats backing out?

[ger]

I think the bolt may have stretched or come loose over time, but the fact that the pulley moved means that the keyway is probably damaged, hope its not to bad to be fixed.

Anybody trying to sell a good 1.6 low mileage engine, from a 91-93?
Will know if i need it by sat week.

Just covering the bases, i want to back on the road as soon as i can.

In the meantime i will fit the new SS exhust and work on mounting the IC.

And hope for the best


Ger

[Geese]

when the pulley was right what was she like on power? back to normal ?

Then as the bolt slipped she lost it all again?

[ger]

yeah, running really nice there for an hour or two.
nice tick over and smooth part throttle, didn't give it to much wellie though.
going to start dismantling this week in the evenings.

Need to make one of these to hold the crank in place.

http://www.miata.net/garage/hsue/LoctiteCrank2.html

Geese can you get me a bit of steel to do the job? or if its handy I could pay you to fab one for me, I don't have much spare time at the mo.

If you are free sat week I could do with a hand on the crank fix.
I will have all the stripping done by then and the crank nose exposed for inspection.

ger