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-   -   Wobble on the Crank Pulley (https://www.miataturbo.net/general-miata-chat-9/wobble-crank-pulley-34882/)

skidude 05-08-2009 11:11 AM

Wobble on the Crank Pulley
 
I've got a '94 1.8, and I noticed yesterday that the crank pulley is wobbling. 160k miles, boosted for about 15k

If I had an early 1.6, I would be looking for a new engine already, but what does this mean on the 1.8s? Do I just need a new pulley, or is it more serious? It doesn't look like the bolt in the middle is wobbling, but it is hard to tell since it's not round. Both the inside and outside parts of the pulley look to be wobbling though.

Also, I have to drive about 200 miles this weekend, is it going to be safe for that or do I need to find some other way to get where I'm going?

supra441979 05-08-2009 11:21 AM

Who did the timing belt last? If you did it, then did you torque the crank bolt? If it's wobbling, then the crank key way is probably damaged. Check if the crank bolt is loose and check back.

Joe Perez 05-08-2009 11:23 AM


Originally Posted by skidude108 (Post 406129)
but what does this mean on the 1.8s?

It means you need to take the pulley off and inspect the crankshaft, pulley, key, etc for damage. This issue is not limited to just the shortnose 1.6, it can happen to any car when the pulley is not properly secured.

At best, you'll find that the damage is minimal and that you can simply fit a new key and use a new crankshaft bolt to re-assemble the engine.




Also, I have to drive about 200 miles this weekend, is it going to be safe for that or do I need to find some other way to get where I'm going?
I wouldn't drive to the grocery store with a wobbling crank pulley, much less 200 miles.

skidude 05-08-2009 11:50 AM

A local shop did the timing belt last, about 50k miles ago. I did the water pump about 10k miles later, but I didn't remove the crank bolt, just the other little ones that hold the pulley on. (I couldn't get the crank bolt off)

so at best I just need a new crank bolt, and at worst I need a new crank?

Joe Perez 05-08-2009 11:56 AM


Originally Posted by skidude108 (Post 406150)
so at best I just need a new crank bolt, and at worst I need a new crank?

I'd add a new woodruff key and possibly a tube of Loctite 660 "Quick Metal" to the best-case list, but essentially that's it. I've only ever come across pulley wobble once in person, and in that situation, the crank was slightly dinged up however it was able to be re-assmbled with a new bolt & key, did not require the Loctite, and so far as I know is still running strong.

When it comes time to re-assemble, just make sure you've got a good torque wrench capable of accurately measuring in the ~ 125 ft/lb range. It's usually not necessary to use the special service tool to lock the crank, just put the transmission into 5'th gear and set the parking brake hard.

If it does turn out that the crank is damaged beyond repair, you'll probably find it both easier and cheaper to simply buy a used engine and drop it in, as opposed to doing a rebuild. Your old engine would have some residual value as a core for someone doing a full build.

Vashthestampede 05-08-2009 12:18 PM


Originally Posted by supra441979 (Post 406137)
Who did the timing belt last? If you did it, then did you torque the crank bolt? If it's wobbling, then the crank key way is probably damaged. Check if the crank bolt is loose and check back.

+1

Did you check the bolt?

I definitely wouldn't take it on a trip. If you have a local dealership the parts are probably around $10. I would get on it asap.

hustler 05-08-2009 12:52 PM

a little safety wire goes a long way.

SamS 05-08-2009 12:57 PM

Did you check the 4 bolts that actually hold the pulley on? I had 3 of them shear a couple years ago, probably over-tightened the little 6mm bolts. Everything was fine for me after I installed 4 new grade 10.9 bolts properly torqued.

skidude 05-08-2009 01:14 PM

I haven't checked anything at all yet, I just noticed this last night and am in the process of graduating college(tomorrow), moving apartments(Sunday), and it's very stressful. On top of all that, I have all of $13 in the bank, so I'm sort of at a loss for what to do. Luckily I have access to a loaner in the form of dad's old 911 that I can use for a bit while I get this thing back on the road.

Joe Perez 05-08-2009 01:21 PM


Originally Posted by skidude108 (Post 406205)
I have access to a loaner in the form of dad's old 911 that I can use for a bit while I get this thing back on the road.

Wow, you have such a hard life.

Endat 05-08-2009 01:35 PM

I'm repairing the crank in my 90 tomorrow or sunday.. there's no wobble but it's experiencing the same timing retard under 4k rpm... if you lived closer I would show you how to do it.

Joe is right about the Loctite 660 and a new key.. should work nicely, it got my last miata working again at 142k and running strong until it was parted out at 180k

Vashthestampede 05-08-2009 01:37 PM

Shit.....in that case rock the 911 for a bit to celebrate graduating. Its not a hard fix to swap in a new key and bolt, just takes some time.

Congrats and goodluck with the crank.

yertnamreg1218 05-08-2009 01:44 PM


Originally Posted by skidude108 (Post 406205)
I haven't checked anything at all yet, I just noticed this last night and am in the process of graduating college(tomorrow), moving apartments(Sunday), and it's very stressful. On top of all that, I have all of $13 in the bank, so I'm sort of at a loss for what to do. Luckily I have access to a loaner in the form of dad's old 911 that I can use for a bit while I get this thing back on the road.

This reminds me of myself, except my bank account is <0 (god damn rent!!!), my pulley is fine, and my dad doesn't have a 911.

Congrats on finishing school! I know mine has been a bitch and a half to get through.

skidude 05-08-2009 01:52 PM

Thanks, I know the 911 is a pretty sweet deal. not quite as fast as mine, but it's a porsche so it's still a blast.

Sounds like the odds are in my favor for it being just a bolt and locktite fix. Is there somewhere to find a write-up on this fix, and what parts to buy? I've never heard of this problem except on the early 1.6s and I've never paid much attention because I have a 1.8.

hornetball 05-08-2009 04:03 PM

Excellent write-up at Untitled Document. It covers the early 1.6. Your configuration will be different, but the article will give you a general idea of what you're in for (did you say you did your own water pump? -- if so, you've already done 90% of what's required). I have a '90 and did the fix at 150,000 (15,000 miles ago). It's been bullet-proof. I'm driving 100 miles a day with engine RPMs continuously above 4K. It's a happy Miata.

Relax and enjoy your accomplishment. I'd say the chances that there is anything seriously wrong or unrepairable are negligible. But, use your Dad's Porche in the meantime.

Joe Perez 05-08-2009 04:13 PM


Originally Posted by skidude108 (Post 406228)
Thanks, I know the 911 is a pretty sweet deal. not quite as fast as mine, but it's a porsche so it's still a blast.

What year is the 911? I've driven some of early 80s vintage, and they're certainly a workout.


Is there somewhere to find a write-up on this fix, and what parts to buy?
Writeup:

1: Remove crank pulley, timing belt, etc.
2: Inspect condition of crankshaft, taking note of damage to flat end as well as keyway.
3: Re-assemble using new woodruff key and main bolt, applying Loctite 660 to keyway if necessary.

Parts to buy:

1: Woodruff key
2: Crank bolt
3: Loctite 660 (if needed)

skidude 05-11-2009 05:06 PM

The 911 is a 1987. It's not too bad of a workout, the steering is pretty light for a no-ps setup. The clutch is a little brutal, but nothing a little practice can't take care of.
I know my turbo project was a success because I keep driving this car around thinking "where's all the power??"

As far as the crank wobble is concerned, I just had a chance to open the hood, and 3 of the 4 bolts holding on the pulley are gone. Looks like I didn't torque them down very well when I did the WP. Anybody know the size I need to buy?

Braineack 05-11-2009 05:10 PM

m8 or m6 cant remember.


my wobble was the pulley itself was all warped, replaced the one off my spare motor and life was good again.

SamS 05-11-2009 05:52 PM

M6x1.00, 99% sure. 15mm long maybe? Use some loctite and don't overtorque them or they'll shear like mine did.

Vashthestampede 05-11-2009 06:06 PM

3 out of 4 gone!


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