Possible keyway repair or not - what ya think??

[gslender]

Hi,

I came back from a long drive up Mt Tambourine in my lovely 1991 LE, and only when I pulled up did I hear this tack-tack noise.

Upon further investigation the crank pulley was moving around a lot!

After taking the main pulley and exposing the cam drive pulley, I saw something I didn't want to see... on a long nose engine too!



And then finally, I now see why the key broke off... it was a worn keyway, but mainly on one side.



So, repairable or bin it?

G

[sailaholic]

Probably cost more to repair then a compete used engine.

Sent from my GT-I9100 using Tapatalk 2

[gslender]

Probably cost more to repair then a compete used engine.

What are you buying used 1.6 engines in good condition? and where/who from ??

G

[manga_blue]

If the rest of the motor is good and it's only the key way that's damaged then I'd say the key repair is worth a try.

If the nose of the shaft is worn or damaged to the point that a new timing belt pulley won't fit perfectly straight and very snug then I'd bin it.

[gslender]

If the nose of the shaft is worn or damaged to the point that a new timing belt pulley won't fit perfectly straight and very snug then I'd bin it.

Existing timing belt pulley looks ok. It looks like the last part of the keyway is mostly worn/widened.

Are you recommending a new pulley and plate? I guess that's a good insurance to reduce the amount of play amongst the parts that are likely to contribute to movement etc.

Also, how would you repair it - some GB Weld to ensure there is minimal key movement, and then loctite to ensure it all stays tight?

G

[manga_blue]

New pulley, new key and new centre bolt is standard practice - pretty much essential in fact.

Sorry to point someone to google but in this case it's the best option .... what you'll get from my link is about 5 different approaches to the same problem. Read all the Loktite and long nose repair pages and condense your approach from all of them.

http://www.google.com.au/#hl=en&rlz=1C2GGGE_enAU454AU459&sclient=psy-ab&q=pulley+repair+site:miata.net&oq=pulley+repair+site:miata.net&gs_l=hp.12...2826.10282.0.14402.28.27.0.1.1.4.568.8428.2-16j5j3j3.27.0.les%3B..0.0...1c.1.6.psy-ab.-4JxwhxvMSY&pbx=1&bav=on.2,or.r_qf.&bvm=bv.43828540,d.dGY&fp=c4123f922dd4a43&biw=1308&bih=683

[NMX516]

I had the same problem in my previous 5, but caught it sooner than it looks like you have. The only proper solution (everything else is a compromise) is a new crank. I got a good used crank for a lot less than the cost of a new one from Mazda - approx $1500.

You could get a used NA6 engine, or NA8 or NB8 too for that matter, for a lot less than the cost of a rebuild/new crank. MX5 Plus sell used engines.

[NitroDann]

Compromise in what, if you are going to junk an engine why not try to fix it for 50 bucks first?

Dann

[gslender]

New pulley, new key and new centre bolt is standard practice - pretty much essential in fact.

Sorry to point someone to google but in this case it's the best option .... what you'll get from my link is about 5 different approaches to the same problem. Read all the Loktite and long nose repair pages and condense your approach from all of them.

http://www.google.com.au/#hl=en&rlz=1C2GGGE_enAU454AU459&sclient=psy-ab&q=pulley+repair+site:miata.net&oq=pulley+repair+site:miata.net&gs_l=hp.12...2826.10282.0.14402.28.27.0.1.1.4.568.8428.2-16j5j3j3.27.0.les%3B..0.0...1c.1.6.psy-ab.-4JxwhxvMSY&pbx=1&bav=on.2,or.r_qf.&bvm=bv.43828540,d.dGY&fp=c4123f922dd4a43&biw=1308&bih=683

Thanks for that.... this has given me hope and I'll let you know and probably update my blog with the process for others to find on the interweb.... my wear isn't any wear as bad as those in that miata.net guides... so I have hope it will be ok!

[NitroDann]

Honestly, get the stud lock locktite or equivalent and a new key, put the key in and the pulley on with locktite and locktite the bolt in.

The pulley will never come loose again without HUGE force. Been here done this.

Dann

[gslender]

Did the key way loctite repair and all seems fine. Actually, its a little zippier which may have meant it was worn and retarding the cam timing for a while.

Will post back again if any issues appear, but my advice would be to give it a go. Much, much simpler than an engine replacement!

G

[bruce]

That is a good result!