distorted crankshaft pulley

Archives of Posts to the NZ MX5 List back in 2003

distorted crankshaft pulley

Post by daca.robinson » Mon Nov 24, 2003 2:37 pm

I have a 91 model and recently had repairs to the pulley or something on the crankshaft( the key was slogged out), but i have noticed the seems to be out of centre when the engine is at idle.
it looks like the pully has 4 smaller bolts i assume this splits the pulleys do they have to be match or i is self aligning. can anyone give me advise before i take it back to the workshop
Dave Robinson...

lou Girardin

distorted crankshaft pulley

Post by lou Girardin » Mon Nov 24, 2003 3:35 pm

It sounds like the pulley is misaligned after the repair. Take it back, it'll
eventually fail if left like that.


distorted crankshaft pulley

Post by daca.robinson » Mon Nov 24, 2003 3:41 pm

Thanks Lou.


Shane Petterd

distorted crankshaft pulley

Post by Shane Petterd » Tue Nov 25, 2003 8:27 am

Hi Dave.

I really feel that you should investigate this problem, I would suggest a
chat with your local Mazda Service Manager. Historically there has been a
problem with broken crankshafts on early MX-5's. The problem usually with
1990 and early 1991 models. The fault is related to the crankshaft front
key and pulley bolt.

Failures are often caused by the removal of the pulley bolt and camshaft
sprocket to allow front crankshaft seal replacement. Failure to correctly
torque the pulley bolt, misalignment of the pulley or over-tightening of the
pulley bolt, which when over-stretched can result in a lose pulley. All
will cause wear to the keyway and the resultant loose pulley. A loose
pulley imbalance can lead to a broken crankshaft.

I would suggest a quick read of the all the literature on
http://www.miata.net/garage/ in the Engine Section before this turns in to a
very costly repair.

Hope this helps.

Shane Petterd


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