Miata thrust bearing failure analysis

Me talking about my recent thrust bearing failure on the 1.6L Miata engine rebuild.
My video detailing the "soft clutch" symptoms I felt: • Miata clutch pedal som...
Article about 99' Miata thrust bearing failures: www.miata.net/...

[@gavintaylor6528]

crank might be chewing them out may be a spot there its waring on by the looks plus you mentioned spun bearing on block so could be a issue there

[@1Cobranut]

This is a long-time known issue with Miata motors. They had a huge recall for them, but the issue was never fully solved.
Are you starting your engine with the clutch depressed?
That's putting a lot of load on the thrust bearing when it has no oil pressure.
I always bypass the clutch switch on all my cars, and never start with the clutch depressed.
Also, a high performance clutch will put more stress on that bearing.

[@DanielHankewycz]

@@1Cobranut thanks for the comment. I've heard the recall issues on the 99 Miata motor. Never heard of issues on my year.
As for the clutch switch thing, I started my Miata with the clutch switch and never had issues until this rebuild (had the car for 8 years before this). After this experience though, I will be bypassing the switch knowing now what can happen with the extra load + no oil pressure.

[@dan88rx7turbo22]

Um with the clutch pressed in meaning clutch is disengaged that puts pressure on the Throw Out Bearing , he’s talking about the thrust bearings on the crankshaft , if anything having trans disengaged from engine flywheel would put less stress on anything having to do with the engine

[@DanielHankewycz]

@dan88rx7turbo22 no, he is correct. The throw out bearing is pushing on the clutch assembly (really pressure plate) which is attached to the crankshaft. Therefore it is putting thrust load on the crankshaft too while the clutch pedal is depressed.

[@rubbersoul3723]

Bro! That's weird as f*ck!

[@martygt3357]

Trying to rebuild on a budget is the main problem you have here is my guess. Source a junkyard block, 2 junkyard cranks, and a bunch of good new parts and do it yourself. And now you do not know what caused the failure. The answer is not BUYING A CRATE MOTOR from some rebuilder either. Better to trust a race shop rebuilder with a slew of CNC and lathes. to check everything. I had a friend who rebuilt/freshened his race motor himself to save money and learn a little. He quit doing it because the expert motors made a little more power and lasted longer.