What will happen if the clutch release/throw out bearing fails?

Question

I drive a 1988 Mazda RX-7 non-turbo 5spd.

The previous owner claims the clutch was done last July(little under a year ago) and I have no reason to doubt such claims. I do believe the clutch release bearing was not installed correctly. When the clutch is not pushed in, there is a spaceship kind of noise(almost the noise a EV makes when accelerating). When I accelerate there is the same noise. However, when I put the clutch in the noise goes near silent. It gets louder the higher the RPM when in neutral.

I am no mechanic, however after some searching on the internet it seems to be the clutch release/throwout bearing. I am pretty tight on money so I would like to hold back on the repair as long as possible without causing any serious damage. I can imagine that I would be racking up the labor costs and I am not equipped to do the job myself.

The question is, what happens if the clutch release bearing completely fails? Will there be collateral damage to anything else or will I just find myself unable to shift?

Answer 1

The noise you describe is a VERY common issue with the transmission in the model of RX-7 you are driving. As a matter of fact, my current RX-7 (1991, 220k miles) has this exact same issue.

Based on your description, the noise is almost certainly coming from the transmission's input shaft bearing - not any part of the clutch assembly, or anything that would have been replaced during a clutch replacement. The only true fix for it is a disassembly of the manual transmission itself, and replacement of the affected bearing.

Essentially, all you can really do between now and eventually replacing that bearing is to keep the gearbox oil level full and clean. Some suggest trying different oils (e.g. Royal Purple) but that would only (if anything) reduce noise, and is not really addressing or repairing the issue. The good news is, it's not typically an issue that will cause you to "get stuck somewhere" unless it gets bad enough for the bearing to completely fail (unlikely as long as you keep that fluid clean and full!). You can usually drive with it making that noise indefinitely.

Answer 2

If the noise is only happening when the clutch is engaged (pedal out), it's not the throw out bearing. You'd only hear the noise when you push on the pedal. This is because the only time the throw out bearing is being used is when you are pushing the pedal down. It won't contact the clutch fingers any other time, and therefor cannot make noise with the clutch engaged. The noise you are suggesting indicates to me the front bearing in the transmission is on the way out (or has expired).

EDIT: To actually answer your question about the TOB ... If the TOB fails, it will ultimately be destroyed (assuming the TOB stops spinning as designed when engaged). When it stops spinning, it will in turn destroy the clutch fingers. This will entail a complete clutch replacement, sans the flywheel (unless it needs replaced for other reasons).

Answer 3

if the TOB fails, you will usually hear a loud grinding or squealing when you depress the clutch pedal. Eventual failure will destroy the clutch pressure plate, and clutch disk, and could possibly damage the throwout bearing lever, which could punch a hole in your bell-housing, or damage your flywheel.