Knock when clutch pedal depressed.

[ian Simpson]

Two years ago my 28 A developed a heavy knock when I depressed the clutch pedal. The knock was once per engine rev and disappeared when the pedal was released. I sought opinions from several auto mechanics (none with A experience) who all suggested I replace the clutch throw-out bearing.

This was done by pulling the rear axle, torque tube and transmission. The throw-out bearing was a little rough and was replaced. All other components were inspected and seemed in good condition. After everything was bolted up and the knock was still there when the car was started.

Next the starter was pulled and inspected. The bushes appeared worn, the armature and brushes very worn and the bendix was falling to pieces. An identical rebuilt one was obtained and installed. The noise disappeared.

Last week I installed new motor mounts all around. Before the work I started the car and moved it to give working room in the garage. No noise!.

Yesterday I started it to take a test drive - THE NOISE IS BACK!

Any suggestions other than a box of matches?

[tbirdtbird]

Not sure why a starter would be pulled for this complaint, but I guess it was a good thing if it was a mess.
Nonetheless, the starter is a red herring; it has nothing to do with the clutch being in or out. Pure coincidence that the starter work made the noise go away briefly.
Too bad the pilot bearing in the flywheel wasn't changed out when the throwout bearing was done. Often you do them together. If it comes to that, be sure that the machined stub on the front of the tranny input shaft isn't worn; else it will never engage the pilot bearing properly if at all.

[J Franklin]

Check for excess clearance in the thrust bearing.

[Mitch//pa]

Originally Posted by J Franklin

Check for excess clearance in the thrust bearing.

times 2 crankshaft endplay

[George Miller]

Originally Posted by Mitch//pa

times 2 crankshaft endplay

x3 crank end play

[Smog Tech]

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I have seen this happen before with a 29 Model A. Turned out to be the flywheel hitting inside the bell housing.

[colin1928]

X4 end play

[Fred]

Originally Posted by tbirdtbird

Not sure why a starter would be pulled for this complaint, but I guess it was a good thing if it was a mess.
Nonetheless, the starter is a red herring; it has nothing to do with the clutch being in or out. Pure coincidence that the starter work made the noise go away briefly.
Too bad the pilot bearing in the flywheel wasn't changed out when the throwout bearing was done. Often you do them together. If it comes to that, be sure that the machined stub on the front of the tranny input shaft isn't worn; else it will never engage the pilot bearing properly if at all.

It stays @ 100 % of the time ENGAGED !! ???

[tbirdtbird]

define engaged. If the bearing is worn or the stub, the two will only make marginal contact at their circumference, thus the input shaft can wobble, thus giving noise. think about it before hitting the caps. How about some constructive suggestions rather than waste a post

[ian Simpson]

Thank you all for your help. I should have said "when the clutch pedal is depressed" rather than " when the clutch is engaged".

Any thoughts why the noise was not present for two years?

Thanks again

Ian

[Tom Wesenberg]

I'd guess for the first two years the rear of the thrust bearing wasn't worn enough to be a problem. It might now be worn enough for the flywheel to move forward and hit something, like a starter bolt.

[newshirt]

I've seen this exact thing happen when starter bolts were too long.

[RUNNERBUN]

I agree with newshirt, Starter bolts to long plus maybe some excess in crankshaft end play.

[tbirdtbird]

be careful the Derf meter reads zero

[zzlegend]

Originally Posted by tbirdtbird

be careful the Derf meter reads zero

Hum,,,,,,,,where is my mirror?

[ian Simpson]

Thanks again everyone, you have given lots of help, hopefully I can get back at it soon.

Ian

[ian Simpson]

Originally Posted by tbirdtbird

be careful the Derf meter reads zero

and my patience runs thin with dumb quotes

My apologies to 'tbirdtbird' for my rough response but his attempt at jocularity was posted very shortly after receipt of some bad news of a personal nature. I will attempt to reign in my bad temper in future.

[tbirdtbird]

the entertainment inherent on this site is amazing!

[George Miller]

There is one more possibility. The flywheel ring gear might be moving towards the back of the engine. If the ring gear has been changed, as with a lot of reproduction parts they did not get it right. The ones that I have used have to big of a ID. This will make a noise when you push in the clutch if it is moving.

[rocket1]

Try this remove the starter,start the engine with the crank,watch that grip on the crank handle,any more noise?