Flywheel grinds on start - on shutdown spins and "poofs"

[H.M.]

Or that's what it sounds like to me.

When I start the car I sometimes hear a grinding for a second after the motor starts. It sounds like it's coming from the starter motor.

When I shut off the car it sounds like the flywheel is spinning, or like there's a suction somewhere. This goes on for a second after the motor's off and then I hear a "poof", kinda like a vacuum had been released. I hear this coming through the short ram.

The starter motor has less than a 1000 miles on it.

Both these sounds started at the same time.

Any ideas?

[Losiracer2]

is your ignition switch sticking?

[batever]

As to the first sound, it could be that a clutch inside your starter is not working right...the one that disconnects the starter motor from the crankshaft once the engine starts moving of its own accord (usually, at speeds of over 1000rpms this is supposed to disengage, so the starter motor gears, which offer a high gear ratio (i don't think it;s a gear reduction, I think it's the opposite, so if the starter motor iis turning at 1 rpm the gears turn the crankshaft at 20-30 rpm) on the order of between 20:1 and and 30:1 (this is from memory) don't spin like crazy at like 20,000 rpms or whatever). . Just a guess.

As to the second one, I'm not clear from your description what's happening exactly and don't have any ideas right now.

If your starter motor is staying engaged the whole time you are driving, and then only dropping off once you start the car, that could be the issue...i don't know how long it would last doing that though. Think of the rpms the starter motor would be experiencing at 2000rpm engine speed--again, 20k-30K I believe

[batever]

As to the first sound, it could be that a clutch inside your starter is not working right...the one that disconnects the starter motor from the crankshaft once the engine starts moving of its own accord (usually, at speeds of over 1000rpms this is supposed to disengage, so the starter motor gears, which offer a high gear reduction on the order of between 20:1 and and 30:1 (this is from memory) don't spin like crazy at like 20,000 rpms or whatever). . Just a guess.

As to the second one, I'm not clear from your description what's happening exactly and don't have any ideas right now.

****
another possibility is that IF
IF your starter isn't turning off, that could explain both noises. I would check into that, as others have suggested.

what would happen in this scenario is the starter disengages from the flywheel at the appropriate speed, but keeps spinning from electrical power while you drive. (but with no load on it). When you stop, once the engine drops below say 1000 rpms, the starter clutch now reengages with the flywheel until both spin down to zero.

I don't know what the "puff" sound is, unless what you are hearing is air being compressed and forced out of the engine during this fairly quiet scenario (making it possible for you to hear). It shouldn't be coming out of your air intake but maybe you can hear it from there. I know when I turn the engine by hand with the motor off it makes a "puff" sound so maybe that's what you are hearing.

this scenario sounds very probable as a cause of your symptoms.

[H.M.]

Ok, thanks for the help.

I replaced the (new) starter motor and the grinding on start up went away. So I guess I got a bad rebuilt starter.

The "poof" on shutdown is still there BUT with the hood closed and when I'm not actively listening for weird sounds it's not that noticeable. So I'm thinking it's probably been there for a while but I never noticed it till I had the first weird sound.

BTW - it's exactly the same type of sound the engine makes as it compresses if you turn the crankshaft by hand when you're going to TDC. So I'm guessing it's not that big a problem and I was just over sensitive.