Engine stalls when clutch is engaged (miata content): Grassroots Motorsports forum: Grassroots Motorsports Magazine

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Dec. 19, 2008 4:27 p.m. Helterskelter Reader

Alright, so I'm having a very strange problem with my miata. This started today while I was out running errands for my boss.

Anyhow, when I press the clutch in, the car makes a high-pitched screeching noise and the motor stall. The motor idles fine in neutral, revs normally, and seems otherwise healthy when driving in gear. The problem only occurs when I engage the clutch. My guess is that a spring or bearing failed associated with the clutch (especially since this was a sudden failure)?

It's a '99 with ~75k miles on it, no codes were thrown. The clutch felt fine and had no problems before this happened. If there's any additional information I can supply that would be helpful, let me know. Thank you, in advance, for any replies. This is my only car, and I need it to get to work, ect. So I would like to diagnose this problem asap so I can plan an appropriate time to fix it.
Dec. 19, 2008 4:41 p.m. John Brown SuperDork

Totalled, pay me $750.00 and deliver it to Lansing, Mi.
Dec. 19, 2008 5:10 p.m. Helterskelter Reader

Please refrain from being a prick. I'm annoyed enough that I have to find alternate transportation while I replace the clutch in my DD without useless and obnoxious commentary. I would like to know what is the most likely suspect failure item before I pull it apart.
Dec. 19, 2008 5:21 p.m. Type Q HalfDork

Right off the top of my head I am guessing that the throw out bearing is in trouble. Though I have never heard of one causing the engine to stall.
Dec. 19, 2008 5:41 p.m. Feedyurhed Reader

You need to contact the Miata guy on this board. He's associated with Flyin' Miata in some capacity but I can't think of his name right now. Can anyone else here jump in with the guys name?
Dec. 19, 2008 5:44 p.m. Keith SuperDork

The guy's name is Keith :) Of course, a faster way to get in touch with FM is usually to call 970 464 5600.

You don't really want to hear this - and I hate to be That Guy on the internet forum who always jumps to the worst conclusion - but get the crank end play checked immediately. Do not drive the car until you know if this is within spec. If you're lucky, all you need is a new thrust washer. If you're not, then you might be looking at a new engine.

I really hope it's something else like a throw out bearing or a pilot bearing, but I've never heard of them stalling an engine. Still, there's always a first time.

A really bad thrust bearing (or one that's fallen out) is known to stall the engine, and 1999 Miatas have had this problem. Did you feel any pulsing through the clutch pedal before this happened?

Why would a thrust bearing cause this? Because when you press in the clutch, that's what you're pressing against. A worn or missing thrust bearing lets the crank push up against the main caps, and this resistance (as the crank machines both itself and the block) is what stalls the engine. If the thrust bearing is that bad, then you don't have any oil pressure and your cams are busy destroying themselves and the cam journals as you drive. Did you know that the oil pressure gauge in a 1999 Miata is really just telling you that you have a minimum of 7 psi oil pressure, nothing else?
Dec. 19, 2008 5:55 p.m. Feedyurhed Reader

Feedyurhed wrote:

You need to contact the Miata guy on this board. He's associated with Flyin' Miata in some capacity but I can't think of his name right now. Can anyone else here jump in with the guys name?

Thanks Keith. I always look forward to your intelligent answers.
Dec. 19, 2008 5:58 p.m. MCarp22 New Reader

I hope it's not a '99 thrust bearing failure, i think i've heard of that causing the engine to stall when the clutch is pressed.

And in the time it took me to research that, keith posted. lol!
Dec. 19, 2008 6:02 p.m. Feedyurhed Reader

MCarp22 wrote:

I hope it's not a '99 thrust bearing failure, i think i've heard of that causing the engine to stall when the clutch is pressed.

And in the time it took me to research that, keith posted. lol!

Yup........ya gotta be quick around here.
Dec. 19, 2008 7:18 p.m. TJ Reader

Helter, I am not trying to be a prick, but your engine stalls when the clutch is disengaged....it is engaged when the pedal is up.

I think Keith is right unfortunately.
Dec. 19, 2008 11:19 p.m. benzbaron New Reader

Wonder if you could speed shift it. I did that a couple times on my bike to see if it was smoother which it wasn't.
Dec. 20, 2008 9:30 a.m. Helterskelter Reader

Thanks Keith, I figured you would respond with that . I was worried about the #4 bearing failure as well. Although I thought the general rule was if the car was past 20k miles, it was extremely unlikely to happen? The car is currently at 75k. I guess it's time to check crank end-play before I do anything else. If it has failed, I suppose that means a whole new engine. I did feel some pulsating in the pedal right when I first started the car, which worries me further. If the crank end-play is within spec should I drop the transmission and hope it is the clutch?

Prior to this failure, oil was changed in regular intervals and oil consumption was minimal. Also there were no prior noises or other warning signs.

Also to clarify, by "clutch engaged" I really mean disengaged, i.e when the pedal is pushed in.

Is there anything else besides #4 bearing failure that would cause the motor to stall when the clutch is disengaged?
Dec. 20, 2008 10:41 a.m. Keith SuperDork

The TSB for the thrust bearing had to do with some incorrectly machined blocks, apparently. But there was a mid-year change in the bearing size and I suspect the late blocks were being fitted with early bearings. Anyhow, while that particular batch of engines had a problem that usually manifested early, other engines are not immune. I've seen a fresh factory crate 1.6 spit a thrust bearing out immediately, and I've seen another engine suffer badly from a bearing that was installed backwards. Still, both were immediate failures. A heavy clutch will put stronger loads on the bearing leading to faster wear - that's why FM includes a clutch switch override with every clutch so you can start the car without putting load on the thrust bearing.

If you do have bad end play, then it's time to pull the engine and see what the damage looks like. If it was simply a matter of the bearing coming out and the car hasn't been driven, you may get away with very little damage. If the pulsation through the clutch pedal didn't manifest itself until immediately before the failure, you may be lucky.

If the end play is good, then I'd drop the transmission and look at all the clutch-related bearings. I've seen what happens to an aluminum flywheel if the pilot bearing seizes (it's not good for the flywheel) but I don't know what would happen in the case of a factory steel one . A way to check that with the assembled car would be to see if the engine stalls when the transmission is in neutral and the clutch pedal is depressed - if not, then that's what we could be looking at.