02-12-2017, 01:15 PM | #1 |
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Knocking Noise
Started my 30 Fordor and there is a knocking sound from the what sounds like the rear of the engine or bell housing. After 30 seconds noise stopped. Shut engine down and restarted and no noise. Shut engine down and waited for 15 minutes and restarted and the knock was there again, 30 seconds later no knock. I guess I need to find a Model A mechanic.
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02-12-2017, 01:19 PM | #2 |
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Re: Knocking Noise
First ck the oil.. if it persists try it without the belt.. noises can radiate from the source
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02-12-2017, 01:26 PM | #3 |
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Re: Knocking Noise
I did check oil, it's full.
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02-12-2017, 01:53 PM | #4 |
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Re: Knocking Noise
Removing the belt is a good idea. I suggest trying to exactly locate the noise. There are quite a few things that can make noise at the rear of the engine/bellhousing area.
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02-12-2017, 01:56 PM | #5 |
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Re: Knocking Noise
Just thinking, but it could be a bad valve or worn bearings. Try putting it in gear and letting out the clutch a little to put a load on the crankshaft. If the noise changes it could be a bearing. If not then it might be a valve. If a noise disappears after 30 seconds it indicates that oil drained away from a worn area when the engine stopped and then worked back into the worn area after 30 seconds of engine running.
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02-12-2017, 02:09 PM | #6 |
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Re: Knocking Noise
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02-12-2017, 02:10 PM | #7 |
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Re: Knocking Noise
Does moving the clutch pedal change anything?
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02-12-2017, 02:25 PM | #8 |
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Re: Knocking Noise
I'll have to wait for a while to try clutch just tried and no noise too soon.
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02-12-2017, 02:35 PM | #9 |
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Re: Knocking Noise
I had a knock once and it was the ring gear that had slipped on the flywheel a bit, and was hitting the casing. Hammered it back into place gently and it's stayed put ever since...no more knock.
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02-12-2017, 03:35 PM | #10 |
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Re: Knocking Noise
It could be piston slap. My Town Sedan would knock (Cluck) on startup and the noise would just melt away after 30 seconds after the oil got up into the cylinder. I was careful to keep the rpms low on startup. I drove the car 5000 miles and never had to fix it! Ed
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02-12-2017, 05:53 PM | #11 |
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Re: Knocking Noise
I did try a couple of things that were asked. I started the engine after a while and the knock noise started, pressed the clutch and no difference in sound, let out on clutch in gear and no sound difference. Knock noise stopped after about 20 - 30 seconds as usual. Hopefully it will be what you had Ed. I will get in touch with local Model A Club and see where to take the care to be looked at. Thank you for the responses.
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02-12-2017, 06:19 PM | #12 |
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Re: Knocking Noise
You could also run a compression check to see if there is any difference in the cylinders.
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02-12-2017, 06:20 PM | #13 |
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Re: Knocking Noise
Sounds like having your club look at it is a good idea.. keep us posted
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02-12-2017, 08:21 PM | #14 |
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Re: Knocking Noise
Sounds like a center main to me. Try shorting out the center plugs while it is knocking. If it reduces it or it goes away you found it. It wont be that loose, just needs adjusting.
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02-20-2017, 02:23 PM | #15 |
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Re: Knocking Noise
George I did what you suggested and the knock almost completely disappeared. I have sent an email to the local club but haven't heard from anyone yet. The noise still goes away on its own after 30 seconds or so.
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02-20-2017, 05:02 PM | #16 |
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Re: Knocking Noise
Glade you found it. It goes away because the oil gets in there and cushions it. It will keep getting worse the more you drive it. You should be able to remove some shims and get the right clearance.
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02-21-2017, 12:10 AM | #17 | |
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Re: Knocking Noise
Quote:
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02-21-2017, 12:32 AM | #18 |
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Re: Knocking Noise
Piston slap or center main are the main things I can think of. My 29 engine had the center main babbit completely gone, and it made a very loud rattle at any speed over idle.
My 28 engine has piston slap, and it's a lighter ticking noise that never goes away due to the amount of slop. |
06-10-2017, 06:25 AM | #19 |
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Re: Knocking Noise
Follow-up
After weeks of searching for a mechanic that could and would work on my engine its in the shop. The mechanic called yesterday and asked me to stop by. When he dropped the pan there were aluminum pieces in the pan. They were not shavings but small pieces. There were no shims on any of the main caps. Since it was Friday he didn't want to take the caps off until Monday morning the see were the pieces came from. Any ideas I can fret over for the weekend?? |
06-10-2017, 07:02 AM | #20 |
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Re: Knocking Noise
No fretting over the weekend, wait until you hear/see about the bearings :-)
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06-10-2017, 07:04 AM | #21 |
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Re: Knocking Noise
Sounds like Monday morning you will hear that as a "minimum", you will need to provide new Babbitt.
Might add: One possibility that could have been worse: Say nothing ..... do nothing ..... keep driving ..... throw a connecting rod which penetrates one side of your cast iron block. Last edited by H. L. Chauvin; 06-10-2017 at 07:15 AM. Reason: added note |
06-10-2017, 09:42 AM | #22 |
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Re: Knocking Noise
Yup - George nailed it. Chunks of aluminum (actually, Babbitt) on the bottom of the pan or dipper tray invariably means a rod or main bearing has lost its Babbitt. It sounds as though in your case it's the center main, the one that normally goes first due to the crankshaft's whipping action. Shorting #2 and #3 as George suggested will confirm this. I would have also shorted each one individually, though, to eliminate a rod bearing in #2 or #3. The Babbitt chunks may look shiny like aluminum or be a dull gray, all depending upon the Babbitt's composition. I rather doubt that the pieces are aluminum, which if true would cast suspicion upon a damaged piston skirt. But a damaged piston's noise would not go away after 20-30 seconds, as you are experiencing. A center main's knocking might be reduced in this amount of time, but it won't go away on its own. In all likelihood, you have lost the Babbitt in the center main = re-pour time. 'Sorry.
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06-12-2017, 09:25 AM | #23 |
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Re: Knocking Noise
Not to hijack the original post but I got the exact same symptoms. 20 to 30 seconds knock goes away. Tried George Miller's suggestion of shorting out cylinders two and three to confirm a bearing problem. In fact, I shorted out all four one at a time. Result is no change in knocking sound. Question is, do I drop the pan looking for pieces of Babbitt.....if none found, do I plasti gauge the mains and rods? Any suggestions would be greatly appreciated.
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06-12-2017, 11:29 AM | #24 | |
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Re: Knocking Noise
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09-23-2017, 10:00 AM | #25 |
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Re: Knocking Noise
Knocking Noise Update, complete engine rebuild done by Doug McPherson in Vero Beach. Boy does she sound different. I'm picking up today from mechanic. Babbitt worn slap out in all caps, cracked block and high compression head, bored 80 over with sleeves and one sleeve dropped down and something with valves.
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09-23-2017, 10:38 PM | #26 |
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Re: Knocking Noise
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