Go Back   The Ford Barn > General Discussion > Model A (1928-31)

Sponsored Links (Register now to hide all advertisements)

Reply
 
Thread Tools Display Modes
Old 07-06-2018, 11:03 PM   #1
Bud Man
Member
 
Bud Man's Avatar
 
Join Date: Sep 2016
Location: Grapevine, Texas
Posts: 59
Default Knocking Sound Comes, Then Goes

Odd one for the group. When I start my engine after the car has been idle for a bit, I get a dull, deep knocking/thumping sound from the engine compartment. Pretty sure it's the engine itself, but oddly, the knocking always completely disappears after the engine has run maybe 5 - 6 seconds, and doesn't reappear until it again has set a while. Advance stays retarded the whole time. What would cause the noise to disappear? Oil circulation would seem the logical reason for the end of the knocking, but would it subside that quickly?
Bud Man is offline   Reply With Quote
Old 07-06-2018, 11:29 PM   #2
Y-Blockhead
Senior Member
 
Y-Blockhead's Avatar
 
Join Date: Jul 2011
Location: Redondo Beach, CA
Posts: 3,876
Default Re: Knocking Sound Comes, Then Goes

Bud Man, Similar thing happened to me ~ 2 months ago. First start after sitting about a week or so and a deep knock then goes away.

And of course it does it on the morning of the Annual OC Pancake Breakfast, can't miss that! When we got home I drained the oil and got some chunks... The rear main finally decided to 'go away'.

I'm thinking with the bearing compromised, the oil drains out of the last reservoir in the valve chamber when the car sits for a few days. So the rear main (in my case) starts up 'dry'. As soon as it sees oil it quiets down.

I suggest you drop the pan and have a "look see".


__________________
Y-Blockhead
'30 Briggs Town Sedan
'55 Ford Ranchwagon
_________________________________
And once again that is just my 1 worth.


https://www.youtube.com/watch?v=aH2TvmjxIFM

Last edited by Y-Blockhead; 07-07-2018 at 11:25 AM.
Y-Blockhead is offline   Reply With Quote
Sponsored Links (Register now to hide all advertisements)
Old 07-06-2018, 11:59 PM   #3
Railcarmover
Senior Member
 
Railcarmover's Avatar
 
Join Date: Apr 2017
Location: Sacramento
Posts: 1,145
Default Re: Knocking Sound Comes, Then Goes

Same issue on an engine Im building for a friend,Thumps for the first few minutes then quiets right down..rods and mains good,cam thrust spring good..spring missing from oil pump,found the oil pump 'set screwed' at the plug.Best I can figure the cam endplayed hard when the pump was dry,something the spring was designed to absorb..
Railcarmover is offline   Reply With Quote
Old 07-07-2018, 12:36 AM   #4
Tom Wesenberg
Senior Member
 
Tom Wesenberg's Avatar
 
Join Date: May 2010
Location: Mpls, MN
Posts: 27,397
Default Re: Knocking Sound Comes, Then Goes

Center main is usually the first to go.
Tom Wesenberg is offline   Reply With Quote
Old 07-07-2018, 06:50 AM   #5
machineman64
Member
 
Join Date: Jun 2012
Location: miles city, mt.
Posts: 40
Default Re: Knocking Sound Comes, Then Goes

Tom nailed it, mine had a knock at startup then would go away after a few seconds took the pan off found the center main lose removed .003 of shim all is quiet now.
John
machineman64 is offline   Reply With Quote
Old 07-07-2018, 07:47 AM   #6
George Miller
Senior Member
 
George Miller's Avatar
 
Join Date: May 2010
Location: NC
Posts: 2,944
Default Re: Knocking Sound Comes, Then Goes

Tom got it center main is loose.
George Miller is offline   Reply With Quote
Old 07-07-2018, 08:07 AM   #7
WHN
Senior Member
 
Join Date: Mar 2017
Location: Old Lyme Connecticut
Posts: 1,005
Default Re: Knocking Sound Comes, Then Goes

Try easy fix first.

Change oil, add four quarts of 20w-50 and one blue bottle of STP.

Also put MMO in gas.

If still making the same noise in a few hundred miles. Than you have to think that it could be something starting to go wrong.

Model A’s can make any number of noises at one time or another. Just like any 90 year old guy.

I know there are people that are not going to agree with what I have mentioned above, but it’s only a $20.00 outlay.
WHN is offline   Reply With Quote
Old 07-07-2018, 08:17 AM   #8
katy
Senior Member
 
katy's Avatar
 
Join Date: Jun 2015
Location: Alberta, Canada
Posts: 2,015
Default Re: Knocking Sound Comes, Then Goes

Quote:
Originally Posted by Bud Man View Post
Odd one for the group. When I start my engine after the car has been idle for a bit, I get a dull, deep knocking/thumping sound from the engine compartment. Pretty sure it's the engine itself, but oddly, the knocking always completely disappears after the engine has run maybe 5 - 6 seconds, and doesn't reappear until it again has set a while. Advance stays retarded the whole time. What would cause the noise to disappear? Oil circulation would seem the logical reason for the end of the knocking, but would it subside that quickly?
Had the same thing once on a 302 Ford, start it up after sitting o'night and it would knock for 1 or 2 seconds. Replaced all rod bearings with .001" undersize rod bearings and knock went away.
Disremember exactly but that engine probably had 60 or 80K miles on it at that time, about 40 years ago.
__________________
Don't go away mad, just go away.
katy is offline   Reply With Quote
Old 07-07-2018, 04:30 PM   #9
Bud Man
Member
 
Bud Man's Avatar
 
Join Date: Sep 2016
Location: Grapevine, Texas
Posts: 59
Default Re: Knocking Sound Comes, Then Goes

Many thanks to everyone for their inputs on this. WHN, I did exactly what you suggested about two weeks ago, new 20-50 and STP, but it's had no effect, so didn't get lucky on that one. Dropped the pan this afternoon, and no traces of metal debris in the oil, and nothing visually apparent, as well. Will address the center main possibility tomorrow and see what I find. Are we talking about removing the center main cap and peeling a thickness of shim away, then re-torquing the cap to 70-80 ft lbs? Thanks again!

Bud
Bud Man is offline   Reply With Quote
Old 07-07-2018, 04:48 PM   #10
daveymc29
Senior Member
 
daveymc29's Avatar
 
Join Date: Sep 2010
Location: Danville, CA
Posts: 1,304
Default Re: Knocking Sound Comes, Then Goes

You should find out what clearance you have now on the center main then remove the proper amount of shims to get it back into specs. Some say to use plastigage and others not so much for using that, I have heard of adding shim stock between the journal and the main cap to see how much it takes to lock the shaft, then remove the appropriate number of shims to reach specks. Some cut their own shim stock from an aluminum drink can. Use micrometer to measure thickness and go from there. In younger days I removed one layer of shim stock from each side and since I could still turn the engine with the crank I called it done. Sold the car so I don't know the precise outcome of that. It worked fine while I had it.
daveymc29 is offline   Reply With Quote
Old 07-08-2018, 06:54 AM   #11
pooch
Senior Member
 
pooch's Avatar
 
Join Date: Sep 2010
Location: South Coast NSW Australia
Posts: 2,595
Default Re: Knocking Sound Comes, Then Goes

Put some copy paper in the centre main and see if the crank will still turn.
pooch is offline   Reply With Quote
Old 07-08-2018, 09:43 AM   #12
BILL WILLIAMSON
Senior Member
 
BILL WILLIAMSON's Avatar
 
Join Date: Dec 2010
Location: FRESNO, CA
Posts: 12,558
Default Re: Knocking Sound Comes, Then Goes

Pull OFF the # 2 & # 3 plug straps & start it. If the noise is GONE, it's the center MAIN! Take off the upper bell housing inspection cover, with a socket & extension on a pressure plate bolt, see if the flywheel will rock back & forth about 1/8" or so. If it does, the FLYWHEEL BOLTS ARE LOOSE!
Bill W.
__________________
"THE ASSISTANT GURU OF STUFF"
BILL WILLIAMSON is offline   Reply With Quote
Old 07-09-2018, 03:37 PM   #13
Bud Man
Member
 
Bud Man's Avatar
 
Join Date: Sep 2016
Location: Grapevine, Texas
Posts: 59
Default Re: Knocking Sound Comes, Then Goes

Well, I dropped the pan and it was an identical issue to what Y-Blockhead described. Rear bearing has let go, unfortunately. The engine is tired anyway, so a planned rebuild may now be coming a bit sooner.

Thanks again to everyone who responded!
Bud Man is offline   Reply With Quote
Old 07-09-2018, 04:24 PM   #14
Y-Blockhead
Senior Member
 
Y-Blockhead's Avatar
 
Join Date: Jul 2011
Location: Redondo Beach, CA
Posts: 3,876
Default Re: Knocking Sound Comes, Then Goes

I was hoping for your sake that I was wrong...
__________________
Y-Blockhead
'30 Briggs Town Sedan
'55 Ford Ranchwagon
_________________________________
And once again that is just my 1 worth.


https://www.youtube.com/watch?v=aH2TvmjxIFM
Y-Blockhead is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Sponsored Links (Register now to hide all advertisements)


All times are GMT -5. The time now is 11:41 AM.