Knocking sound

pdora

pdora

Senior Member
Car makes a regular knocking or pounding sound at startup. Gets faster as engine revs. Nearly disappears when clutch is pressed in (disengaged).

Disconnected fan belt and made no change.

Does this sound like a clutch issue?
 
Sounds like too much crank end play. End play is usually loudest at idle. Pushing on the clutch stops the crank from slapping in and out.
 
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Does it get quiet a minute or so after startup if you don't push the clutch? If so it is likely a worn center main bearing and when oil finally gets to it, it quiets down. That is another reason to run a small oil line from the pump to the center main.
 
My 29 Tudor sounded great at idle, so I bought the car. After I got it on the road and hit 20 to 25 MPH the engine sounded and shook like a worn out combine.

The crank had a lot of end play and the center main was gone, except for a couple of small thin pieces hanging out the edge.

Did this knocking start all of a sudden, or did it come on gradually? Have you used a stethoscope to try to locate it? Have to shorted any plugs to see if the noise changes?
 
FURTHER TESTS AND OBSERVATIONS AS REQUESTED

1. Sound does not go away on its own if clutch is not depressed.

2. Shorting plugs, one at a time, had no effect on the sound.

3. Using the stethoscope it seemed like the sound was coming from the front of the engine, perhaps around the timing case or the pully. I am not very experienced in use of the stethoscope, so I can' be to sure of this observation.

4, Background:Symptoms developed gradually over a period of approximately four hours of run time consisting of around 8 short trips and one longer run of 15 miles. At first the sound was barely present at startup but seemed to disappear once I started driving. When I started it up today it was blatantly obvious.

Here is another item which, looking back, might be related: During this same time frame I noticed that when up shifiting when I put in the clutch the engine seemed to growl or buzz as though something was loose. I could avoid the sound by shifting very gently with minimum RPM.

Thanks so far.
Any more recommended tests?
 
if the timing gear is loose you can check by taking of the dist cap and turning the crank back and forth, if its loose the crank will turn, some times quite a bit, before the dist rotor moves, should be very little travel before the rotor moves
 
Pdora, there is a simple test to determine if the thrust is excessive. Have a friend sit in the car and depress the clutch while you watch the front pulley. Have the friend let the clutch out and you try to pry the pulley to the rear. Any noticeable movement is probably too much with this test.
 
A loose timing gear can sound like many loose tappets. Its worse at idle and smooths out with more speed. The clutch noise could be the throwout bearing or too much thrust play. If the thrust is excessive, it will wear on the timing gear each time it moves.
 
I think your timing gear is on its way out. Just take the side cover off and take a look

mike
 
pdora said:
Where is the side cover, how so it open it and what am I looking for when I get inside?

Thanks,

PAD
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it is a small cover on the same side as the valve cover. It has 2 large bolts easily visible, and is also attached by two oil pan bolts below and three of the timing cover bolts.. When its off, you can see the edge of the timing gear. Look for excessively worn or broken teeth. Also check that its tight by levering it with a screwdriver from the back. Any back and forth movement means either the nut is loose, or that its one of the old types with a metal center. Those types loosen from the metal center and need to be replaced. If it is simply a loose retainer nut, the timing gear cover needs to come off . That means supporting the engine at the oil pan before you remove the cover, as it is part of the front motor mount system.
 
Also when you pry the gear forward to check for good spring and plunger pressure, be sure to pry near the center of the gear, and not on the outer edge.
 
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