[C1] Knocking Noise
Thread Starter
Racer
Joined: Aug 2013
Posts: 345
Likes: 29
From: Starkville Mississippi
That is random and does not sound like wrist pin or bearing knock to me....doesn't have the tinny sound of an inspection cover or timing chain cover "hit" either...
Its almost like something occasionally hitting a valve cover maybe and it seems louder near the dipstick to me. I'd absolutely be removing the valve covers for a look-see...
I would also do the spark plug wire "pull while running" test...you should get about 50-100RPM drop in idle speed (just to eliminate a plain old "miss" as the issue) and if the noise abates then I'd say its a bearing - a wrist pin often has a sort of a double knock. Again, I don't think its either of those though.
This is a long, long shot but I'd check that fuel pump pin in the actuator arm to see if its "walking out"...
Its almost like something occasionally hitting a valve cover maybe and it seems louder near the dipstick to me. I'd absolutely be removing the valve covers for a look-see...
I would also do the spark plug wire "pull while running" test...you should get about 50-100RPM drop in idle speed (just to eliminate a plain old "miss" as the issue) and if the noise abates then I'd say its a bearing - a wrist pin often has a sort of a double knock. Again, I don't think its either of those though.
This is a long, long shot but I'd check that fuel pump pin in the actuator arm to see if its "walking out"...
Team Owner
Joined: Aug 2007
Posts: 58,061
Likes: 7,146
Army
i replaced the fuel pump a few months ago and that thought has occurred to me. It seems I should be getting an indication of fuel pump problem through the stethoscope but no unusual noises. I did the spark plug wire pull with no change. When I get “off the road” I’m going to start taking things apart, valve covers first. Then easiest to difficult. The knock is significant enough that I can feel it with my hand on the drivers side fender. I’m worried and appreciate all for help. I’ll keep folks posted. Jim
Race Director
Joined: Apr 2015
Posts: 17,571
Likes: 3,460
From: Fresno California
That is the strangest, most random engine knock I've ever heard. Does not sound like a bearing to me. I'm in the 'pull the valve covers' group for starters. Almost sounds like a misfire pop through the carb with the air cleaner on, but yours is not on the car when it's making the noise...too muffled to be an intake valve, IMO. Exhaust valve pop? Very strange, indeed. Throw a vacuum gauge on it and watch the needle when it knocks to see if you have a glitch in the valvetrain.....
Safety Car
Joined: Mar 2009
Posts: 4,191
Likes: 951
From: Corpus Christi, TX
FWIW, the noise doesn't sound at all like a rod bearing or wrist pin, or for that matter a collapsed piston skirt. All those noises are regular in time and with the motor speed. Also unlikely to be noise from slop in the valve train, which also is regular in time and with motor speed. Possibly a bad plug wire - I have had stock wires' conductors break inside the insulation where the fault was invisible. A way to tell would be to pull the plug wires one at a time and wait long enough each time so that you might find which cylinder causes the noise. A quick pull off of each wire might not keep each cylinder dead long enough to find the culprit. That would also help you track down whether you have an intermittent misfire from a bad valve. A bad intake valve will cause light backfiring under load. Another possibility but less likely is a bad head gasket, failed between #5 and #7. That can cause preignition on #7, but the noise IIRC is a sharp metallic clunk like a rod or pin, or even detonation.
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Burning Brakes
Joined: Aug 2013
Posts: 1,071
Likes: 322
From: palm springs ca
If you are going to look for a broken spring and you don't see one, then feel for one. The broken spring will/or can look good when in the up position. I found them by running my fingers around each spring and feeling for a sharp spot which was the broken spring. They seem to pop out of place when compressed and return in place when up. Doesn't seem like that is true, but I found them by taking the advice of the master mechanic at Chevy when I was a mechanic.
They popped out, then back in place.
Dom
They popped out, then back in place.
Dom
Team Owner
Joined: Aug 2007
Posts: 58,061
Likes: 7,146
Army
The vacuum gauge is an excellent idea....here are some symptoms and animations that can aid in diagnosis...click on any one to see a sample:
http://www.secondchancegarage.com/public/vacuum1.swf
http://www.secondchancegarage.com/public/vacuum1.swf
Thread Starter
Racer
Joined: Aug 2013
Posts: 345
Likes: 29
From: Starkville Mississippi
Thread Starter
Racer
Joined: Aug 2013
Posts: 345
Likes: 29
From: Starkville Mississippi
The vacuum gauge is an excellent idea....here are some symptoms and animations that can aid in diagnosis...click on any one to see a sample:
http://www.secondchancegarage.com/public/vacuum1.swf
http://www.secondchancegarage.com/public/vacuum1.swf
Le Mans Master
Joined: Feb 2008
Posts: 6,482
Likes: 1,918
From: Folsom CA
That is a very odd sound and rhythm. At this point I would put a dial indicator on the front snout of your crankshaft and force the crankshaft forward and then rearward to check your thrust clearance.
Force it all the way rearward and set your dial to zero. Force it forward to see how much it is moving.
The way your sound is so strong and with an odd rhythm I wonder if your thrust bearing has worn away. With too much thrust clearance the crank can move and things start to hit that should not.
Maybe a crankshaft counter weight hitting something hard inside the engine. The worn thrust allows the crank to float which could produce really odd contact noises.
That is my WAG after listening to your video.
Re Reading your first post I see no way a thrust would suddenly go away because you parked the car so this is an odd one.
Mark
Force it all the way rearward and set your dial to zero. Force it forward to see how much it is moving.
The way your sound is so strong and with an odd rhythm I wonder if your thrust bearing has worn away. With too much thrust clearance the crank can move and things start to hit that should not.
Maybe a crankshaft counter weight hitting something hard inside the engine. The worn thrust allows the crank to float which could produce really odd contact noises.
That is my WAG after listening to your video.
Re Reading your first post I see no way a thrust would suddenly go away because you parked the car so this is an odd one.
Mark
Last edited by Westlotorn; Jan 18, 2019 at 10:51 PM.
Thread Starter
Racer
Joined: Aug 2013
Posts: 345
Likes: 29
From: Starkville Mississippi
I really appreciate your going to the trouble of thinking through this issue and posting the clearances. It has really been a strange problem. I’m afraid your diagnostics are beyond my capabilities but if my drive in the morning brings resolution, catastrophic or otherwise, I’ll let you and all know. Thanks again. Jim
Race Director
Joined: Jan 2003
Posts: 17,681
Likes: 3,678
From: Central Arkansas
If you are close to a Harbor Freight store a dial indicator and magnetic base are pretty inexpensive and are fine for this type work. Kind of hard to get good leverage to move the balancer from above but if you are under the car you can probably move it forward and back a few times easily and eyeball it to see if movement looks excessive. Movement of .01" is not visually a lot.
Thread Starter
Racer
Joined: Aug 2013
Posts: 345
Likes: 29
From: Starkville Mississippi
If you are close to a Harbor Freight store a dial indicator and magnetic base are pretty inexpensive and are fine for this type work. Kind of hard to get good leverage to move the balancer from above but if you are under the car you can probably move it forward and back a few times easily and eyeball it to see if movement looks excessive. Movement of .01" is not visually a lot.