Does anyone know what a wrist pin knock sounds like? - Rennlist Discussion Forums
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Old 10-24-2003, 09:52 PM   #1
tdatk944+S4
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Unhappy Does anyone know what a wrist pin knock sounds like?

I rebuilt my motor last year and now I have a knock that starts maybe 30 seconds after start and dissapears after 1 minute. Kinda sounds like a rod bearing knock but it goes away after it warms up. It is definately NOT cam followers or injectors. Man I;m worried. Has anyone had their oil pan baffle go south and what did it sound like?
I have verry good oil pressure 4+ bar, good compression and no oil blow by.
I had a friend at work that thinks it's a wrist pin bearing. Didn't replace them at rebuild.
Help
Tim
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Old 10-24-2003, 10:02 PM   #2
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My best guess: BAD VALVE LIFTERS! I had the same thing last year. go ahead and see about another. if ya need one, I have 7 left. I'll sell ya one. pull off your cam tower, and hit the button on each valve lifter. if it pushes in, that's a dead lifter. Lemme know.
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Old 10-24-2003, 10:08 PM   #3
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Quote:
My best guess: BAD VALVE LIFTERS! I had the same thing last year. go ahead and see about another. if ya need one, I have 7 left. I'll sell ya one. pull off your cam tower, and hit the button on each valve lifter. if it pushes in, that's a dead lifter. Lemme know.
Thanks,
Been there last year. I have 6 or so myself. Definately NOT cam followers. The knock is much lower in the block area.
The saga continues.....

Any others?
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Old 10-24-2003, 11:51 PM   #4
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OK
I guess I'll tear it down and post the answer. The 944 forum is getting lame for tech secessions. Anyone care to rebutt?
Later

Last edited by tdatk944+S4; 10-25-2003 at 01:14 AM.
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Old 10-25-2003, 12:13 AM   #5
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Sounds like a wrist pin to me

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Old 10-25-2003, 12:15 AM   #6
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isnt that when some old guy has joint problems and they put a pin in his wrist and it makes a knocking sound when he moves his wrist a certain way




(that was really unnessacery)im sorry
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Old 10-25-2003, 12:20 AM   #7
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Shaun,
Can you give specifics? Man I need to know before I pull the motor AGAIN.
Please say it's the oil pan baffle.
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Old 10-25-2003, 10:43 AM   #8
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I never had an oil pan baffle go bad so I do not know what that sounds like. I can't imagine a noise the baffle would make going away after a short period of time.
What happens with a wrist pin is that it raps for a little while until the engine gets warm and expands enough to "tighten" it up and the noise goes away. My girlfriends 3.8 Sable has been doing this for 6 months. It only makes noise when you first start it in the morning.
You may be able to start the engine with 1 sparkplug disconnected at at time and determine which cylinder it is.

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Old 10-25-2003, 11:26 AM   #9
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Before I'd go tearing that engine apart looking for the cause of your knock, I'd sure use a stethoscope and try to pin down the location of that knock first. Also, I would be inclined to believe that if it is a wrist pin knock, it would be apparent as soon as you started your cold engine, and then go away. Just like Shawn describes above.
I'd also try the spark plug removal durring knock condition also (carefully, be safe!)
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Old 10-25-2003, 07:34 PM   #10
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This also sounds like a possible piston slap. To much piston cylinder clearance. In either case you might be able to tell or get more info by pulling different plug wires while its running. If theres no bang then the piston is not being pushed as hard. If you are affraid to pull them 1 by 1, then start it each time you pull a different wire off. When you pull each wire make sure you ground it though. The spark is trying to go somewhere. And if it can't find a ground at the end of the wire it can go back to the dme. I have seen bad wires kill a dme.
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Old 10-26-2003, 04:18 PM   #11
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I had the bolt on the camshaft's timing gear start backing out. The seal began to fail and lost oil pressure at the front of the cam. I swore it had a piston slap on the #1 cyl. The car enventually died due to the rotor hitting the dist cap. I would say to take a look at that. It's up front and simple.
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Old 10-26-2003, 04:33 PM   #12
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lets see...more unfortunate stuff that happened to me: could it be a main pulley separating? Dad took it apart to clean it, torqued the bolts too tightly, and 2 broke, the imbalance made the other 2 loosen and the pulley started to vibrate. that made a loud knocking sound. thought I spun another bearing, shipped it to the dealer, and they told me it was the pulley. glad I had a spare...
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1987 924S

1988 944 Turbo S- Rogue Tuning M-Tune, 18 PSI, Lindsey Stage II intercooler, Tial wastegate, SBC-iD boost controler. 310 RWHP, 351 ft-lbs on pump gas
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Old 10-26-2003, 04:33 PM
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