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Join Date: Mar 2009
Posts: 249
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Piston Slap???
I know trying to diagnose a noise without hearing it is impossible but I figured I would ask for some opinions based on the symtoms and facts.
1996 993 3.6 varioram motor 29k miles. Prototech turbo conversion running 6 psi of boost. Knocking noise that can be heard mostly from inside the car from just off idle to about 2,200 rpms then goes away (or can't be heard). The noise is not present when cold. It appears when warm. Of the 3 people that heard the noise none feel its rod rap. One feels its piston slap. From what I read here if it were piston slap it would be there when cold and disapear when warm. Additional facts to know. The motor had a bad smoking problem related to turbo oil draining that has since been fixed. I wonder if what we are hearing is the pistons contacting the heads due to carbon for burning all of that oil. Any and all opinions welcome Last edited by K24madness; 10-11-2009 at 09:20 PM.. |
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10-11-2009, 07:04 PM
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Join Date: Oct 2008
Location: Nash County, NC.
Posts: 8,508
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Although you have hydraulic rockers, I had worn rockers that sounded like piston slap in a 77. After I pulled the rockers and replaced them problem was solved.
22K is low for that type of wear Bruce |
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10-12-2009, 03:22 AM
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Quote:
Did the noise go away with increased RPM like mine does? I kinda eliminated the top end just because of the frequency of the noise is not twice the RPM's like most cam related noises would be. Going to do a leak down and use stethoscope this week. |
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10-12-2009, 04:55 AM
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Join Date: Oct 2008
Location: Nash County, NC.
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cam noise would be half engine speed. I bought a new set of 2.7 s and replaced them and still had the noise so you can see I was determined it was piston slap. With the new ones then I had to look elsewhere.
Bruce |
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10-13-2009, 05:04 AM
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Engine noise.........
Sounds like the noise is going away once the oil pressure gets to a certain level. Could you have a bad chain tensioner causing some chain slap? You should try listening to various areas of the engine using a stethoscope. You can get one fairly cheaply at most auto supply stores. That would at least identify what part of the engine the noise is coming from. Good luck!
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FEC3 1980 911SC coupe "Zeus" 3.3SS god of thunder and lightning |
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10-13-2009, 06:43 AM
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The oil pressure was another thing I considered. When cold it is high so maybe that is why it's not present then.
Going to do a leak down and use a stethescope this weekend. |
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10-13-2009, 06:58 AM
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Zeus (god of thunder and lightning)
