oil change+new tank of gas= ROD KNOCK?
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oil change+new tank of gas= ROD KNOCK?
This has me worried a little I changed the oil today in my 95 SC400, put 5 litres or 5.28quarts. Took it out shortly after to fill up on gas. It is about a 30 minute roundtrip. Get back to the house and I have the windows down and no A/C. As Im slowly pulling up the drive and into the garage, I hear a knock 1,2,3,4,1,2,3,4 knock knock knock, Sounds like you are taking your knuckle and knocking it on a wooden table at a quick pace. It's not a really fast knock, just a methodical knock at low(below 1,000) rpms that is pronounced.. With the car in park or nuetral, nothing noticeable. I took it out for a quick spin right after I heard the noise to see if I could hear it on the road as I accelerated, nope, sound was not there. No lag in performance. I did put it in drive andheld my foot on the brake, reving it up to 1k rpm the sound gets faster but not louder. Over 1k rpm, the sound is drowned out. With A/C on, you can't hear the knock
Oil on the dipstick shows right in the middle of low and full. Did I starve it of oil? 5 quarts is what it calls for. Bad gas? Chevron 93 octane. The sound def. seems to be coming from the top. I did get a slight stutter the other day so I am about to change the cap/rotor/coils/plugs and wires.
Any thoughts guys? It is entirely possible this sound could have been present for some time because I don't drive without my A/C on, its texas in the summer.
It sounds very similar to this BMW minus the airy exhuast sound...just the knockhttp://www.youtube.com/watch?v=M70r6WC_9Dw
Oil on the dipstick shows right in the middle of low and full. Did I starve it of oil? 5 quarts is what it calls for. Bad gas? Chevron 93 octane. The sound def. seems to be coming from the top. I did get a slight stutter the other day so I am about to change the cap/rotor/coils/plugs and wires.
Any thoughts guys? It is entirely possible this sound could have been present for some time because I don't drive without my A/C on, its texas in the summer.
It sounds very similar to this BMW minus the airy exhuast sound...just the knockhttp://www.youtube.com/watch?v=M70r6WC_9Dw
Last edited by FireCode; 08-14-10 at 10:52 PM.
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Castrol GTX 5W-30
I officically have no clue what it is..took it for another quick spin...I can powerbrake it to 1500rpm and hear nothing. You only hear this knock at low idle to about 800rpm with it in drive or reverse. As soon as the AC comes on when it is in drive, the sound goes away. I really don't think it could be engine knock by these symptoms but what do I know. I can sit there in nuetral and rev it to 4k and hear nothing except a great sounding engine
I officically have no clue what it is..took it for another quick spin...I can powerbrake it to 1500rpm and hear nothing. You only hear this knock at low idle to about 800rpm with it in drive or reverse. As soon as the AC comes on when it is in drive, the sound goes away. I really don't think it could be engine knock by these symptoms but what do I know. I can sit there in nuetral and rev it to 4k and hear nothing except a great sounding engine
Last edited by FireCode; 08-14-10 at 11:47 PM.
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Likely piston slap, not rod knock. Piston slap would be more evident at low rpms like you're describing. You can try a heavier oil like turbodremz mentioned. It may soften the harshness of the sound.
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Honestly, and I know this probably isnt it cause it seemed to idle smoothly, it sounded like a spark plug was missing. Did you happen to put your hand on the engine at all to see if you could feel vibrations that were in sync with the knocking?
Drive the car, get it hot, check the oil level and see if it does it again.
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After listening to the video again, that doesn't sound like rod knock, also like mentioned it would be RPM dependent. Now I'm not too familiar with BMW engines, but if piston slap is an issues with them, rip it out and replace it with a 2JZ..cause I have experienced piston slap, but it was with an r/c car nitro engine which uses a ringless piston, not to mention it was a cheap one
Honestly, and I know this probably isnt it cause it seemed to idle smoothly, it sounded like a spark plug was missing. Did you happen to put your hand on the engine at all to see if you could feel vibrations that were in sync with the knocking?
Drive the car, get it hot, check the oil level and see if it does it again.
Honestly, and I know this probably isnt it cause it seemed to idle smoothly, it sounded like a spark plug was missing. Did you happen to put your hand on the engine at all to see if you could feel vibrations that were in sync with the knocking?
Drive the car, get it hot, check the oil level and see if it does it again.
I just felt for vibrations. It is coming from the passenger side of the engine whatever it is. It just sounds like someone is lightly tapping there knuckle on a wooden table.So weird though becuase you only feel it with ac off and in drive.
Last edited by FireCode; 08-15-10 at 10:47 AM.
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Maybe I will get brave enough and stand it front of it with the ac on and in drive with the parking brake on to see if I can still feel the knock. SO far, I have only done it with no ac. I just don't trust the parking brake haha
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Interesting theory. I did do one semi hard pull(enough to break the tires loose in 1st) up to about 40mph right before I got home last night. Wouldn't that be a *****, crack the flex plate 2 seconds from my house.
Although the more I listen to vids, it really doesn't seem, like a flex plate...no chatter.
Although the more I listen to vids, it really doesn't seem, like a flex plate...no chatter.
Last edited by FireCode; 08-15-10 at 02:42 PM.
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change the oil to a thicker oil. when you started the car in the morning it didnt knock because cold oil is thicker and once the car warmed up so did the oil, hopefully thats all it is good luck.
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Thanks guys. I will change the oil. The car runs perfectly other than this weird knock sound at idle (you cant even hear it in traffic) like someome is taking a rubber strip similar to a belt, spinning it around in circles and having the tail end of it repeatedly hit a wooden table.
Last edited by FireCode; 08-16-10 at 07:36 AM.