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ENGINE NOISE

Posted: Fri Jan 08, 2010 3:22 pm
by 8543bob
I BOUGHT MY "M" BACK IN APRIL FROM GSA. ITS BEEN RUNNING GREAT, BUT ALWAYS HAD A SLIGHT RAPPING NOISE ON ACCELERATION OR IN NEUTRAL WHEN YOU INCREASE RPMS. THE RAP DOES NOT HAVE A RYTHEM TO IT BUT SEEMS TO VARY IN SOUND. THE OTHER DAY I WAS STICKING A PIECE OF REFLECTIVE TAPE ON THE FRONT PULLEY TO CK IDLE RPMS, STARTED THE ENGINE GOT UNDER THE CAR TO HIT THE TAPE WITH THE LIGHT; NOTICED THE RAPPING SEEMED TO BE COMING FROM THE FRONT OF THE ENGINE. THIS ENGINE STARTS IN 15F WEATHER WITHOUT A PROBLEM. I KNOW THE TOP END HAS LITTLE TO DO WITH THE LOWER END; JUST THOUGHT I WOULD GIVE YOU ALL THE INFO I HAVE. BEFORE I DROP THE PAN I AM LOOKING FOR YOUR BEST SUGGESTIONS ON WHAT I MIGHT FIND. THANKS BOB

Posted: Fri Jan 08, 2010 7:07 pm
by Lifer
It could be "advance warning" of a rod bearing failure on the #1 or #2 cylinder, but they usually chatter most when decelerating or running free. It could also be a number of other "less expensive" problems. Kind of hard to say without actually hearing it or a more accurate description of the sound.
I'd suggest using a mechanic's stethoscope to try and pinpoint the exact location of the sound. If you don't have one, use a "broomstick stethoscope." (Just cup your hand around the end of a broomstick or long dowel, hold it to your ear, and touch the other end to the suspected area on the engine. You'll be amazed at all the stuff you can hear! ;) )
Once you have pinned down the location, give us another holler and we'll go from there.

Posted: Fri Jan 08, 2010 7:55 pm
by Josh
I agree with Lifer... probably a rod bearing. But, could maybe be a broken valvespring? :?

Posted: Sat Jan 09, 2010 6:37 am
by cuz
Could also be a fuel pump drive arm.

Buy the mechanic's stethoscope. They are not expensive. Then you can have your eye on the end of the probe instead of your head facing sideways with the broom handle. This is very important when you are probing around a part that moves a lot! :wink:

ENGINE NOISE RE-VISITED

Posted: Fri Jan 15, 2010 8:29 am
by 8543bob
GOOD MORNING, FINALLY GOT THE WEATHER, THE TIME AND A STETHOSCOPE TO RE-VISIT MY INTERNAL ENGINE NOISE. WITH THE STHETHOSCOPE I SEEMED TO HAVE NORROWED, WHAT SOUNDS LIKE CLICKING, THRU THE STHETHOSCOPE, TO THE LEFT CENTER OF THE LOWER ENGINE, RIGHT AROUND THE DIST. COULD IT BE THE DIST DRIVE MAKING THE KNOCK/CLICKING???
THANKS BOB

Lifter

Posted: Mon Jan 25, 2010 1:17 pm
by carolinamv
Could it be a simple lifter out of adjustment? -Jay