Knocking Sound

[djdani3l10]

Been a while since i last posted, but the bonneville is making a knocking sound.

The knocking sound is very similar to the knocking sound a harmonic balancer would make, thus i changed the harmonic balancer, unfortunately it wasnt that.

Im thinking it might be the lifters but not completely sure. Im opening up the engine after finals, so about dec 12.

So looking for any suggestions as to what it could be, and what upgrades i could do to the engine while its opened up, if there are any upgrades i could do.

Thanks for the read, and hope you could help me out!

[maxi426]

It would be nice to narrow it down before you start tearing it apart. Have you tried running it with the belts removed? Does it make noise only in the first few seconds when you first start it cold, only under a load, only when it's cold, only when hot, at high RPMs, only at idle?

[garagerog]

I agree with maxi, start by removing the serpentine belt to rule out an accessory like the PS pump making the noise. If it's not an accessory, use a mechanics stethoscope to narrow down the location of the noise, top of the motor? probably in the valve train, lifters or rockers maybe. Bottom of the motor? not good news as that probably means bearings. Has this car ever had a coolant leak and the LIM/UIM repair done?

[djdani3l10]

Okay to begin the sound seems to be in the middle top of the engine, the engine has been absolutely perfect until it made this noise, the car didnt make any noise, then after 2 days of not driving the car at start up it made this noise, as rpm are increased the noise goes away, never had a leak and no repairs done.

My dads thinking its the lifters.

thanks

[djdani3l10]

And oil pressure is perfectly fine.

[maxi426]

Usually valve train and bottom end noises get louder with engine speed. Possibly collapsed or cracked piston skirt. If you brake torque it, does it get louder? Suppose it could be a collapsed lifter that pumps up at higher oil pressure/engine speed. Tuff to tell without being there. If you think its' a lifter, you could remove one valve cover at a time. While the engine is idling you can put your hand on each rocker. You should be able to feel the difference in the rocker with the offending lifter. Good luck

[djdani3l10]

Harmonic Balancer lifters and rods changed and still has the noise

So tomorrow ill be taking the oil pan off and taking a look

[MKMike]

Here are 2 good articles on pinpointing the issue:
http://www.remanufactured.com/Engine_Diagnosis_101.htm
http://www.foxvalleymarc.com/Tech_secti ... oises.html
Note that the first article mentions a sludged up engine and tells you not to use any type of flush but to change the oil every 500 miles or so until the sludge is cleared out by the detergents in the oil.

Hope these helps you find the source.

[djdani3l10]

I took the bottom apart, and narrowed it down to a piston slap.

[MKMike]

Thanks for reporting back on the cause.