Noisy wipers

[CenturyAero]

After I run the windshield wipers for around 5 minutes on my 1979 Century they start to knock right at the point where they reverse direction. This will continue till get to my destination. The next day they are quiet till running about 5 minutes then the knocking starts again. I don't seem to find any looseness in the linkage. Anyone have thoughts on what the problem might be ?

thanks, Randy in Portland, OR
second and long time owner of 1979 Buick Century Aero Sedan

 

[fleming442]

You may want to inspect the attaching arm to the motor. I believe, it has a little slot, which if worn, will not be detectable unless under load as the nut puts tension on it.

 

[CenturyAero]

Thank you fleming442. I will take a close look there.

 

[airboatgreg]

Check the washer pump timing, spring and cam. If not aligned or worn parts it will knock pretty bad. Do the wiper blades work smoothly when the knocking is going on?

 

[CenturyAero]

Thank you airboatgreg. I had replaced the original blades complete instead of just inserts and the wipers work smoothly before and during the knocking noise.