Originally posted by JCE
My owners manual says to adjust the parking brake between maintenance checks by applying the parking brake for about 10 seconds while driving at 30 MPH and holding the brake relase handle out. Is this in addition to the cable adjustment above, or what exactly does this procedure do? Thanks for the insight.
Even though the parking brake shoes don't really see any wear (if properly adjusted), they tend to loose friction coefficent over time, and this manifests as a lack of parking brake holding power even though the lever (center pull lever on my 190E) is snug after a few clicks.
Not sure why this happens, but performing the procedure you mentioned will burnish the shoes and disk hat section a bit and return the normal effectiveness to the parking brake so it will hold a moderate grade when the lever is pulled up with normal force and about six clicks.
If your parking brake lacks holding power, but there is not excess lever or pedal travel, this procedure should result in a signficant improvement in holding power.
On designs were the parking brake function is a cable that actuates the rear drum or disk service brakes , this problem will not occur, but on the Merc design were a dedicated set of shoes bear against the disk hat section (same as the 65-82 Corvette) this loss of parking brake effectiveness is common, but the fix is easy.