I serviced my brakes (both front & back) about 18 months ago. Had all 4 rotors cut, & installed new ceramic pads & replaced emergency brake hardware as well. Vehicle drove fine & I have only put about 4K miles since that time. Recently I started to develope pulsation in pedal & a very choppy feeling when braking. Inspected all 4 wheels. Pads look fine, pull rotors off & checked for warpage by laying metal straight edge across rotors. They look fine to me & rotor surfaces show normal wear. Caliper pistons retracted back-in easily using a C-clamp. Also I checked to make sure that I don't have any play in the front wheels from top to bottom. All seems tight with front end. While the front calipers were detached from rotors with pads off, I had someone lightly pump pedal with engine running & I noticed that the top piston (front calipers have dual pistons) pertrudes outward while bottom piston barely moves. This is true for both sides.
Is this normal for the top piston to pertrude outward (after 4 or 5 taps of the brake pedal) while bottom piston barely moves & if so why?
Next as I was reading over your info on replacing rotors & caliper; you mention the caliper should move freely from side to side on the slide rails.
How is this checked? Is it done with the pads & calipers re-attached & before touching brake pedal (while pistons are still retracted)? Also how much play should there be?
Lastly, any thoughts on what is causing this pulsation & choppiness when applying my brakes? Chopiness is noticeable to anyone riding in vehicle.
Please advise back @ earliest convenience. I will increase my donation should the amount of written exchanges warrant it.
Thank you in advance for your forth coming reply.
Monday, February 21st, 2011 AT 6:54 AM