[Shop-talk] Squeaky brakes

[Richard Beels]

Don't know your specific car, so general advice...

how's the surface of the rotor?  old crappy rotor and new pads are a 
recipe for crappy braking.  if they're both new, have they been bedded in?
6 quick decel runs of 60-10 should get the brakes up to temp and get 
a good transfer layer on the rotor.  if they smell after 2-3 stops, 
keep going, that's just the initial burn off of remaining 
volatiles.  make the stop aggressive but don't get on the ABS.  Don't 
stop during the runs and do them right after each other.because we 
want the brakes to heat up.  They might fade too, so beware - safety 
and all that.  Then coast to a stop (use e brake if it's internal to 
rear rotor) and do a _quick_ check of each rotor to make sure they're 
all hot and stinky.  Then go for a 5-10 minute drive to cool the brakes down.

Anti-seize on where the pad slides is wrong. brakes are too hot and 
it turns to glue.  I use either syl-glide or the permatex purple 
ceramic lube.  there should be thin metal (Stainless!) clips that go 
over the caliper (bracket) that the pads actually ride on.  and the 
pads should move in and out easily by hand.  but not so loose that 
they can wiggle clockwise/counterclockwise when looking at the back 
of the pad (if that makes sense).

something i see occasionally is too much lube in the guide pin, which 
can cause "hydraulic push" and the pin doesn't fully retract at rest.

if the pads have a shim clip, it needs a dab of purple goo in between 
the shim and the back of the pad.  I also rub a little purple goo on 
the piston edge that touches the back of the pad, around the whole 
lip/edge.  eliminating non-lubed metal to metal contact is the goal here.


At 05/16/2017 at 14:28, Shakespearean monkeys danced on 
eric at megageek.com's keyboard and said:
>OK, I'm at my wits end (it's true that was my STARTING point, but still)
>
>I bought a new (to me) 2007 Mercedes GL450.  It's in great shape, 
>garage kept and clean.
>
>After a week or so, the brakes make the typical squeal when applied 
>lightly after a longer trip.
>So I checked all the pads. They were almost brand new.  So I blew 
>them out with air (note, I didn't disassemble them at this time.)
>Another week so goes, squeal get worst.  Drives my crazy.
>
>Last night, I pulled apart each wheel, cleaned everything.  I added 
>CRC Anti-noise goo to the back of the pads, cleaned the caliper pins 
>and applied permatex caliper pin lube to them.  Finally, I placed a 
>bit of never-seize silver goo to the matting points of the pads and 
>calipers (After wire brushing the surfaces to clean them.)
>
>Blew everything clean and reassembled.  This morning, I got a little 
>squeal after my 50 min commute to work.
>
>WHAT CAN I DO NEXT?  I hate brake squeal, and it kills me when I do 
>so much work and don't get any real results.  What am I missing?
>
>Should I try to 'rough up' the pad surface? And if so, what is the 
>best method to do this?


Cheers!