Re: [diesel_mercedes] 220 115 master cylinder help

Two failures I have experienced which caused the calipers to lock.

One was a rubber brake line that delaminated inside, causing fluid to
flow out, but when it flowed back, the flap of rubber folded back
causing a "one way valve"

The second was tight brake pad backing plates. The new brake pads are
cheap, the edges are plasma cut with considerable tolerance. When you
apply the brakes, the pads heat up, heating the metal backing plates. If
there is no/little clearance, these will heat up, expanding into the
caliper. They will not release the brakes. The brakes will continue to
apply, heat more, expand more... You will need to stop for about 5
minutes to cool the expanded metal. Then you can drive until you hit the
brakes again. File off the sides of the metal backing plates to make
them smooth. debur the edges so they can slide. Removed any rust/crud on
the sliding surfaces. A LIGHT coating of silicone may help on the edges.

I have had a lot of bad master cylinders. Even brand new ones were
garbage. If the fluid in your brake reservoir is black, your master
cylinder seals are degrading. Brake fluid is clear and should stay that
way. I'm wondering if the older seals are not compatible with DOT3,4 fluids.

Carl


On 3/30/2014 11:09 AM, Atwood,Warren wrote:
>
> The RF caliper did not lock up previously. Pads were worn half way
>
> and heavy glaze. Replaced pads, and booster. Did not change the MC,
>
> it works on the bench when I bled it. Hoses are least 15 years old.
>
> Will replace all hoses this week.
>
> Bench bleeding did help – at least have a firm pedal.
>
> thanks for the feedback
>
> *From:*diesel_mercedes@yahoogroups.com
> [mailto:diesel_mercedes@yahoogroups.com] *On Behalf Of *Aleph93
> *Sent:* Sunday, March 30, 2014 7:57 AM
> *To:* diesel_mercedes@yahoogroups.com
> *Subject:* Re: [diesel_mercedes] 220 115 master cylinder help
>
> Was the RF caliper locking up before? (pulling to one side, wearing
> faster, glazing the rotor)
> Is that the same one that no fluid comes out of?
> Is the Master cylinder new?
>
> Try the old method of someone stepping on the pedal.
> While bleeding my wife's Volvo, one of the bleeder valves wouldn't bleed
> with the pressure bleeder, yet did so with the old method.
> Volvo's are weird, there are 2 lines going to each front caliper, one
> just for the front brake, and another that also connects to one of the
> rear brakes, so if one line broke you'd still have both front brakes.
> Extra safe, yet more time to bleed.
>
> Rob
> '85 300D
> Garden Grove, CA
>
> On 3/30/14, 3:16 AM, diesel_mercedes@yahoogroups.com wrote:
> > 220 115 master cylinder help
> > Posted by: "WARREN ATWOOD"menlotrail@yahoo.com menlotrail
> > Date: Sat Mar 29, 2014 9:20 pm ((PDT))
> >
> > Replaced the brake booster and front pads.
> > Bench bled the master cylinder
> >
> > Problems bleeding the system. Using a Actron vacuum brake bleeder,
> and cannot get all the air out.
> > No brake fluid coming out of the front brake calipers.
> > RF caliper locks up.
> > Is there a residual valve in the system? Traced the lines and did
> not see one.
> >
> > Any thoughts on what could be the problem ?
> >
> > Many thanks,
> > warren
>
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