[T2] Rear brake problem, brakes lock when braking

[Daniel Martinelli]

Thank you all for your help, we really appreciated your insights, friendly
help and your compassion.

Sooo, we solved the problem, finally.

Quick recap:

MOT tested the our VW Baywindow and the verdict was: Back brakes lock up
when doing an emergency brake, car is not road worthy.

So we tried to fix the problem by replacing the following.

1. New proportioning valve and new brake pads on the front brakes

MOT says: No good

2. New brake drums and shoes rear brakes
3. New brake hoses

MOT says: No good

4. Refurbished the cylinders on the front disk brakes
5. New Master brake cylinder

And the culprit was: The guys at the MOT!

In the end we gave up and went to the VWbuswerkstatt in Winterthur. The
owner (Thomas Böhi, great guy, he knows his stuff,
http://www.vwbuswerkstatt.ch) tested the brakes and stated: The brakes are
fine!

Böhi took the bus to the MOT and showed the guys there how to properly
brake test a vintage vw bus and guess what: The bus passed the MOT!

There was never a problem in the first place. Turns out, that to test the
brakes on a vw bus you have to slam the brakes really hard and everything
just works great. But since nowadays all new cars have ABS, the 'experts'
at the MOT were just too sissy on the brakes.

So, at least we have a brand new brake system :-)

Cheers!

Daniel



On Tue, 22 Jan 2019 at 17:19, c.dreike <c.dreike at verizon.net> wrote:

> There are only so many things that could be going on.
> 1. proportioning valve setting is wrong
> 2. friction on rear shoes is too high (contamination?)
> 3. friction on front pads is too low (oil contamination?)
> 4. wrong sized pistons either front or rear (don't know how that could
> happen)
> 5. wrong master cylinder (don't know how to fit the wrong one)
> 6. Parking brake mechanism (cables etc...) too tight
> 7. brake booster doing something weird
>
> Did I miss anything?
> I don't think the metal brake lines would have anything to do with this.
>
> Chris
>
>
> On 1/19/2019 5:09 PM, c.dreike wrote:
> > Could the new proportional valve have a problem?  I know that
> > adjustable proportional valves are available.
> >
> > Chris
> >
> > On 1/19/2019 5:28 AM, Daniel Martinelli wrote:
> >> Yes, they do look fine but we decided to refurbish them, as we have the
> >> parts and see what happens
> >>
> >> Daniel
> >>
> >>
> >> On Sat, 19 Jan 2019 at 02:37, Robert Camacho <bcoldpro at aol.com> wrote:
> >>
> >>> How old are the rear brake shoes? Have those been visually inspected?
> >>>
> >>>
> >>> -----Original Message-----
> >>> From: Daniel Martinelli <daniel.martinelli at gmx.ch>
> >>> To: Type2 list <type2 at type2.com>
> >>> Sent: Fri, Jan 11, 2019 8:33 am
> >>> Subject: [T2] Rear brake problem, brakes lock when braking
> >>>
> >>> Dear all
> >>>
> >>> A friend of mine has a weird problem with his T2b camper rear
> >>> brakes. When
> >>> braking hard, on the road, the rear brakes lock up. We replaced the
> >>> front
> >>> disk brake pads to no avail, checked the caliper pistons and they
> >>> are fine.
> >>> Tires are almost new and correctly inflated.
> >>>
> >>> On the test stand, when tested independently the rear and front
> >>> brakes work
> >>> perfectly.
> >>>
> >>> We thought it could be the proportional valve, replaced it but the
> >>> problem
> >>> persists.
> >>>
> >>> Sooo, apart from the proportional valve, what could influence brake
> >>> distribution from front to back? We are at a loss here.
> >>>
> >>> Any thoughts?
> >>>
> >>> Thanks a lot
> >>>
> >>> Cheers!
> >>>
> >>> Daniel
> >>> _______________________________________________
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> >>> https://www.type2.com/lists/type2/listinfo
> >>>
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