Date: Sat, 27 Jun 2015 09:17:46 -0400
Reply-To: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Subject: Re: Low Brake Pedal, Caliper Piston Movement.
In-Reply-To: <CAB2Rwfgd6qmaBF-tXkG_j-9dV4k82GDxpJcgz4fn3_vbSzv=9A@mail.gmail.com>
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There is nothing different about the Vanagon brake hydraulics as compared to most any car 1967 and later. The dual circuit design is to provide a back up in case of a hydraulic failure. Some cars will split the brakes diagonally, one front and opposite rear on a circuit. This is common in front heavy front drive cars.
Properly adjusted there should be a small gap between the lever and the adjuster. For adjuster to work when the hydraulics push the shoes out the arm has to free of pressure on both side for the wheel to turn easily. The threads should not be lubed with a heavy grease or ant-seize. That wheel has to be able to turn freely.
New shoes will feel a bit soft until they seat into the drums. New pads in front will also take more motion until they seat and harden although that is almost imperceptible.
Back the hydraulics, the beauty of the system is the pressure will be evenly distributed. Braking effect front to rear is balanced by the cylinder and brake friction designs and the Vanagon also has a pressure reducer for the rear. This reducer functions on tilt. Yes jack up the back you reduce the rear force. Larger tires on the back and you reduce both the force and effects of the brakes. The goal here is to reduce the possibility of rear wheel lock-up and the resulting spin out.
So when the pedal is a little low due to a bad adjustment or wear or what have you, at the point the pedal gets firm the braking effect to all the wheels will be normal. The calipers will work as they should. If a circuit should fail, the pedal will travel real far and then stops inside the master cylinder will cause the reaming circuit to work. To get a feel for this open a bleeder and work the pedal. You will feel this. Try for both front and rear. There is slight difference in the height of that secondary activation. Open a front and rear at the same time and you will now know a total failure.
A soft pedal can be caused by a number of issues. To rule out adjustment set the parking brake and try. If the pedal operation remains firm you are good hydraulically. If you need to regularly pump you still have air in system or a bad check in the master cylinder. If excessive travel and everything is ruled out then you most likely have a bad rear brake pressure regulator. Find a shop with a brake pressure gauge set to test.
Dennis
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of Neil N
Sent: Friday, June 26, 2015 2:46 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Low Brake Pedal, Caliper Piston Movement.
the Vanagon brake hydraulic is set up differently.
1/2 of MC is for fronts etc.
As noted in Bentley (and previously missed by me), and as you obviously know, if shoes are set properly, e-brake cables are ok, then the gap between each e-brake lever on shoe is properly eliminated via adjustment at e-brake equalizer bar, the e-brake works just fine. That said, since I'd backed off the nut at equalizer bar quite far (in a somewhat ignorant effort to take those parts out of shoe adjustment situation), I had to "mess around" with the e-brake cables to ensure that the noted gap was taken up properly. i.e. I found that even after gap was eliminated, if I levered slightly on the shoe at lever, thus pulling on the cable, this would cause a small amount of gap to reappear.
Thinking now, doing this on one cable/lever may simply have pulled on the other thus causing a gap between lever and adjuster bar??
For others who may have been in this position (not understanding e-brake / shoe adjustment relationship), I think of these two systems as separate things, even though they are obviously related. i.e.
properly adjusted and functioning shoes should work fine in spite of slack e-brake cables. This is why one sets shoe adjustment, then e-brake. AND, the e-brake once adjusted, should not affect brake shoe position, at rest.
As has been noted already by folks far more knowledgable than me!
Neil.
On 6/26/15, sailingfc @dslextreme.com <sailingfc@dslextreme.com> wrote:
> If you are not getting a firm pedal, l would say you are not getting
> effective braking from the calipers. I don't know if our vans have a
> diagonal hydraulic circuit like the old Rabbits/Sciroccos did, where
> the you had one front and the diagonal rear brake on the same circuit
> in case of a failure..
>
> My current parking brake shoes are adjusted to the point I get slight
> drag when I spin the wheels and at one click of the parking lever, it
> will hold in my slightly inclined driveway.
--
Neil n
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