Brakes Issue

[Brian Davies]

Hello I have recently gotten rid of my other garage-queen car, so now I have more time to work on fixing up the ol' 356...

The most pressing issue I have with the car is the brakes just don't work. These are handy things, so I want them to work.

Car: 1960 Roadster with drum brakes

Modification: stock master cylinder was replaced with a dual-circuit model out of... I think a 912? My dad did the work a long time ago and said he used recommended parts so it "should" work.

Symptom: When the car is first driven, there is no braking from any wheel except the right front. The pedal feels "right", but it seems like all the brake force goes to that one wheel and it locks up almost instantly. The car barely will even stop and it pulls hard right on braking. After you use the brakes a few times, the problem partially resolves, and you get less pulling and a little better braking but still nowhere near good enough. The right front always locks up first. It's very hard to drive the car like this because you have to leave a TON of following distance and go SLLLOOOWWW just in case someone cuts you off or something. I also confirmed it's the right front with a infrared heat measuring gun thingy. The front right drum is hot and the other three are cool.

So... ideas? Could this just be as simple as adjusting them? I have never tried to work on drum brakes before. Is this master cylinder the issue? I was thinking of going back to the stock master cylinder but I think I'd have to make all new brake lines, blah blah... lot of work. Plus it's less safe as the stock one was a single circuit as I understand it. Is there a how-to somewhere with how to correctly adjust the brakes or check operation?

Thank you for any advice you have to offer!

Brian

[Ron LaDow]

Brian,
You're right about brakes being handy.
It sounds like they haven't been touched in quite a while, so a total rebop of the system seems indicated. If you are not willing to spend a lot of time, it's prolly one of those 'buy it' services.
Hoses, check/rebop master and slave cylinders, check all the springs and brackets, reassemble and adjust. I just don't see it as a 'fix this thing and hope'.

[Martin Benade]

I would suspect you have some sticking brake cylinder pistons. They tend to do that sitting around, especially if the storage is not perfectly dry. You should probably take them apart and rebuild or replace the cylinders. Your master cylinder is hopefully a VW part which is set up for all drum brakes, unlike the 912 part.

[Doug McDonnell]

And be sure to replace all four rubber brake hoses. They fail internally.

[Martin Benade]

I agree, an important addition.

[Tom Martinez]

Maybe the front brake cylinders are installed backwards, negating the servo action. Check out the Registry Restoration Guide volume ii, page 69. I just did a complete brake job from shoes to master cylinder and it would be an easy mistake to make.

[Vic Skirmants]

+1 on Tom's comment. Fairly common problem. You can look through the brake adjusting holes in the drum and see if they are correct. If they are installed properly, then sticking cylinders is definitely next on the list. Also, a leaking wheel cylinder will cause a brake to lock up.

[Brian Davies]

Update: Watched some youtube videos on volkwagen bug drum brakes and learned a lot about how they work and how they are adjusted.

There is nothing leaking. The car sits a lot in the same spot in the garage, so if anything were leaking, I would see it I think. I do think something could be installed wrong/backward because my father put the car back together after a multi-year body restoration process and I think he was sort of in a hurry and it's definitely possible he missed something that would be easy to mix up.

When the weather warms up (at least a month from now or more) - I will start checking into this stuff that you fellows have suggested.

Thank you so much for the help! This is a really cool car that is a family member, but it has some work that needs to be done to get it in tip-top shape.

Brian

[Dick Weiss]

Since the M/Cyl. was replaced, make sure there's at least a 1mm clearance between the pedal pushrod-to-the-M/C's piston--
feel by hand; this makes sure the piston returns rearward fully to allow fluid to fill the the piston's cavity during activation.

I assume the brake cyls. were bled correctly thru the bleeders and the M/C's reservior was kept topped up during bleeding(?).
Make sure the drum liners are intact w/o any corrosion--especially the B drums and any unusual contacts of the shoes--their
arcs should fully fit the liner IDs.

Finally, adjusting the brake shoes fully tight, then backing off around 4-to-6-teeth (only adjust 1-tooth @ a time!) to release
the shoe(s) should just clear the drum liner--are they round enough as just a small drag exists but the drum (w/or w/o the wheel installed) can be turned?

If the liners aren't round and during braking you get 'pedal pulsing', you may need a drum/liner truing; front brakes will give a feedback via the steering wheel and a light handbrake pull (not fully) will determine the rear brake effect.

Dick

[Richard Shilling]

A 912 master cylinder won't work on drum brakes. The master cylinder for disc brake cars does not have a valve to maintain residual pressure on the hydraulic system. Drum brake masters do have such a valve, so start with the correct master cylinder.

If you are not used to working on brakes, please leave it to a professional. "Going through the brakes" can be expensive and is always difficult, here are the steps:

Inspect the metal brake hoses, replace any with any sign of rust. Replace all flexible brake hoses. Remove the drums and check for roundness and max diameter. Overhaul or replace the wheel cylinders. Replace the new or relined brake shoes using new springs and light brake lube where the shoe touches the backing plate and on the adjusters. Adjust the brake shoes. Replace the master cylinder with one for drum brakes, either single or dual circuit, that has been pre-bled on the bench. Bleed the brakes. Re-check the brake shoe adjustment. Press as hard as you can on the brake pedal for a couple of minutes to make sure the pedal doesn't sink slowly to the floor assuring that there are no leaks. Test drive the car, being careful, and start with slow stops graduating up to very hard stops. Final check on the brake fluid level.

Drive your 356.

[Steve Proctor]

I would add arcing the shoes to the drum if at all possible. Local vendors that can / will do this are growing fewer all the time. I found a fork lift maintenance facility that was able to do mine.

STP

[Larry Coreth]

Just to underscore Richard Shilling post below is what the factory shop manual says !
Good source to consult when making changes.
Note Yes a 912 M/C is just a dual-circuit version of the 356C M/C.

[Brad Ripley]

Master cylinders in the 356 period were marked with a label around the body of the cylinder. Earlier it was an aluminum band and later a vinyl sticker. Here are photos

[Dick Weiss]

Richard,

I don't get into the dual M/Cs much, but a slight correction to your statement about the differance between the disc brake and drum brake
M/Cs; the disc brake M/C has the so-called (internal) purge disc for collapsing the pressure to release the pads and it has a blue strip around the body. The drum brake M/C does not have the internal disc, but it can have one installed during its re-assembly; I've done a couple many years ago when the disc M/Cs weren't readily available--even modifying VW M/Cs to fit the 356 mounting to the bulkhead.

Dick

[Larry Coreth]

Richard, Dick and interested parties,

After reading your posts one could be confused because both of you have left out critical info !

1. Both M/C's (drum & disk) have check vales at the foot of the M/C, just of different design and functions.
2. The drum M/C has the check valve type shown below such that a residual pressure is maintained in the
brake system controlled by the spring pressure on the check valve disk.
3. The disk brake M/C check valve has a similar function as above, however the residual system pressure is
designed to remain only briefly, then collapse. The "purging passage" (see my post above attachment)
allows the system pressure to go to zero after a short time (1-2 seconds), thus allowing the pads to retract
completely.
A word to the wise, when posting technical info, be sure to present all the pertinent facts. Remember too many "old wives tales" have been promoted by "a little bit of knowledge" ! From personal experience I know it is easy to do.