Braking System on 1962 220 Sb
 

Can anyone provide a good step-by-step guide on rebjuilding the braking system on this car, where to get the parts and so on. I also have a master cylinder that has the brake switch in it, which is a pain in the butt quite frankly. However, the brake pedal is very spongy, my friend says it is the master cylinder, for which I have a rebuild kit. The brakes are about the only mechanical thing I haven't rebuilt yet on this car, so any help would be much appreciated (it has a booster in the engine compartment, driver side front - can anyone explain the use of this, I think this is 'power assist'?). Anyway, when stopped on a hill with the brake pedal down, the pressure slowly drops and the pedal goes to the floor, and the brakes come off, after a couple of pumps it is OK. I have never done a lot of brake work, but I think it will be good to learn! Tips are appreciated, also, i think I may want to replace all the brake lines just in case they are rusted. Thanks,
Rory

Your power brake accumulator is probably like the attached picture if it is mounted next to the radiator. If you try to rebuild it yourself you'll need some expertise. I recommend a specialist. When you do rebuild your entire brake system, insure that you replace all the hoses. I initially replaced just my front with Stainless/teflon and ended up with a problem of swelling old rubber rear hoses causing brake lock!

That's a classic symptom of a master cylinder going bad,

The booster sits behind the master cylinder, and provides stored vacuum to reduce the amount of effort at the pedal. So when you depress the pedal, vacuum is released and assists the pressure on the brakes.

And when you get around to the shoes - they can be relined/resurfaced as replacements are hard to find. But hitting old shoes with emory paper can bring em back to life if they've got more than 1/8" or more suface left on em.

Always think "Brake System" when you're working on it. So as mentioned above, replace/rebuild the works.

If you have a brake system that is working for the most part, then you know most of the compontents are actually "okay." In other words.....you're not complaining of a super hard brake pedal which would indicate brake booster failure....and you're not complaining of brakes pulling to one side, or brakes dragging, so you know your calipers and rear wheel cylinders are okay, as are the brake flex hoses.

Your chief complaint is the fading pedal, which is certainly the master cylinder as pointed out already. Start by rebuilding that, and yes, replace all the flex hoses. Personally, I wouldn't replace the metal brake lines at this point. Pull the drums and inspect the shoes and pull back the dust boots on the wheel cylinders and check them for weeping fluid. Replace as needed.

Adjust the rear shoes properly before bleeding the system. After that, replace the brake fluid every 2-3 years.

I get alot of stuff from German Parts and Restoration here in San Luis Obispo. www.gpr.com

brakes
 

the remote booster Gregg pictured is exactly like the one in my 63 220b. I have it all apart and can't find cup seals for it. If anybody knows where I can find seals Id like to know. People will rebuild it for big money but no body will sell a kit. I am driving the car with it bypassed. Pedal pushes hard but stops OK. you probably have four drums as I do. the front drums have two wheel cylinders each. I replaced a rear wheel cylinder and it was easy. The shoes were all new when I bought the car and I don't drive enough miles to wear them down. Your master cylinder is probably exactly like mine. I couldnt find a kit so I rebuilt it with a kit from a 66 chevelle it worked pretty good but I saw a NOS master cylinder on ebay and I bought it and put it in. Any way the rebuild is easy.Undo the bolts, pull it off firewall. there is a big clip in the end under the rubber boot. pull that out and every thing slides out document the order that things come out . clean the bore with emery cloth and put the new stuff back in. be sure to bench bleed it before you re- install.

Unlike modern cars with integral brake booster, the separate remote-mounted booster/servo units DO have a separate master cylinder that can leak and cause brake fluid to fill the vacuum chamber. If you are NOT loosing brake fluid and stopping effort hasn't increased dramatically, the servo is probably OK.

An other thing that causes a low brake pedal on these early Fintails, is malfunctioning of the friction-type self-adjusters attached to each brake shoe. They were stuck on my '60 220Sb and eventually caused a low brake pedal on initial application, which would then 'pump-up'. I was able to 'manually' adjust mine by prying them with a large screwdriver and my brake pedal is reasonably firm now.

If you're stopping with a firm brake pedal, that then SINKS while stopped, and you are NOT loosing brake fluid, I'd suspect a faulty master cylinder first.

Happy Motoring, Mark

Thanks for all the info guys, that is helpfull for me. The booster is something I haven't even looked at yet, and by the sounds of it, it may be difficult to get parts for it from what Pat was saying. The other problem with the brakes, and maybe the same thing, is that when stopped at a light, and with the car on a slight incline, when taking the foot of the brake pedal, the car doesn't move (ie. on such a slight incline gravity alone should make it move), it feels as if even though I have taken my foot off the pedal, the brakes are still lightly applied. When I clutch out, no problem, no funny sounds or anything. Quite frankly, the whole braking system I find scary. We have rebuilt pretty much every thing else on this car, so the brakes are the last mechanical thing... The Master Cylinder rebuild kit is an ATE and MB part # 000 586 00 29, just picked it up on Ebay. Hopefully it is the right size, I didn't think about that, just that he said it was right for my year and model in the Ebay description (item #7992364461).

Thanks again for all the info, if anyone knows whether the 'sticky' brake is connected to the Master Cylinder problem, or if it is something completely different that would help. This weekend I am putting on a new rear bumper and reinstalling all the dash board components since the wood has been totally refinished and varnished. Looks great!

Rory

On my drum braked Benzes, the most common cause for the brakes sticking has been defective rubber brake hoses. They will look fine but can swell up internally, trapping the brake fluid and keeping one brake applied. It usually doesn't happen on all 4 brakes at once, though that's not impossible. Also the aluminum brake shoes can corrode to the pivot bolts and stick. I haven't experienced it, but I've also heard of the power brake servo sticking, causing the brakes to lock on.

Happy Motoring, Mark

A guy at work here who has done a lot of brake work said that the spongy-ness is caused by an air bubble most likely, and to bleed off a bit of fluid at each brake. He said he had a similar problem where at stop position, the pedal would sink to the floor, so he bled out a bit at each brake, and it was OK after that. Also, he said that could also be the problem with the brake light switch, but that means a bubble in the master cylinder more than likely. A whole lot of bleeding will have to be done I suppose, or I can drive around and pump it in the mean time.

Also, he suggested using Dot 3 - I have no idea what is in there now though, I don't think there is any way to test. I know not to mix a 3 and a 5, but is there any way to test what is in there already (I am not sure where/who last added brake fluid, but it wasn't me).

Thanks
Rory

and you're using DOT4 instead of DOT3 fluid..... dot3 will slip through rubber seals, you understand, a question of heat plus the fact that Vintage MB rubbers are made from natural materials instead of synthetics.

By all means, bleed the system and see if more normal brake operation results. This won't fix plugged brake hoses though.
DOT 3 was the standard brake fluid used in most American and foreign cars for many years. DOT 4 is similar but has a higher boiling point and it's now required for most European cars. I believe DOT 4 can be used where DOT 3 was specified, but not the other way around.

DOT 5 is silcone brake flud and can't be mixed with the other two.

Happy Motoring, Mark

The friend of mine who is more mechanically minded said it seemed to be that the master cylinder was the problem. The brakes start out hard, and then the pedal slowly sinks when in the stop position. I assume, hope, the rebuild kit will work that I got on Ebay (mentioned above)... I hope I won't have to replace it with something else like Pat did above. Once the rebuild is done, I will bench bleed it as suggested, and then do the whole system once that is back in, and then, hopefully back to normal. This is my first foray into brake work, so your comments are much appreciated!

I bought a master cyl kit on ebay. the guy said fit 220b . Pulled mine apart and kit didnt fit. It was a 15/16ths. kit and my master cyl had a 1'' bore. be carefull taking stuff out in case it doesnt fit and you have to put it back in. I made the mistake of cutting the seal off the piston before I knew the new kit didn't fit and I was stuck untill I found another kit. I will put a pic of my master cyl so you can see if the same type.

Pat, what do think about resleeving it so it does fit? I am going to consider that option too. There is a local machine shop who does excellent work for cheap, he resleeved my number 1 and 2 cylinders, and did an excellent job. Wish I had done the head at the same time... I was talking to a guy yesterday evening about replacing all the brake lines and all that since they are looking a little corroded. So will look into that as well. I will replace the hoses too - anyone know where to get the proper hoses for this car?

Thanks
Rory