190sl brake question

Hi All,

My 190sl brakes work fairly well, but after some use (like while going down a long hill with stop signs) the brakes will stick on slightly. The brakes will be on enough to cause the car to slow down while coasting, and hold its postion in neutral at a stop light, but not on enough to keep me from driving off under power. btw- this car has the remote master brake booster.

One person says that's the way the car is supposed to be, another says I need new brake hoses, and a third is telling me I need to rebuild the brake booster. Anyone had this or have any ideas?

Thanks,
Eric

[Arthur Dalton]

It is quite common for older brake hose to become contricted and cause this type of problem, but if you find that all the brakes seem to drag, [ mostly after heavy usage, as you state],the problem may well be in the master pushrod clearance adjustment.The pedal free play should be 6-8 mm, which is about 1 mm at the pushrod-and piston.
If there is no clearance /free play, the
compensating port in the master will not let
the fluid to release completely in the pedal up position. Under hard braking , the heated fluid can not return completely to the res. and results in dragging of the brakes.
Jacking of the car to check for drag and opening bleeders will help in finding your problem. This rod has an adjuster and is simple to check before changing parts .
I do have the Factory Workshop info on this
procedure and the entire braking system that
I can send you if need be.
Arthur

[Jim Villers]

Arthur is quite correct on all counts. A couple of symtptons to check before jumping into the job. Driving about 15MPH, brake hard. If the car swervers to one side, you probably have the brake hose problem suggested above. Disconnect and plug the vacuum hose to the brake booster and do your hard braking test. If you do not feel the brake drag, the problem is in the power brake unit. I this is the case, you have two options, spend a LOT of money to fix it or, as I do, just drive without power brakes. BTW join the 190SL Group if you are not already a member and join us in Minneapolis for the national gathering this summer.

Jim Villers
1961 190SL

Thanks Gentlemen, for your quick replies.

I'll do the tests you recommend, and report back!

Eric

[bstreep]

Erich,

I'm new here, just found this forum. Couple of other things to look at. I don't know what year your 190sl is. On the back of the booster MAY be a small filler hole with a hex plug (I'm thinking maybe 14mm). If your booster has this (the early boosters did), this should be filled with clean mineral oil. Check and make sure that the "filter" on the front of the booster is clean. Another test to see if you need to rebuild your booster is to put a piece of paper over the screen in the front, and with the engine running, have someone press the brake. It should "suck in" the paper. Also, an indication that your booster is leaking is white smoke in your exhaust (burning brake fluid). This assumes you are using regular brake fluid. All else fails, bleed system with clean fresh fluid. Then look at booster rebuild. These brakes SHOULD hold just about anything.

quote:

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Originally posted by EricH:
Hi All,

My 190sl brakes work fairly well, but after some use (like while going down a long hill with stop signs) the brakes will stick on slightly. The brakes will be on enough to cause the car to slow down while coasting, and hold its postion in neutral at a stop light, but not on enough to keep me from driving off under power. btw- this car has the remote master brake booster.

One person says that's the way the car is supposed to be, another says I need new brake hoses, and a third is telling me I need to rebuild the brake booster. Anyone had this or have any ideas?

Thanks,
Eric

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Bill Streep
San Antonio
'57 190SL

Thanks for the suggestions on my car.

I replaced both front hoses. While I was working on it I've decided to also take the gas tank out to put a plastic coat on the inside. As soon as I get that back in, I'll try the additional booster troubleshooting.

Eric

Thanks to Jim, Arthur, and Bill for their trouble shooting help.

I've replaced both front brake hoses since they needed it and disconnected the remote booster. Now I'm wondering about rebuilding the booster. Has anyone done this? Here is a link I found on a source for rebuild kit and instructions. http://members.aol.com/valueadded/maint/booster/booster.htm