brake assist

[n/a]

Hi everyone

Ever since I bought my car I have had trouble with the brake assist. I have changed the booster twice, the master cylinder once, and the vacuum hose as well, but I dont feel any difference after these changes. Brakes are hard, like there is no assist at all. I can drive the car fine as is, but my wife cant stop the car as the brakes are too hard for her. Any ideas where to go from here? Telling me not to let my wife drive is a good start, but I would really like to get this fixed. I live in central NH and if anyone can recommend a good mercedes machanic, that would be great. I have owned my 1969 280 sl for 3 years and I saw another pagoda once, so this isnt exactly a hotbed for 280sl's. Any advise is appreciated.

Regards

Lowleadman

[jeffc280sl]

I think you have a vacuum leak somewhere.  I had a similar problem when I installed a new booster.  The new booster came without a bushing which needs to be installed at the location where the booster and brake assembly bolt together.  This bushing prevents the booster bracket from compressing on the brake assembly as you tighten the bolt.  The brake assembly or arm needs to swivel in this location to maintain a vacuum seal.



Jeff C.
1970 280SL 4-speed

[norton]

Could this be the rubber brake line problem again, Where the rubber brake lines swell and harden with age and restrict the flow of fluid, If your rubber lines are old, you should check for this.

[norton]

Just read your other post about rear end work, what caused the brake fire? Could that have been caused by bad rubber brake hoses, not allowing the caliper to retract?

[n/a]

I am not sure what caused the brake fire. I was taking my 40 min after work spin. I was near home and at a stop sign. I smelled something burning. I asked the wife if it was us burning up, and she replied she didnt think so. Once underway again, the oder disapated. I drove the final 1.5 miles to my home. When I got to the driveway, my brake pedal went all the way to the floor, I was able to drive up the driveway. When I shut the car off and got out, white smoke was pouring out from the rear driver's side brake. I took a look under the car and there was a fire betwen the wheel and the shock. I was able to put the fire out easily and quickly, but the heat generated did not disapate until I had poured water from a garden hose on the wheel for 45 min. When I discussed the issue with the person I bought the car from, he commented that brake fires were somewhat common in the 280sl. Wonderful. He sent me a bunch of parts, including the brake lines. My uneducated guess is that the brake locked up for some reason which generated the excessive heat and either brake fluid or grease caught fire.

lowleadman

[rwmastel]

quote:Originally posted by lowleadman

When I discussed the issue with the person I bought the car from, he commented that brake fires were somewhat common in the 280sl. Wonderful.

I don't agree with this at all.

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

[A Dalton]

An easy test for swollen flex hose is to have someone press pedal without engine running and open each bleeder , one at a time .
 The pedal should go down with very little pedal pressure.  
[ No brake assist needed].. They should also be about the same ..
 Look for good fluid flow when you do each bleeder..
 What happenes with swollen hose is the resticted flow is overcome with the high pressure of the brake system, but the return pressure is nil and not enough to overcome the swollen restrictions ... therefore, not allowing the  piston to release the pads from the rotors/drums...the hose starts acting like a one way check valve...[that is where your fire may have started ]
 A stuck caliper will do the same , but if the pad releases when you open the bleeder , you know it is the line swollen shut ..and not a frozen caliper.
 Another easy test is to jack suspect wheel off ground and press brake as hard as you can... now see if the wheel can be hand turned when pedal is released... if not, open bleeder.. if it now turns , you have a bad hose on that wheel... if it still won't turn, you have a stuck caliper/piston..
 Swollen flex lines are so common on older cars that one should just change them all and get it over with ... including the clutch slave hose on stick..