Hi there, mercedes lovers!
I've got a 77 450 sel w/ 125k that has a clear issue w/ the brakes. The car stops, but it takes a very firm foot on the pedal before the brakes engage. Also, I hear the faint sound of escaping air pressure (a 'fffffsssssshhhhffff' sound) as I step on the pedal. I'm not sure if I need a new master cylinder, a new brake booster, just a seal, or even just a brake bleeding. I would obviously like to fix my brakes before I bump into someone the hard way, but I don't want to replace the wrong part. Suggestions?

Also, anyone w/ the know-how to answer the above question can probabely answer an unrelated one regarding fuses for the same model: is there a good upgrade for the ceramic fuses? I have heard that corrosion is a problem w/ these ceramics.

michaeld

 

Def sounds like a brake booster.

Fuses can be a problem. I think they make some that have copper ends that wont react with the holder that they are in. Others would know more than I about this one.

 

If this IS my brake booster (and that seems like the likeliest culprit) I wonder if I need to replace the unit right away. I can get a new booster pretty reasonably, but I am NOT looking forward to crawling under my dash trying to reach 4 inaccessible bolts. I understand that a booster doesn't undermine the integrity of the braking system - it just makes it easier to apply the brakes. Is that correct, or would I be destroying my brakes and/or increasing the chance of a brake failure if I don't take care of this right away?

 

To be honest with you, I would replace it right away. Your brakes are probably the most valuable safety device in your car, and personally I wouldn't risk that. Essentially without the brake booster it is like driving the car without power assisted brakes. Same effect as coasting without the engine on. It shouldn't destroy your brakes or anything, but it could destroy your car if you weren't quick enough to fully depress the brakes in an emergency stop!

Martin

 

Thanks for the valuable input. This would force me to take it to someone, as I just don't know if I want to climb under the dash to disconnect/reconnect the booster. I don't perceive my ability to stop as an issue now, but I frankly don't know how or to what extent the current condition could change.