Pops 300e: Brake Problem...

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Chip L - 27 Oct 2006 13:13 GMT

I'm driving my 82 y/o father's '86 300e for a couple weeks. 170k mi.
The car runs / rides great except it has one serious safety issue.

After starting and pulling away (ie pulling out of drive way) , the car
has almost no brakes. I'm 6', 220 lb and pressing hard on the peddle
has almost no effect on the braking. I've found that pumping will kick
in some braking but I'm concerned for my pop's safety. The brakes
work normally after the car hits the road for a few minutes.

Thoughts appreciated.

Chip L

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macdrone - 27 Oct 2006 13:29 GMT

> I'm driving my 82 y/o father's '86 300e for a couple weeks. 170k mi.
> The car runs / rides great except it has one serious safety issue.
[quoted text clipped - 8 lines]
>
> Chip L

It needs a new brake booster or the lines need bled

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Richard Sexton - 29 Oct 2006 02:34 GMT

>> I'm driving my 82 y/o father's '86 300e for a couple weeks. 170k mi.
>> The car runs / rides great except it has one serious safety issue.
[quoted text clipped - 10 lines]
>
>It needs a new brake booster or the lines need bled

Possible, if there's a hissing noise it's the booster. But these really
don't fail very ofen even going back as far as the 50s. M/C's fail decades
defore the booster does from what I've seen and in the general case (which
of course by no means ensures a correct diagnosis here! I'm just saying
what's most likely given the symptoms).

It could be the lines and if the brakes were just worked on it'd be my first
guess but they really don't just open up like that and leak.

Also usually air in the lines and a bad booster give pretty constant symptoms,
of they're all over the place weird sumptoms agaim I suspect the M/C.

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Roland Franzius - 27 Oct 2006 14:03 GMT

Chip L schrieb:

> I'm driving my 82 y/o father's '86 300e for a couple weeks. 170k mi.
> The car runs / rides great except it has one serious safety issue.
[quoted text clipped - 6 lines]
>
> Thoughts appreciated.

No brake asisistance by vacuum booster. Reason may be the valve not
holding the vacuum for a day or a leak somewhere in the vacuum lines
system.

Or is your pedal going down to the floor? This means air in the
hydraulic system, old gaseous fluid or just worn pads and discs.

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Roland Franzius

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Chip L - 27 Oct 2006 14:40 GMT

The pedal does not go to the floor or close to it. The only odd thing
about the pedal is that, when the lack of braking occurs, the pedal is
very firm -then will creak (fluid/rubbery sound - not metallic) and the
pedal will slip down a bit.

> No brake asisistance by vacuum booster. Reason may be the valve not
> holding the vacuum for a day or a leak somewhere in the vacuum lines
> system.
>
> Or is your pedal going down to the floor? This means air in the
> hydraulic system, old gaseous fluid or just worn pads and discs.

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T.G. Lambach - 27 Oct 2006 17:32 GMT

Brake booster.

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Richard Sexton - 29 Oct 2006 02:24 GMT

>I'm driving my 82 y/o father's '86 300e for a couple weeks. 170k mi.
>The car runs / rides great except it has one serious safety issue.
[quoted text clipped - 4 lines]
>in some braking but I'm concerned for my pop's safety. The brakes
>work normally after the car hits the road for a few minutes.

Sounds very much like a master cylinder failure to me. Not a terribly expensive
part and you got nearly 25 years out of the old one.; now it's time to chnage it.

Given the age of the car, if you plan on keeping it change the booster too. While
some may last a while (a long while) there's a different feeling running
around in a 25 year old car with all new brake hydraulics as there is running
aruond in one with the original quarter century old parts.

Check the dates stamped on the brake hoses too, anything
5 yrs or older has to be replaced without question.

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Tiger - 03 Nov 2006 15:16 GMT

I would also change out the brake booster vacuum line... not the booster.
The vacuum lne tends to break at the checkvalve.

I also would check the master cylinder after replacing the vacuum line. You
might need a new master cylinder cap.

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