khaled1960

I have a mercedes E500 03 with 150k miles on it. it has a brake warning in white on the screen and i went to a mercedes dealer thinking it was the sbc hydraulic unit and they would fix it under the warranty but it turned out to be the Hydraulic Pressure Reservoir and it costs 1200$.
my question is what does this part do and how important is it and will it affect the car if i didn't fix it ?
and where can i buy one used or cheaper ?
thanks

vettdvr

Accumulators are used to provide a surge to have smooth application of pressure. W/o going through the system the electric pump supplies pressure which stores in an accumulator to provide capacity when needed.

YES you need one.

khaled1960

would there be any risk of the breaks suddenly not responding while drive it without fixing it ?

vettdvr

I can't answer on MB brakes but I do know in the systems I have designed that without accumuilator massive stress can be put on lines and result in line failure therefore system failure. I can specualte on the design that if you depress the pedal use all the stored pressure then have to have a 2nd application the system might not have adequate pressure when you need it and then have longer stopping distance.

ozusa

Yes. If the reservoir fails, there goes your brake pressure.

The main questions are
(a) how many different ways can it fail and
(b) are any of them really ugly to your safety and that of others?

I think the answers are
(a) several and
(b) yes, some failure modes will be ugly

I suggest you get it fixed.