esprit hydraulics - why do they get bled so often?

[bojangles]

I have never had to bleed brakes or clutches unless they were taken apart. It is a closed system and air should never enter.
But I hear over and over again that bleeding solves 1/2 problems out there..
as an engineer I just dont get it....
Same for the internal seals, they just dont wear out on other cars...
totally strange..
on a side note I put a used accumulator in my S4s brakes and it went from a 1-2 pump cycle to a 5-6 pump cycle..
better but not perfect..
and the pedal still dives down a half inch when the abs activates.... i dont accept that is normal

[karlfranz]

bojangles said:

I have never had to bleed brakes or clutches unless they were taken apart. It is a closed system and air should never enter. But I hear over and over again that bleeding solves 1/2 problems out there.. as an engineer I just dont get it.... Same for the internal seals, they just dont wear out on other cars... totally strange..

Most "everyday" cars are engineered for maximum reliability. Supercars are engineered for extreme performance. Usually these two are diametrically opposed design criteria. Lotus also did some poor choices in materials in order to save costs. I would gladly have paid an extra $1,000US to have the car built completely with stainless steel hardware. Some of the fasteners on my car were already rusted on delivery when new.

bojangles said:

I put a used accumulator in my S4s brakes and it went from a 1-2 pump cycle to a 5-6 pump cycle.. better but not perfect..

5-6 presses of the brake pedal between pump cycles is considered the normal operating parameters of the system.

[GKP]

As you know, brake fluid is hydroscopic. In other words, it just loves to absorb water. It'll manage to do this through virtually any sealed container, be it the carton on the garage shelf or the resevoir under the bonnet. When this water gets hot (as calipers tend to do) it expands and releases the dissolved air contained in it.

Any car, be it a supercar capable of 200 mph or Aunty Mauds shopping hack, should have it's brake fluid changed every 12 months.

Only difference being, Aunty Maud probably won't notice her brake pedal getting slightly mushy or give her braking system such a vigorous workout throughout the year.