Gazzol - Brakes

[Malc]

The bakes appear to be soft (like they are extremely over servod) but work great, after a while the pedal gets firmer and firmer (brakes still work very well) untill they start to bind. After a while (could be 10 secs upto 5 mins) they release themselves and become soft again. I'm begining to think that I may have two different problems which is confusing matters somewhat.
It could be that I have made the link rod between the pedal and the transverse link too long, this could be why they start to bind after the (possibly faulty???) accumulator has managed to build up pressure.
I spoke to a guy who was a BMW teccie when this system was current and he said that the system never really gave any problems except for the accumulators so thats my best guess at the moment. I'll have to bite the bullet and order a new accumulator, its a big pill if it's still the same afterwards though.

Gazzol,
Things that may help, make you think or can dismiss straight away!

Have you any adjustment in the linkage? It is possible that when you take your foot off the pedal the servo and hence the master cylinder is not returning to the "rest position"

I was told a failing accumulator results in a wooden pedal and the assistance becomes dependent on engine speed thus the speed of the PS pump.

Run the car then switch off the engine and pump the brake pedal. If the accumulator is "good" you should get the feeling of assist for a few pumps as it were. If this feeling dissappears after only one or two pumps then I would suspect the accumulator.

Are you using the original PS pump or did you fit one from the car that had the accumulator? Don't quote me on this but the output pressure from you current pump maybe too low?

Have you changed the brake flex hoses? the standard "rubber" ones can swell internally over time and act like a check come bleed valve

Accumulators are available secondhand/reconditioned and new from none BMW sources at reasonable prices, such as GSF (German Swedish and French) and the usual culprits such as Munich Legends and your local scrappy!

Malc

 

[gazzol]

I made the link rod myself and as I said I think I made it too long as I can't make it any shorter so I'll have to chop a bit off the threaded portion so I at least have some adjustment.
I have had some experience with the accumulators failing on some of the many E28s I owned over the years, it goes something like this: Flying down a country lane at full tilt, press brakes nothing happens :shock: , press brakes again everything locks up blue smoke everywhere :shock: , slow down to allow the adrenalin to subside notice a nasty smell .

The accumulator is holding fluid under pressure in reserve as it were cause if I pump the brakes with the engine off the fluid rises in the reservoir and then drops once the engine is started however the strange thing here is that the pedal doesn't feel any worse once all the reserve has been used. Strange eh? The pump is the standard item but I don't feel that this is the issue but I could be wrong.
Anyway I'm not worrying about it at the mo, I'm having a mechanical brake from the car and am concentrating on enjoying it