750iA -88 Brake problems

[Petteri75]

Just got the car, MY 88 (manufactured 11/87). Very basic trim, driven 280 000kms. It has minor problems but there is also one potentially bigger one.

The brake pedal goes all the way down engine on or off. When it pressed for a longer period, somewhere it starts to hiss and I guess a pump of somekind starts to work. The brake stops and holds the car on a e.g. hill without need to pump.

Discussing with mechanic, this could be a symptom of using a wrong hydraulic oil, ATF instead of CHF. The questions:

-What can be broken? Brake servo? Pressure accumulator? Valve (what valve?)?

-Are any of the parts of the brake servo / assistant system interchangeable with e.g. 735 or E34?

[CharlesAFerg]

wait, a 750i or iL, if it's an I, you're very lucky to have in imported car.
Shogun should have all the info for you, he's the head honcho expert on all E32, particularly the high end 750il and even the Highline models.

[Petteri75]

No no, I am in Finland where E32 750iA:s can be had with civilized length (used from Germany). So it is the normal model, not Lang. I was under the impression, that the mechanics under 750iA and 750iAL were the same, just that latter has 25cm more length on its body?

Anyhow, just found out that about the H31 (or something like that) hydraulic system. Yes, now I would like to change the brake servo from hydraulic to a normal vacuum-operated - the brake feel is told to be better.

[shogun]

I am just on holday in Germany for 4 weeks, so no details here. Go to th E32 expert forum
http://www.bimmerboard.com/forums/e32/

To convert to vacuum operated system is basically possible from the H31, visit my website and look for the link to Max Fretter, he has done it but on a 735 (old 735 also had H31 system and later it was changed to vacuum operated). But there is little space in the 750 engine room.