Hi fellows.
'86 745 NA - Bendix brakes
I had this problem with the high idle of 1400 rpm and more.
When applying brakes it went down. I thought its a bad booster.
I got from the local junkyard a booster/master cylinder unit
with an almost new check valve for 40 $. Same model, because
I was not sure about compatibility with other ABS-equipped volvos.
Idle is OK now. No problem in engine running.
Installation was not so difficult (13mm nuts),
though you need long fingers for some nuts.
Thanks for the FAQ help, especially the bleeding procedure.
My brake light is still sometimes on, I think its the
differential valve.

Some information:
The MC(master cylinder) has 7/16 nuts to connect the brakelines.
Also the front bendix have 7/16 bleeder screws.
The rear had 9 mm bleeder screws.
I don't know if that is on all 700 volvos.
Sir Ringlee : Would be nice if you include the nut-sizes in the FAQ's.

I used the Valvoline synpower brakefluid - 5 $ a quart in Kragen.

The hose for the bleeder screw is the same size as the hose
from intake to fuel pressure regulator.
I don't have the right size in clear hose (also Kragen and Autozone
don't have it - why? ), so I took a 2 inch piece from an old FPR-black hose
and attached a smaller clear hose to it and into the jar. - Works fine.
Next time I'll look for the right size of clear hose before I start.

Thanks for all the help

PS: Don't drink AND drive - you might spill your drink ;)