Re: Brake bleeding, rear wheels

[e6941tb@gnn.com]

Meron wrote:
> 
> To all,
> I have not been able to pressure bleed the rear wheel, here are the
> details:
> subject car is 86 5Kcstq wit ABS
> 
> -I rigged a pressure cap to allow compressed air into the MCylinder and
> used 10-25 PSI for pressure
> -the strainer is removed from the MC
> -the MC is full of pentosin
> -the ABS is turned off with the ignition off
> -the ABS is turned off with the ignition on
> -the ABS is turned of with the car running
> -the ABS is not turned off, car not running

Presence of ABS on my '89 200 or lack thereof on my ex '85 5000 has
never made any difference to the bleeding procedure. Just bleed the
brakes with the ignition off, no need to fool ABS.

> -brake pedal pushed in (mechanically, via a bar between the seat and the
> pedal)

Wrong. You are not getting any brake fluid in the MC. Either release it
completely for pressure bleeding or have an assistant pump it for you.

> -bled the  MC, plenty of pentosin from both lines

I hope by "Pentosin" you mean the light yellow DOT4 brake fluid, made by
Pentosin (the Company) and NOT the light green G7.1 hydrolic fluid made
by the same company. It would be a VERY costly mistake!

> -bled the brake lines after the ABS hyd. unit, steady run of fluid but not
> a gayser!
> -moved the lever of the brake proportioning valve lever, no difference
> -bled the brake proportioning valve, very little pentosin
> -looked for a hight sensitive proportioning valve, did not find any

The prop valve is hight (load) sensitive and is located in front of the
LT RR wheel. Jack the car up, locate the valve and insert a 6mm drill
bit between the lower spring hook and the roller (Bentley for 89-91 200)
to fool the valve into thinking that the car is fully loaded so it will
bias the brake pressure 50-50% FR-RR. On an empty car it is about 80-20%
FR-RR. (That IS the main reason why you want the better tyres in the
front!)
The trick is to make the drill bit stay there. I use a gummy window
insulator. Just don't forget to remove the drill bit after you are done.

The bleeding procedure is standard (Bentley): 
1. Clutch slave (w/pressure bleeder only!)

2. Brakes: RR-LR-RF-LF-RR

One more thing, Avi: no more than 10psi on the pressure bleeder, you are
risking the MC seals at 25psi!

Igor Kessel
'89 200TQ