I looked to see if anyone had an answer for a proportional valve question I had plus they were 2 years and older. So I hope this helps someone in the future.


MY STORY:::

With 100k on the car, brake pedal got really stiff and was stopping on it's own.

Got it on a lift and front brakes were locked. Rear brakes were OK(so I thought).

Did not find any leaks anywhere on my garage floor or noticed seepage under the car at brake system parts.


WHAT I DID:::

Checked for damaged brake lines and nothing
Checked fluid level and ok
Checked Brake Booster noise and no excessive noise
Checked rear cylinders and both were leaking

Replaced Brake Master Cylinder. Here is a Pic of the old MS. NOTICE fluid looks very bad!!!


Before installing new master cylinder I checked inside booster as much as I could to see if any fluid was going in there, just in case. And Pic of installed MS.


O.... MAKE SURE TO OBVIOUSLY BLEED THE MS OUTSIDE IN A VICE OR SOMETHING!!!

BLEEEEEED like crazy, y?
***Get that old fluid out the system and make sure no air is in the lines.

AFTER BLEEDING STILL THE BRAKES WOULD BE A LITTLE FIRMER BUT NOT ENOUGH. I HAD THIS AIR PRESSURIZED BLEEDER THAT KINDA HELPED BUT TRIED THE OLD SCHOOL WAY BUT NOTHING HELPED.


-------------------------------------------

WHAT I DID #2

After calling people and asking questions like crazy narrowing down the symptoms and also looking online, IT SEEMS these cars have serious problems with brake issues all over even in Germany lol...

PROPORTIONAL VALVE IS NEXT. It is at the left rear side of the car on this model without a/c.

When my front brakes locked up, it kinda messed up the proportional valve bc i had to really press the brakes to stop taking it to the shop ASAP...

Here's the pic of the Prop valve with the new one on the side.



****** BEFORE ANYTHING MAKE SURE YOU KNOW YOU WILL MAKE A MESS!!!*******

1. Remove spring
2. Remove brake lines first
3. Then remove Prop Valve from metal bracket
NEW PROP VALVE COMES TO THE RESCUE
4. Install brake lines first to simplify screwing the thread going in
5. Two bolts for the Prop Valve on the side (you'll see I promise)
6. Install spring


******BEFORE BLEEDING, MAKE AN ARTIFICIAL WEIGHT FOR THE VALVE BECAUSE IF NOT IT WILL PREVENT FLUID FROM GOING PROPERLY THROUGH THE PROPORTIONAL VALVE******

******HOW TO MAKE AN ARTIFICIAL WEIGHT FOR PROP VALVE: In simple words, make sure before you bleed, both little holes like this******


BLEED:

RIGHT REAR

LEFT REAR

FRONT RIGHT

FRONT LEFT


What to expect:::


Pray to God thats all you have to do


THIS IS TO HELP SO MORE INFO I DIDN'T SAY PLEASE POST... ENJOY YOUR BRAKES, IT MIGHT SAVE YOUR LIFE...