Mystery Part

[Bernard Littau]

> I’m trying to figure out what this loose part on my 1990 200Q is.
> It’s a small cylinder of metal and black plastic a little smaller in
> diameter than a beer can and about 3 inches long.  It is on the
> passenger side just in front of the right rear wheel and about a
> foot in from the side of the door in its own little cavity.  It has
> several of what look to be brake lines going into it.  Anyone know
> the name/function of this device and whether it should be solidly
> mounted (it is loose, but not in danger of dropping off)?

Mine is mounted solid to the body of the car.  I've been told this mystery
part is some kind of proportioning valve for the rear brakes whose purpose
is to reduce brake pressure to the inside rear wheel on a hard turn.

This is apparently to reduce the chance of a lock up on the unweighted
wheel.  I believe this valve you mention only reduces pressure to the
passenger side wheel on a hard right turn.  On a hard left turn, it does
nothing, the brake proportioning valve connected via a spring to the drivers
side wheel will reduce pressure on both rear brakes.

Interesting in that this means the car has different braking characteristics
in hard left and hard right turns.

Best,

Bernard Littau
Woodinville, WA
'88 5ktq