5000tq Brake Warning Light Still comes on sporadically

[Bernard Littau]

> I am having some problems with my 5000tq. It recently had the Power
> Steering pump, hydraulic hoses, and bomb replaced. The bomb was replaced
> with a used one that when taken off of the car, was working.
> Here is my problem, while driving; the brake warning light comes on
> sporadically. When the light comes on, I still have brake assist, and
> power steering. It does not seem to happen at any given time, not when
> turning, and not when stepping on the brakes.
>
> I have noticed that there is some pentosin leaking from the top of the
> reservoir, as if there is air in the system?  Could that be causing my
> brake light problem? I have checked the fluid levels and everything is
> full. With the car off, I get about 30 pumps of the brake petal before
> it goes hard.
>
> Any Ideas where to go next? What could be causing the brake light coming
> on?

Hi Joe,

The brake warning light comes on for three reasons (sensors):

1) low brake fluid level
2) low pentosin fluid level
3) low hydraulic pressure

1 and 2 are sensed by the floats in the caps of the reseviours.
3 is measured at the booster behind the brake master cylinder.

The fact that you have 30 pumps means that it is not likely to be the low
hydraulic pressure.  I've only seen the low hydraulic pressure warning come
on at startup, and when braking.  Again, these occur when you have a bad
bomb.  If the pump were bad, the warning would likely be on all the time.

The fluid level sensors usually trigger the warning when cornering or
braking, sometimes when on steep or bumpy roads.  As soon as you flatten
out, the warning goes away.

You can disable the sensors one at a time, or just connect one of the three
at a time, to narrow down your search.

Best,

Bernard Littau
Woodinville, WA
'88 5ktq