RE: Brake pressure problem '86 5KTQ

["Buchholz, Steven" <Steven.Buchholz@kla-tencor.com>]

> Replaced the bomb (twice!), but the "brake" triangle light 
> still flashes for
> the first two minutes or so after start up, then goes away.  
> There's plenty
> of Pentosin and brake fluid in the reservoirs.  Plus, the brakes feel
> 'un-assisted' for the first mile or so, then all of the 
> sudden - they will
> work fine (Also, the car will pull slightly to the left upon 
> braking under
> 'non-assist' mode, then when the brakes suddenly return to 
> normal, the car
> straightens out).  Bad master cylinder?

... I think that the bomb gets a bad rap sometimes ... just because the
brake warning comes on does not mean that it is necessarily the pressure
accumulator (AKA bomb).  There is a well defined test that should be made
any time the bomb is suspected, that being the test to confirm that the
brake assist continues for 30 brake depressions after the engine has been
shut down.  There are two other suspects in the assist system that need to
be questioned, one is the hydraulic pump, and the other is the brake
booster.  Based on your description of the problem you may have a weak pump,
or a leaky booster.  I don't know that Bentley prescribes anything other
than a pressure test for the pump, but it does have a test for the booster.
If I were in your shoes, knowing that the bomb is OK I'd check the booster,
if that is OK replace the pump.  On your car the pump for the steering is
separate from that for the brakes, but if you are noticing any oddness with
steering this might be the confirmation that you'd need to know that the
pump should be replaced ...

Good luck Duane!
Steve Buchholz
San Jose, CA (USA)