RE: Brake pressure problem '86 5KTQ (pump & bomb?)

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

> My '86 5ktq parts car has just one pump pressurizing the 
> hydraulic brake
> booster and the steering rack, just like my '87 5ktq driver 
> and my "new"
> '91 200tq20v.  The latter shows no brake warning sign in the 
> instrument
> panel square where my '87 showed the red triangle when that 
> car's "bomb"
> was bad, but the '91 "fails" the 30-pumps-to-hard-pedal test 
> after engine
> shut-off.  Is there a different "bad bomb" dashboard warning 
> on the '91?

You may have what appears to be a single pump hooked up to the drive belt,
but there are in fact two individual pumps in that mechanical package ... as
you can tell by the fact that there are separate high pressure lines from
the pump to the steering rack and the brake pressure accumulator.  The older
cars like my ur-q have a single pump and the bomb has a pressure regulator
valve scheme to supply pressure to the brakes and steering.  

What you would notice as a bad bomb indication for any of the cars you
mention is the brake warning in a situation where you press quickly and hard
on the brakes, like in a panic stop.  The pump cannot supply enough fluid
quickly enough to support this sort of thing, and that is why the light
comes on.  If your only problem was the bomb you would not see the brake
warning at any other time.  

HTH!
Steve Buchholz
San Jose, CA (USA)