Re: Type 44 bomb replacement & brake question

[Orin Eman <orin@wolfenet.com>]

> At 11:35 AM 10/4/1998 -0400, you wrote:
> >Mike,
> >
> >Question, how were you able to figure out whether problem with you brakes
> >was the bomb or something else.  I have an 84 5ks, and I sometimes have to
> >push the pedal all the way to the floor for the brakes to engage, and other
> >time not.  I can usually reproduce it if I push the brake pedal down
> >slowly.  Is this symptomatic of a bad bomb?  Thanks in advance for your
> >help, I just saw your post, and thought you would be a good person to ask,
> >since you've recently been through this sort of thing.  BTW, I'm relatively
> >new, just signed up mid-summer, and mostly just read posts, trying to
> >collect knowledge.  When I do post its usually a quesiton, hopefully soon I
> >will be able to end the one way relationship.  Anyway, if you could help me
> >out, I'd be grateful.
> >
> >Thanks again,
> >
> >Steve
> >
> >PS- as a college student, I must ask, how much does the bomb cost? :)  
> >


> Steve - 

> Don't feel bad about being new at this - we all started there once (except
> maybe Phil Payne, who was evidently born with a microfische in his mouth .
> . .).

> What you are describing is more indicative of a bad (failing) master cylinder.

In this case, it does sound that way.

However, a sinking pedal can be caused by the bomb/brake servo in a
couple of ways.

With a dead bomb and the engine running, when you press the brake
pedal it will drop a tiny bit as it uses up whatever hydraulic pressure
there is, then it stops.  When the next pulse of pressure comes along
from the pump, it drops a little more.  The pedal pulsates as it goes
down.  Feels kind of like the ABS cutting in.

Secondly, I believe the servo and bomb check valves can interact in a
manner that allows the pedal to drop a fair way, then engage the
master cylinder with no brake assist.  This would be a dead bomb
with a dead check valve that lets pressure back from the servo into
the bomb.  I had an 86 5ks which exhibited this symptom _with a new
master cylinder_.  I want a brake servo to take apart to see how
much relative movement is possible between the input and output
when there is no hydraulic pressure.

Orin.