Run away! IT'S A BOMB!!!!

[Mike Arman <armanmik@n-jcenter.com>]

>Subject: Run away! IT'S A BOMB!!!! 
>
>This is a multi-part message in MIME format.

Ooooh, shame on you!!!!!



>
>Well, not exactly :-P
>After locating my braking problem I have found it to be a bad bomb. =
>After running the car for a few min. then shutting off I can't even get =
>1 depression out of the brake before it goes solid.

Yes, that's the bomb.



>After finding this out I was wondering exactly where the bomb is =
>located?!? I found a suspicious looking item behind the left front =
>fender, is that is. It is blue and cylindrical. If it is does that mean =
>that I have to remove the entire quarter panel to get to it?


No, that's a vacuum reservoir. Don't bother it; It isn't the problem.


The bomb lives just under frame rail under the left motor mount (so you're
in the right area, anyway). It is black, and is a sphere with a cylindrical
"handle" sticking out of the back of it - hence the name: It looks like a
WW-I German "potato masher" grenade.



>Also wanted to know if I could use a bomb from a previous model year? I =
>have an '87 5kcstq. The car with the good (hopefully) bomb is an older =
>'84-86'ish 5kt model. I also know of a junked coupe of the same vintage. =
>Are any of these compatible with what I have?
>

There are two types - one uses a neoprene "O" ring to seal the pressure
hose to the bomb inlet (this is the late type) and the other uses aluminum
crush rings (early type). The bomb itself appears to be essentially the
same despite different part numbers. I seem to recall some discussion about
this (I asked the same question a few years back, when I was in the same
fix), but I don't recall the exact answer.

In any event, the issue is moot - the older bomb is likely to be in worse
shape than your newer one. It seems the pressure leaks out from age, and
the cure is a recharge (there's a lister in Colorado doing this - no
personal experience) or replacement with a new bomb. Grit your teeth and
spring for it - your car IS NOT safe to drive with a dead bomb.


Here's a repeat of my post on changing the bomb:


>Finally got around to changing the bomb on my 86 5KS - chased everyone
away, took the phone off the hook, decent weather (no rain on Saturday for
a change  - turns out it DOES rain more on Saturday than any other day - it
HAS NOT been my imagination all these years!)
>
>Phil was right - *BIG* difference!
>
>Procedure - jack up car, WAY up, remove LF wheel.
>
>Using tubing wrench (7/16"), loosen brake line on inboard side of bomb.
Access is kind of tight (what else is new?) so use a regular open end 11 mm
wrench to undo the fitting - 1/6 turn at a time.
>
>Using 17 mm wrench, loosen and remove banjo fitting on bottom of bomb.
Recover two crush washers - you won't use them again, but you don't want to
leave any old ones in place accidentally.
>
>Loosen hose clamp at rear of bomb, pull hose off spigot, and drain
precious pentosin into a waiting container. I used a 2 liter Diet Coke
plastic bottle - maybe two cups of Pentosin is all that comes out, but the
height of the bottle let me place it under the still-dripping hose and kept
the driveway from becoming a mess.
>
>You will be AMAZED at the black glop and garbage that comes out of this
hose!!!!! Rubber bits, dead bugs, god knows what else.
>
>Using 10 mm socket, remove nut at front of bomb, and two nuts securing top
of front bomb mount.
>
>Withdraw bomb to front of car. Wash hands, wash face, clean glasses, get
back under.
>
>Insert new bomb most of the way - leave yourself a little room to get at
the hoses. Start 11 mm brake line connection, run it down but not tight,
since the bomb isn't supported by anything yet and you have nothing to
tighten against.
>
>Attach banjo fitting, using two new copper or aluminum crush rings which
you bought in advance - they are cheap, and any type 44 Audi owner should
have a dozen or so in assorted sizes right at the top of their parts stash.
>
>Connect hose from Pentosin reservoir (the one the glop came out of) and
tighten the clamp.
>
>Assemble front mount, tighten the 6 mm nuts. Tighten brake line (11 mm),
banjo fitting (17 mm), crawl out, clean up.
>
>Remove jack stands, put LF wheel back on, lug nuts to 80 ft lbs. Car on
ground.
>
>Open hood, refill Pentosin reservoir (use about 80% of what you drained
out - leave the remaining 20% with the bits of black glop in the bottle -
discard), top off. Reconnect two wires to pressure switch that controls
Hal-the-onboard-computer (don't tell Phil you disconnected them - he'll
have a fit!).
>
>Start it up, go for a ride, try brakes. WOW! The pedal effort is somewhat
less than with a dead or almost dead bomb, but what is impressive is the
RATE of deceleration - it is like you just drove into a giant pot of glue.
Step on the brakes, and forward motion CEASES - NOW!
>
>Total time, a little over an hour, not pushing very hard. Faster next time.
>
>If you need a bomb, I now agree totally with Phil - DO IT! - don't put it
off.


Best Regards,

Mike Arman