Brake bleeding adventure story. Suspect: Brake booster?

[shaved240]

Ok so here's my dilemma. I Can't get brake pedal on my car to feel "right". I've probably pushed through about 5 of the bigger size brake fluid bottles through the whole system and my pedal still goes all the way to the floor!!! The car will barely stop if I apply the brakes on a hill (with the car completely stopped to a slow roll down the hill). To bleed the brakes I'm using a motive power bleeder.

Here's a little background:

So my brake booster line going to the manifold needed to be replaced because I swapped in my 16v motor. So I couldn't get the dam one way valve that's on the brake booster to come off. I tried pulling it out with pliers, and completely broke a good piece of it off, then it fell into the brake booster (great!!). So I said the hell with it, the brake booster should still work. So I started the car, and the brake booster worked just fine. So Knowing it worked fine It was a relief sort of. So I then proceeded to bleed my brakes because I added r-brakes up front, with blocked off ports on the proportioning valve up front, and a proportioning valve in the rear with blocked off ports as well (same exact setup I had on my old car that worked great!).

So I go to bleed the brakes and I cannot get the brakes to work! I've gotten all of the air out of the lines with the power bleeder, yet the pedal goes all the way to the floor! Great, grand, wonderful!! So I start the process of elimination. I plugged the master cylinder ports and pushed the brake pedal while i was inside the car. The dam pedal went all the way clear to the floor, which means that fluid was bypassing the seals internally. Took off the master cylinder, tested it on the bench and pushed the cylinder with a screw driver. The dam cylinder wouldn't budge at all. So the master cylinder worked on the vise, but didn't work with it attached to the car? interesting. I started messing with the little push rod that comes out of the brake booster. I repositioned it, then put the master cylinder back on (with the ports plugged still) and was able to replicate what I was seeing when I had it in the vise (aka when it was working). So I said to myself, "great, now lets bleed the system". Bled the system and the pedal is still going alll the way to the floor! mother effing POS.

That is where I stand today. Brakes not working, car not being able to be driven. So I pose this question: I thought regardless if the brake booster works or not, I should still be able to have working brakes right? Because its just a rod that's pusing on the brake that directly transfers to the master cylinder.

GRRRRRRR!!!!

[lummert]

I say you need that brake booster working, the master cylinder is designed for use with a brake booster.

[bigbret]

Yeah the system is designed to work together. The brakes should work without the booster if all else is functional. The brakes will be extremely hard to depress though. I suspect a bad master that is leaking internally?

[adrianpike]

Sounds like a dead master cylinder, and the whole vice shenanigans were a false positive.

[shaved240]

Originally Posted by adrianpike

Sounds like a dead master cylinder, and the whole vice shenanigans were a false positive.

ok the only thing is the master cylinder looks brand spanking new? so does the reservoir. I know before I bought the car the brakes worked excellent.

[whispacloud]

Took off the master cylinder, tested it on the bench and pushed the cylinder with a screw driver. The dam cylinder wouldn't budge at all

It should push EASILY with the lines open, IE not plugged. (I wasn't clear how you were testing it)
If it doesn't it means that there is 'gunk' built up and needs to be rebuild/replaced, regardless of how new it looks.

So I pose this question: I thought regardless if the brake booster works or not, I should still be able to have working brakes right? Because its just a rod that's pusing on the brake that directly transfers to the master cylinder.



Even if the brake booster fails, you SHOULD still have brakes.
That would be the same condition as if you plugged the vacuum connection.
The brake booster has one job: to provide less pedal effort.

What you're describing is leaking fluid pressure.
It's either leaking inside the MC or externally somewhere.
If the fluid doesn't go down in the reservoir, the it's an internal leak.

[shaved240]

Originally Posted by whispacloud

Took off the master cylinder, tested it on the bench and pushed the cylinder with a screw driver. The dam cylinder wouldn't budge at all

It should push EASILY with the lines open, IE not plugged. (I wasn't clear how you were testing it)
If it doesn't it means that there is 'gunk' built up and needs to be rebuild/replaced, regardless of how new it looks.

So I pose this question: I thought regardless if the brake booster works or not, I should still be able to have working brakes right? Because its just a rod that's pusing on the brake that directly transfers to the master cylinder.



Even if the brake booster fails, you SHOULD still have brakes.
That would be the same condition as if you plugged the vacuum connection.
The brake booster has one job: to provide less pedal effort.

What you're describing is leaking fluid pressure.
It's either leaking inside the MC or externally somewhere.
If the fluid doesn't go down in the reservoir, the it's an internal leak.

The master cylinder was plugged when I tested it. When its plugged the piston doesn't move, when it isnt plugged it moves freely.

[twistedtree]

If everything worked before until you dropped a piece of the check valve down into the booster, then I think you found the most likely cause of the problem.

[TrickMick]

Originally Posted by twistedtree

If everything worked before until you dropped a piece of the check valve down into the booster, then I think you found the most likely cause of the problem.

[ray b]

first get the booster off and get the bit OUT
check for air leeks
the booster is a big rubber air/vac bag

then bench bleed the master
you donot need a bench to bench bleed
just a short line to loop back to the brake fluid rez
FROM THE MASTER OUT
DO BOTH SIDES

THEN AND ONLY THEN BLEED THE REST OF THE SYSTEM
if you do clear the air at the top in the master first
it is never coming out down low

[shaved240]

Originally Posted by TrickMick

hey durp master. maybe you didn't read all those other things that were installed

[shaved240]

Originally Posted by ray b

first get the booster off and get the bit OUT
check for air leeks
the booster is a big rubber air/vac bag

then bench bleed the master
you donot need a bench to bench bleed
just a short line to loop back to the brake fluid rez
FROM THE MASTER OUT
DO BOTH SIDES

THEN AND ONLY THEN BLEED THE REST OF THE SYSTEM
if you do clear the air at the top in the master first
it is never coming out down low

I have no idea how to take the brake booster apart. it looks like the whole unit is crimped together in some fashion or another.

I'm just going to the junkyard and getting a used unit and go from there.

[TrickMick]

Originally Posted by shaved240

hey durp master. maybe you didn't read all those other things that were installed

au contraire mon du.. I *DID* read all of it...
you posted that it was the "same exact setup I had on my old
car that worked great"...n'cest pas?
soooo..if the only thing(s) DIFFERENT are your "fussing w/the drive rod"
and dropping a chunk of valving into the booster what would YOU expect
to be the problem????

I was essentially SECONDING "twisted tree" in his observation...I was tempted
to preface it with a comment about 'Capt. OBVIOUS' but relented and
let the emoticons do the work for me....

if you DIDN'T have WORKING EXPERIENCE with an identical "system" then
further investigations would be called for...since you ARE familiar with the
mods - I would expect you to be able to sort that in double quick special
secret overtime .....

once someone pointed out the OBVIOUS I would expect you to be
gobsmacked then, again,

[lummert]

Take the booster off the car and turn it so that the hole for the check valve is at the lowest point, then shake until parts fall out.

[TrickMick]

Originally Posted by lummert

Take the booster off the car and turn it so that the hole for the check valve is at the lowest point, then shake until parts fall out.

quote the confuddled OP:
"I have no idea how to take the brake booster apart. it looks like the whole unit is crimped together in some fashion or another.
I'm just going to the junkyard and getting a used unit and go from there. <

a second on the emotion from "lummert" who, disguised as Capt OBVIOUS
sorts the problem in short order....





(it's a helluvslot FUNNIER using just the emoticons!)

[shaved240]

Originally Posted by lummert

Take the booster off the car and turn it so that the hole for the check valve is at the lowest point, then shake until parts fall out.

I'll give it a shot, but ultimately I was going to replace the brake booster anyhow to rule that out completely.

Did everyone forget about how the brake pedal wasn't activating the piston in the master cylinder? this was my original concern, but it seems that its being overlooked.

And to durp master,

Yes it's the same setup as my old car, but not the same master cylinder and brake booster. I'm not trying to diagnose if its anything except the brake booster or master cylinder.

[ray b]

Originally Posted by shaved240

I'll give it a shot, but ultimately I was going to replace the brake booster anyhow to rule that out completely.

Did everyone forget about how the brake pedal wasn't activating the piston in the master cylinder? this was my original concern, but it seems that its being overlooked.

And to durp master,

Yes it's the same setup as my old car, but not the same master cylinder and brake booster. I'm not trying to diagnose if its anything except the brake booster or master cylinder.

then you broke something off
push rod or mount to petal

[shaved240]

ok what order does everyone recommend for bleeding the brakes? i'm starting with caliper furthest away from master and working my way to the front.

[TrickMick]

Originally Posted by shaved240

I'll give it a shot, but ultimately I was going to replace the brake booster anyhow to rule that out completely.

Did everyone forget about how the brake pedal wasn't activating the piston in the master cylinder? this was my original concern, but it seems that its being overlooked.

And to durp master,

Yes it's the same setup as my old car, but not the same master cylinder and brake booster. I'm not trying to diagnose if its anything except the brake booster or master cylinder.

dammit man YOU CAN'T HAVE IT BOTH WAYS....*NOW* the story is a "different
Master Cylinder and Booster"....it is therefore most assuredly *NOT* " the same exact setup I had on my old car that worked great

I think it wise for you to visit DAVE BARTON'S "big brake page" (where he DOES
mention using DIFFERENT master cylinder)....see:
http://www.davebarton.com/volvo240bigbrakes.html

I'm trying DESPERATELY to help you....(and refrain from rancor in the process)...
witholding information makes the job harder... go read Dave's stuff....it is FULL
of HIS "experiences" doing brake conversions and MAY afford you some surcease
from the "brake bleedin blues".....

[MistrThou]

When you bleed brakes and push the pedal completely to the floor, you are operating the master cylinder past it's normal operating range. Over the years, it's entirely possible that gunk/crap built up behind the seals and pushing them further in the bores may have wrecked it.

It's entirely possible to have wrecked your master cylinder when you bled the brakes.
Now I'm not saying that is what happened for sure, so check first the first thing that broke (booster) then proceed with the brakes.

Is your power bleeder one that pressurized the reservoir, or sucks from the caliper bleeder?

[shaved240]

Originally Posted by MistrThou

When you bleed brakes and push the pedal completely to the floor, you are operating the master cylinder past it's normal operating range. Over the years, it's entirely possible that gunk/crap built up behind the seals and pushing them further in the bores may have wrecked it.

It's entirely possible to have wrecked your master cylinder when you bled the brakes.
Now I'm not saying that is what happened for sure, so check first the first thing that broke (booster) then proceed with the brakes.

Is your power bleeder one that pressurized the reservoir, or sucks from the caliper bleeder?

Firstly I know the master cylinder is good because I tested it, but I'll replace it because I have a like new spare so I don't have to think about that anymore.

The power bleeder is the type that pressurizes the brake reservoir.

And I have read Dave Barton's site a bunch of times that's how I had my r-brakes set up on my other 242 turbo.

So on the list of things to do:

-replace master cylinder
-get plastic **** out of brake booster.

One further note: When the brake pedal depresses it feels like its going to built up pressure then at the last second you hear this loud pshhhh sound coming from the brake booster. Don't know if that even says anything but yea.

[shaved240]

brake booster is off.

found the parts that I broke off inside plus some other junk floating around in there. The pieces are so big that I can't even pull them out (not sure what there purpose is). I'm going to grab another booster from the junkyard then.

[twistedtree]

Sounds like the pieces that dropped in might have caused some other internal parts to break. This might explain everything.