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Old 11-19-2011, 07:27 PM   #1
volvo
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Default brake pedal to the floor...a few pumps and its fine. new master?

Hi guys,
Went and did the first really long drive in the 240 this morning: 3 hour and 15 minutes from central Long Island to East of Hartford, Connecticut, and then again the return trip.

While taking Rt 91 North, after not touching the brake pedal for a while (15-20 minutes) I went to slow down and got scared: the brake pedal went to the floor! Then in an attempt to slow down, i pumped the pedal 4 or 5 times and it came back up and behaved as it did before. I got to Hartford, met a few friends, and drove back and no issues...always testing once in a while to make sure I had brakes.

The brake fluid level is fine. As I drove back home, i started hearing a bit if a metallic grinding sound when stepping on the brakes, but i replaced the front pads on this car in May of 2011 and did the rear pads 2 weeks ago.

When i did the rear pads i also noticed that the brake fluid was very very dark and upon closer inspection there was a dark residue floating on the fluid. I syringed out the fluid from the reservoir, pulled the reservoir and cleaned it out with gasoline. Dried it out with compressed air and re-installed on the master and topped off with fresh fluid.

What do you guys think that pedal drop was?

Also what does the white plug with the hose fitting do on the brake booster?


Thank you!
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Old 11-19-2011, 08:03 PM   #2
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Yes you need a new braking system complete.
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Old 11-19-2011, 08:11 PM   #3
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If you put gasoline into your master cylinder you've contaminated all the seals in the braking system. Every bit of rubber should be taken off and tossed in the bin. Master cylinder seals, brake hoses, caliper seals. The whole lot is scrap.

You cannot use a mineral oil based product on a braking system, any cleaning is done with methylated spirits, denatured alcohol I think in American speak.
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Old 11-19-2011, 08:28 PM   #4
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Completely new braking system...really?????

I don't think i explained it properly. I removed the reservoir, cleaned out the crud inside with gasoline, blew it all out with compressed air and then put the reservoir back.

It was dry when I put it back on. I didn't pour gasoline into the brake reservoir while it was mounted on the master cylinder.

Last edited by volvo; 11-19-2011 at 08:45 PM..
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Old 11-19-2011, 09:07 PM   #5
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Phew. Then you should be fine - sounds like you need to do a complete flush/re-bleed of the braking system.

But if it was me, I'd just replace the master cylinder , flush and rebleed the system and go from there as you could just be wasting your time doing this with the existing
master cylinder , especially if it indeed is bad.

Now .. if you would have dumped gas into the reservoir without removing it, then you would in effect destroyed the entire braking system.. But it sounds like you didn't do that.

That's all about all I can offer - just start w/ that - odds are you'll be just fine once the master cylinder has been replaced.
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Old 11-19-2011, 09:07 PM   #6
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Phew. Then you should be fine - sounds like you need to do a complete flush/re-bleed of the braking system.

But if it was me, I'd just replace the master cylinder , flush and rebleed the system and go from there as you could just be wasting your time doing this with the existing
master cylinder , especially if it indeed is bad.

Now .. if you would have dumped gas into the reservoir without removing it, then you would in effect destroyed the entire braking system.. But it sounds like you didn't do that.

That's all about all I can offer - just start w/ that - odds are you'll be just fine once the master cylinder has been replaced.
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Old 11-19-2011, 09:51 PM   #7
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with regard to the original question this is how mine was acting when it was leaking from the junktion block warning switch port
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Old 11-19-2011, 10:24 PM   #8
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Here's an old brake problem diagnosis check list that I've posted on other boards. It's kinda generic, but it's a good starting point:

Quote:
You could first try the old "Ten Second Brake Test," see what you get, and then post the results here so someone can offer suggestions. This test is pretty generic and applies to most vehicles.

The Ten Second Brake Test

Before you go tearing things apart, do the 10 second brake test:

1. With the engine off, pump the pedal until all vacuum in the booster is eliminated.
2. Pump the pedal again a few times until you get a firm pedal.
3. Plant your arse firmly in the seat and push on the pedal as hard as you can, and hold the pressure for 10 seconds.

Preliminary Diagnosis:

If the pedal goes straight to the floor, you have a completely burst brake line.

If the pedal goes down fairly quickly, there's probably a loose fitting, leaking line or hose, or a blown caliper/wheel cylinder seal.

If the pedal goes down slowly, it's could still be a fitting, but not as loose, a seal, but not as bad, a pin-hole leak in a line, or the master cylinder seals.

If the pedal is just mushy but firms up a bit with some pedal pumping, there's probably air in the lines, a swelling brake hose due to a soft cover or worn/frayed wire mesh inner sheath, or the fluid level is low.

If there are no apparent problems after 10 full seconds, start the engine. If the pedal is mushy or drops excessively with the engine running, check that the booster is not building up excess vacuum (not common, but possible).
Oh yeah, the white plastic thing at the booster is the check valve. It holds the vacuum in the booster to allow for an emergency stop if the engine quits.
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Old 11-19-2011, 10:26 PM   #9
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Quote:
Originally Posted by andysbeta View Post
Phew. Then you should be fine - sounds like you need to do a complete flush/re-bleed of the braking system.

But if it was me, I'd just replace the master cylinder , flush and rebleed the system and go from there as you could just be wasting your time doing this with the existing
master cylinder , especially if it indeed is bad.

Now .. if you would have dumped gas into the reservoir without removing it, then you would in effect destroyed the entire braking system.. But it sounds like you didn't do that.

That's all about all I can offer - just start w/ that - odds are you'll be just fine once the master cylinder has been replaced.
I will be bleeding the system tomorrow. New fluid, etc.
I'll be looking for a master cylinder on Monday to put in...unless I can find one tomorrow as well.

Wish me luck.
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Old 11-19-2011, 10:28 PM   #10
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Quote:
Originally Posted by John2x240 View Post
Here's an old brake problem diagnosis check list that I've posted on other boards. It's kinda generic, but it's a good starting point:

Oh yeah, the white plastic thing at the booster is the check valve. It holds the vacuum in the booster to allow for an emergency stop if the engine quits.
good info
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Old 11-19-2011, 10:30 PM   #11
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Quote:
Originally Posted by Coupe' de Grace View Post
with regard to the original question this is how mine was acting when it was leaking from the junktion block warning switch port
Can you tell me where that junction is located. I will look into that as well.
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Old 11-19-2011, 10:35 PM   #12
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It's near the bottom of the left front inner fender. Follow the brake lines down from the MC and you'll find it.
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Old 11-19-2011, 10:55 PM   #13
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Quote:
Originally Posted by Fivehundred View Post
If you put gasoline into your master cylinder you've contaminated all the seals in the braking system. Every bit of rubber should be taken off and tossed in the bin. Master cylinder seals, brake hoses, caliper seals. The whole lot is scrap.

You cannot use a mineral oil based product on a braking system, any cleaning is done with methylated spirits, denatured alcohol I think in American speak.


The residual petro-chemical that soaked into your MC seals has been transferred into your braking system.

Personally,I'd buy calipers,flex hoses,junction block,MC, and flush the hard lines with methyl alcohol.
Or simply buy a complete brake system at the JY to be sure.


Anyways..
Here is some reading material ..

Section 5
The Volvo dual diagonal braking system.

http://www.k-jet.org/files/greenbook...n_5_brakes.pdf
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Old 11-20-2011, 08:42 PM   #14
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Wished you'd asked before performing your MC res. cleaning job first. Always a good idea for the inexperienced, and the experienced too at times.
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Old 11-20-2011, 09:00 PM   #15
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Quote:
Originally Posted by Redwood Chair View Post


The residual petro-chemical that soaked into your MC seals has been transferred into your braking system.

Personally,I'd buy calipers,flex hoses,junction block,MC, and flush the hard lines with methyl alcohol.
Or simply buy a complete brake system at the JY to be sure.


Anyways..
Here is some reading material ..

Section 5
The Volvo dual diagonal braking system.

http://www.k-jet.org/files/greenbook...n_5_brakes.pdf
Why does he need new Calipers? He said he cleaned the Reservoir detached from the MC so not affecting any of the seals. First before going out and buying all new parts, check for leaks or a possible small crack in a line.

I had a tiny little pin hole in one of my lines and everyone told that I had to replace everything. First check for leaks before replacing everything cause you might end with the same problem after all is replaced cause of a small leak.

Edit: Does your car have ABS? I have ABS and ive driven a few 240's with ABS and they seem to have a slightly mushy pedal. Im not sure why but thats primitive VOLVO ABS for you.
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Old 11-20-2011, 09:14 PM   #16
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Quote:
Originally Posted by volvo View Post
- SNIP -
The brake fluid level is fine. As I drove back home, i started hearing a bit if a metallic grinding sound when stepping on the brakes, but i replaced the front pads on this car in May of 2011 and did the rear pads 2 weeks ago.

When i did the rear pads i also noticed that the brake fluid was very very dark and upon closer inspection there was a dark residue floating on the fluid. I syringed out the fluid from the reservoir, pulled the reservoir and cleaned it out with gasoline. Dried it out with compressed air and re-installed on the master and topped off with fresh fluid.

What do you guys think that pedal drop was? -SNIP-
pull ALL THE WHEELS and look at BOTH PADS on each caliper...METALLIC GRINDING
is something you DON'T WANT TO HEAR whilst braking...

grotty fluid (especially BLACK RESIDUE grotty is indicative of SEAL WEAR (in the MC)

w/car in PARK (engine running) stand on the brakes w/a "HOLY SHlT I'M GONNA DIE
effort...if the pedal S-L-O-W-L-Y sinks to the firewall go ahead and buy a NEW master
cylinder 'cause yer gonna need one (the fact the the pedal has *gone to the floor* means
you've already pushed the seals past the "rust / crud / scarring point"...if it holds SMILE
as you've got some use left...if not replace as soon as the $$$ appear for it....

whilst yer down looking at ALL OF THE PADS - LOOK AT ALL OF THE LINES AND
FITTINGS...*ANY* dampness is cause for concern.....
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Old 11-20-2011, 09:29 PM   #17
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how did you bleed the brakes? did you ever bottom out the brake pedal? i've done that before. good way to lunch an old mc.
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Old 11-20-2011, 10:57 PM   #18
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Quote:
Originally Posted by ziddey View Post
how did you bleed the brakes? did you ever bottom out the brake pedal? i've done that before. good way to lunch an old mc.
Whats wrong with bottoming out the pedal bleeding the brakes?
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Old 11-20-2011, 11:26 PM   #19
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You probably have a shot master cylinder and seals. Replace them both and you'll probably be fine.

I've had the same thing happen (twice!) that you had - deteriorating seals allow the fluid to squirt around the piston and back into the reservoir on easy braking. Stomping hard on the brake pedal "seats" the seals and allows the brake system to function. I woudn't rely on it for too long, however

Re the bleeding: After a bit of use the surfaces of the master cylinder that don't get routinely swept by the pistons get a bit of roughness to them. If the piston is then pushed past them (for instance in bleeding), then the rough surfaces tears the seal up.
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Old 11-20-2011, 11:35 PM   #20
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Quote:
Originally Posted by Texas240 View Post
Whats wrong with bottoming out the pedal bleeding the brakes?
BRAKES 101:
on a NEW master cylinder you can push the seals hard enough at the bottom
of the "stroke" to slightly deform them - as they come back past the compensating
port in the master cylinder the seal gets a small scar in it..leads to premature failure

in an OLD master cylinder there is an accumulation of seal bits / rust - corrosion and
a *stuff ridge* of grot that builds up at the end of the *normal stroke* - if you "bottom
out the pedal you push the seals thru this "wall of crap" and they get cut / scarred /
sliced / ripped ....leading to failure...yearly flushing of the fluid (as in a COMPLETE
FLUID CHANGE OUT) will help stop the crud / corrosion ring of crud and gives you
the best chance at long life in the cylinder...
often unlearned / unskilled mechanics will "force the pistons back" whilst replacing
pads..this runs ALL of the accumulated mung in the system BACKWARDS THRU
the master cylinder leading to premature failure (if you have an ABS system onboard
you run the risk of forcing all the crap into the control valves in the ABS "block" and
effectively destroying THAT high $$$$ piece of gear...
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Old 11-21-2011, 12:37 AM   #21
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Quote:
Originally Posted by TrickMick View Post
BRAKES 101:
on a NEW master cylinder you can push the seals hard enough at the bottom
of the "stroke" to slightly deform them - as they come back past the compensating
port in the master cylinder the seal gets a small scar in it..leads to premature failure

in an OLD master cylinder there is an accumulation of seal bits / rust - corrosion and
a *stuff ridge* of grot that builds up at the end of the *normal stroke* - if you "bottom
out the pedal you push the seals thru this "wall of crap" and they get cut / scarred /
sliced / ripped ....leading to failure...yearly flushing of the fluid (as in a COMPLETE
FLUID CHANGE OUT) will help stop the crud / corrosion ring of crud and gives you
the best chance at long life in the cylinder...
often unlearned / unskilled mechanics will "force the pistons back" whilst replacing
pads..this runs ALL of the accumulated mung in the system BACKWARDS THRU
the master cylinder leading to premature failure (if you have an ABS system onboard
you run the risk of forcing all the crap into the control valves in the ABS "block" and
effectively destroying THAT high $$$$ piece of gear...
I have yet to have any problems that source...
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Old 11-21-2011, 12:51 AM   #22
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"... often unlearned / unskilled mechanics will "force the pistons back" whilst replacing pads."

Sorry for a lunkhead question, but don't you have to force the pistons back to fit the new pads? This is a bit of a threadjack, but I always try to pick up tips from the masters when I can, and hope I've not been doing it wrong all these years.
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Old 11-21-2011, 02:08 AM   #23
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If you open up the bleeder screws when you push back the pistons most of the old fluid will come out of them (do work up a way to contain it - makes life much easier).
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Old 11-21-2011, 10:59 AM   #24
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Quote:
Originally Posted by saq View Post
If you open up the bleeder screws when you push back the pistons most of the old fluid will come out of them (do work up a way to contain it - makes life much easier).
^V^ (and a BIG PLUS 1)
*BINGO*

the added plus of this "way of doing it" is you get a bit fresh fluid every time when
you're done as you "top of" the reservoir!
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Old 11-21-2011, 02:43 PM   #25
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Thanks. That had never occurred to me.
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