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Discussion Starter #1 (Edited)
For the longest time the brake pedal on my ARC has been really flat compared to the other cars I have. I recently had to change the rear rotors and pads so why not do a complete fluid flush with Pentosin DOT4 while I had the wheels off. I've had the car for a little over a year so I didn't know when the last time the brake system was serviced. I used a motive euro power bleeder to push the fluid through the system. For the first few weeks the pedal was nice and stiff, and very responsive. I soon as you applied pressure to the pedal you could immediately feel the brakes grabbing.

Fast forward a few weeks later and my pedal feels worse than before I bled the system. Upon first pressing down on the pedal it goes pretty much more than half way down and feels like there isn't any pressure in the system. Its only in the bottom half that my brakes begin to grab now. After the first application of pressure to the pedal, if I release my foot and then right away re-apply the pedal it has full pressure within the first 25% into the braking. I also feel there is a slight delay in the pedal coming back up, i find it used to rest faster.

My first thoughts are either the inner seal on the mater cylinder is gone, or this is a booster problem( I sometimes here a faint hissing noise from under the dash when pushing on the pedal...normal?) any thoughts?

Thanks.
 

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For the longest time the brake pedal on my ARC has been really flat compared to the other cars I have. I recently had to change the rear rotors and pads so why not do a complete fluid flush with Pentosin DOT4 while I had the wheels off. I've had the car for a little over a year so I didn't know when the last time the brake system was serviced. I used a motive euro power bleeder to push the fluid through the system. For the first few weeks the pedal was nice and stiff, and very responsive. I soon as you applied pressure to the pedal you could immediately feel the brakes grabbing.

Fast forward a few weeks later and my pedal feels worse than before I bled the system. Upon first pressing down on the pedal it goes pretty much more than half way down and feels like there isn't any pressure in the system. Its only in the bottom half that my brakes begin to grab now. After the first application of pressure to the pedal, if I release my foot and then right away re-apply the pedal it has full pressure within the first 25% into the braking. I also feel there is a slight delay in the pedal coming back up, i find it used to rest faster.

My first thoughts are either the inner seal on the mater cylinder is gone, or this is a booster problem( I sometimes here a faint hissing noise from under the dash when pushing on the pedal...normal?) any thoughts?

Thanks.
Sounds like master cylinder starting to go. As soon as you have to start "pumping" the brakes to get them a bite, it's typically a cylinder problem.

Haven't experienced this on my Saab but have on a prior vehicle.
 

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Discussion Starter #3
Thanks I'm leaning towards the master cylinder as well. Of course though I"m on vacation for the next week and every auto parts place won't get it to me in time, and neither will online stores.

Also I read awhile ago on another forum of someone having brake issues and they said to check the "Brake Booster Vacuum Pump"? Where is that on this car?

Thanks
 

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I would agree with the assumption that the seals in the master are knackered.
Never had it with a car but its quite common on motorbikes and is usually caused by old brake fluid becoming more acidic and eating the seals along with dirt particles wearing them away.
 

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Discussion Starter #5 (Edited)
Thanks for your input guys,

Now question is, should I buy rebuilt or new. When it comes to my brakes I don't like to cheap out on them. So far the only rebuilt ones I can find are made in china ones for around 150 bucks, or go new for 300 to 400. Of course Saab had to use their own m/c instead of a generic off the shelf one. So they're hard to find.
 

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Discussion Starter #6
could this also be the vacuum pump for the brakes going?
 

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could this also be the vacuum pump for the brakes going?
There is a possibility. I would have the brakes pressure bled. Bleeding by foot/vacuum can still allow air to go back in. Pressure bleeding will not.

Master cylinder can be damaged by foot bleeding especially if someone stomps on the pedal.

Try doing a pressure bleed, If not check all lines that go to break booster for leaks.
 

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Discussion Starter #8
There is a possibility. I would have the brakes pressure bled. Bleeding by foot/vacuum can still allow air to go back in. Pressure bleeding will not.

Master cylinder can be damaged by foot bleeding especially if someone stomps on the pedal.

Try doing a pressure bleed, If not check all lines that go to break booster for leaks.
I did pressure bleed. I used a motive power bleeder, but didn't fill the unit. I just used it to apply pressure to the master cylinder reservoir and then went around the car bleeding the valves. I would disconnect the unit after each wheel and top up the m/c
 

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I did pressure bleed. I used a motive power bleeder, but didn't fill the unit. I just used it to apply pressure to the master cylinder reservoir and then went around the car bleeding the valves. I would disconnect the unit after each wheel and top up the m/c
Hmm that is strange then. Defiantly check the vacuum pump it has been known to fail on our cars. Well the seal that is. If that is not the issue then the master cylinder or the brake booster itself. The other 2 are very rare but ive seen one.
 

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Discussion Starter #10
Are there any signs I can check for a dying pump? Hissing noise...all three of those parts are not cheap
 

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I have had all sorts of issues with soft pedal feel after doing the brakes on my Aero. I have bled them many times, using different methods including the Motive...which BTW was the worse as it didn't seem to work as I expected.

I know the 2.8T has a vacuum pump for the brake system as these motors don't make as much vacuum as the 2.0, but I am not sure if you car has it. There are a few check valves in the vacuum system that tend to get brittle and this may be a source of your issue....



Sean
 

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Discussion Starter #12
I have had all sorts of issues with soft pedal feel after doing the brakes on my Aero. I have bled them many times, using different methods including the Motive...which BTW was the worse as it didn't seem to work as I expected.

I know the 2.8T has a vacuum pump for the brake system as these motors don't make as much vacuum as the 2.0, but I am not sure if you car has it. There are a few check valves in the vacuum system that tend to get brittle and this may be a source of your issue....



Sean
Hey Well the thing is It was fine for at least 2 weeks after using the motive to pressure bleed the system. I also used it on my MK4 Golf when I did the brakes and so far that car braking well. As for the vacuum pump, when I look up the parts listing for this car it shows a pump which sits behind the PS pump. Where can I find these check valves? and what method did you find worked best for bleeding the system on this type of car?

Thanks Sean
 

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Hey Well the thing is It was fine for at least 2 weeks after using the motive to pressure bleed the system. I also used it on my MK4 Golf when I did the brakes and so far that car braking well. As for the vacuum pump, when I look up the parts listing for this car it shows a pump which sits behind the PS pump. Where can I find these check valves? and what method did you find worked best for bleeding the system on this type of car?

Thanks Sean
The pump is behind the power steering pump. For the check valves follow the vacuum line that leads to it. I don't think you can buy them separate comes as as complete line.

This is the tool that is the best for bleeding the brakes


You just simply apply pressure then starting at the rear right bleed that first then rear left right front and finally left front.
 

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Well, Saab has a different bleed order since it is a dual zone braking system for safety....but honestly I tried it their way and the traditional way and it's no better. If you had the pedal feel perfect after bleeding and its slowly going soft, did a re-bleed bring it back? If so I would think something is leaking.....master, slave or caliper. My issue is that I haven't been able to get the firm pedal back at all.


The 2.0 vacuum lines with check valves are a lot cheaper then the 2.8T cars. Often I have seen comments about one under the battery going, and another in the side of the fender. If you use a Mighty-Vac style pump with the car off, and plug it into the lines somewhere, you should be able to add a small amount of pressure and listen for air leaks.


As a side note, it was my first time with the Motive and I am assuming I did something wrong. I filled it with fluid, and pressurized it, but the line from the reservoir to the motive never full filled with fluid...there remained an empty area I assume was an air bubble? I ended up taking it off and doing it manually again using the 2 person method, although have also done the gravity method a few other times....



Sean
 

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Discussion Starter #16
I haven't had a chance to bleed the brakes again. We're in a deep freeze where I am so I'll have to wait until it gets warmer. I have a vacuum pump for gravity bleeding I might try that next.
 

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A failing booster, vac pump or check valve would give a hard to push brake pedal.From your description the pedal is easy to push but goes nearly to the floor before the brakes start to work. Second application of the pedal is slightly better.This is almost certainly due to air in the braking system somewhere. It only takes a few air bubbles to give the symptoms you descibe, and may only be a single bleed nipple that is not tight/leaking.I'd manually bleed each caliper using a simple tube on the bleed nipple whilst slowly getting someone to pump the pedal down, closing the bleed nipple just before the bottom of each pedal stroke so as to not get any air in. You should be able to see if there are any bubbles in the lines.
 
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