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Discussion Starter · #1 ·
Hello everyone. I'll start by apologizing if this topic has been preveously covered.
I replaced my front brake pads today and when I drove it I found the pedal was soft and will go all the way to the floor if I leave foot presure on it. I didn't crack the bleeder when I pushed in the caliper pistons, to fit the new pads. Do I have to reset the anti skid system? If so does anyone know how? Or did I damage my brake master cylinder? Does anyone have any ideas? Please help if you can. Thanks
 

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Hi there sorry to hear that. But did you take of your cap to the brake reservoir, if not you may have turned the diaphame backwards inside your master cylinder. Take it to a good brake shop they can fix it but you must likely have to replace it should coast about 150 to 200 to replace it. But that is what I think happen to it.
 

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Discussion Starter · #3 ·
No, i didn't take the cap off. :-(. $$ mistake. This is a new one for me. I've replaced brakes on other vehicles before and always at the very least loosened the cap. I don't know why I didn't this time. Costly mistake.
Thanks for the reply.
 

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Discussion Starter · #4 ·
Update: I disconnected the battery, ECM and ABS Unit. While they were disconnected I checked the pedal to see if it would build up presure with the engine off. I got good presure and a firm pedal. It didn't go to the floor. After about ten minutes I reconnected everything I started it up and went for a drive. Pedal was good but not fantastic. It doesn't go to the floor anymore and the truck stops pretty good even in a simulated emergency stop. Not sure what fixed it but it is now 100 percent better. I think I can get it better by replacing the brake fluid and bleeding the system. That brake fluid has been in there since 2005.
 

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In my experience some of the soft/mushy brake pedeal after a brake pad replacement is normal. I don't quite understand it enough to explain it but in squeezing the cylinder piston you contract it further than it needs to be to make contact with the rotor and you may also be messing with the level of the fluid in the master cylinder. 340titan is spot on when he said to remove the cap on the brake fluid reservoir. I do this plus remove some of the fluid so it doesn't overflow. To avoid moisture absorption I keep the cap off for the minimum time necessary.

If you bleed the brakes using the two person method (or any other method that involves pressurizing the system) you should not encounter the soft/mushy brake pedal when you first drive it - or at least not to the extent you encountered. I don't know about the vacuum bleed method.

Brake fluid should be replaced every 2 to 3 years. This varies depending on who you ask. The manual specifies DOT 3, but I believe that DOT 4 is compatible. Do NOT use DOT 5 in a DOT 3/4 system as bad things will happen. Not all brake fluid is the same. DOT 3 from one manufacturer could have a much higher boiling point than DOT 3 from a different manufacturer. DOT 3 specifies the lowest boiling point a brake fluid must adhere to (Dry:205 °C (401 °F) Wet:140 °C (284 °F)). In normal driving you are unlikely to need the higher boiling point of DOT 4 but if you want to spend the extra money go right ahead.

I'm using AMSoil DOT 3 in my Titan which has boiling points of 274°C (525°F) and 156°C (313°F). The cheap crap at Walmart is probably fine, it''s not like Walmart makes their own automotive fluids. I saw references that indicate at one point in time the SuperTech Walmart brand of brake fluid was manufactured by Quaker State. Good luck finding a published spec that details the boiling point.

If you want to read more:
http://bimmer.roadfly.com/bmw/forums/e39/8995265-1.html
http://en.wikipedia.org/wiki/Brake_fluid
 

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I know this is an old thread.

I discovered this by accident. I changed my front rotors and pads on my 2007 Titan and afterwards the brakes were soft and would not pump up. I read several post across several sites and everyone was 1) air in lines - NO in my case. 2) bleed and re-bleed 3) bad booster 4) start over at #1 .

While you are trying to pump up that soft pedal, with the engine running. Turn the steering full left and right several times. My brakes were soft and pedal would sink to the floor. While I was scratching my head trying to figure out why (and Googling to find solution -- and finding none) I got my son to help pump the brakes and turned the wheels so I could look at lines and see if I damaged them. They were firm after pumping and turning the wheels through their full range of motion.

The only connection I can think of is the power steering pump is connected to the vacuum system and turning the wheels helped do something to the booster.
 
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