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Unread 01-09-2010, 05:57 PM   #1
JeepJinx
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Brake pedal soft

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Unread 01-09-2010, 06:42 PM   #2
Carl48
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After shutting off the engine, wait about a minute or two then press the brake pedal... you should get a couple of vacuum assisted applications then the pedal should firm up and under moderate pressure not fall towards the floor. Now, step on the brake pedal with light pressure and start the engine...pedal should fall a little way toward the floor and stop as the engine starts and vacuum builds up. If all this checks out, the booster and master cylinder are probably OK.

The vacuum canister you mentioned is known for cracking and causing a vacuum leak...check it out.

You said the PO did some brake work. Make sure the front calipers are installed with the bleeders on top. Also, check the rear brake adjustment...too loose can cause a soft pedal.

May want to see about getting the system pressure bled...could be air in the system from all the maintenance...especially if the PO did not bench bleed the new master cylinder before installing it.
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Unread 01-09-2010, 06:59 PM   #3
RockRodHooligan
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X2 on the master cylinder needing to be bench bled, thats the first place I would look
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Unread 01-09-2010, 07:33 PM   #4
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Unread 01-09-2010, 09:17 PM   #5
Carl48
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Pressure bleeding the system should take care of the whole system, no need to remove the master cylinder. A brake shop usually does it this way.

Also, one other thought, over a period of time the flexible brake hoses at each of the wheels may get soft and spongy. This will cause them to expand slightly when you step on the brake pedal and apply pressure to the system. The hose expansion will cause the pedal to feel soft. But...check out all the other stuff first.

btw, if you have ABS, a DRB (dealer scan tool) will be required to completely bleed the system.
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Unread 01-09-2010, 09:53 PM   #6
lowicz96
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I redid my master and blench bleeding is not fun, at all. Even afterward i had a spongy pedal which i figure was my rear brakes because the rear brakes should grab before the front. I redid my rear brakes and now its great!! pull the drums and make sure all the hardware is in place and adjusted properly
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Unread 01-09-2010, 10:12 PM   #7
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Unread 01-09-2010, 10:17 PM   #8
lowicz96
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Pressure bleeding is pushing fluid from the wheels up to the master that requires a pump. The opposite of what you did, "gravity bleeding"
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Unread 01-09-2010, 11:35 PM   #9
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Unread 01-10-2010, 12:01 AM   #10
lowicz96
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Quote:
Originally Posted by JeepJinx View Post
Well, I would say that my method was pressure bleeding, as I had a helper apply brake pressure, as I opened each bleeder valve and allowed the air and old fluid to be bled into a clear container of brake fluid. Isn't that pressure bleeding? Wouldn't that evacuate all the air from the system, including the master cylinder?
Using a helper to pump the pedal is just the normal way to bleed brake. This with NOT get the air out of the master. The master needs to be bench bled to remove all air.

Opening all 4 bleeder valve and letting the system drain while adding fluid at the reservior is gravity bleeding. (good way to change brake fluid)

Pressure bleeding is using a pump at the wheel that pushes the fluid and air up to the master. Most shops do this cause its easy for them. I dont know if it gets the air out of the master or not
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Unread 01-10-2010, 12:10 AM   #11
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Unread 01-10-2010, 12:16 AM   #12
lowicz96
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If it doesnt have a torque spec, i would say just snug it. You dont want to over tighten it
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Unread 01-10-2010, 03:13 AM   #13
Carl48
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Repair manual spec says 23 ft-lb on the front caliper banjo fitting bolts on the brake hoses, and yes it is best to use new crush washers.

Gravity bleeding (just letting the system drain) is slow and may introduce moisture into the system.

The hand vacuum pump method is strictly speaking not pressure bleeding. Pressure bleeding is done with a special fitting that goes on the master cylinder and compressed air is used to force fluid thru the system. It is best left to be done by a brake shop.

This is not to say that the gravity method or hand pump method won't work for you. You may have to try several things before getting all the air out (if that is your problem). Pressure bleeding at a brake shop could be your last resort.

Last edited by Carl48; 01-10-2010 at 03:36 AM.. Reason: clarity
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