Help, Soft Brakes!

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Help, Soft Brakes! - 1/13/2007 6:52:16 PM    windpower79106   Posts: 3 Joined: 11/6/2006 Status: offline The brakes on my '89 Suburban never seem to be right. I replaced the master cylinder and took it to a shop to bleed the brakes (seemed like my MityVac wasn't able to pull all the air out at the rear cylinders.) The shop said they bleed the lines for a really long time before they got a firm pedal. It is two weeks later, and the brakes are getting soft again. Any idea what is really wrong? The level of fluid in the master cylinder never seems to get any lower, and I have not found any visible fluid leaks. I bought this truck from my father-in-law because it has a new GM engine and transmission, and parts are cheap. I have found so many things wrong with the engine install that I am starting to lose patients. If I could just iron out the brake problem, I feel like I can get through the other nit picky problems. Help save this Suburban and myself from an early grave! Post #: 1

RE: Help, Soft Brakes! - 1/14/2007 9:46:38 PM    golfer   Posts: 610 Joined: 10/8/2006 Status: offline Have you checked the rear wheel brake cylinders for leakage ?  The front brake flex hoses may need replacing. < Message edited by golfer -- 1/14/2007 9:47:12 PM > (in reply to windpower79106) Post #: 2

RE: Help, Soft Brakes! - 1/15/2007 1:43:01 PM    windpower79106   Posts: 3 Joined: 11/6/2006 Status: offline I attempted to bleed the brakes yesterday. Lots of air in the lines. So much so that after an hour of pumping my brake bleeder, I gave up.  No rear cylinder leaks, but I will check into front hose flex. Any idea how the air is getting into the system? (in reply to golfer) Post #: 3

RE: Help, Soft Brakes! - 1/16/2008 5:57:36 PM    bigbodychevrolet   Posts: 2 Joined: 1/16/2008 Status: offline Don't forget about the rear brake hose. Might be swelling up. would explain soft pedal, low pressure for unsuccessfull bleeding, and no loss of fluid... (in reply to windpower79106) Post #: 4

RE: Help, Soft Brakes! - 1/24/2008 5:29:15 PM    Brownz5   Posts: 2 Joined: 1/24/2008 Status: offline I have a 93 Suburban and if I remember correctly there was a brake related recall.  Not sure if it included the 89 year model. (in reply to bigbodychevrolet) Post #: 5

RE: Help, Soft Brakes! - 1/24/2008 6:08:09 PM    RickCoMatic   Posts: 9 Joined: 1/24/2008 Status: offline You need the "Pressure Bleed" treatment. Brake shops have a tool that forces fluid through your system via a Master Cylinder Cover that has an Inlet Port where Fluid can be pumped-in under pressure. Bleed the FURTHEST Wheel Cylinder away from the Master and work your way to the closest. That ought to do the trick and get all that Air out of there. It will also find any leaks that you may have failed to detect during previous bleeding attempts. _____________________________ Rick Massey 04 Monte Carlo LS (in reply to Brownz5) Post #: 6

RE: Help, Soft Brakes! - 1/24/2008 8:21:21 PM    73shark Posts: 2198 Joined: 4/17/2006 Status: offline I found that when I was using a Mityvac to bleed brakes, that it was actually sucking air past the piston seal into the caliper.  That's when I decided to put an air fitting on a master cylinder and pressure bleed like RickCoMatic suggested.  A lot easier to boot. _____________________________ GM perf. exh, GM CAI, Superchips, Lund step tubes, billet grill, LED tails, Lloyd mats, rear console, GM flaps, silver calipers, black bow ties, tint (in reply to windpower79106) Post #: 7

RE: Help, Soft Brakes! - 1/24/2008 8:32:55 PM    shawnvw   Posts: 954 Joined: 1/18/2008 Status: online The first and most important step in doing a master cylinder is to bleed all the air from the master cylinder in a vise before installing it. pumping the brake pedal will not get all of the air out because of the slight angle of the unit once installed in the car. I know most of the aftermarket kits come with bench bleeding kits and have instructions telling you how to do it. Could also be a bad master.....did you get a new or Reman? The were huge problems with the reman units a while back, and even though remans were way cheaper....they were not worth the headache. (in reply to 73shark) Post #: 8

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