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jumpjg

Stupid Brake Bleeding Questions

10 posts in this topic

I think I screwed up. I was replacing brake pads/rotors and thought the brake fluid could use refreshing (old & dark). I sucked out all the old fluid in the reservoir with a turkey baster & refilled it with new fluid. I was alone & don't have a bleeder bomb so this is the process I used. I attached a clear vinyl hose to the rt/front bleeder, ran it uphill about 18" then down into a container with the end submerged in fluid. I opened the bleeder & pumped the brake pedal (engine off) to the floor about 10 times, not closing off the bleeder in between pumps, occasionally checking & replenishing the reservoir. Slow, deliberate strokes to the floor, remove foot and allow the pedal to return on its own, wait a few seconds in between pumps to let the fluid recharge into the MC bore. Fluid ran out nice & clean. Repeated the process on the left front. Did not observe any air in the hose coming out of the caliper, nor did I see any air being drawn into the caliper when the pedal was released. Buttoned everything up - no muss, no fuss.After the job was done, I started the truck and with power assist the pedal can be pushed to the floor, not so with engine off. No brake warning light on the dash. I'm new to the truck, not familiar with hyd power assist, but I assume I still should get a solid pedal. I guess I got some air into the system, not sure how. Weather has been too wet to crawl around under the truck lately so I haven't tried bleeding the rear brakes. Haven't taken it out for a road test either - I think it would stop but with diminished performance. Just dropping a line to see if there are any peculiar tricks to bleeding the system on these trucks. All of the plumbing on the wheel well associated with the 4 wheel ABS looks like a good place for an air bubble to get caught up in. Appreciate any suggestions.Joe in St Louis

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Thats how I bleed my brakes but I didnt run the clear hose up hill, just straight down into a jar. I ran almost 2 large bottles of fluid through it to make sure it got all the old fluid out. I dont remember if I had a soft pedal because its been a couple years. Take it for a little drive and see if it stops feeling soft.

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Same here... :shrug:

Posted Image

The only thing I could give for an idea is the fact the system might not of been bleed for a very long time and the crud built up in the master cylinder and when your pressing to the floor you pushed the piston into the crud ripping the seal. I heard of this happening on a few other forums but never actually seen it so don't jump out buying a master cylinder right off...

But you might double check your bleed job with a second person and do the ol' 2 person bleeding...

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Joe, I fought that same problem for SIX WEEKS! I literally went through GALLONS of fluid to get them to firm up. I tried FIVE different master cylinders, two sets of calipers, replace all rubber hoses and most of the steel lines and still could not get a firm pedal. Finally I got a consistent 1/2 pedal on the first pump but could still push the pedal to the floor if I tried. I gave up after even taking it to a dealer to see if they could get me brakes, but they claimed the brakes were fine. Anyhow, after about a year the pedal is fine! I have no idea as to why or how they got better, but they did. BTW, I have been working on brakes since there were drum on all four and no power brakes...... Yea, I am that old............:cry:

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I even went so far as to put thread tape around the bleeder threads just so they wold not suck air back in.........

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I'm fighting this on an 85 Mercedes diesel. New front calipers & master cylinder. I expected an hour to do the master since it isn't rocket science. Have literally run gallons of fluid through the system. Used the old school pump & hold then release bleeder, gravity bleed, & pressure bleed. Pedal is still soft. I thought MC was bad (original equipment NEW Mercedes MC), replaced with another new MC & have the same problems. My next strategy is to power bleed where the lines come out of the ABS & go to the calipers. I figure it is only a short distance between the MC & ABS. Once I know that is clear through the ABS, I'll reconnect the lines & bleed at the calipers.

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Think back a long time ago when I got my first 76 Dodge Jamboree motorhome I went through simular problems with the brakes having a soft pedal and needing to double pump the brake to be firm. Bled it out numberous times... Changed the Master cylinder... Bled it some more... Checked the rear drum adjustment... Bled it some more... Honed the rear slave cylinders... Bled it some more... Changed the Vacuum booster... Bled it some more... Arrgh... Come to find out it was just because the front pads where too thin... You might check your pads and shoes to be sure they are serviceable...

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Appreciate everyone's comments. I took the truck out for a ride & it stops fine without the pedal going down too much, but it still seems a little soft. Makes me concerned with how it will react with a load hooked up.I've been playing around with this stuff for a long time too. To give you a clue I started out with a '48 Chrysler New Yorker Club Coupe that I paid $15 for......No, I'm not that old! (that was in 1972).I thought about the "sucking air back in past the bleeders" thing too. Possible but I doubt it because of the fluid head pressure on the bleeder (hose going uphill for 18"), and if it did happen, gravity still allowed fluid flow from the reservoir out the caliper until the bleeder was tightened. And I doubt if the problem is due to worn out pads/shoes - rotors & pads are new. The reservoir was never allowed to go dry so it didn't suck air in that way. I'm wondering if when the pedal is returning to the up position after a pump, if the cup on the M/C piston collapses and allows air to enter into the system from the pedal end of the M/C bore. If that be the case then a power bleed should be adequate to flush out any trapped air bubbles. I probably should flush the rear system first before I get too carried away. If no joy, then I might try to build by own bleeder bomb - I'll keep you posted. Joe in St Louis

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Joe, that is exactly the way mine went and now I have a good high pedal. I don't know if I could lock the front brakes or not, but it sure stops good. Give it some time and see what happens. Something else I did was every once in a while as I was using the truck I would crack both front bleeders and allow the fluid to gravity bleed for a second just to make sure the air was getting out.

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