The Stovebolt Site Forums The Shop Area Engine Shop Brake Bleeding has me wore out!

Ok here's the downlow. I have been driving my truck lately where when the brakes are applied the pedal stops about couple inches from the floor and when pumped will be better. I said to myself this just isn't safe ecspecially for panic breaking and I took her off the road till I get her fixed. I adjusted my brakes so they have a light even drag. I went out and bought some Speed Bleeders and have those installed. Each time I bleed a wheel I pump slowly 5 times for each wheel and watch the MC so it doesn't go dry. Just got done bleeding them for the third time and the pedal is the same. Too close to the floor and kinda spongy. I have tried all the suggestions in the archives and to no avail have I been able to make them better. Any help or advice would be appreciated! 1958 Chevy 3200 stock brakes.

Try a new master cylinder.

Are your rear emer. brake cables good? you might have the cables adjusted too tight holding the shoes off the anchors. Its hard to adjust brakes by using a slight drag methed. The shoes float in there & may be rubbing from being off center. Back off the emer. brake adjustment & adjust all the brakes till you get a heavy drag & back the adjustment off about 4 notches.
Like Mr. Luvr says if you havn't done the master cyl. lately put a kit in it or get a new one. If you have done all that bleeding you coulnt have more air in it unless it is drawing it in somehow.

I'll try the emer. brake thing first cause it's an uneven drag at first when adjusting. If that doesn't work then I'll move on. Thanks alot guys!

I know this is a stupid question but....check all brake lines real close to see if you see any moisture (brakefluid) anywhere. Its possible to have a TINY pin hole and you have not noticed it. If it leaks bad then you would see it on the ground or the m/c would be low when you checked it.
I'm leaning toward the m/c to but some lines are hard to get all the air out.

What has been done to the master? Has the pedal rod adjustment been changed?
Scott

I'll check over the lines when I can. 48bigtrucks, to my knowledge the pedal rod adjustment has not been touch since we bought the vehicle 10 years ago. My brother used to drive the truck before it became mine and only thing he did was a MC rebuild with a kit. After he did that and I started to drive it that pedal went down like 2 inches max and was rock hard! I can't remember when it started this right off, my mind is in a whirl with finals 2 days away. Thanks for the help!

You may still have an adjustment problem. The only other thing would be an internal master cylinder problem. When I do a complete brake redo, I adjust the brakes out tight to the drum to eliminate any chance of an adjustment problem, especially on Huck brakes. Then I bleed until it feels right. Now, on these trucks with the masters under the floor, I only power bleed, which forces the air out without the master being involved. If the brakes still don't work/feel right, it almost has to be the master then,
Scott

I have run across this problem before...
I suspect you have a frozen wheel cylinder piston, when the brake pedal returns, a vacuum is created, allowing air to suck past the
wheel cylinder cup seal....Check all wheel cylinders for freedom of movement....Give it a try.....

I did brakes for a living for years and that is one I never thought of although I firmly believe now that I ran into it on an International 2-1/2 ton flatbed that we could never get the brakes bled good enough. That one was an old farm rig that sat 10-1/2 months out of the year and then was used to haul fruit in the fall.

Way back when, when I started out as a sophomore in high school autoshop the instructor taught us to adjust the brakes tight so that the wheel didn't turn and then back off 11 clicks. That always seemed to work pretty well on the older rigs.

In my own experience both as a working mechanic and a hobbiest at home I have found that with most rigs that have sat for a while it is better to go ahead and rebuild or replace all of the brake cylinders. They are the part of the car that hates inactivity the most and usually are the first thing to give problems on a rig that sits for long periods of time.

It usually shows up when while bleeding, 1 cylinder keeps on bubbling air, you have a good pedal that will gradually fade to the floor....

make sure that you are bleeding the cylinder that is the farthest from the master cylinder first, then the next farthest first and so on.

Don, I've tried starting from the farthest and moving in. I have also tried the shop manual way that is driver rear, passenger rear, driver front then passenger front. I just don't get it yet. I will try later and report back. Right now it's below freezing outside, so this Texas boy ain't gonna go out and mess with it anytime soon, oh and there is snow on the ground!

Actually, you bleed the longest line first, in this case, the left rear as indicated in the manual. If there's no bubbles at the bleeder and the pedal is still mushy/low, then either there's an external leak or, judgeing from the description, and internal leak in the M/C.

I just got done talking to my brother about something and he asked about my brakes. He said when he was driving it and had some brake problems the MC was leaking especially around the boot. I went out side and crawled under the truck to get a good look and there was fluid dripping of the boot and the outlet end. You guys think I should rebuild it again or get a whole new MC. $29 or $159 from NAPA so what say ya'll?

have you tried a helper when bleeding brakes? have him or her pump pedal tree times and hold to floor, you crack a bleeder screw till all fluid comes out, they don't let up on the pedal till you close the bleeder screw, you yell pump it up and on to another wheel cylinder.

6tvette, no I haven't been using a helper since I went out and bought those speed bleeders. They're supposed to keep from sucking anything back in when you let off the pedal. So I have been treating them as such.

I vote for what 6tvette says...I have been doing it that way for 45 years plus, and it has always worked.

Stuart

ApacheFiend, it looks like you have answered your own question .

The leak from the M/C is a significant thing.

You choose what yer wallet will stand, rebuild or new.

I'm sure you will remember to inspect the old m/c for pitting and any other damage in the bore before you decide which option to take.

Take the master cyl. apart. There is a little funnel in the resorvior with a tiny hole in it that goes into the cyl. Check to make sure this hole is open. You may have to get a tiny piece of wire to clear it out. Check for any pits in the cyl. If there are any too deep to hone out you will need a new master cyl. THe price you mentioned sounds kinda high.

UPDATE! Ok After I took my finals today, (HOORAY I'M ON CHRISTMAS BREAK!!!) I went to NAPA and picked up some stuff. A MC rebuild kit, some brake fluid and a cylinder hone. I took the MC off the truck and disassembled it. The boot has a couple of holes and I found one good sized pit in the cylinder. I decided to clean it up and hone it out. I've been honing till one of the stones has just about wore out. The pit is better but still there. I haven't had to deal with pitting in brake cylinders before, so can there be a little pitting or is it any pitting is no good. I'm leaning toward getting a new MC, what do the experts say?

My opinion is, don't risk your life on "probably good enough" brakes. Be a darn shame to save a few bucks but have the brakes fail catastrophically on the road.
Shop around for the master cylinder - you might get a better price. The new MC for my '51 GMC from Obsolete Chev in Nashville GA only set me back about $80. No core needed.

David B

Brake fluid is hydroscopic, hence the reason to change the fluid yearly or you will get pitting and rusting. Any pitting and/or rusting is bad. get a new master cylinder. Then check the wheel cylinders, if you have rust in the master cylinder, most likely the wheel cylinders are toast as well.

Find someone with a power bleeder when you are done (or rent one). I was lucky and a co-worker was a former ASE mechanic that decided to go into design. I did 3 brake jobs and had them all bleed in less than a half an hour.

If during bleeding of the brakes the fluid is brown, keep bleeding until it is as clear as new fluid.

Scott, I think you want the word Hydrophilic, having an affinity for water.

i looked both words and you both are correct .

correction, Hygroscopic - Absorbs water. Absorbing up to 7% by molecular weight just in an open container sitting on the shelf.

After 3 years, Brake fluid is saturated by pulling moisture thru the reservoir breather in the master cylinder

I usually get hydroscopic and hygroscopic mixed up during typing.