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Username Post: Rear drum brakes can't bleed, need help!        (Topic#365894)
impalatom 
Senior Member
Posts: 330
impalatom
Loc: Florida
Reg: 03-17-01
07-24-21 09:53 AM - Post#2823806    

It has been probably 20 years since I changed the rear drum brake shoes on my 65 Impala. I have not done much work on my cars lately since I am getting older, and I am beginning to forget some of the things I used to know concerning car repairs.

Problem, I noticed a wet spot on the back side of the left rear backing plate. I suspected either a leaking wheel cylinder or a bad brake line. I opened up the drum and found that the wheel cylinder was leaking. I changed it out with a new part from NAPA. I cleaned everything back up and put it together. All seemed O.K. with reassembly. I then tried to bleed the replaced wheel cylinder using wife in car to pump and hold brake pedal while I cracked open the bleeder valve. Only a very small amount of brake fluid appeared in the clear plastic line attached to bleeder. Brake pedal would not go to floor at all. Yes, there is plenty of brake fluid in the reservoir.

Tried bleeding several times but no flow of brake fluid. So, I thought I would try to bleed the right rear wheel cylinder, (have done no work to this side and the brakes have been working for 20 years). Same problem, when wife pumps and holds brake pedal, I crack open the bleeder valve on right rear brake cylinder and see just a bit of fluid enter the drain tube but no flow. Also, brake pedal does not go to floor. Again, plenty of fluid in the master cylinder.

I am obviously missing something. Any suggestions what I am doing wrong?

Just a fyi, I converted the front brakes to Corvette disk brakes some years ago. I also replaced a leaking caliper about 6 months ago, no problems bleeding it and getting the brakes working again.

I have an adjustable proportioning valve on the rear brake line just after the dual master cylinder. Does that adjustable proportioning valve come into play at all here? Grasping for straws I wonder if it is turned to the point where the flow to the rear drums is restricted. I really don't like to mess with that adjustment as I don't remember how to adjust it back. Funny how my mind starts to guessing/questioning when I can't figure this out.

Any suggestions would be greatly appreciated.



65 Impala SS convertible
2018 Silverado LTZ crew cab


 


wagonman100 
Site Ambassador
Posts: 15320

Loc: Baltimore, MD
Reg: 11-27-04
07-24-21 11:32 AM - Post#2823812    
    In response to impalatom

Not to cast dispersions on your wife, but is she pressing on the pedal hard enough? Did you have her pump it up 3 or 4 times and then hold the pedal? Ask her if it felt like the pedal dropped easier when you opened the bleeder.
I was trying to bleed the brakes on my ‘99 Silverado and had a similar problem. Turned out the person I had helping me wasn’t pushing on the pedal hard enough and not far enough down.
If you had a factory type proportioning valve I would say you need to reset it. Sometimes the internals will shift to one side with the pressure differential when you open one side of the system.
I made a pressure bleeder for mine so I can do it by myself, but Lisle makes a one man bleeder you can get from an auto parts store. It’s just a cup, a longer hose to connect to the bleeder and a short hose that goes to the bottom of the cup lid. You put a little fluid in the cup so the end of the hose doesn’t suck air, put the cap on, hook the hose up to the bleeder, open the bleeder and pump the pedal. The two drawbacks to it are the cup is fairly small and you can’t see if no more air bubbles are coming out. But I’ve used it and it works.

Jay
Friends don’t let friends drive Fords.

1999 Silverado Z71 4X4 extra-cab short bed
1983 Malibu Fauxmad - tubbed
1978 El Camino Kustomized
1972 Monte Carlo
1957 210 handyman wagon
1957 Nomad sport wagon
1957 Cameo Carrier


 
Shepherd 
Frequent Contributor
Posts: 2296

Loc: Lake George, NY
Reg: 11-11-15
07-24-21 11:50 AM - Post#2823815    
    In response to wagonman100

I would open the prop valve all the way, of course count the turns to restore the setting when done. Then see if you get proper flow in the rear.




 
Anonymous 

07-24-21 12:01 PM - Post#2823818    
    In response to impalatom

The proportioning valve controls the rear brakes pressure. Reduces pressure so they don't lock up. The valve could be stuck, or adjusted incorrectly. I guess the easiest place to start would be to mark your valve, then open it a half a turn and see if you get more fluid at the rear wheel cylinder. After that we can start looking at other reasons like blockages, master cylinder etc.



 
jayoldschool 
Poster
Posts: 66

Reg: 09-03-18
07-24-21 12:16 PM - Post#2823822    
    In response to Impalas4ever

Did you also install a disc/drum master when you did the front Vette discs?

Jason

65 Impala convertible 327/250 Maderia Maroon/black California black plate car


 
impalatom 
Senior Member
Posts: 330
impalatom
Loc: Florida
Reg: 03-17-01
07-24-21 12:46 PM - Post#2823826    
    In response to wagonman100

Well, not sure DW was pushing brake pedal hard enough or not, over the years she has helped me bleed brakes and it always seemed to work before. Usually she could feel the pedal going to floor when I cracked open the bleeder, not so now.

65 Impala SS convertible
2018 Silverado LTZ crew cab


 
impalatom 
Senior Member
Posts: 330
impalatom
Loc: Florida
Reg: 03-17-01
07-24-21 12:48 PM - Post#2823827    
    In response to Shepherd

Trying to open up the adjustable proportioning valve will likely be my next try. I don't remember this being a problem in the past on this car, but it has been a number of years, like twenty years ago!

65 Impala SS convertible
2018 Silverado LTZ crew cab


 
impalatom 
Senior Member
Posts: 330
impalatom
Loc: Florida
Reg: 03-17-01
07-24-21 12:52 PM - Post#2823828    
    In response to jayoldschool

  • jayoldschool Said:
Did you also install a disc/drum master when you did the front Vette discs?



I bought a complete front disk brake conversion kit from Stainless Steel Brake Parts about 20 years ago and installed it. It included the dual master cylinder and rear proportioning valve. When I changed to to the Vette front disk brakes about 5 years ago I didn't change anything to do with the master cylinder or the proportioning valve. Brakes seemed to have worked correctly the last five years up until I tried to change the leaky rear wheel cylinder.

65 Impala SS convertible
2018 Silverado LTZ crew cab


 
brasii 
Contributor
Posts: 176

Loc: FRANCE
Reg: 11-09-07
07-25-21 12:16 AM - Post#2823844    
    In response to impalatom

Have you changed the rear central brake hose ?

impala 66 convertible


 
impalatom 
Senior Member
Posts: 330
impalatom
Loc: Florida
Reg: 03-17-01
07-25-21 01:52 AM - Post#2823845    
    In response to brasii

  • brasii Said:
Have you changed the rear central brake hose ?



No brake line work at all. Brakes were working fine b4 I pulled the drum on the wheel with the leaking wheel cylinder.

65 Impala SS convertible
2018 Silverado LTZ crew cab


 
6T5 
"4th Year Gold Supporting Member
Posts: 280
6T5
Age: 69
Loc: Asheville, NC
Reg: 07-22-17
07-25-21 02:51 AM - Post#2823849    
    In response to impalatom

It sounds like your proportioning valve is off center to the front and not allowing fluid to the rear because of the wheel cylinder leak on the rear...

...Ed

1965 Impala SS


 
bobb 
Super Senior Member
Posts: 5882

Loc: paradise
Reg: 09-05-03
07-25-21 09:17 AM - Post#2823863    
    In response to impalatom

back track. start cracking lines starting at the t on the rear end and see if fluid will bleed out.

70 L camino, grampa engine, g-force 5 spd, road rage suspension. Pray first before all else fails.


 
impalatom 
Senior Member
Posts: 330
impalatom
Loc: Florida
Reg: 03-17-01
07-25-21 03:25 PM - Post#2823883    
    In response to 6T5

  • 6T5 Said:
It sounds like your proportioning valve is off center to the front and not allowing fluid to the rear because of the wheel cylinder leak on the rear...



No, there is no combo front/rear proportioning vale in this system. The proportioning valve is adjustable and is located on the rear line coming out of the rear reservoir of dual master cylinder. Front brakes are totally isolated from the rear brakes.

65 Impala SS convertible
2018 Silverado LTZ crew cab


 
Shepherd 
Frequent Contributor
Posts: 2296

Loc: Lake George, NY
Reg: 11-11-15
07-25-21 04:39 PM - Post#2823886    
    In response to impalatom

Disconnect the line out of the prop valve, see if you get good flow.



 
mjc1 
Senior Member
Posts: 1735
mjc1
Loc: Burlington Ontario Canada
Reg: 09-15-04
07-26-21 05:19 AM - Post#2823905    
    In response to Shepherd

The classic blocked rear flex line. Just went through this with my 65.

1965 Laurentian post, 1967 Grande Parisienne 4DR HT
My Flickr page



 
jayoldschool 
Poster
Posts: 66

Reg: 09-03-18
07-26-21 07:25 AM - Post#2823907    
    In response to mjc1

I as well dealt with the blocked rear line on my 65 C10. Was bleeding after a failed RR wheel cylinder, then all of a sudden, no fluid, and hard pedal. New line, bled out perfect. They deteriorate internally. Crack the rubber line where the hard line enters. Pump. Fluid? You found your problem.

Jason

65 Impala convertible 327/250 Maderia Maroon/black California black plate car


 
Stinky 
Senior Member
Posts: 1763

Loc: Whitewater, CO
Reg: 05-25-01
07-26-21 10:57 AM - Post#2823921    
    In response to jayoldschool

I think bobb gave you good advice. Start at the MC, crack the line and have her step on the brake...It should be a geyser.

Start working your way back.

Or, if the gentleman that suggested that your rubber brake line is clogged (they don't last forever...Bob Daley told me, about 30 years ago..."The parts made of rubber on the car, give you all the problems.")....start at the rear and work your way forward.

Try, opening the bleeder, have her step on it and hold it, then close it. Open and step, close and release and see if you get anything dif. This is unorthodox, but on new stuff, sometimes I have trouble getting fluid in the system. Once I get enough fluid in the system will bleed normally.



 
impalatom 
Senior Member
Posts: 330
impalatom
Loc: Florida
Reg: 03-17-01
07-27-21 04:25 PM - Post#2823992    
    In response to Stinky

I will change out the rubber brake line as soon as I can locate one. I checked the flow thru the adjustable proportioning valve and there is flow. Keep my fingers crossed that will fix the problem.

65 Impala SS convertible
2018 Silverado LTZ crew cab


 
goldss 
Newbie
Posts: 17

Age: 67
Loc: Grayslake,Illinois
Reg: 08-13-09
07-28-21 09:34 AM - Post#2824039    
    In response to impalatom

I put these on all four corners of my 1970 El Camino and replaced the wife(helper)years ago. https://www.russellperformance.com/mc/speed-bleede...



 
Dads65SS 
Silver Supporting Member
Posts: 20
Dads65SS
Loc: Toronto, Ontario
Reg: 07-16-12
07-29-21 04:56 PM - Post#2824131    
    In response to goldss

Your problem sounds exactly like what I was experiencing with my rear brakes, and the cause turned out to be the rear rubber hose. It seems that corrosion of the end fittings causes pressure on the rubber hose within, and the actual opening within the hose is very small to start with!

Before I discovered the rear bleeding problem, I assumed that the rear brakes were working fine, but that obviously wasn't the case. Goes to show how little the rear brakes contribute to the braking in everyday driving.

I ran into a challenge when replacing my hose. The hose that is specified by the application charts (e.g. Dorman HD81229) was fine for the male thread end that goes into the brass tee block. This is a 7/16-20 NPT. The other end was 3/8-24 female inverted flare, and it didn't fit my hard line coming from the combination valve. Turns out my car has a 1/4" line, not the 3/16" that would work with this hose. I don't know if that's because it's a Canadian built car or if it was changed at some point. I found a different hose (Dorman H64888) that worked for me.

Bob

'65 Impala SS Coupe 327 w TH350


 
impalatom 
Senior Member
Posts: 330
impalatom
Loc: Florida
Reg: 03-17-01
07-30-21 02:57 PM - Post#2824175    
    In response to Dads65SS

I am hopeful my problem is indeed the rubber hose. I ordered from Rock Auto and expect it mid next week. It sounds like this is a familiar problem to many. I am surprised I had not run it across it in the past.

65 Impala SS convertible
2018 Silverado LTZ crew cab


 
nicholes 
Newbie
Posts: 7
nicholes
Reg: 11-11-20
07-31-21 04:03 PM - Post#2824219    
    In response to impalatom

The way I used to bleed the rear brakes was by having someone press hard as some one suggested , and if that don't work crack THE LINE STEEL LINE GOING INTO THE WHEEL CYLINDER OR HOSE TO A CALIPER AND YOU SHOULD SEE FLUID AND BUBBLES COME OUT THE LOCK IT DOWN REDO IT SEVERAL TIMES.



Edited by nicholes on 07-31-21 04:04 PM. Reason for edit: No reason given.

 
junky 
Valued Contributor
Posts: 3735

Loc: Northeast CT
Reg: 06-27-10
08-01-21 10:01 PM - Post#2824272    
    In response to impalatom

I suggest replacing all the rubber brake lines, and once you get the brakes bled, stand on the brake pedal with both feet and push as hard as you can. If the pedal suddenly goes to the floor, then you have either a defective master cylinder or you blew out a steel line. Better to have it fail in your driveway that on the highway when you have to make a panic stop. Brake lines rust from the inside to the outside, so they look good visually, but can fail when you need them the most.

Never argue with an idiot. He'll drag you down to his level, then beat you with experience.


 
nicholes 
Newbie
Posts: 7
nicholes
Reg: 11-11-20
08-03-21 07:14 PM - Post#2824421    
    In response to junky

You are right Junky they rust inside , it happened twice to me Luckily in the drive way.
on
2 different cars,



 
impalatom 
Senior Member
Posts: 330
impalatom
Loc: Florida
Reg: 03-17-01
08-06-21 01:06 PM - Post#2824652    
    In response to impalatom

As a final follow up I got the rubber brake hose changed out today and bled the rear brakes. All is working as it should. Thanks to all that identified the rubber hose as the likely culprit.

65 Impala SS convertible
2018 Silverado LTZ crew cab


 
rcr3 
Site Ambassador -"17th Year" Silver Supporting Member
Posts: 3516
rcr3
Age: 69
Loc: MANHEIM PA. U.S.A.
Reg: 11-24-02
08-07-21 03:28 AM - Post#2824669    
    In response to impalatom

Glad you got it fixed!

'67 Camaro survivor
'06 Z71 Sierra Ex Cab
'37 Chevy cp.SOLD!!6/7/14
'00 S10 Ex Cab BUILT FOR EVERYDAY,NOT JUST THE HOLIDAYS
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