brakes Brakes Won't Bleed!

[schoir]

'71 2002 has not been driven for 8 or 9 years.

 

Hooked up a Motive pressure bleeder to the brake fluid reservoir and cranked up the pressure, first to 15 psi, then to 20 psi.

 

Opened the bleed screw at the right rear slave cylinder and no fluid would come out.  Same result at left rear and at each of the three bleed screws on each of the front calipers.  No fluid.

 

Opened the bleed screw on the clutch slave and fluid flows freely.

 

Disassembled the clutch slave cylinder and found lots of "gunk" in the cylinder but no damage to the bore, so I replaced the seal and other parts to rebuild and reinstalled it.

 

If I step on the brake pedal with a bleed screw open, some fluid drains out but it takes a great deal of pressure on the brake pedal.  IIRC, in the past, when bleeding brakes manually (i.e., without a pressure bleeder, using an "assistant") that same procedure would allow the brake pedal to go down to the floor with relatively light foot pressure.

 

I've been bleeding brakes on my vehicles for forty years but have never run into this roadblock.

 

Is it possible that the old brake fluid has turned into such gunk that it won't flow through the tiny orifice on the inside of the bleed screws or is there some other cause?

 

Regards, Maurice.

 

 

[esty]

i'd disconnect the brake lines from the cylinders and see if fluid flows from lines

[M3M3]

- i would not use 20psi on a 2002 brake system.  you risk blowing out the friction fit connectors on the brake and clutch MC's.  15psi is the highest i would use.

 

-how old are your soft rubber lines?  do what esty says, disconnect hard line at cyl to see if fluid comes out.  if not, disconnect at the next junction closer to the MC. 

 

-do the fronts bleed ok?

 

-yes. old brake fluid can turn to sludge because of the moisture it absorbs over time.

[bill.in.mt]

You could also try suction on the bleed screw and see if that gets things moving. Harbor Freight sells a cheap suction bleeder tht works OK.

[jscaptura1]

I had this problem after changing the calipers and steel lines.  Went to bleed the brakes, almost no fluid came out, then disconnected the rubber brake lines(original) and almost no fluid drained from them.  Then changed all 4 rubber flex hoses & presto!  No problems bleeding them.  When we were bleeding the brakes before I changed the flex hoses, the pedal was very difficult/almost impossible to depress. 

+1 on mlytle & esty on disconnecting the lines, that is what did the trick for me.

[Mike Self]

Second the motion on the flex brake lines.  If they're old/original they tend to swell up internally so little fluid will pass through.  Both rear wheel cylinders are fed through a single flex hose, so a swollen hose will affect both rear cylinders.  And the front hoses are notorious for this problem.  Usual symptoms are dragging/sticking calipers as the hoses will act like one way valves, keeping fluid from flowing back through them when the brakes are released. 

 

Front hoses are easy to replace (all four are the same); the rear hose is a PITA as it lurks up above the rear subframe and is hard to get wrenches on to remove. 

 

cheers

mike

[Koblenz]

Question.  Clutch slave.  Is that to be bled when you are bleeding the brakes?  I just replaced the MC without bench bleeding it before install.  (BTW, how do you do that?)

 

Today we bled the system again (vacuum) and while the braking has improved, I still would like more pedal response.  Is there a pedal travel adjustment?

 

OP, I have heard of situations such as yours that improved after the 2 rear hoses were replaced.

[schoir]

Mystery solved!

 

Esty... Thanks for getting me on the right track.

 

mlytle.  I did just that, disconnecting at each next junction closer to the master cylinder.  First disconnected the brake line from behind the slave cylinder as Esty suggested and there was no real improvement.  It would only flow when I pressed (hard) on the brake pedal.

 

I then disconnected both of the hard brake lines where they go into the left front caliper.  No flow.

 

I then disconnected both of those lines where they connect to the end of the flexible brake lines closest to the caliper.  No flow.

 

I reconnected those and started to disconnect one of the hard brake lines from to the top of one of the flexible lines.  Gusher!     

 

I have now replaced all four flexible brake lines at the front with stainless steel braided lines that I've been storing for 15 years... (Still in their original package).  Both front calipers now bleed correctly from each of the three bleed nipple on each caliper!

 

 

Next up will be replacing the flexible brake lines at the rear subframe.

 

So, jscaptura and mike... You guys were right on the money!  Thanks for the input.

 

I've owned the car since new and I don't think I ever replaced those lines, despite the best of intentions.  Apparently the rubber inside must have swollen shut inside from the four decades of exposure to brake fluid.  I hadn't driven it in about 8 or 9 years and it was stored after being my daily driver for the first fifteen years of its life.

 

I was starting to believe that my rebuild of the brake master cylinder was the culprit but that appears to be fine.  When I take the car down off its jackstands I will be able to test it properly.

 

Regards, Maurice.

Edited October 1, 2013 by schoir

[schoir]

Question.  Clutch slave.  Is that to be bled when you are bleeding the brakes?  I just replaced the MC without bench bleeding it before install.  (BTW, how do you do that?)

...

The clutch hydraulic system is normally bled from the clutch slave cylinder after completing the bleeding of the brake system.

 

If you are using a Motive Power bleeder, press the clutch pedal all the way to the floor and keep it there (with a wooden stick wedged between the pedal and the front seat).  Then open the bleed screw and wait until any air bubbles disappear and fresh fluid starts to come out.  Close the bleed screw and remove the stick from the pedal and test the operation.

 

If you are doing it manually, you need an assistant.  Have the assistant depress the clutch pedal and hold it there firmly while you first open and then close the bleed screw before the assistant releases the clutch pedal.  The repeat this cycle three or four times, again looking for no air bubbles present and fresh fluid.  If you use a different color brake fluid each time, it's easy to see when the fresh fluid arrives.  I alternate between Ate Super Blue DOT4 and Ate Gold DOT 4.

 

Regards, Maurice.

[Koblenz]

Thanks Maurice.  With each bleed I come closer to strong brakes.

[FunkyLaneO]

If you use a different color brake fluid each time, it's easy to see when the fresh fluid arrives.  I alternate between Ate Super Blue DOT4 and Ate Gold DOT 4.

 

 

This is great advice but sadly ATE Super Blue is no longer legal for sale in the U.S.

http://hooniverse.com/2013/08/16/braking-news-ate-super-blue-deemed-illegal-for-us-distribution/

[schoir]

Mystery solved!

 

Esty... Thanks for getting me on the right track.

 

mlytle.  I did just that, disconnecting at each next junction closer to the master cylinder.  First disconnected the brake line from behind the slave cylinder as Esty suggested and there was no real improvement.  It would only flow when I pressed (hard) on the brake pedal.

 

I then disconnected both of the hard brake lines where they go into the left front caliper.  No flow.

 

I then disconnected both of those lines where they connect to the end of the flexible brake lines closest to the caliper.  No flow.

 

I reconnected those and started to disconnect one of the hard brake lines from to the top of one of the flexible lines.  Gusher!     

 

I have now replaced all four flexible brake lines at the front with stainless steel braided lines that I've been storing for 15 years... (Still in their original package).  Both front calipers now bleed correctly from each of the three bleed nipple on each caliper!

 

IMG_0392.JPG

 

Next up will be replacing the flexible brake lines at the rear subframe.

 

So, jscaptura and mike... You guys were right on the money!  Thanks for the input.

 

I've owned the car since new and I don't think I ever replaced those lines, despite the best of intentions.  Apparently the rubber inside must have swollen shut inside from the four decades of exposure to brake fluid.  I hadn't driven it in about 8 or 9 years and it was stored after being my daily driver for the first fifteen years of its life.

 

I was starting to believe that my rebuild of the brake master cylinder was the culprit but that appears to be fine.  When I take the car down off its jackstands I will be able to test it properly.

 

Regards, Maurice.

I have now replaced all six flexible brake lines with stainless steel braided lines and was able to bleed all four wheels and the clutch without any further complications.  The fluid now flows freely from each bleed screw with just the normal recommended 15 psi on the pressure bleeder.

 

For future posters running into this problem, there was another clue that should have tipped me off early on.  Since the brakes were marginal the last time I drove the car 8 or 9 years ago and the rotors were heavily rusted, I decided to replace the rotors.

 

When trying to install the rotors, it was extremely difficult to spread apart the brake pads.  The fluid level in the reservoir was also not rising, so both of those clues should have signaled to me that there was a blockage in one or both of the brake lines leading from the caliper up to the brake master cylinder.  Now it is relatively easy to spread the brake pads (or press in the caliper pistons) and you can easily observe the fluid lever rising in the master cylinder.

 

Thanks again for the insight which helped to make this a satisfying repair!

 

Regards, Maurice. 

[M3M3]

Yeah!