Bleeding Issues

[CDL1542]

Hi all,

Had a setback recently with brakes. I have installed: new hoses, hard lines at the drumps, pads, rotors, calipers, rebuilt the drums, and a new master cylinder. I have bled brakes before and as usual started with the furthest from the master cylinder (start with the rear left, then rear right, front right, front left). My issue is starting with the rear right, I'm not getting any fluid to pump from the master cylinder to the bleeder. Even when completely disconnected this doesn't work. I am assuming that I have a blockage in the hard lines and wanted some advice on clearing it. I am using the old school method of pumping the pedal and want to know if investing in a pressure bleeder might work or if I'm missing something altogether. I DID bleed the master cylinder without issue.

 

Chris

[Zed Head]

Does the pedal pump up, but no fluid will come out of the open rear brake line no matter how hard you push?  Or does the pedal just never pump up?  The first would be an indicator of a blockage, the second, a blockage and a pressure build problem.  You might bleed the fronts well to allow easier pressure buildup and see if that will blow any junk out of the line.

[CDL1542]

Just now, Zed Head said:

Does the pedal pump up, but no fluid will come out of the open rear brake line no matter how hard you push?  Or does the pedal just never pump up?  The first would be an indicator of a blockage, the second, a blockage and a pressure build problem.  You might bleed the fronts well to allow easier pressure buildup and see if that will blow any junk out of the line.

The pedal never pumps up which I thought was odd. I'm not too sure how I should go about remedying this issue. Any recommendations?

[Zed Head]

Have you bled the fronts yet or are you trying to be methodical?  I would jump ahead to the fronts.  Sometimes have you go through the cycle a few times.

If there's a ton of air in the front calipers you might be draining the reservoirs without realizing it.  Pumping the fluid down until air is being pushed in then it all comes back out when you release the pedal.  Or, you might be letting the pedal come back too far when pumping and going too slow.  You want to pump quickly, and low on the pedal, so that the return hole in the reservoir is not uncovered for long.  But that's with the fronts.  The calipers hold a lot of fluid, and can hold a lot of air.

Then, of course, there's always the upside down caliper problem.  The bleed screws need to be on top.  Easier to get to on the bottom but not where the air is .

[CDL1542]

Just now, Zed Head said:

Have you bled the fronts yet or are you trying to be methodical?  I would jump ahead to the fronts.  Sometimes have you go through the cycle a few times.

If there's a ton of air in the front calipers you might be draining the reservoirs without realizing it.  Pumping the fluid down until air is being pushed in then it all comes back out when you release the pedal.  Or, you might be letting the pedal come back too far when pumping and going too slow.  You want to pump quickly, and low on the pedal, so that the return hole in the reservoir is not uncovered for long.  But that's with the fronts.  The calipers hold a lot of fluid, and can hold a lot of air.

Then, of course, there's always the upside down caliper problem.  The bleed screws need to be on top.  Easier to get to on the bottom but not where the air is .

 I was trying to be methodical with it and "do it right the first time". I upgraded the front brakes to 4 piston calipers and have used one way bleed screws in addition to a one man bleeder for a while and was using that method. I will give it a shot tonight and see what happens. Once the fronts are done (hopefully) do you think that would help with the rears? Also, if I'm unable to build pressure in the front, would that indicate a broken seal in the MC?

[Zed Head]

The dual piston master cylinder relies on pressure buildup in both systems to work properly.  The pistons are stacked.  So if one system doesn't build pressure you lose about 1/2 of the total stroke, which makes everything difficult.

People often have problems bleeding the brake upgrades.  Calipers from other cars end up oriented incorrectly.  I'd make sure that the end of the passage from the bleed screw is actually at the top of the piston cylinder.  You can tell from the casting shape.  Some calipers have the screw in one spot and the passage goes sideways to the piston bore.  And four piston calipers probably have even more volume than the stock calipers, plus two high spots per side for bubbles to sit in.  Study the calipers and where the bubbles would be.

If you don't have a helper, position a mirror over the reservoirs, or contort yourself, and watch what happens when you pump.  That's how I discovered my upside down caliper problem.  Large volume leaves, then large volume comes back.  That's not right.

[EuroDat]

Try bleeding the master cylinder first. There are two bleeders on the side.

When you bleed it, close the bleeder and release the brake pedal slowly. The holes in the MC bore to the reservoirs are very small and need time to fill the MC bore.

Completly disconnecting the brake line will probably not help you much because an open line will allow air back in a lot quicker than fluid via the holes from the reservoirs. The fluid will just go back and forward when you pump the brake pedal.

Keep at it. A dry brake system can take a while before you get the fluid down to the rear drums.

[Zed Head]

2 hours ago, CDL1542 said:

as usual started with the furthest from the master cylinder (start with the rear left, then rear right, front right, front left). My issue is starting with the rear right,

 I DID bleed the master cylinder without issue.

I thought I saw this about the MC, but just noticed that you said "as usual...start with rear left", but then you said your "issue is starting with rear right".  Not sure if you meant that you had already done rear left, and the problem started at right, or if you started at right and had the problem.

That's a good point about the open line from Euro.  I have speed bleeders on the back cylinders so that I can pump large volumes through the lines.  They close on the return stroke.

[CDL1542]

To answer a few quick comments, I meant to say start with the rear right and did start with a fully bled MC. I do have speed bleeders on all four corners as well so that air doesn't get pulled back in as well as using a one man bleeding system.

I'm going to give some ideas a shot in a couple hours and post back later tonight and see how it goes.

[Jeff G 78]

Not that it matters much, but the Left Rear is actually the correct starting point on a Z due to the brake line routing.  It sounds like the MC needs to be bled again.  

[CDL1542]

Been a while since I updated this. I got in the shop and took your advice and started with the Left Rear after bleeding the master again. I successfully bled all four corners without issue and firm pedal pressure throughout, but now have no pressure at the pedal. Any thoughts?

[Zed Head]

How much time passed between the firm pedal and the no pressure pedal?  Something's missing.

If the reservoirs are still full of fluid then the pedal should push the pistons and the pistons should move fluid, like they did when you were bleeding them and everything worked right.  If the reservoirs leaked fluid then you could see air getting back in to the system.

Maybe you just have bad seals in the master cylinder.  They may have been shrunken before but all of your pedal pressing opened them up.  Maybe they took their natural smaller diameter set while sitting.  The sitting allowed them to collapse and stop working.  If so, a hard fast pedal push should open them up again.  Just guessing.  Odd situation.