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> Bleeding Brakes, Trouble with one caliper
Deusexmachina77
post Mar 25 2023, 10:13 AM
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I replaced the two front calipers with rebuilt calipers. The system was drained. I bleed the brakes starting in the rear and going to the front. I've run into an issue with the driver's side front caliper.

I have fluid making it to the caliper, as the bottom has fluid coming out with no air bubbles. But when I went to the top bleeder, I only got air. It never filled up with fluid. I removed the bleeder screw to make sure it wasn't clogged. We peddled the car continuously, and only just air. This went on for a while.(IMG:style_emoticons/default/headbang.gif)

There are no fluid leaks in the system.
Any thoughts would be welcome.
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davep
post Mar 25 2023, 10:19 AM
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If you are pushing out air, then you just have to keep at it.

BUT, is your reservoir still full?
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Deusexmachina77
post Mar 25 2023, 10:23 AM
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QUOTE(davep @ Mar 25 2023, 11:19 AM) *

If you are pushing out air, then you just have to keep at it.

BUT, is your reservoir still full?



Yes.
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Deusexmachina77
post Mar 25 2023, 11:50 AM
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I tried for 20 min. Nothing is coming out of the top bleeder screw, and nothing is leaking. I even removed the screw. Not a drop.
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r_towle
post Mar 25 2023, 12:35 PM
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QUOTE(Deusexmachina77 @ Mar 25 2023, 01:50 PM) *

I tried for 20 min. Nothing is coming out of the top bleeder screw, and nothing is leaking. I even removed the screw. Not a drop.

sadly....push pedal to floor, tighten bleeder...then do that again and again.
pumping just pushes air in an out.
I use a vacuum bleeder, its easier.

rich
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emerygt350
post Mar 25 2023, 03:42 PM
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I use a ten year old. I open, he pushes n holds, I close, he releases. It is father son bonding at its best.
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davep
post Mar 25 2023, 04:33 PM
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Yes, the correct procedure is to press pedal 2 or 3 times, then hold in down position until bleeder screw is opened and then closed closed; there should be some pedal movement down as the screw is opened. Only open the screw while the system is pressurized. Always have the tip of the hose attached to the bleeder under the fluid level in the collection jar so that you can see the bubbles come out, but no reverse flow. The only way to properly bleed is to use pressure, the higher the better, so using the pedal is best for a final round.
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IronHillRestorations
post Mar 25 2023, 05:45 PM
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Bleeding Brakes
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bkrantz
post Mar 25 2023, 08:33 PM
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Pressure bleed.

Vacuum bleed.

Gravity bleed.
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mlindner
post Mar 26 2023, 05:22 AM
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I use davep procedure, works great. Mark
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technicalninja
post Mar 26 2023, 09:04 AM
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Sometimes the bleeder feed inside the caliper is closed shut with old rust and debris.

I would NOT expect this from a PMB caliper.

When I rebuild any caliper, I always run a drill bit through the bleeder cavity and its feed.

Sometimes you get a load of crap on your drill bit.

I choose a drill bit smaller than the diameter of what I am cleaning.

I'm not removing any metal from the caliper body.

Using the drill bit solely for the purpose of careful cleaning.

I have enough trouble with cheaply rebuilt calipers that I don't use them at all if I can purchase factory new.

I once got a Centric (decent brand usually) that had a piece of gum placed beneath the bleeder to make it seal into the completely rusted out seat.
It had been "rebuilt" in Mexico...
I'm guessing that they pay the workers by the number of calipers finished, the workers are NOT car people, and they DO NOT CARE!
That "hung" a Honda CRV on my lift for a day. As I use my lift to feed my family that's a big deal for me.

It is possible to bleed all of the air out of that caliper using the lower bleeder.
You just have to make the working bleeder into the upper one.
My dad had a 964 that had two left calipers on it...
The right side had to be removed from its mounting and the caliper was turned upside down. Push the pads back a bit and install a piece of wood between them.
Hold caliper in bleeder "up" position to complete the bleed.

I had to slightly loosen the hard-line connections and remove the U clip that held the hard line to rubber connection to the strut housing. This allowed just enough flex to invert the caliper.
Tighten up connection lightly in the upside down position, bleed, then slightly loosen again to re-install the caliper.

The "big red" Brembo calipers on this car had only 1 bleeder per caliper and the calipers themselves were extremely expensive which forced the work around I just described.

Worked fine but was a bit of a PIA to do.

Don't get brake fluid on you. It's hydroscopic and absorbed easily through your skin.
This is why brake fluid feels WARM when it's on you. It's seeping in...
Either the kidneys or the liver (can't remember which one) cannot process it and it stays there for the rest of your life.
It's cumulative and I'm a bit worried as I got this important information way too late...
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914e
post Mar 26 2023, 11:05 AM
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QUOTE(emerygt350 @ Mar 25 2023, 02:42 PM) *

I use a ten year old. I open, he pushes n holds, I close, he releases. It is father son bonding at its best.


I ran out of ten year olds, now I have bleed brakes on Sundays when the 20 year olds show up for Sunday dinner.
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emerygt350
post Mar 26 2023, 02:44 PM
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We double checked the venting this morning and did another bleed across all brakes as well. He really enjoys it, and my car can lock them up now with almost perfect balance (no pulling to either side).

Glad I checked the venting again. Driver inside was dragging and passenger outside was about .o10 rather than the .004.

I would say that both clymers and Chilton's say .008 on the venting but that seems a bit excessive.
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davep
post Mar 26 2023, 04:36 PM
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THE official statement on venting clearance (post 9):
http://www.914world.com/bbs2/index.php?showtopic=85967
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930cabman
post Mar 27 2023, 01:57 PM
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QUOTE(914e @ Mar 26 2023, 11:05 AM) *

QUOTE(emerygt350 @ Mar 25 2023, 02:42 PM) *

I use a ten year old. I open, he pushes n holds, I close, he releases. It is father son bonding at its best.


I ran out of ten year olds, now I have bleed brakes on Sundays when the 20 year olds show up for Sunday dinner.


+1, will the same thing hold for 30 and 40 y/o daughters, or maybe we can move into the next generation
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Deusexmachina77
post Mar 28 2023, 09:03 AM
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Thank you, everyone, for your advice, as I will use this knowledge as I continue to bleed the brakes. It turns out that on this particular caliper, the cross-over seal was in the way.

So, now I have flow. But I will try to get a firm brake peddle using this advice.

Thank you.
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Deusexmachina77
post Mar 29 2023, 01:28 PM
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QUOTE(r_towle @ Mar 25 2023, 01:35 PM) *

QUOTE(Deusexmachina77 @ Mar 25 2023, 01:50 PM) *

I tried for 20 min. Nothing is coming out of the top bleeder screw, and nothing is leaking. I even removed the screw. Not a drop.

sadly....push pedal to floor, tighten bleeder...then do that again and again.
pumping just pushes air in an out.
I use a vacuum bleeder, its easier.

rich


Which vacuum bleeder do you prefer? I tried one that hooked to my compressor, and all it did was suck a whole liter of expensive fluid out. Granted, I didn't know what I was doing but I kept waiting for air bubbles to stop.
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Deusexmachina77
post Mar 29 2023, 01:33 PM
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Don't get brake fluid on you. It's hydroscopic and absorbed easily through your skin.
This is why brake fluid feels WARM when it's on you. It's seeping in...
Either the kidneys or the liver (can't remember which one) cannot process it and it stays there for the rest of your life.
It's cumulative and I'm a bit worried as I got this important information way too late...
[/quote]


@technicalninja I appreciate all your comments and suggestion but especially this last one.
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Superhawk996
post Mar 29 2023, 07:04 PM
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QUOTE(Deusexmachina77 @ Mar 29 2023, 02:28 PM) *

I kept waiting for air bubbles to stop.


Air bubbles will not stop when using a vacuum bleed. Air will get sucked around the loose threads of the bleed nipple. It still is pulling fluid into the caliper. You just can’t gauge completion by lack of bubbles.

Now do a pump & dump bleed - you should have a better pedal and then you can judge air bubbles without the vacuum on it.

I frequently use the combination of vacuum bleed then manual pump and dump when bleeding brakes.
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davep
post Mar 30 2023, 02:45 PM
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One aspect of the "pump the pedal" method that does not get enough credit is that when the system is highly pressurized by using the pedal it compresses bubbles into very small bubbles that can more easily move and not get hung up in the pressure regulator for example. I can start off in many ways, but always end with the pedal pumping.
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