Rebuilt Calipers--how do I get brake fluid into them-(feeling dumb )(85 300D)

[Carrameow]

I just rebuilt my Front brake calipers on my 85 300D.
How do I get Brake Fluid into them?
I have tried pumping them, opening different connections,vacuum and a pressure bleeder and they are still dry as a Bone at the Bleed valves.
I don't feel too smart. I got at least a working grasp of Fluid Mechanics and engineering, but I cant get the brake fluid to dribble. Last two times I did this, I remember it was a piece of cake.
What am I doing wrong?

Rebuilt Calipers--how do I get brake fluid into them-(feeling dumb )(85 300D)

[RKreutzer]

Hi Carrameow,

If I recall right from the last time I replaced the brake hoses on my Suzuki, you need to do it with 2 people. When bleeder hose open, one person presses down the brake pedal and leaves it down. Then the second person closes the bleeder valve and then you release the brake pedal. Then you press down again, open valve etc. So you get "one way" out the valve only and don't suck in air again. Make sure the brake fluid reservoir does not run dry in between. Bleeder valve on second caliper needs to be closed, too.

Otherwise, could your rebuilt have left something clogged?

Good luck

Reinhard Kreutzer

[Kestas]

After installing empty calipers, I usually leave the bleeder screw open for a while to "gravity bleed" the calipers. This removes the bulk of the air and gives a good starting point for two-man bleeding. After gravity bleeding, I sometimes find all the air is gone and the brakes are good-to-go.

Bleed the brakes just like Reinhard said. I just rebuilt the calipers on a VW and had to bleed all four wheels like Reinhard said to get rid of the "spongy" feel on the pedal. Not a hard job - takes only a few minutes but you do need the second person to press the pedal while you open and close the bleeder valve. I attach a plastic hose to the bleeder valve that goes into a container after I put the wrench on the valve so I don't have a mess under the car while bleeding. Another benefit from bleeding all four wheels (remember to keep the fluid level up in the master cylinder while you do it) is that you replace the old brake fluid with new stuff.
Morris

[engatwork]

Make sure you watch your master cylinder closely. There are a couple chambers there and you want to make sure you are getting fluid into the correct chamber.

[csnow]

Does not make sense.
As Kestas said:
Normally, without touching the pedal, with the bleeders open, gravity should have fluid flowing to the calipers within a few minutes.
Anyone who has disconnected a brake hose can tell you that the reservoir gets drained.
Bleeding is just to displace any residual air pockets.

That said, I've never run this particular system completely dry. Is there some special issue with bleeding the ABS pump, or something? Perhaps someone else can jump in here...


Tech tip: Better to leave the MC full of fluid while doing downstream brake work to minimize bleeding issues afterwards. To prevent the reservoir (and MC) from draining, wedge the brake pedal down. This closes the ports. You can improvise some sort of stick or bar, and slide the power seat to push it down.

[Kestas]

Csnow, was it my post that needed clarification? I didn't intend for the person to walk away from the car until the master cylinder ran dry. Gravity bleeding is helpful to develop good pressure and flow for subsequent two-man bleeding. One won't get good pressure with a high volume of air in the system because of the difference in compressibility between air and fluid. I'm also not sure if this would work on an ABS system.

Good tip on blocking flow at the master cylinder. I may need to use that trick some time.

[csnow]

Nah, I was pretty much just seconding what you said, not adding much of substance to the conversation...

Also really puzzled why gravity is not kicking in for this fellow...

[ctaylor738]

Are you sure your bleeders or passages are not clogged with rust from watery brake fluid?

Do you get a drip if you unscrew the flex line from the metal one? It could be that the flex hoses are plugged.

I have always been able to get them dripping before starting the bleeding.

[Kestas]

Chuck's right. At this point you need to "bracket" the problem.

[Carrameow]

I kept on pumping the brake pedal with a hose coming from the bleed valve to a jar of brake fluid. Finally i felt the driver side piston "burst" and the hose started passing fluid and bubbles. Te same trck then worked on the passenger side.

When I rebuil the brake calipers I used Soap to lubricate the seals when i shoved the pistons back in. Did they lock? Also I really retracted the psitons to accomodate new pads and rotors; I used a C-clamp and really shoved them down. I guess the combinaton of my "genius" in these two ideas is what locked them up.

[Kestas]

Soap It's recommended to use brake fluid to lubricate the seals before installation. I'd be cautious of introducing non-approved stuff that would mix with the brake fluid.

SOAP???? - No way - brake fluid or caliper lube only!!!