Bleeding Brakes

[Voldog]

What size wrench is the bleeder valve? I want to pick up the proper wrench for the bleeding. Can I use a box wrench? I don’t want to strip the flats using an open wrench.

I used a ratchet 7/16 box wrench and it fit. I tried a 10mm first but it was small. Am guessing its probably an 11mm but I don't have one. I didn't use a socket. Just by doing the fronts I could feel a noticeable firmness on the brake pedal. I do believe it also slightly shortened the travel of the pedal.

I just ordered replacement gasket and tubing from Motive. Once I get them and repair my bleeder I will rebleed all for wheels, this time inside my heated garage.

[Astro14]

I use a 6 sided deep metric 1/4” socket to break them loose. Whatever size fits snugly. If the bleed screws are rough, replace them.

Line wrench to bleed.

Most people WAY overtorque them. Think inch-lbs...not foot-lbs...

[billr99]

Thanks Bill. I wondered that too. But it seems very unusual that the engagement point would change after a pump or two, don't you think. I guess I'll just have to satisfy myself and bleed it if you know what I mean...

Here is a bit more info that might be worth reading thru concerning what the guys over on the R forum call "Ice Mode". http://forums.swedespeed.com/showthr...602-Brake-Fade. I know other than the calipers used the hydraulic bits used on the XC are the same as the R. Software is also a bit different as well but this "Mode" might still might explain the phenomenon.

Cheers,

Bill

[billr99]

I used a ratchet 7/16 box wrench and it fit. I tried a 10mm first but it was small. Am guessing its probably an 11mm but I don't have one. I didn't use a socket. Just by doing the fronts I could feel a noticeable firmness on the brake pedal. I do believe it also slightly shortened the travel of the pedal.

I just ordered replacement gasket and tubing from Motive. Once I get them and repair my bleeder I will rebleed all for wheels, this time inside my heated garage.

Yep, 11 mm brake wrench is best but I have seen some different ones (10mm) if the nipples have been replaced.

Cheers,

Bill

[pbierre]

I watched the YouTube (Sweden '90XC) using the Motive Bleeder. The main negative for this tool is the large amount of air pushed into the brake system before the good fluid starts flowing. You can see in the bleed out at the 1st caliper how this air gets broken up into hundreds of tiny air bubbles going through the system. I know from biotech fluidics instruments I've worked on how air bubbles cling to low-flow nooks in the piping.

This gizmo needs to be designed so that it self bleeds the air between the pressure tank and the reservoir before the bleeding starts. I can think of a design in my head where the connecting hose has 2 opposite flow tube paths....the air vent path gets clamped off after all the air has been pushed past the clamp point. Then, there is a solid thread of brake fluid from the pressure tank all the way to the master cylinder.

When I flush my brakes, I'll do it the old fashioned way where my wife pumps the brake pedal.

[billr99]

I watched the YouTube (Sweden '90XC) using the Motive Bleeder. The main negative for this tool is the large amount of air pushed into the brake system before the good fluid starts flowing. You can see in the bleed out at the 1st caliper how this air gets broken up into hundreds of tiny air bubbles going through the system. I know from biotech fluidics instruments I've worked on how air bubbles cling to low-flow nooks in the piping.

This gizmo needs to be designed so that it self bleeds the air between the pressure tank and the reservoir before the bleeding starts. I can think of a design in my head where the connecting hose has 2 opposite flow tube paths....the air vent path gets clamped off after all the air has been pushed past the clamp point. Then, there is a solid thread of brake fluid from the pressure tank all the way to the master cylinder.

When I flush my brakes, I'll do it the old fashioned way where my wife pumps the brake pedal.

I knew an old Volvo mechanic (like 40+ years of experience) that had the same opinions concerning either the Motive or using a vacuum pump. So he would just open up the bleeder and just gravity-bleed the circuits. He did that on my 850R after a SS line changeout and amazingly, it was a perfect bleed. Didn't seem to use much more fluid to do a complete bleed than using one of the other methods.

BTW, I've used Motives when I was involved in SCCA and never had any issues with it on street-style systems (Showroom Stock and Improved Touring) or full blown race setups (Formula Ford and SpecRacer Ford). Main reason I use it on my street cars.

Cheers,

Bill

[howardc64]

I use Motive only for air pressure. So fill reservoir with new fluid and let air pressure push it out. If you siphon out most of the old fluid out of reservoir and fill it before starting, I can can do 2 brakes pretty easily before refilling and finish up.

I did this because filling Motive with reservoir was messy and seemed wasteful. Oh, and no air bubbles introduced.

[pbierre]

I just completed a brake system flush.

I knew it was time after suctioning out a sample from the reservoir into a 100cc syringe....the fluid was black in the syringe. Fresh fluid is amber.

Howard's got it right that you start by suctioning as much old fluid out of the reservoir as possible, then top off the reservoir with new fluid.

As an experiment, I hooked up the syringe though a short tube to passenger-side rear caliper. After opening the bleeder valve, I pulled a suction on the syringe, but it did not draw any fluid. I concluded that you have to be depressing the brake pedal (pumping forward from the master cylinder) to get fluid moving. Applying suction alone at the bleeder valve does not do anything. So, I had my helper pump the brakes to push through the clear fluid. This is a good system flush process....it expelled about 6-7 oz. of brake fluid.

Has anybody tried a vacuum technique/gizmo for brake flush? How does it work?

I find that 90% of the work bleeding/flushing the brake system is jacking-up, removing/remounting the wheels.

[pbierre]

Bill, question: To do a gravity bleed, how to you get venting at the master cylinder? Do you have to hold the brake pedal depressed?

[billr99]

Bill, question: To do a gravity bleed, how to you get venting at the master cylinder? Do you have to hold the brake pedal depressed?

He just left the cap off the master cylinder. Its been over 10 years but I'm pretty sure he didn't have the pedal depressed although the more I think about it, the ports in the MC wouldn't be open otherwise. You'd think that even with that there wouldn't be enough flow to get the air out; but it did work well and I was a unbeliever. Myself, I have only ever used the technique on hydraulic clutches where attempting to pump fluid through results in the pedal going to the floor and staying there. Doing a gravity bleed in this kind of situation may not get a perfect bleed but gets enough fluid into the system to allow for a more conventional technique to finish it off. Now when I replace calipers, I use something similar by making sure the pistons are all the way back before mounting the new caliper, then with the brake line attached, I'll open the bleeder (without the pedal depressed BTW) until I get good fluid flow. At that point, I'll close the bleeder, give it a pump or two at the pedal to seat the pads against the disc, then do either a pump technique or Motive to finish off.

Cheers,

Bill