I am about to replace all 4 brake pads and bleed the brake lines with new fluid. My question is can I change 1 set of pads and then bleed that line then move to the next wheel. Or should I change all 4 sets of pads then go back and bleed the brakes. Or should I bleed all 4 wheels then go back and change the pads?

Secondly, which order should I use to bleed the brakes? I have seen people reccomended several different orders. If I am going to do one wheel at at time it would be easiest if I do RF then LF then LR then lastly RR.

Thanks

Kurt

 

Change all 4 pads, then bleed all 4 four corners.

You need to compress the pistons in to be able to fit the new pads, so you're going to push all the fluid back up into the resivour anyways.

 

You really shouldn't push brake fluid through the system in the opposite direction. The master cylinder was designed to push fluid in one direction, and you can damage the seals inside the cylinder by forcing fluid in the opposite direction. Just crack the bleeder when you are pushing the piston back into the caliper. As for bleeding procedure, this is a good place to start...

https://www.s2ki.com/s2000/topic/995...eding-revised/

 

Not sure if this is true. The piston needs to move in both directions, in order to release pressure which is applying the brakes. The seals in most master cylinders are double-edged, so the piston can move in either direction and the seal is maintained.

In any event, the piston is going to have to go backwards, when you change pads --- due to the difference in thickness between a worn and new pad.
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It is absolutely true that it "can" damage the master cylinder. There is a difference between the piston moving back and forth moving back and forth on its own accord, and forcing brake fluid in the opposite direction through the master cylinder.

The way a master cylinder works, is that when you first press your foot down on the brake pedal, the piston inside the master cylinder seals the valve to the reservoir (if this didn't happen brake fluid would also be pushed into the reservoir every time you pressed the pedal, which we know doesn't happen. This is why you can compress the brake pedal with the lid of the reservoir off when bleeding brakes), after that seal is made a plunger inside of the master cylinder is what pushes the brake fluid to the calipers as you apply more brake pressure. When you release the pedal, the plunger moves back to its original position via a spring, and the piston that sealed the valve to the reservoir moves back as well, allowing brake fluid to flow from the reservoir to the inside of the master cylinder to make up for the brake fluid that was displaced due to brake pad wear.

When you force brake fluid back through the master cylinder, in the opposite direction, pressure will build inside the master cylinder, and with nowhere else to go, it will force brake fluid past the seal to the reservoir. This is something that the master cylinder was not designed for.

I am not saying that this is guaranteed to cause a failure, just that is should be common practice to crack the bleeder when you are pushing a caliper piston back into the caliper. You will be saving your master cylinder from undue wear and also getting part of the bleeding process out of the way.

 

I believe the rearward movement of the brake master cylinder's piston is limited --- by how the MC is constructed. The piston can only move as far back to where the holes (or "valves" as you said) line up with the reservoir. That's why the brake fluid often overflows when you compress the caliper pistons too much.

At least, that is my experience with MC's. I haven't worked on a the S2000 MC, so I don't know if it is designed different than a standard master cylinder.

 

Could you possibly clamp off the brake line a short distance from the caliper to prevent brake fluid from pushing back into the master cylinder? Obviously, you would use a clamping device that wouldn't puncture/damage the brake line. I've seen the mechanic [Edd China] on the TV show "Wheelers Dealers" do this quite often when doing brake work. He seems like a very competent mechanic. I've also seen someone use metal needle nose vice grip pliers with an old piece of brake hose fitted over the each side of the plier to protect the cars brake line when clamping the brake line shut. Not saying this is a better method, just a possible option.

 

Confused. If the line is fully clamped off, it will be impossible to move the piston back in. Brake fluid is not compressible.

I can only see this working if the bleeder is opened.

 

Billman where are you!? Can you enlighten us on danger of brake fluid being pushed back into the reservoir during a pad replacement? I've heard that it can damage your abs and now your master cylinder.

 

bingo.

open the bleeder with a line attached so you don't make a mess everywhere. Then compress the cylinder. Close the bleeder.

that's what i've always done during a pad change.

darcy