Soft brake pedal (1 Viewer)

[SnoFJ]

So I just finished rebuilding my knuckles and installed new calipers while I was at it. After bleeding the brakes and taking the car for a test drive, the brake pedal goes really far to the floor before I feel anything. Any tips?

 

[nigelsiam]

When you pump the brakes do you get more pressure? Does it still go to the floor after a couple pumps?

 

[mbmt]

I have the same issue. If I pump mine a few times it gets better. Interested in responses.

 

[RadarFJ40]

Bleed. Then bleed. Then bleed some more. If that doesn't work repeat above steps.

 

[Malleus]

Sounds like there's air near the master cylinder. Try bench bleeding it, then bleed the lines again.

 

[Pin_Head]

You need to bleed it productively so that you get the bubbles out. If you don't see bubbles coming out, you are wasting time. The most reliable way is the 2 person method where you pressurize the system with the brake pedal before you open the bleeder valve and then shut the bleeder valve while the fluid is flowing before you let back up on the pedal. If you put a piece of clear plastic tube on the bleeder, you can watch the bubbles come out. Brake bleeding gizmos don't get the tough bubbles out.

 

[SnoFJ]

Sounds like there's air near the master cylinder. Try bench bleeding it, then bleed the lines again.

I can do that with leaving it on the car right? Just run a hose from the bleeder valve back up to the master cylinder and keep pumping/filling

 

[SnoFJ]

You need to bleed it productively so that you get the bubbles out. If you don't see bubbles coming out, you are wasting time. The most reliable way is the 2 person method where you pressurize the system with the brake pedal before you open the bleeder valve and then shut the bleeder valve while the fluid is flowing before you let back up on the pedal. If you put a piece of clear plastic tube on the bleeder, you can watch the bubbles come out. Brake bleeding gizmos don't get the tough bubbles out.

That's what I did. Upgraded to a big brake kit on my GS300 and didn't have any issues. I guess I'll just have to keep bleeding more

 

[jvazquez53]

Bleed. Then bleed. Then bleed some more. If that doesn't work repeat above steps.

Bleed the master cylinder, then the whole system..

 

[Malleus]

I can do that with leaving it on the car right? Just run a hose from the bleeder valve back up to the master cylinder and keep pumping/filling

I would probably run it into a transparent container. (glass is always risky on a concrete floor) It takes me two people, one to pump and hold the brake, and watch the master cylinder reservoir, and one (me) to crawl under and crack the bleed valve. Replacing the reservoir fluid with what's just drained is risky; the air might be dissolved in the fluid and when it's reintroduced into the master cylinder, well you get the idea...

Remember there are 5 bleed points, one at each wheel and the LSBPV, behind the fuel tank, on the rear side of the crossmember. See FSM, pages BR-30-36 and BR-6-7.

 

[SnoFJ]

I would probably run it into a transparent container. (glass is always risky on a concrete floor) It takes me two people, one to pump and hold the brake, and watch the master cylinder reservoir, and one (me) to crawl under and crack the bleed valve. Replacing the reservoir fluid with what's just drained is risky; the air might be dissolved in the fluid and when it's reintroduced into the master cylinder, well you get the idea...

Remember there are 5 bleed points, one at each wheel and the LSBPV, behind the fuel tank, on the rear side of the crossmember. See FSM, pages BR-30-36 and BR-6-7.

That's what I did when bleeding the lines at the caliper, but you mentioned bench bleeding the master cylinder. I was wondering if there was anyway to bleed the MC without taking it off. I found multiple videos of people who ran a hose front the front DS caliper to the master cylinder. they opened the valve on the calipers, pumped the brakes andfilled the reservoir as needed until it was essentially a full loop. They kept pumping the brakes to cycle the fluid from the MC to the caliper and back so any air in the MC came back to the top through the hose and just bubbled out

I tried what I said and the pedal feels a little better. My only real problem now is time. I can't get to it until next weekend since vacations over and work leaves me with little to no time during the week. Will it be OK to drive on until I can get to it?

 

[Pin_Head]

You can bleed the master by just removing the hard line and putting your finger over the hole and have someone push the pedal down while bleeding the fluid into a shop rag. Cover the hole before they let up on the pedal to keep air from getting sucked back in.

 

[Malleus]

That's what I did when bleeding the lines at the caliper, but you mentioned bench bleeding the master cylinder. I was wondering if there was anyway to bleed the MC without taking it off. I found multiple videos of people who ran a hose front the front DS caliper to the master cylinder. they opened the valve on the calipers, pumped the brakes andfilled the reservoir as needed until it was essentially a full loop. They kept pumping the brakes to cycle the fluid from the MC to the caliper and back so any air in the MC came back to the top through the hose and just bubbled out

I tried what I said and the pedal feels a little better. My only real problem now is time. I can't get to it until next weekend since vacations over and work leaves me with little to no time during the week. Will it be OK to drive on until I can get to it?

The amount of air in the lines probably isn't enough to seriously affect the brake operation, given that you've already bled them once. Just realize you're not going to have the rock hard, factory new, pedal feel.

I don't reuse brake fluid that has been bled out of the lines, on the principle that if there's entrained air in the fluid, it will recombine eventually into the largest bubble that the air volume can support, and I don't know ahead of time if that's going to be significant. $10 worth of brake fluid isn't worth my health. I reuse it on non-life safety hydraulic systems.

@Pin_Head is right, I won't say I haven't done that before; I will say I cussed a while when the fluid went all over the engine compartment. You need the plugs the ports are blocked with in the new box to seal the master cylinder if you bench bleed it.

 

[jvazquez53]

The amount of air in the lines probably isn't enough to seriously affect the brake operation, given that you've already bled them once. Just realize you're not going to have the rock hard, factory new, pedal feel.

I don't reuse brake fluid that has been bled out of the lines, on the principle that if there's entrained air in the fluid, it will recombine eventually into the largest bubble that the air volume can support, and I don't know ahead of time if that's going to be significant. $10 worth of brake fluid isn't worth my health. I reuse it on non-life safety hydraulic systems.

@Pin_Head is right, I won't say I haven't done that before; I will say I cussed a while when the fluid went all over the engine compartment. You need the plugs the ports are blocked with in the new box to seal the master cylinder if you bench bleed it.

I do have factory like brake feel on one of my 1992 FJ80.

 

[SnoFJ]

Bled the master cylinder, all 4 corners, and the LSBPV. Took about 2 tries before anything came out of the LSBPV. So I'm assuming that's where alot of my air was. Regardless, feels alot better now. Now the only problem is just me second guessing myself lol. But I think it's good to go considering the improvement I can feel. Thanks for the help.

 

[Malleus]

Bled the master cylinder, all 4 corners, and the LSBPV. Took about 2 tries before anything came out of the LSBPV. So I'm assuming that's where alot of my air was. Regardless, feels alot better now. Now the only problem is just me second guessing myself lol. But I think it's good to go considering the improvement I can feel. Thanks for the help.

Happy motoring!