Brake pedal feel after bleeding system?

[WeightIsTheEnemy]

Just bled my brakes using the Motive power bleeder and the pedal doesn't feel all that firm afterwards. Pretty sure I got all the air out but I'm considering doing it again because I have a track event in a few weeks and I don't want to risk it boiling over. I tested it with some pretty hard stops and the pedal doesn't drop too far, but it's spongier than I'm used to when just flushing a system. It's fine for street use but I just wonder how well it'll hold up under the heat of the track pace.

How firm is your brake pedal after a fresh bleeding of the system?

[Mag]

should be hard, there's still air in there. easier to bleed if you have someone pumping brake, while another releases air, do this repeatedly until no air bubbles present when releasing.

[kestrel74]

I have the motive bleeder also, but still had to do the brake pedal thing to get it right.

[MattG]

Mine's always a bit spongy, that's the nature of this car.

When I first bled mine with a Motiv, I started with bleeding the clutch, and the MC went dry before fluid had gone though the Motiv's hose (I had sucked out most of the old fluid from the reservoir first). Any chance this happened to you? In my case it was an easy fix as the clutch doesn't require special procedures to get air out of the system (like the brakes would, due to the ABS unit).

[WeightIsTheEnemy]

I too started with the clutch but kept the reservoir and MC full of new fluid throughout the entire process.

One thing I should have mentioned in the original post is that after I finished the clutch and rear calipers, I found that the front bleeder nipples were too large for my hose (that just doesn't sound right...). Anyway, the autoparts stores were closed for the night and I got a larger hose the next morning. I left the Motiv connected to the reservoir overnight with about 15psi. I wanted to leave it sealed so that the new fluid wouldn't be exposed to air. Probably shouldn't have left it pressurized though. When I came out with the new hose, it had leaked some fluid at the reservoir connection. I reset the pressure, found no leaks, and finished the job. Perhaps air got in the system in that process?

[codymac]

Originally Posted by WeightIsTheEnemy

Perhaps air got in the system in that process?

Not unless the master cylinder reservoir was dry.


I use a Motive and do mine as a one-man operation - never had an issue.

[TimMullen]

Has the system ever been apart or had air "sucked in"? If you have air in the ABS system, it will be very difficult to get it out. They only real way is to use an ABS scan tool (like the Lotus Scan Tool) to put the ABS into "bleed mode" where it opens (actually continuously cycles) the internal valves and and allows the fluid/air to be flushed out of the ABS.

The other possibility is that there is air trapped in the front calipers. The fluid enters the inside of the caliper at the top, crosses over to the out side at the bottom, and "vents" out the bleed nipple at the outside top. If there is air in the inboard side of the caliper, it will not be flushed out.

To flush air out of the front calipers, you have to remove the caliper, turn it upside down while bleeding fluid, then turn it back right side up and continue bleeding. The idea is to get the fluid to flow out the inside bottom (at the top as it's upside down) to the outside of the caliper. Then the bleeding will allow the air to pass out the nipple.

You may have to do the "full" bleeding of the front calipers to remove any trapped air.

[Mark16q]

had mine bled by the dealer and pedal was much firmer after the bleed. Huge improvment.

[ChrisH]

I just changed my brake fluid with a pressure bleeder over the weekend, and it worked perfectly. The pedal is a bit firmer now as well (although it was pretty good even before I changed the fluid).

Some notes: (may be already obvious to you, but for others ...)
- Before attaching the pressure bleeder, suck the fluid out of both sides of the car's reservoir (both sides), then fill the reservoir with new brake fluid.
- I kept the pressure at about 5 psi.
- I also bled the air out of the lines from the pressure bleeder so that the fluid level remained at the full mark in the car's reservoir the whole time. (Do this by attaching the pressure bleeder, pumping up the pressure, loosening the cap very slightly at the car's reservoir (to slowly let air out), wait until the line from the bleeder is full of fluid, and then quickly tighten the cap.)

[TimMullen]

Originally Posted by ChrisH

- I also bled the air out of the lines from the pressure bleeder so that the fluid level remained at the full mark in the car's reservoir the whole time. (Do this by attaching the pressure bleeder, pumping up the pressure, loosening the cap very slightly at the car's reservoir (to slowly let air out), wait until the line from the bleeder is full of fluid, and then quickly tighten the cap.)

I wouldn't recommend this at all. If the cap doesn't reseal just right, you will be spraying brake fluid all over the place. Since brake fluid "eats" paint, this is never a good idea.

I just fill the reservoir, fill my EZ-Bleed, and pressurize it. Some air may get into the reservoir from the bleeder, but there is a sufficient volume of space that there will always be fluid in the reservoir, even with a small pocket of air above the fluid. Never had a problem getting air into the brake system (except for that time that I ran the EZ-Bleed bottle empty on another car ).

[Domino]

My brake pedal was like mush before I bled, but after a flush with the Motive, they are great now. I would go out and activate the ABS a few times then bleed again.

[WeightIsTheEnemy]

Well, not sure what the root cause was but I activated the ABS a bunch and then re-bled the brakes (skipped the clutch this time) and got some air bubbles out. Pedal feels much firmer and I feel much more peace of mind for this weekend's track event!

Thanks guys!

[TimMullen]

Originally Posted by WeightIsTheEnemy

Well, not sure what the root cause was but I activated the ABS a bunch and then re-bled the brakes (skipped the clutch this time) and got some air bubbles out.

No need to re-bleed the clutch after flushing the fluid. The re-bleed after the ABS activation is to get any air out. Sounds like it worked.

[Z-dculus]

get yourself a vacuum kit and do it in half the time with half the frustration. If i can do it pretty much anyone with half a brain can.

[RoadDad]

Z, which vacuum kit do you have?

[Z-dculus]

Originally Posted by RoadDad

Z, which vacuum kit do you have?

hey bud,

i just got the craftsman kit at sears, which comes with the pump and a dozen attachments or so so everything you need is right there. around 60 beans, although after purchase i've seen other kits for cheaper without the crafstman name on the side that looked identical, if not better. my only complaint about the craftsman kit is the jar is an opaque white- a clear jar would be ideal to really see the "color change" exhibited by the new fluid purging the lines. There's also no gasket on the jar, which i thought was odd. Instead they give you a gel (feels like petroleum jelly basically) to rub on the top rim/under the lid to create the air tight seal. I had to really "schmootz" it on to get it to seal properly.

[Fritzanthony@gmail]

I just got my front broke pads changed (replaced with stock pads) and now during track use on occasion I am getting a hard brake pedal. The brake pedal just seems to firm up and braking power is slightly reduced but if I lift and reapply it goes to normal.

Can anyone help?

[dominus22]

First let me tell you that i have had experience using diferent vacuum and preassure bleeders and none of them work as good as the original way of doing things and that is pumping the brakes, now what i found with lotus is that it helps alot if you have the car runing, due to the abs hydraulic unit that is installed in the car sometimes air gets traped in the unit. With the car runing in a well ventilated area have some one help you pump the brakes 3-4 times and start bleeding from the right rear>>>left rear>>>front right>>>ending with the left front this should eliminate any problem with air in the system make sure you follow the sequence other wise you will only be pushing the air around the system and not bleeding it out

[xtn]

My one attempt at bleeding the brakes with vacuum - pulling the fluid through from the bleed nipples - was not satisfactory.

#1. The threads of the bleed nipples will let air in.
#2. There is some resistance to fluid flow in the system when it's under vacuum.

This results in air just moving into the caliper via the loosened bleed nipple threads and being sucked right around back into your bleed hose. It just gurgles and minimal fluid flows out. If you accidentally loose vacuum (your hose falls off the nipple for example) you're going to get a bubble of air introduced into the caliper.

I don't know what the resistance to flow is. Perhaps the master cylinder is being sucked into the pressed position, cutting off the open circuit from the reservoir?

xtn

[SuperVixen]

I would bleed it again to be safe. I recently had my calipers painted and had to bleed the brakes twice because they didn't feel right after the first time. Turns out there was a stubborn air bubble.