Soft brake pedal

[mwrohde]

All -

I've got a soft brake pedal. I've just bled the brakes hoping it was air (I know about pumping the pedal and thought it got firmer. meh). Pedal is still soft.

So, now I'm thinking fluid must be squeezing by a cylinder. How do I tell if it's the master cylinder or a slave cylinder?

Thanks,

Matt

 

[mwrohde]

I'm going to give this just a little nudge back to the top, and enhance it with another question.

My reading indicates that there are two likely culprits here. One is the master cylinder, the other is the ABS . . . . controller?

I've further read that the test is to pull the ABS fuse. If the pedal firms up then the ABS module is the problem. If not then it's the master cylinder. Is that a sound approach?

If so, it looks like pulling the ABS fuse is kind of a pita. Is there any reason I can't simply unhook the electrical connections from the ABS module instead of pulling the fuse?

Thanks,

Matt

 

[LittleCaesar]

Any bubbles? Bleeding with a one or two man man method?

No slave cylinder for ya if you are driving an automatic.

 

[mwrohde]

Any bubbles? Bleeding with a one or two man man method?

No slave cylinder for ya if you are driving an automatic.

One man. Vacuum pump. Pretty sure it's not air in the line. Slave cylinder on every wheel.

 

[JRZEE2000TR4LTD]

One man. Vacuum pump. Pretty sure it's not air in the line. Slave cylinder on every wheel.

What??

 

[JimPA]

mwrohde - When the 4Runner is started after sitting for a lengthly period, how long does the ABS pump run? Does the ABS pump ever start to run while you are braking?
Are you running factory sized calipers?

 

[mwrohde]

What??

That is the nature of hydraulic systems. There is a master cylinder and there is one or more slave cylinders. In the case of a breaking system there is a slave on every caliper and drum.

mwrohde - When the 4Runner is started after sitting for a lengthly period, how long does the ABS pump run? Does the ABS pump ever start to run while you are braking?
Are you running factory sized calipers?

Second question first - I'm pretty sure they are factory calipers. I don't know how long the abs pump runs. I've never noticed it on any of my cars. Is this something I hear?

 

[Buckaroo]

If you have air leakage at the rear wheel cylinders, the front calipers or the brake lines, you should likely see evidence of external fluid leakage- have you added fluid to the reservoir? On the rear, you should pull the brake drums on both side and on the front you should pull the calipers on both sides to make sure you get a good look. Regarding the Master Cylinder, you can check for external leaks at the fittings and the face of the booster but it would most likely be an internal leak that doesn't cause fluid loss....just loss of pressure.

Also, just bled my brakes last weekend using my new Mityvac. I could not get good, consistent vacuum and had to go back to the 2 person method - worked fine. Make sure you bleed all four wheels in the correct sequence (RR, LR, RF, LF) while keeping the reservoir level above the min.

Buckaroo

 

[JRZEE2000TR4LTD]

That is the nature of hydraulic systems. There is a master cylinder and there is one or more slave cylinders. In the case of a breaking system there is a slave on every caliper and drum.

There are no slave cylinders at each wheel. The kind of component you're referring to is a proportioning valve, which the 4runner doesn't have. The hydraulic fluid goes into the rear brake wheel cylinders and front calipers.

The problem your having could be one of several things, air in the system somewhere, bad master cylinder, power booster.

Does the pedal feel spongy or is the pedal travel too far when pushed?
What does the pedal feel like when the truck isn't running?
How far does your E-brake handle pull when engaged?

 

[LittleCaesar]

Grab a helper and try the two man method.

Never have pulled the connectors to the ABS modulator but have pulled the ABS fuse. It takes about 15 minutes at the most. I'd try to get the ABS to activate in the road, then come back and then bleed it again.

 

[mwrohde]

The hydraulic fluid goes into the rear brake wheel cylinders and front calipers.

I suspect this is a difference in vocabulary more than anything. The hydraulic fluid, when pushed into the wheel cylinders and calipers, pushes on what behaves as a slave cylinder causing movement at that end. A master cylinder without a slave cylinder is a hydraulic leak.

Does the pedal feel spongy or is the pedal travel too far when pushed?

Yes to both. Soft pedal, long slow travel.

What does the pedal feel like when the truck isn't running?

I don't know that I've tried this and I've now got the master cylinder sitting on my work bench. I've got a new one that should be at the parts store across the street any minute. I'd have waited for more diagnostics, but I don't do "sit still" very well.

Is it ok to push on the brake, and thus the booster, without the master cylinder behind it?

How far does your E-brake handle pull when engaged?

E-brake feels just fine to me. And it works.

I also pulled both electrical plugs that plug into the ABS whatever-it-is. That caused no change in feel at all. As a bonus, I now have an ABS light that won't go out.

 

[mwrohde]

Grab a helper and try the two man method.

That's the afternoon plan.

 

[JimPA]

...
Second question first - I'm pretty sure they are factory calipers. I don't know how long the abs pump runs. I've never noticed it on any of my cars. Is this something I hear?

[If the 4Runner has been sitting for a long period of time.] When you turn the ignition to the ON position, you will hear a pump start up. This is the ABS pump and it is priming the system. It typically runs for ~20 seconds then stops. I noticed when I had small leak at the bleeder after priming, the ABS pump, of course, never stopped. If you turn the ignition to the START position, then it is hard to hear the pump.

In Speedy's video, at 21:26 you can hear the ABS pump running.
https://www.youtube.com/watch?v=dRaYaytYkIY

 

[mwrohde]

I'm going backwards. New master cylinder is installed. Bled all four again (in the prescribed order). I left the battery unplugged for half an hour or so.

I still have a soft pedal. I still have an ABS light. I now have the bonus "Break" light on, too.

Getting rum and calling it a day.

Thanks for the help.

 

[JimPA]

Been there. I read on these forums people stating if their ebrake wasn't adjusted they had a soft pedal. I couldn't wrap my head around how, but many people reported this. I just did the Tundra 199 MM brake upgrade on my 2001 4Runner, new pads front and back, new rear drums, new rear hardware so the brake system is fresh in my mind. I'm no expert but if your pads are worn, maybe that could give you a soft pedal.

As for the brake indicator light, verify your ebrake is full released (just to state the obvious).

As for the ABS indicator light, you need a code. Not sure if an OBD would show the fault. Here is a link where someone uses a jumper to read the codes. I would try a OBD reader. https://www.youtube.com/watch?v=IZLpQZf2oWk
Without a code reader, I would guess you may be low on brake fluid.

Does the ABS pump stop running after ~20 seconds?

 

[Chuckles89]

I have driven two 3rd gen 4Runners and both had soft brakes. Mine have been bled three times by me and have new pads all around. The master cylinder/ booster looks to have been replaced at some time, but I have no idea when it was. I just decided to live with it. I did disable the ABS and it's a lot better with panic stops.

 

[mwrohde]

The truck has been sitting 11 hours. I don't know if that's long enough or not.

I don't hear anything when I turn the key to "on" except 3 clicks. I don't know if the clicks are related to the breaking system in any way.

The e-brake appears to be working correctly. In neutral with the brake off I can push the truck forward. With the e-brake set the truck doesn't move. Brake light is on either way.

There are no codes pulled from the ECU. I'll try the way linked in the vid after work.

 

[JimPA]

On my 4Runner 11 hours is long enough to hear the ABS pump to come on. The pump comes on because pressure in the ABS system is below set point. Opening and closing a bleeder always caused my ABS pump to start.

I think you are now troubleshooting the BRAKE and ABS indicator lights and shelving the soft pedal. So to me the next logical step is to verify the ABS system fuses and verify any harness you took apart are fully seated. The ABS pump not starting MAY be because the ABS system has a fault.

After you verify the (2) items above your next step is to look at how you replaced the master cylinder. Did you bench prime the master cylinder? In one of speedy's video, when he is replacing the old brake fluid, he states if you allow the fluid to go below the low line on the brake fluid receiver, you will have to take the 4Runner to the dealer., I found a link that talks about replacing a master cylinder on a 2001. http://www.toyota-4runner.org/3rd-gen-t4rs/73272-2001-master-brake-cylinder-issue.html In the thread the OP has a procedure to bleed the master cylinder, accumulator and lines.

In the link the person calls the ABS pump the brake booster pump. I'm not sure which term is correct. I never replaced my master cylinder take my suggestions with a grain of salt.

 

[mwrohde]

I'll read that thread.

What the hell is a "brake fluid receiver"? And an accumulator?

 

[JimPA]

I suck.
"brake fluid receiver" = brake fluid reservoir
"accumulator" = http://www.villagetoyotaparts.com/showAssembly.aspx?ukey_product=2093745&ukey_assembly=323789 see 47950D