No Brake Pedal (1 Viewer)

[Toyotaoh]

1996 252,000 mi

This past weekend I experienced a noticeable drop in braking power, losing more and more pedal. I crawled underneath and saw no leaking brake lines. The driver rear caliper though was clearly leaking from the piston.

I replaced the caliper this afternoon, bleed out the wheel and took if for a spin. No change/ no pedel. I am thinking maybe air got into the system and now I need to bleed the whole thing out (4 wheels and the leveler)? Or am I moving in the wrong direction?

 

[Pin_Head]

More information please. Does the pedal rise when you pump it? Is the pedal firm?

 

[Toyotaoh]

It rises back but no the pedal is not firm. I have about half or less braking capacity. It goes straight to the floor then slowly rises back up.

 

[stu8319]

I would definitely bleed the system first, but it also sounds like what mine did when the booster went bad.

 

[Pin_Head]

If it has half the braking capacity, chances are the the master cylinder is bad.

 

[flintknapper]

If it has half the braking capacity, chances are the the master cylinder is bad.

Yep.

 

[Toyotaoh]

Well I'd rather replace a master cylinder than a booster I suppose.

Should I bleed the entire system first or just assume its the master cylinder? Hate to bleed the whole thing twice.

 

[flintknapper]

Well I'd rather replace a master cylinder than a booster I suppose.

Should I bleed the entire system first or just assume its the master cylinder? Hate to bleed the whole thing twice.

Yes, bleed first. No doubt you have air in the system.

Hard to get air out of the ABS and LSPV. IF after a good brake bleed you continue have a poor brake pedal, look to the master cylinder.

 

[Toyotaoh]

Thanks again.

How best is it to deal with the LSPV? I know that you bleed each wheel farthest to closes, but at what point is the LSPV bleed? Between the two rear wheels or after each wheel has been bleed?

 

[Toyotaoh]

Also, will have MC here in the morning. Am I okay removing it tonight and switching out the other first thing in the AM? I'd avoid a second trip, core charge and can get the truck moving (I hope) in the morning.

 

[Malleus]

Order is farthest from MC to closest, so RR, LR, LSBPV, RF, LF.

It helps to move the actuator (rod) up and down while bleeding the valve. This ensures that no air is trapped between the valve spool sections. Also, the bleed screw on the valve is smaller than the screws on the calipers. Just in case you screw one up.

I have speed bleeders on my trucks and really like them. Don't buy then from a parts store; the aftermarket brands are cheap and leak. (Not mentioning Dorman by name...)

I also like a pressure bleeder. It removes the need to bench bleed the MC and makes the job a one man one banana affair.

You will have trouble getting the air out of the ABS, if you've driven it after replacing components and opening the system. If you open the system, bleed the air out and then drive it, it's unlikely the ABS will be affected. If you have driven it with air in the lines, you'll have to activate the ABS and bleed at least twice.

 

[Toyotaoh]

Thanks. When the problem first started on Saturday, I was not sure if it was my imagination or I was losing brake capacity. When I drove on Sunday, it was very clear I had lost quite a bit of capacity. The brakes were very spongy and went to the floor. Truck still stopped, but needed twice the stopping distance. I parked it, crawled under in the evening expecting to find a leaking line, but all I could find was the driver's rear caliper leaking and a noticeable decrease in the level of fluid in the reservoir. I replaced the caliper last night, pushed some air and quite a bit of fluid through the line and thought my problems were solved, but it was every bit as bad as before I replaced the caliper. I did a quick test drive in the driveway, but it was evident that I had very little pedal.

So my question is, is this enough to introduce air into the ABS? My hope is that honestly the caliper, while needing to be replaced, was a red herring and not the cause of my braking issue and the real issue is a failing MC. So that said, If I have a failing MC, does that introduce air into the ABS?

 

[Malleus]

Yes, to all. You also have air in the LSBPV.