Hey, I've been having some brake problems for a few years now. The prolbem is the pedal needs to be pushed almost to the floor before the brakes start stopping the car. There's no resistance or firmness at all.

So far, I've replaced a leaking wheel cylinder, checked all the brake lines with a flashlight, except near the fuel tank where they seem to disappear somewhere, replaced all the brake bleeder screws, bled/flushed the system 3 times and replaced the master cylinder. The fluid level also doesn't drop at all in the reservoir.

Does anyone know what I should try next? I'm afraid it may be the boo$ter because I've read somewhere else that it's possible for brake fluid to leak into the booster and swell up the diaphragm causing the booster to boost too much. When I replaced the MC there was brake fluid where the gasket sits.

 

well I'm still having the same problem, but when I took off the rear wheel recently that I thought had a leaky wheel cylinder I noticed the fluid keeps returning, and it's not brake fluid it's oil. So I blew the axle seal. Someone mentioned to me that my brake problem might be due to soaked brake pads. Does this sound reasonable to anyone. I mean when I touched the pads they didn't seem that soft, but they might be very soft when they're stopping a 2 1/2 ton vehicle.

Other than this I still have no idea what's causing this issue. Obviously, the wheel cylinder didn't have to be replaced and neither did the MC. I just wanna solve this problem without wasting anymore money.

 

The axle seal leak isn't enough to cause that great of a brake problem. I just had my seals replace without any notice in the braking.
My braking is very similar. I took my 4runner to a brakes for less where they had a special for brake inspection. A dead caliper cylinder was discovered and a deteriorating threaded brake line as well. It wouldnt be a bad idea to go have a shop check it out then you do all the work. I have yet to replace and fix these parts but when I do, I know what to go to first.

 

the master cyl will push enough fluid to stop the truck. if the pedal is going to the floor before stopping, you either have air in the lines or a bad master cyl letting fluid get past the seals. if the reservoir is losing fluid, look for leaks but it doesn't sound like an external leak.

try pulling the fuse to the ABS. it may be activating and giving room for fluid to expand.

 

Tommy, did you have the pads replaced after you fixed the axle seal? The theory is that the pads get soaked by the fluid and cause a spongy brake pedal.

DrCoffee, I've flushed the system a few times, just replaced the master cylinder, and the fluid level doesn't go down at all. So should rule out the MC, air in lines and leaks.

 

A gremlin that is tough to fix is air in the ABS mechanism. You may need to have the dealer power bleed the system. It may be time for professional intervention.

 

˟˟˟˟ with a capital $. Be nice if I could find a place to do just an inspection and not expect to fix it too.

 

2 thoughts:

1. diagnose the master cylinder. Pump the pedal, then push and hold. does the pedal slowly go to the floor? if so, you either have a leak (which it sounds like you already checked for) or a bad master cylinder.

2. do these have a load sensing proportioning valve that needs to be bled like the older trucks?

 

If the rear shoes (the brake pad of drums) are soaked, which mine were, they will stick to the drums and a thunk sound will occur when you leave a stop. It's best to replace the shoes and clean the drums. Mine hadn't been leaking for long so I just let it be for a month or so, till I'm assuming friction and heat dried them out. No more thunk.
As for this causing a "sponge" feeling, I highly doubt it. These shoes aren't thick enough to have a noticeable change in the feel of your braking. Maybe an inch think or so

 

Tommy, I figured the same thing about the pads just drying out from braking, but they're staying soaked, obviously from the leaking axle. I never hear a thud , though, when I take off from a stop.

Jason, I already replaced the MC with a new oem one and no change whatsoever. Also, mine doesn't have a load sensing valve.

I think the next thing I'm gonna do is hook up my pressure bleeder and look around for leaks. I might even take one line out from the MC and plug it and watch the pressure, then do the same for the other line. Then, I could narrow it down to one brake line.

When I last flushed the brakes with it, the pressure wasn't holding. So, maybe there is a leak somewhere, but he found himself the best damn hiding spot.

 

Have you checked anything with the brake booster? I don't know much about brake boosters, but that seems to be the only part you haven't checked yet. maybe an issue with the booster or possibly the linkage up under the dash that connects to the pedal?

 

Your Emergency brake is working ??

You do use it?

That is what keeps the rear shoes adjusted

Shoes out of adjustment and very worn drums will cause the long pedal travel.

oil soaked brake shoes never dry out.

They can sometimes be cleaned with a few cans of brakeclean but really should be replaced

 

I'm sorry. I forgot to mention the thud sound is from the shoes/pads sticking to the drums then peeling off when you start moving again. Your best bet is to start testing the brake booster, looking for that nearly impossible abs leak, or the hidden air leak in the system.
You are putting something under the brake pedal when bleeding the system, correct? It would be horrible to over stress a new MC. Can you go over your brake bleeding process for everyone?

 

Spark, it's kind of looking like it might be the booster, I'm just hoping it's not. Way more money than I want to spend. Haven't thought much about the linkage. The pedal's smooth enough and I don't hear any clunking going on in there, but still possible.

Wyoming, E brakes working and the rear pads have been adjusted using it. Last time I took the drum off it was on there pretty good, so everything's properly adjusted. I'll take your advice and just change the pads after I replace the axle seal.

Tommy, as far as my bleeding process. First I had someone push on the pedal, then I unscrewed the bleeder screw until the fluid stoppe flowing, then I closed it off and had them let go of the pedal. I did this until no more bubbles were seen and then moved to the next wheel. I started from the passenger rear wheel and worked my way closer to the MC at the front driver side wheel.

I flushed the brakes using new bleeder screws with check valves, so I didn't need anyone else to do it.

Then I flushed it again, after I replaced the MC, using a pressurized Motive brake bleeder.

Sometimes the pedal would feel a bit improved afterwards on the first push but would then sink down and return to its crappy state.

 

http://answers.yahoo.com/question/in...4195710AA7MI1c

I hate to refer to an outside source but here's a simple answer. I'd refer to the fsm for testing before replacing

 

Hey guys, So it's been maybe 4-5 months since I last flushed the runner, but when I checked the fluid today it was dark already. The fluid level also appeared to be a little lower. But even if we assume the level is still the same, is it normal for the fluid to darken after only 4 months?

Just to recap the issue in this thread for anyone new, my pedal goes nearly down to the floor. Braking is fine, it's just the pedal. I've flushed the system 3 or 4 times, I've checked the lines twice and never saw or heard any leaks, even when I had it under pressure with a Motive bleeder. I also replaced the MC, no change.

I'm thinking the fluid shouldn't be this dark in only 4 months, and if that's the case then it's safe to assume there's a very elusive leak going on. Any insight?

 

Change the brand of fluid you use. I had the same issue with Valvoline Dot3 and it darkened is months. I switched to ATE Super Blue Dot4. Still looks great 2 years later.

 

What about your load sensing proportioning valve? I don't see that mentioned anywhere yet. Did you bleed that also? You should bleed that only after bleeding at all 4 wheels. And if it's leaking you wouldn't necessarily notice it since the fluid would just drip right on to the ground.

Sorry, but I don't know what you're driving. I see mention of ABS so I'm assuming it's newer than an 80's model.

 

Where is the load sensing proportioning valve located? 98 limited in my case.

 

It should be located near the rear axle. Possibly mounted on the underside of the body or on one of the frame rails. I'm not exactly sure where. Follow your rear brake lines from the wheels back and you'll get to it eventually. It'll have a bleeder valve on it. Sorry I can't be more help on that.