I need some help getting rid of a spongy brake pedal after bleeding...

So I've been replacing my rear brake lines this weekend.
Had a line bust on me as I was pulling out of the lot at the local Wall-mart :-/

at this point, I've replaced the line running from the front to the rubber line at the axle, a new rubber line, new wheel cylinders, and new calipers up front.

I bleed the brakes with a vacuum bleeder, as far as I can tell, I've got no air in the lines. followed the standard bleeding order (RR, RL, FR, FL)

As it stands, I have a spongy pedal when the truck is running, and both the red brake warning light and the yellow ABS light is on.

I did not touch the mater cylinder, Combination Valve, or the Rear Anti-Lock Valve.

Do I need to try and bleed theses in addition to each wheel? What is the procedure? I see that PDF version of the service manual states to bleed them, but does not say HOW to bleed them.

Anyone able to offer some advise?

 

Item 1 - if you still have the factory rubber hoses on the front calipers, grab new ones and replace them.

Trust me, your brakes and everyone in front of you will appreciate that *grins*

Item 2 - I see you used a vacuum bleeder. In order to properly bleed the master cylinder, you would need to pressurize the system and crack the fittings at the master cylinder (the PROPER way is to do it on a bench, but eh.)

However, if it bled out, your rear anti-lock valve has some air in it (almost guaranteed!), and you'll need to get that bled out.

For that, for 1995, the instructions are about three pages in the factory service manual. If you have it, it's section 5, page 49. (I got my copy from the download link here ...)

RwP

 

Thanks for the quick reply man!

As for #1, a new set of hoses is defiantly on my short list.

I think I have a pressure bleeder at my parents house, though I doubt that I have the proper cap to fit the master cylinder. Do I need a cap for both fill ports, or can I do it with only one cap to the pressure bleeder, and leave the normal cap on the other fill hole? (Maybe switch when I do the other line?)

To bleed the combanation valve and RWAL valve, do I need to crack open and bleed each and every line going in/out? As it stands, the only line I was able to get open was the new one to the rear wheels I just installed.

I started spraying the others with PBblaster to see if that'll help break em loose.

Just for S&G, I pulled the battery negitive wire, and that seemed to clear the lights. The pedal still feels softer then I think it should, thought it is stopping the vehicle OK.

However, there is also a hissing sound when the pedal is pressed.

 

Would a bad Booster check valve cause a spongy pedal or the hissing sound?

I pulled the check valve out to do the test outlined in the factory service manual. I could not get it to hold vacuum, and the vacuum pressure dropped rather quickly. I can actually (very slowly) suck air through the large port on the valve.

 

When I replaced all my brake lines, I used a vacuum bleeder. Never had a problem with it in the past. But............ brake pedal was low, etc. I talked to a mechanic, and he told me this. Have someone set in the truck, crack open a rear bleeder and slowly push brake pedal down. Hold pedal down and tighten the bleeder. release and pump up. Repeat several times.
This worked.
IMO the vacuum bleeders are fine for changing the fluid, but on a long run they do not have the capacity to pull enough fluid and push the air ahead. I think that the brake line flows fluid at half capacity, not filling the pipe. The air pocket stays on top and the fluid flows under it. Maybe not a good way to explain. But that is what I think happens.

 

Yes, a bad booster is usually (as in, as far as I know, 100%!) indicated when the brakes "HISSSSSSSSSSSSSSSSSSSSSSSS" when you put your foot on them.

Usually, a bad master cylinder is also ... the most common failure of the booster is that the master cylinder leaks at the MC/booster seals, and the brake fluid destroys the rubber inside. But not always ...

A bad MC would also explain the spongy feel.

RwP

 

My copy of the 1995 manual states to fill the master cylinder up, put the bleeder screw's bleeder hose into a container filled with brake fluid (using a clear hose), and crack the bleeder screw in the proper sequence until fluid starts to run out. THEN you vacuum bleed.

I didn't have this problem with the Harbor Freight pneumatic bleeder ( this one: http://www.harborfreight.com/brake-f...der-92924.html ) and either the Cougar or my 1988 Dakota, just hooked it up, filled up the supply reservoir, and started it to sucking.

Well, minor problem - on that longest run (RR IIRC) I had to stop part way through and refill the supply, because it was at 1/4 left when fluid started out the back. Wasn't a problem because I had both tanks where I could see them at the same time, so I knew when it started running into the suction side and could stop it, top off the supply side, and start off again.

Then again, I had blown the lines clear with air while the rear wheel cylinders were out, so I KNEW it would take a bit *grins*

That step where someone pumps it up and you bleed it until the pedal drops to the floor? On master cylinders, than can blow out the seals if there's any grit or grime in the brake fluid ... which is why I don't do that anymore.

RwP

 

Ralph, I never said to push it to the floor. I said push it down and hold it. I assumed that it is known its not a good idea to go all the way to the floor.
The harbor freight bleeder is the same one I have. Again, no blockages in my lines. They were all new.
Back to the OP. Its your vehicle, but I would try bleeding them with a second person as I described above. It worked for me, it may or may not for you.
IMO its crazy to throw a booster and master cylinder at it until you are sure that's your problem.
As far as a bad brake booster goes, in my experience when it goes bad, the brakes are hard, (no assist) somewhat like using the brakes with the engine off.
Again, in my experience when a master cylinder goes bad, usually you notice it when the truck is at a stop. Sitting there with your foot on the brake and over time it starts going down.
For a little time and a pint of fluid, pressure bleed the rear, by brake pedal or a pressure bleeder. Ill bet that is your problem. But then again we are all guessing at this point.

 

It's not a guess if it hisses when you apply the brakes. You can get a leaking booster that still boosts.

My past experience so far has been hiss, but boost - with leaking master cylinders. My experience, however, is extremely limited *grins* compared to professional mechanics.

So - one thing's not a guess, the bad booster. The master cylinder I'd recommend because they're cheap enough and it's a lot easier to change the booster if you remove the master cylinder (you can DO it with it still connected, it's just a severe pain in the toochus with the MC in the way).

Master cylinders can be had new from RockAuto (Centric brand) for under $35 as I type this, booster is $64 with a $10 core included, but a booster/MC combo is only $122 with a $30 core included (makes both ways about the same total price after returning core). This is of course up to the OP ... but that hissing, I'd be willing to bet money is a bad booster.

RwP

 

OK again, I am making some assumptions here. But
The OP said that he blew a brake line when pulling into a parking lot.
Now I assume the brakes were ok before this happened.
Fast forward he replaced brake lines and now has a spongy brake pedal.
Could he by chance also now have a bad brake booster and master cylinder?
Sure its possible, but not likely.
Again, bleed the rear by brake pedal pressure or a pressure bleeder.


BTW to answer the OP question on using a pressure bleeder on one of the two openings of the reservoir? No. If you look under the caps, at the top, there is a opening to allow fluid to cross over. So if you try to pressurize one side, its going to bleed over to the other side. There is a dam at the bottom of the reservoir to keep one cylinder in fluid if a line breaks etc. Hince the dual cylinder.