Need RTH for spongy brake problem before and after rebuild (1 Viewer)

[ericb1]

History: My brakes are "spongy" for lack of a better word. The pedal depresses almost to the floor and then there is slight resistance for a few inches before the brakes engage. Over these few inches of resistance, the pedal travel is spongy and at no time "firm".

1. I replaced all soft lines about 3000 miles ago as they were the shortest link in my suspension travel, so all new lines.
2. Over the weekend I replaced all calipers with NAPA rebuilds, EBC Greenstuff pads, Napa rotors X4
3. LSPV and ABS have been deleted
   
4. I have bled the brakes via a vacuum bleeder on all 4 corners until my hands bled, and my knees wept.

Despite all this my symptoms still exist. During the brake bleed for the new lines I was depressing the pedal and worry I may have damaged the MC by over traveling . Can anyone give me an idea so I don't keep throwing time and money all over the place. Thank you

 

[NLXTACY]

4 corners? What about the LSPV?

ABS? If so, did you cycle it then bleed?

 

[benjrblant]

4 corners? What about the LSPV?

ABS? If so, did you cycle it then bleed?

You can bleed all four corners as long as you'd like but if you don't bleed the LSPV, you're missing a major component of the system. Last brake flush I did, LSPV had more air in the line than any caliper.

Bleed, in order: PS rear, DS rear, LSPV, PS front, DS front. Take it to some sandy/gravel area, lock up the ABS to cycle that pump and those lines, then bleed in order again.

 

[ericb1]

Sorry, I will update original post. LSPV and ABS have been deleted

 

[benjrblant]

Ah, well, if the ABS and LSPV are gone I'd suspect either the master could have air or there could be a booster/vacuum leak somewhere?

I haven't had the best luck with vacuum bleeders. Maybe I'm vacuum challenged.

 

[woodsman 44]

I vacuum bleed mine after changing F&R calipers, lines and pads

Brakes were still spongy, drove it around for awhile then vacuum bleed again and it stops like a champ now.

Air gets trapped in the brake system and doesnt always gets out on first or second purge

 

[ZackR]

Try the gatorade bottle bleed method and reply back with the results. I bet you'll be surprised since its able to flush so much volume through the system so easily (bubbles hidden way up there will finally make it out). Plus your knees and hands will thank you.

 

[ericb1]

OK, So I used a VERY large VOSS glass water bottle for a catch, Thread sealer and a zip-tie on the tube and no leaks at all. Every corner got :

1. 20 presses of the pedal befor MC was topped off
2. 5 topoffs / 100 pedal depresses filled the catch bottle
3. repaeted 2X per corner
4. 20 X 5 X 2 = 200 pedal depressions per corner / 800 for the system

I have NO DOUBT that the system has been bled as best as it ever will. My pedal is much more firm, but does not stop the truck well at all. At this point am I correct to assume a MC needs replacing and 800 more pedal pumps in my future? FWIW the action on the MC felt as if something were catching slightly inside, more noticeable on the return. It was not perfectly smooth over the course of travel

 

[ZackR]

Sounds like you are on the right track with the master cylinder being the culprit. With the system fully flushed you probably don't need to push through as much fluid next time.

 

[shocktower]

I learned that the best way, to bleed is a pressure, bleed, a one man rodeo, I have tried those vacuum bleeders and they suck, and not in a good way, I made my own pressure bleeder using a garden sprayer I have about $15 dollars into it, and I am not needing someone to pump brakes I can do them alone

 

[sunrk]

When bleeding, it's got to be done in five places. If bleeding doesn't fix the issue, look at all the flexible brakes likes for damage and/or bulging around crimp joins. If that's not the problem, start looking at the master cylinder being leaky, but that's the least likely cause.

When replacing brake pads it's easy to see if there are leaks from the pistons in each caliper. Rebuilding calipers is not a hard job but is messy and needs to be done carefully. Also old brake fluid which has absorbed water, been subjected to a lot of use, etc. causes pistons (and caliper bodies) to internally corrode. That can make pistons stick, or sometimes leak.

If an 80 is lifted, the braking will change because the LSPV will then be out of adjustment. Lowering LSPV slightly on it's bracket and/or lifting where the spring rod attaches to the rear axle housing is/are the common correction methods, but nothing replaces a proper calibration to 'set' the spring rod to give the right amount of pressure diversion to front and rear.

The Motive Products power bleeder is a good unit for pressure bleeding but the universal master cylinder reservoir adaptor is tricky to get a good seal with. This is what I'm talking about:

flickr page

 

[benjrblant]

@ericb1 , When was the last time the brakes were bled? I've heard of damaging the seals in the master cyl by over-traveling, but if this has been done frequently or recently prior (i.e. 3,000mi ago when you replaced the soft lines, maybe?) I'm not sold on the idea of a bad master cyl seal. Prior to the new calipers, pads, and rotors, were you experiencing any different brake pedal behavior? Were the they bad or just sub-optimal?

When you bled the system most recently for 800 times or so, were there ANY bubbles? It should have been pretty spic n span at that point. Any air would give a lot of clues.

Sounds like you're aware of what you're doing- I'm guessing you've already checked the system / new connections for leaks.

I once flushed a half gallon of fluid through my brakes and a miscommunication with my helper (100% my error) resulted in sucking a planet's worth of air back into the line. Rinse and repeat.


Edit: Reread thread title, spongy before and after rebuild. This leads me to think that the cause of the sponge is something that has not been replaced yet. At this point, with no ABS and no LSPV, new soft lines and new calipers, I'd lean towards master cyl, booster, or some sort of vac leak maybe?

 

[ericb1]

That's sort of the situation. At this point everything is replaced EXCEPT the MC. I believe the booster is working as it's not difficult to press on the pedal, it is assisting me. There are no leaks, everything is new (except MC) and all air is removed

 

[Seth_O]

@ericb1: did you ever find a fix for this? Having the EXACT same issue on my truck. New/rebuilt calipers, new soft lines, LSPV and ABS deleted and countless bleeds, but still soft-soft brakes. I have to get the pedal all the way to the floor to stop the truck. I am beginning to suspect a blown seal in my MC, except I have no swirl in the fluid when I depress the pedal. MC passes the FSM check.

I've started buying DOT3 in gallons at a time since I keep bleeding the brakes as the symptoms so closely match air in the system.

 

[jvazquez53]

I believe it's the master cylinder, did you bench bled?

 

[team420]

Bench bleed! It's a must.

That being said... I've had numerous "soft" new masters that just didn't do the trick.

I have a 4runner that I went thru 4 brand new in box masters from napa (warranty) that all sucked. Ended up taking a used asin off another 4runner with known good brakes, and all has been well since. This was 6 years ago fwiw....

 

[TnTnola]

I had the spongy brakes when I bought my 80. My bro in law is a mechanic and ordered a master cylinder rebuild kit from Toyota. Surely enough, after taking apart the MC he found buildup and debris along the edges at the seal. That buildup of gunk didn't make a tight deal and allow brake fluid to pass. He also adjusted the brake position a smidge. It's located behind the brake pedal.