Sorta Mushy pedal, but only sometimes

[strad]

I don't really have anything to compare brake pedal feel to with this truck (other than the two bimmers, and they are not a fair comparison). But it sure seems like sometimes (especially when the brakes are cold) it takes way more pedal travel than it should to get the thing to stop. So far we've replaced the brake fluid by letting gravity pull it out, always keeping the MC full, but we have not bled it. We're going to bleed the system using the two-person method tomorrow. Could this be a pad issue? As in incorrect pads for the application? The truck appears to be completely stock except for the oversize tires (265s instead of 245s). I don't think the p.o (also the original owner) would have put non-stock pads on it. There is no fluid loss from the master reservoir, so I do not suspect a leak.

Now, we have not let any air into the system at any time, but that does not mean there isn't any from actions by the po or their mechanics. What I'm wondering is, does the ABS pump require special bleeding procedure if it gets air into it? And I guess if it had air in it it would create a mushy pedal logically.

I'm just trying to gather some ideas of where to look.

 

[SunlitComet]

Ensure your rear drum brakes are properly adjusted and bleed you brakes properly. The odds of you getting air into into the abs module that CAN NOT be bled out by regular pressure bleeding are rare. If you actually pulled it of and got air in there the appropriate method to get it out is with a properly softwared bi-directional scanner. You would also be at huge risk of loosing your steering control while hard braking on wet surfaces as a result of creating the problem in the first place. So if you are unsure whether or not you have done so have a properly equipped shop bleed out the unit.

 

[gpracer1]

$20 says you just need to manually adjust the rear shoes with the star wheel adjuster.

Jack up rear, put in neutral, spin wheel and asjust rear brake (each side) untill it starts to drag....done.

 

[strad]

@ sunlit, I'm sure that I didn't introduce air into the system. That doesn't mean there isn't any though. The mechanic that the po's trusted didn't know how to adjust the latch on the tailgate (told them they needed a new latch, which was NLA lol), so maybe there's some other things he didn't know. I'll try adjusting the rear shoes first. I've been driving cars with rear disks for so long that I sorta forgot that the drums could be adjusted. I'll check that out this morning.

 

[strad]

Progress report: Well the drum brakes definitely were out of adjustment. We corrected that. But it still didn't feel right. So I stopped the engine, pumped all the vacuum out of the booster, and floored the brake pedal. I can feel it continue moving to the floor, and if I push hard enough it gets to the floor. We think we have a bad master -- not leaking externally but leaking internally. Does that sound like a proper diagnosis?

There are no leaks anywhere in the system externally. One thing I noticed a couple months ago when we changed the brake fluid was that when I activated the brakes via the pedal, fluid shot up out of the reservoir (had the cover off). I've bled brakes on many other vehicles and never had that happen. Is that supposed to be that way on these, or is that further diagnosis of a bad master?

I already bought the reman'd master. Only 30 bucks lol. I'm used to paying five times that for the same part on my BMWs.

 

[gpracer1]

Yeah some masters squirt out the top. Sounds like yours is bad for sure if it goes to the floor.

 

[mlc596]

I just battled with my brakes and had similar issues and believe it or not, after completely rebuilding my rear brakes, one of my mechanic friends told me it could be the proportioning valve. He told me to turn the car off, pump the brakes up and then kick the living crap out of the pedal. Unconventional yes, but I did this about 6 times and now my brakes work fine, just had to re-seat the proportioning valve. Hope this helps.

 

[strad]

Well here's a laugh. It didn't need a master cylinder. What happened was, we adjusted the drum brakes, and then we discovered we didn't have an 8 mm combination wrench to open the bleeders -- I have every other size under the sun but the one I need. My father-in-law partner in crime tried to make another wrench open it but it was too big -- we thought lol. On my way to the store to get an 8 mm wrench, I noticed that the pedal felt mushy like before, and it seemed to want to keep dropping to the floor if I pushed on it harder than normal. I thought well, the brake adjustment didn't solve the problem, the pedal is falling to the floor, and there are no external leaks, so it must need a master cylinder.

Later that afternoon, after buying the recon'd master, I happened to notice that one rear tire was partially wet. It was not wet when I inspected it before we adjusted the drum brakes. Followed the trail up the backing plate, to the bleed screw!! LOL. So after bleeding that corner and tightening it properly, the brakes are now fine.

All they needed was to have the drums adjusted, and to have all the bleed screws tight (lol).

 

[SunlitComet]

Wash the tire with plenty of soap and water.

 

[gpracer1]

LOL, as long as it is fixed !!!