Mushy breaks ?

[jlewis]

I have a 83 j10 with 360. I am writing you all for your opinion on where to start first. I have changed my break pads, bleeded the breaks, and checked for leaks. What do you think could be my problem? What should I check or replace next? Thanks in advanced for your help.

[TK421]

have you checked the master cylinder? I have abad one on my 70 J4000 and the pedal goes all the way to the floor, needs multiple hard pupms to operate the brake, It's a $40 fix.

[lost1]

Mine had a lot to do with the wheel cylinders as well, though its still pretty darn soft. Master cylinder is my next suspect, but the only reason I didn't touch it first is because I had visible seeping from the wheel cylinders. If you don't have visible leaks I'd do as TK421 suggested

[jlewis]

How do you check if your master cylinder is bad? Or should I just replace it since its cheap?

[jeepjseries]

If you got the money I say go for it.it can't do nothing but help. Is it leaking from the rear between the master cylinder and the brake booster? this is the most common way to tell and a decent amount of fluid loss.

[tgreese]

Generally a bad master cylinder will leak down slowly. You can pump the brakes to get more pedal, but the pedal won't stay up with continued pressure.

Mostly you eliminate everything else, and then replace the master cylinder. The fluid has to go somewhere, so if the wheel cylinders leak, they will be wet. The MC can leak back into the reservoir, so it can leak with no seepage. It can also leak into the power brake booster, but that will show up eventually on the firewall.

If you didn't bleed the brakes well enough, the pedal will be spongy but it won't sink.

[[]V[]AXX]

Did you replace the rear brake shoes? If you did any work on the rear brakes, they almost always have to be readjusted. They have to be pretty tight inside the drum to not give you a spongy pedal.

If you didn't do anything to the rear brakes, and have no leaks at the wheel cylinders, and bled the system properly by opening the proportioning valve, then check your front brake lines. Grab a pair of needle nose pliers and work your way down the hoses looking for soft spots. I've actually had lines that would swell when the brake pedal was pressed. If the outside jacket of your front brake line is cracked, replace the hoses, it will improve your brake feel, even if that's not the problem. If all this doesn't help, then look at your master cylinder. Pull the two nuts that hold it to the brake booster, and separate it from there. Look into the socket for fluid seepage. Besides being a sure sign of a bad master cylinder, brake fluid in the booster will destroy the diaphram in a hurry.

[jlewis]

I just checked and there are no leaks present.

[FSJ Guy]

Generally, when something is mushy, I find that it doesn't break easily.

As for your BRAKES, is this the first time you've bled them? If not, I'll assume that you know how to bleed them correctly.

Did you have a mushy pedal BEFORE you started to work on them?

If they are in fact bled correctly, then I'd suspect your master cylinder. It can leak and not show up on a visual inspection.

[Rocket Dog]

it's the m/c. same thing happen to me....... the brakes would bleed well and seem firm, then, soft. it was about 20... at the zone with a 10.00 core.

I also did the bench bleed on the fire wall since I did have a vise to do it on...... from the cab useing my hand...easy

[rocklaurence]

If there is any question about air in the brakes rent a vacuum system from one of the stores. Theyre GREAT!