So i think i know what the problem is, but wanna be sure.

When i stop at a light, or whenever i have to old the brake on for a while, my pedal will VERY slowly sink down. it doesnt quite get to the floor, but i noticably will loose my holding power, and have to press harder.

Also have a bit of a leak at the vac pump. Looks to be oil? could be steering fluid but im pretty sure its oil. i think the leak is probly unrelated?
I also have park brake and abs lights on.

So correct me if im wrong, but i think its my master cylinder leaking internally?

 

If you can't find brake fluid anywhere and the level doesn't drop, then yes, the master is leaking internally. Check inside the rear drums. A lot of times the master leaks into the booster, so you are likely to have to replace that as well.

 

All of that is correct and reasonable, but, from several years of experience, don't think that replacing the master cylinder and booster will fix your problem. I am 4 or 5 mc's into mine. Not trying to bring you down, unless reality is in that direction . I just took my rig, with fresh disk brakes in the back down to Mexico, with the computor disconnected and I had good brakes for the firat time in a while. I don't want to jump to conclusions, but early results show that the rears have more to do with the problem than just the adjustment. All of the rear components were very recently brand new. Good luck, it is a journey frought with financial potholes,,,Mark

 

Thanx wanna. Is it pretty much guaranteed that I'll need a new booster too if it's leaking there? Or what should I look for when taking it apart?

I've also read some posts about folks gettin the mc and booster already connected. Is that advisable?

And for checking the drums. Could I just check for fluid pooling by feeling through tue adjuster hole? Or just tAkem apart.

Another symptom I forget was that sometimes my pedal feels like it stutters or bubbles or something like that. Not sure how best to describe. Is that probly the same mc issue or something else?

 

Rock auto has the mated ones from A1Cardone,I have bought three of them. The second I didn't think was bad, so I replaced it when I got sudden problems back anyway.When I did the disks, I put the second one back on and it wasn't bad. The movement in the pedal could be the antilock activating, maybe a bad sensor in the pumpkin...Mark

 

Very rarely the RWAL will fail in the open position. A master/booster combo is cheaper and more likely.

You will see fluid when you separate the master and booster.

A loaded booster is what you are looking for if you want to replace the whole set.

If you're losing enough fluid out the wheel cylinders to make the pedal sink, you will be able to see the mess on the inside of the rim(s).

It sounds like air is getting in from your last symptom. Pretty normal for an external leak, not so much for an internal leak. You are sure you aren't losing fluid?

 

I am not saying that the mc is not bad, I am saying that, in my experience, the replacement doesn't necessarily fix the problem like it should. Also.I ws not saying that the modulator was stuck open, I ws saying that the Antilock was being activated by bad data from a bad sensor, but I don't think a new sensor will fix the problem either.I am very cynical about these #%$*(&^%#$$ brakes...Mark

 

double checked for any leaks at the connections and wheels all dry. and if im loosin fluid in the MC is unnoticeable.

just to clarify, My pedal doesnt really just drop, but it will VERY slowly sink down with pressure.

Does the booster need to be replaced if any fluid is present? or is it salvageable in some cases? I guess i dont understand how a booster works, so im not clear of the effects of brake fluid in it.

 

If fluid made it into the booster, it is going to fail sooner than later.

It really does sound like a bad master to me.

 

Listen to the lady, one of mine is doing the same thing. Before i bought my 1st gens., i couldn't even think the word "mechanic" ,------i d#%@ thik it now, yea haaaaaw.

 

I have a new master on mine and it does the same thing. Mine was new not a reman. I just kinda deal with it and don't let anyone drive my truck. I'm also in the process of changing my brake hoses. I'm going to see if this helps at all. Good luck. Like Mark said, these brakes can be frustrating.

Jake

 

This is all that I am saying, that all those rules and stuff that the school of mechanics taught me don't apply to these trucks. In literature there is always a price to pay when a deal is made for super powers. Maybe the witch or warlock that did it said "ok it's going to go real good, But stopping, not so much". They might have had a German engineer from Porsdhe do the brakes, because, Porsches go real good, but stop real bad, at least the older and more valuable ones are like that...Mark

 

ok it so it definatley sounds like the MC but ill keep in my that these trucks brakes are unusual.

On another brake issue. i replaced my caliper to try and stop some pull to the right, that i had while braking, and now its even worse. and it also pulls while just driving now which it didnt befor. When i put the caliper on, and bled the brakes, i couldnt even turn the wheel by hand it was so tight. i should be able to spin the wheels shouldnt i?

does the caliper adjust itself as to where it sits? or did i do something wrong? Also should there be any play in the outer brake shoe in the caliper? mine definatley has some.

 

Sounds like a bad brake line, it wears out and creates sort of a one way check valve and won't let the plunger release...Mark

 

Mine pulls also and my rotors drag more than they should. I replaced both my calipers, master, and booster, turned the rotors (they needed it), and new pads. It still pulls. Then I pulled the calipers and cleaned the slides with a sander and regreased and it still acts the same way. I'm going to do the brake hoses next. When I change them I will flush the lines so that I know everything is good. We'll see how it goes from there.

To answer your question:
Caliper is "self adjusting" they float on the slides but should be released when the pedal is released. Drum brakes run with a little residual pressure on them but disc do not.

Not sure what you mean by play in the outer pad. If you mean its not touching the rotor but the inner one is, its because the caliper hasn't released properly. Like Mark said, I'm thinking brake hose.

That's just my .02 of experience.

Jake