front brakes getting stuck ( NOW ANOTHER PROBLEM )

Do a simple test. When the brakes feel like thay are hanging up, crack a bleeder and see if there is any built up pressure. I suspect one of the components ( prop valve maybe ?) are for a drum brake system , causing about ten pounds of line pressure to be in the lines at all times.

I had this happen to me,it was the master cylinder,It was a remanufacture from the local parts store,as soon as i installed it and drove it 1 time it started to apply the front brakes,the further I drove it the worse it got,after it sat awile it was fine for a few minutes and would do all over,had to replace it as well.

well... this MC was on a sealed bag from factory

To diagnose a drag you must work from the source (the pedal) toward the wheel(s) with the drag. These are actually fairly simple to nail down - especially on a car without ABS.

Keep in mind if you open a bleeder you have eliminated the entire brake system as a possible root cause and accomplished nothing.

When the concern is present, loosen the master cylinder from the booster (or firewall). If the brakes release, inspect the pedal assembly and pushrod for concerns – if OK replace the booster.

If the brakes do not release when the master is loosened from the booster/firewall, working from the master cylinder toward the wheel(s) that are dragging, loosen each line one at a time and see when the drag is relieved. The faulty component will be upstream from the last line loosened that released the brake.

ok, adjusted back the booster rod with a better precision measurement, and does look it fixed THAT...

now I feel some loosen the brakes and getting light on at cluster.

of course will check the tipical, rear shoes adjustment and better bleed IN ORDER ( as stated at shop, were fronts bleed first than rears )

but getting floated back one of the questions:

DO I MUST HAVE PRESSURE AT PRESSURE SAFETY SWITCH ENCLOSURE ? SHOULDN'T BE BOTH, FRONT AND REAR SYSTEMS ISOLATED ONE FROM THE OTHER AND JUST LINKED BY THE DOUBLE ACTION PISTON ? ( what does not mean fluid going throuhght the piston cilinder... or yes ??? )

the system halves are isolated from each other in the prop valve just connected(sort of) w the electrical contact in the middle. With the linings up/air out slghtly crack a line on the side that was good as someone pushes the pedal to shift the valve back centered(have key on so the light will be on & you'll see when it goes out.

yes I got that, BUT now I noticed I'm having a leak at switch ( at stud ). Dunno if the problem is THE switch, or problem is inside somewhere, because PRESSURE at switch what is not enough to hold because is not designed to that.

SHOULD IT EXIST PRESSURE THERE ?

when installed the MC and began to bleed was able to see a squirt coming from below the hex head. Tighten the switch and that leak was over

Light is coming on and off frequently. QUITE OFTEN just with road vibrations.

NOTE again: THIS SWITCH is not like the original with a push in button, is really a fixed stud and does look works similar to earliers kind. Is like the original at exterior ( on top )though

Brakes are working ? apparently yes... but I dunno if PERFECT really as it should be.

Alright I understand what you are saying. I'd take it apart & see if there's any seals/o rings that can be R&R'd

is posible that switch o-ring is gone and that si replaceable, but still.

Is normal brake fluid circulating on normal conditions allong the piston inside the dist block assembly ? I though piston keeped both systems ( rear and front ) isolated and linked between them...

If is normal... then, Is normal to have PRESSURE there to get a leak like a squirt ?

right now since I tighten the switch, is just a small leak on switch stud base. ( does have a plastic bushing there )

Is posible get a Brake failure light on when leak is at SWITCH ? if so... why ? if no one of the rear or front system is failing ? where would move the diferential pressure piston ?

Is not posible ( as far I know ) replace the piston O rings. I can't find the way to dissasemble.

Piece just have about 3 years mounted.

I'm getting somehow desesperatelly about this because I can't be buying stuff from USA anytime, specially when I don't know where exactly is the fail OR if I have to buy once again some probably bad quality piece, IF REALLY IS A BAD QUALITY PIECE .

This is something I fixed 3 years ago thinking on get saved by the next 25-30 years more. These Dist blocks/prop valves are NOT available down here. In fact they weren't either up there in USA 4 or 5 years ago. ( unless NOS )

The fail I got INITIALLY with the original part when I had to replace the dist block/prop valve is one of the MC cilinders deposit getting emptied and the other one getting overflowed. After many pistons, seals and couple of MC changes, simply discovered the fluid was going from one deposit to the other through the dist block.

I hope is not that AGAIN. just a 3 years piece!!! I have drove enough to check difference on MC fluid levels ( one against the other )

I will try to find a new O ring for this switch what as I'm telling you IS NOT THE SAME THAN THE OEM... looks the same from outside but works totally diff. Works like the drums brakes dist block kind switch

That prop valve should be tight as a drum, no hint of a leak which do tend to get worse w time. I dont think that the minor leak you are reporting would cause a psi differential enough to shift the valve over but I'm not for sure but you did just have an issue w one side leaking(or opened up) correct?. If this piece cannot be dissassembled or resealed somehow you may have to bite the bullet & scare up another one. Good Luck.

then also...

Is posible the MINIMAL LEAK I'm getting at switch right now is able to make me feel "uncomfortable" when pressing brakes ?

sorry I posted in the meanwhile you were writting.

in order, once again:

the leak I got INITIALLY was at MC rear piston, not on the rest of the system ( what I'm aware ). That was the FIRST problem I tried to fix changing piston seals first ( didn't work ).

PARALLEL TO THIS got an irregular wear out at driver side brake pads what fixed meanwhile( replaced pads ) and tightened rotor.


One day noticed switch wire was unplugged ( maybe accidentally when replaced the seals, or maybe before that ), plugged and got light on ( most time on and quite often off sometimes when pressing brakes ) so I didn't know I had a problem there, and dunno really since WHEN I had the switch unplugged

Then replaced MC to fix the leak there on back... bleed and still got light on at cluster

Searching the problem for the light cluster reading, FOUND THE BRAKE FLUID SQUIRT I mentioned, below the hex at switch. Found the switch was MISTERIOUSLLY LOOSEN. Removed to check any failure. instaled back and tighten. I though leak there was solved since I didn't find was squirting again.

Got front brakes dragging for a while Light still lighting on frequently, went to a brakes shop replaced caliper seals thinking it was that, got light off.

Apparently the dragging problem wasn't the caliper seals because arriving home I felt again front brakes begining to dragg, so then adjusted the Rod as adviced... with that APARENTLY fixed the dragging, BUT light at cluster is again quite often ON.

Since light was still coming ON, made a CORRECT ORDER bleeding ( from longer to shorter distance ) thinking it could be that what I needed to reset the valve. Still getting light ON ( sometimes even with road/streets vibrations ). Searching for another problem, found the switch plug was wet with BRAKE FLUID what does mean the leak at switch is still there but not anymore below the hex, now at male terminal stud.

that's my situation now. Light at cluster ON around 50% of the time, sometimes just flashing and A LITTLE BIT UNCOMFORTABLE with brakes, even still able to block the brakes if needed.

all good ex for the warning light on most of the time & the slight leak? I'd open one side(not sure which one) & press the pedal to shift the valve back to the middle so it stays off & see if the leak looks fixable

for more exploded view, I can explain the diff on switch assemblies...

the one I have now is the replacement part This same one what I removed the bracket:


what carries the bottom switch on diagram I made and attached, and is "rebuildable" ( I can remove the central stud ), not like the tipical push in kind than originals pieces carries on what are sealed:



Kelsey Hayes in my case but switch is the same on Bendix too.

Now, I can replace the O ring at switch on the replacement piece.. fine, but I don't know if is normal to get a pressure enough to squirt or get wet at top of stud. IF IS NOT NORMAL because brake fluid shouldn't be running through the warning light piston section, then the problem is not really at switch O ring or assembly, and is more at pistons O rings or wherever inside the dist block assembly.

I couldn't find a leak on the rest of the system. haven't dissasembled the rear brakes, to check for wet areas at cilinder, but front deposit at MC ( rear wheels deposit ) IS AT SAME LEVEL SINCE EVER!

checked brake drums for adjustment and leaks... did need a small adjustment ( does the autoadjustment stuff really work ? ), but couldn't find any leak ( unles I'm blind ).

SO aparently the dist block/prop valve went bad JUST THREE YEARS ?

ANYWAY, PLEASE ONCE AGAIN. Is it normal to get pressure at switch section of dist block ? shouldn't be both systems isolated one from the other, rear and front, unless some problem on one of the system making a bypass by the prop valve ?

IT COULD BE THE PROP VALVE ITSELF damaged ( maybe spring went bad ? ) I'm able to repleace that section with another valve and spring from another prop valve, to check.

when I dissasembled the switch I was able to see the piston moved toward to rear.

front brakes are still dragging, just slightly, but still... at this point I dunno exactly what to do.

No, you shouldn't have brake fluid at the switch. There might be a small amount of residual leakage past the shuttle valve seals though. Slight drag ( you should be able to turn the wheels by hand easily ) of the front disc pads is normal. This is what keeps crap from between the pads and the rotors. If you can't turn the wheels by hand, fluid is not returning to the master. Check that you have some free play between the master push rod and the master front cup. Remove the switch. step on the brakes. If you have lots of fluid coming out of the switch hole, the porportioning valve is bad - 3 years old or not. Replace it. Do the warning light adjustment per Rapid Roberts post - after you have bled everything ( and it doesn't make any difference where you start your bleeding proceedure )and fixed any leaks.

thanks...

then definitelly prop valve came bad because is the ONLY leak I have. I'm thinking on the metering valve section stuck and thats why I'm having residual pressure at pads, AND switch piston is getting moved to turn on the light

I know about front brakes dragging, because I'm able to slightly smell the pads burning

According to my supplier, most of those repro iron prop valves are defective.

yes, but there is not another solution for a factory replacement unit ( beside used )

( I'm now thinking on a NOS unit being sold LOOONG TIME AGO! just a few months later I got the repro unit ) at the end nobody bid on it.

THERE SHOULD BE some way to rebuilt old units!!! I can't believe is not way to rebuilt it.

How can I get access to the piston ? removing rear brakes seat ?

My old one should just have O rings broken.