Unkown fitting on rear brake line

[xm20k]

It's only an issue when driving and pumping the brakes a couple times in park causes them to work again. Sometimes they don't work at all and sometime it's while you are breaking, also the front will still stop me but only with the petal all the way down. There is also no leaks, I just replace the rear wheel cyclinders as one of them was leaking. I have also bled them and re check for any air and replaced the brake booster. I might get a new proportioning valve to see if that fixes it too. I have only had this truck since December so I'm still figuring all this out and deeply appreciate all your help, truly thank you.

Sounds more like a bad/wrong master cylinder. If it was prop valve or this load valve not sending fluid to the rear, you'd still have good fronts, and the pedal would feel normal. just no rears. This sounds like the master isn't holding pressure.

Sounds like my old F100 it didn't leak at the rear, but the piston would just push past the fluid and not make pressure unless pumped several times.

 

[Chevy 88]

Sounds more like a bad/wrong master cylinder. If it was prop valve or this load valve not sending fluid to the rear, you'd still have good fronts, and the pedal would feel normal. just no rears. This sounds like the master isn't holding pressure.

That could be. Might just be a funky master cylinder.

Try starting the engine and then pumping the brakes several times, and then stand on the peddle. After 30 seconds, does it bleed down at all? Do you lose any peddle?

 

[bucket]

Failing master cylinder, air in the system or rear shoes out of adjustment are probably the biggest offenders when it comes to the issue you are describing.

 

[tvjthomas]

That could be. Might just be a funky master cylinder.

Try starting the engine and then pumping the brakes several times, and then stand on the peddle. After 30 seconds, does it bleed down at all? Do you lose any peddle?

It does bleed down, when I replace the wheel cyclander the rear shoes appeared to be alright and would adjust out on their own when pressing the petal. They also had plenty of life left to them.

 

[tvjthomas]

It also seems to be more common at lower rpms, hence why I replaced the brake booster and everything feeding it.

 

[Ricko1966]

A bad booster causes a hard pedal not a low pedal. If you are loosing fluid it has to be going some where,find where the fluid is going the shoes moving out when you step on the pedal is not them adjusting. You need to learn how to adjust brakes and you need to find your leak. @bucket has given you good advice. I'd pull the master loose and look at the backside of it,if it's damp it's leaking,that's probably where it is. If its bypassing that is your pedal problem,or part of it.. I also agree I wouldn't pull the load compensating valve if it was plugged the pedal would be high,not low.

 

[Chevy 88]

It does bleed down, when I replace the wheel cyclander the rear shoes appeared to be alright and would adjust out on their own when pressing the petal. They also had plenty of life left to them.

Well, if it repeatedly bleeds down - then there is a loss of pressure. Either through the master cylinder piston seals, or an external leak of some sort. It should hold firm indefinitely.

 

[tvjthomas]

I will have to pull the master and check, bit I have been watching the reservoir closely since the brakes have started feeling strange and visually inspected all lines. So I know there is no leaks.

 

[Ricko1966]

I will have to pull the master and check, bit I have been watching the reservoir closely since the brakes have started feeling strange and visually inspected all lines. So I know there is no leaks.

if you are not loosing fluid no reason to pull the master to look for a leak. Adjust the rear shoes first see what that does. If the pedal still doesn't come up and won't hold pressure AND YOU ARE NOT LOOSING FLUID. Change the master. Sorry I misread I thought post 1 said you had a leak.

 

[Chevy 88]

I will have to pull the master and check, bit I have been watching the reservoir closely since the brakes have started feeling strange and visually inspected all lines. So I know there is no leaks.

A leak that causes the peddle to drop will barf out about about 1/2 a shot glass of fluid with every pump, so it won't take that many pumps before your are either out of brake fluid, or have some driveway art to slip on. The only way the peddle can drop without an external leak, is if the master cylinder is leaking internally. It basically forces fluid from the high pressure side to the low pressure side, by leaking fluid past the rubber seal that is supposed to prevent that from happening. A new master cylinder on Amazon is like $30 on Amazon, usually with free next day delivery.

Just remember to bench bleed it before you install it, to save yourself some work.

 

[tvjthomas]

A leak that causes the peddle to drop will barf out about about 1/2 a shot glass of fluid with every pump, so it won't take that many pumps before your are either out of brake fluid, or have some driveway art to slip on. The only way the peddle can drop without an external leak, is if the master cylinder is leaking internally. It basically forces fluid from the high pressure side to the low pressure side, by leaking fluid past the rubber seal that is supposed to prevent that from happening. A new master cylinder on Amazon is like $30 on Amazon, usually with free next day delivery.

Just remember to bench bleed it before you install it, to save yourself some work.

That seems like it would make the most sense with what's going on, I will probably go ahead and replace that and double check the rear adjustment while I'm at it.

 

[Grit dog]

Coupler

Might work but that’s alot of bending on old brake lines.
I haven’t removed the one on the K20 yet. It’s not hooked up even though some one made a crude extension for it for the lift.

 

[bucket]

if you are not loosing fluid no reason to pull the master to look for a leak. Adjust the rear shoes first see what that does. If the pedal still doesn't come up and won't hold pressure AND YOU ARE NOT LOOSING FLUID. Change the master. Sorry I misread I thought post 1 said you had a leak.

This here^^^ @tvjthomas