Buddy is Having a Brake Issue....

[SCOTI]

My buddy is having an issue w/the 70 ElCamino he's doing w/his sons.

He's going through everything (suspension rebuild, brake inspection & service, engine efficiency & asthetics, interior, exterior, etc....). He's currently servicing some brake issues & we've come across one that's puzzling. When he's trying to bleed the rears, the pedal does not sink all the way down in its stroke. He feels it stops about 2/3rd's of the way down. If he opens the front caliper bleeders, the pedal sinks to the floor & he says they bleed fine.

So far, he's replaced the rear wheel cylinders, the rear rubber hose, blown air through the rear lines (to ensure there was no obstruction), the master cyl, & booster. I've mentioned the prop valve issues I've had on my C10's in the past but his brake system was functional (for all intents/purposes) so it's not like he had a panic stop/failure that would cause a prop valve issue. I'm not even sure the prop valve could be related to his issue....

Anyone experienced this before? I hate to tell him to just keep replacing this or that w/o reason since he's doing this stuff on a tight, blue-collar budget.

Experienced help is appreciated here guys!

[CC69Rat]

So, front bleeders closed, rear bleeders open = 2/3 pedal and it stops?

Vise versa and the pedal has full stroke. Correct? What type MC is he running on it? OE booster? How about the push rod, do you know if he used the stock one ? .. just thinking length, maybe the rod is too long and bottoming out .. but why would it go to the floor with the fronts open .. bizarre.

I'll do some digging.

[cdowns]

if he has factory system it is a great idea to have a factory service manual and follow the factory directions for bleeding brakes// i'd try claping the pin in the center position for proper operation and bleeding

[Tx Firefighter]

Scot, that sounds normal.

Think of it this way, he has isolated brake systems front and rear. The fronts are free of air and fully bled. Therefore, when he pushes the pedal down to bleed the rear, he's always gonna have some pedal left at the bottom of the stroke because the fronts are intact and holding pressure. That explains why the pedal falls to the floor when he opens the front.

You can't expect the pedal to go all the way to the floor since the fronts are building pressure every time you pump them.
Posted via Mobile Device

[SCOTI]

Originally Posted by Tx Firefighter

Scot, that sounds normal.

Think of it this way, he has isolated brake systems front and rear. The fronts are free of air and fully bled. Therefore, when he pushes the pedal down to bleed the rear, he's always gonna have some pedal left at the bottom of the stroke because the fronts are intact and holding pressure. That explains why the pedal falls to the floor when he opens the front.

You can't expect the pedal to go all the way to the floor since the fronts are building pressure every time you pump them.Posted via Mobile Device

I thought this as well but wasn't sure the logic was correct.... That little voice within kept me thinking "if the bleeder is open, the fluid has a path of lesser resistance so the pedal should continue moving until the stroke is limited by travel".

Originally Posted by CC69Rat

So, front bleeders closed, rear bleeders open = 2/3 pedal and it stops?

Vise versa and the pedal has full stroke. Correct? What type MC is he running on it? OE booster? How about the push rod, do you know if he used the stock one ? .. just thinking length, maybe the rod is too long and bottoming out .. but why would it go to the floor with the fronts open .. bizarre.

I'll do some digging.

It is an OE replacement set-up from the local auto parts place. It did the same thing on the original stuff as well but since there were signs of wear, he opted to service things now to ensure safety (1 rear wheel cyl was leaking bad; rear flex line was shot, front flex lines were also shot, & master cyl/booster corrosion).

Originally Posted by cdowns

if he has factory system it is a great idea to have a factory service manual and follow the factory directions for bleeding brakes// i'd try claping the pin in the center position for proper operation and bleeding

I felt the prop valve 'pin' was in the correct position since there was fluid coming from each path (front & rear). My previous experience w/a stuck p-valve prevented flow when the pin shifted. But, I have limited experiences w/stuck or faulty prop valves & figured it's better to ask questions vs assume....