73 C20 front brake issue, The right front caliper will not retract, causing the wheel to almost lock.

[Tennessee bound]

I am scratching my head trying to figure out why the caliper will not retract, even with a C Clamp, and the front reservoir is dry.Is there possibly a Proportioning valve issue?

 

[Ricko1966]

It is probably the brake hose,or the caliper itself. Open the bleeder if it compresses then change the hose. If not replace the caliper. The combination valve would affect both fronts or both rears but not 1 side or the other.

 

[Tennessee bound]

Like some sort of Blockage in the Line?

 

[Tennessee bound]

Thanks Ricko, the calipers and master cylinder are both new. I am waiting for a friend to show up to give me an extra set hands before I crack open anything, your reply is appreciated...

 

[Sad Sack]

Like some sort of Blockage in the Line?

Or collapsed hose, or piston in caliper has seized.

 

[Sad Sack]

Jus' curious, and not mentioned, was any other brake work done recently?

 

[Tennessee bound]

Yes, They were All gone through about a year and a half ago, before I trailer-ed it out to Eastern Tennessee from Bakersfield Ca. I have been firing it up about once a month or so, drive it about 5-10 miles and this happens. I don't have my shop up yet and do not have all of my tools out here yet, working on anything is slow going, rolling around on the gravel is not as easy as it used to be

 

[Tennessee bound]

Jus' curious, and not mentioned, was any other brake work done recently?

Trying to get why the front side of the calipers is dry.

 

[Sad Sack]

Trying to get why the front side of the calipers is dry.

You mean front master cylinder reservoir right?
Cuz fluid has to be going somewhere, no wetness anywhere at all?

 

[Radiohead]

Isn't the front reservoir (front being farthest away from the booster) feed for the rear brakes? Check for fluid leakage at all calipers, hoses, wheel cylinders and at the booster end of the master cylinder. It's going somewhere.

Trust me, at the age of these trucks you are doing yourself a favor to replace the rubber lines. If only from a safety prospective. All things equal, the symptoms you describe is usually a bad hose between the caliper and frame. Then perhaps a stuck piston, but "new" calipers rarely have that problem. Trust Ricko1966 and his admonishments, dude knows his stuff. Some of us here do/did this for a living and he falls in this category.

You will find the passengers side rubber line to be the hardest to do, because of the proximity of the fuel pump. At least it's tight on a big block, the driver's side is comparatively out in the open. On mine, and probably yours too, the line fitting to the hose is 3/8, and the funky nut that holds the hose onto the frame takes a 15/16 socket. That last info nugget came at great expense in the four letter euphemisms account and knuckle coverings department. A crowsfoot line socket is your friend here. Prepare to wear some fluid in this operation unless you are exceptionally talented and/or have a lift vs on your back in the gravel (like this old fart does these things).

GL and 73

 

[Keith Seymore]

Isn't the front reservoir (front being farthest away from the booster) feed for the rear brakes? Check for fluid leakage at all calipers, hoses, wheel cylinders and at the booster end of the master cylinder. It's going somewhere.

Trust me, at the age of these trucks you are doing yourself a favor to replace the rubber lines. If only from a safety prospective. All things equal, the symptoms you describe is usually a bad hose between the caliper and frame. Then perhaps a stuck piston, but "new" calipers rarely have that problem. Trust Ricko1966 and his admonishments, dude knows his stuff. Some of us here do/did this for a living and he falls in this category.

You will find the passengers side rubber line to be the hardest to do, because of the proximity of the fuel pump. At least it's tight on a big block, the driver's side is comparatively out in the open. On mine, and probably yours too, the line fitting to the hose is 3/8, and the funky nut that holds the hose onto the frame takes a 15/16 socket. That last info nugget came at great expense in the four letter euphemisms account and knuckle coverings department. A crowsfoot line socket is your friend here. Prepare to wear some fluid in this operation unless you are exceptionally talented and/or have a lift vs on your back in the gravel (like this old fart does these things).

GL and 73

Not in '73.

Front (large) reservoir feeds front brake system.

When we went to the aluminum master with the plastic reservoir it switched.

But the large reservoir always feeds the front discs.

K

 

[Goldie Driver]

Not in '73.

Front (large) reservoir feeds front brake system.

When we went to the aluminum master with the plastic reservoir it switched.

But the large reservoir always feeds the front discs.

K

Hmmm - my 1980 is set up with the cast iron master cylinder and the reservoir farthest from the pedal , closest to the radiator ( front ? ) feeds the rear brakes.

The one closest to the pedal - that feeds the front brakes - does seem to be the larger one.

https://www.gmsquarebody.com/threads/rear-brakes-locking-up.46675/post-1000187

 

[Turbo4whl]

Like some sort of Blockage in the Line?

Yes, what happens on an old brake hose, the inner lining (bladder) separates. High brake line pressure pushes through and applies the brake. When the pressure releases the fluid cannot return because the bladder (inner lining) acts as a check valve. Brake stays applied.
@Ricko1966 explained how to check for bad brake hose.

 

[Radiohead]

Now I have to go look at mine to double check. It's cast iron too, and I'm leaning towards the closest to actual front reservoir is indeed the front brake one. I suppose I had 80's forward aluminum cylinders in mind earlier. Still, the rest holds up.

 

[Radiohead]

Yup, Keith is correct. So in this application the forward reservoir is for front brakes. That is the first place to look for a leak.

Went and looked at the '79. Sho 'nuff.

You must be registered for see images attach

Pardon the mess