Front brake issue

[79ramp]

I just got my hands on a '79 C30 DRW and I am stumped on a brake issue. Shortly after I got it, the front driver side brake got locked up. Seemed like a caliper issue to me so I drug it home and went ahead and put new calipers and pads on both sides. Parts were cheap so I did not delve into diagnosis to know this was for sure the issue (sort of a 'not a bad idea either way' sorta thing).

Well, it turns out the calipers were not the issue. Both sides have new calipers, pads, and rotors and I am still having the same issue. Here is the part where it gets confusing for me: now the passenger side is locking up and I am getting absolutely no fluid out of the driver side bleeder (or the line). This makes me think it is either a proportioning valve or master cylinder issue. Has this happened to anyone else before? Any thoughts?

One other thing noticed while bleeding the brakes, the pedal does not want to return if it is pushed too far down. Also, both lines did not so much as drip fluid while disconnected for the better part of the day, not sure if that is normal or not on these, every vehicle I've ever done brakes on has always at least dripped some.

 

[Honky Kong jr]

I just got my hands on a '79 C30 DRW and I am stumped on a brake issue. Shortly after I got it, the front driver side brake got locked up. Seemed like a caliper issue to me so I drug it home and went ahead and put new calipers and pads on both sides. Parts were cheap so I did not delve into diagnosis to know this was for sure the issue (sort of a 'not a bad idea either way' sorta thing).

Well, it turns out the calipers were not the issue. Both sides have new calipers, pads, and rotors and I am still having the same issue. Here is the part where it gets confusing for me: now the passenger side is locking up and I am getting absolutely no fluid out of the driver side bleeder (or the line). This makes me think it is either a proportioning valve or master cylinder issue. Has this happened to anyone else before? Any thoughts?

One other thing noticed while bleeding the brakes, the pedal does not want to return if it is pushed too far down. Also, both lines did not so much as drip fluid while disconnected for the better part of the day, not sure if that is normal or not on these, every vehicle I've ever done brakes on has always at least dripped some.

I would put brake hoses on it. The rubber ones and flush the system. Hoses of that age tend to brake down inside and won't allow fluid pressure to release in turn will hold the brake on.

 

[79ramp]

I would put brake hoses on it. The rubber ones and flush the system. Hoses of that age tend to brake down inside and won't allow fluid pressure to release in turn will hold the brake on.

That is one of the next plans. The flare nuts are just rounding off so I'm probably going to end up cutting the hard lines and bending new ones so I should rule those out too.

However, with the issue switching sides like it did, it leads me to think the issue may be elsewhere (not that I haven't been wrong many times before though lol).

 

[79ramp]

New MC is installed, new hard lines and prop. valve are coming, new rubber lines are on the bench, ready to go in once I have the hard lines. If this doesn't fix it, nothing will.

 

[kenneth1669]

New MC is installed, new hard lines and prop. valve are coming, new rubber lines are on the bench, ready to go in once I have the hard lines. If this doesn't fix it, nothing will.

Hey I know it’s been a long time since you posted this but I’m having a very similar problem just on the passenger side. Did all the new brake lines, master cylinder and prop valve fix it?

 

[SirRobyn0]

Hey I know it’s been a long time since you posted this but I’m having a very similar problem just on the passenger side. Did all the new brake lines, master cylinder and prop valve fix it?

OP hasn't posted on the forum since 2018, I wouldn't count on him answering, but if you go into what you have or haven't done and what your symptoms are there are plenty of us that will likely try to help you out.

 

[kenneth1669]

OP hasn't posted on the forum since 2018, I wouldn't count on him answering, but if you go into what you have or haven't done and what your symptoms are there are plenty of us that will likely try to help you out.

My front brakes mainly my front passenger side has been locking up. The passenger side can still spin but the caliper still is pushing on the rotor when letting off the brakes. The driver side I think it’s warped because turning it some spots on the rotor are harder to turn than other spots. I think I made another post about it and they said to start with the brake lines and I just finished up doing taht and it didn’t fix the problem. My grandpa has been saying it’s probably the proportioning valve but I don’t want to take that off and have to bleed the hole system but it’s starting to look like that. The master cylinder is also really old and there are little rust flakes swimming around the reservoir and it’s leaking a little bit. So I was thinking if I have to take the valve off and clean it for replace it I might as well get a new cylinder.

Sorry for the dump of thought and I hope it’s alright that I posted it here or if I should have made a new post. Just wanted to know if my thinking was right or if there is something else anyone would recommend doing first before taking everything apart. Thanks

 

[Turbo4whl]

Most likely the rubber brake hose is the failure. What happens the inner hose bladder (lining) detaches and forms a restriction. The master cylinder produces a very high pressure and it gets through to the brake pad piston. When the master cylinder releases it's pressure, at some point the pressure left in the failed brake hose is not enough to push back through the the hose restriction. The brake remains applied.

 

[kenneth1669]

Most likely the rubber brake hose is the failure. What happens the inner hose bladder (lining) detaches and forms a restriction. The master cylinder produces a very high pressure and it gets through to the brake pad piston. When the master cylinder releases it's pressure, at some point the pressure left in the failed brake hose is not enough to push back through the the hose restriction. The brake remains applied.

I replaced the brake line and it’s still not retracting. I only bled the one side tho should I bleed both and see what happens?

 

[Turbo4whl]

Your grandfather may be correct. Any of the old brake parts could be the problem. Since you stated just the right front brake was locked, that hose might be the answer. I re-read your second post. The rust in the master cylinder is not good.

You must be registered for see images attach

Your grandfather must know that the proportioning valve is where the fluid pressure is split to both front brakes. Usually when it gets stuck, pressure either only goes to the front or the back.

This picture is not the correct valve for your truck but it show the lines in and out.

Are you sure the right caliper is not rusted in place or the piston is stuck?

 

[kenneth1669]

Your grandfather may be correct. Any of the old brake parts could be the problem. Since you stated just the right front brake was locked, that hose might be the answer. I re-read your second post. The rust in the master cylinder is not good.

You must be registered for see images attach

Your grandfather must know that the proportioning valve is where the fluid pressure is split to both front brakes. Usually when it gets stuck, pressure either only goes to the front or the back.

This picture is not the correct valve for your truck but it show the lines in and out.

Are you sure the right caliper is not rusted in place or the piston is stuck?

The calipers are brand new and under 1k miles. I bought a new caliper originally and put it on and it didn’t fix it so I returned it.

 

[kenneth1669]

The calipers are brand new and under 1k miles. I bought a new caliper originally and put it on and it didn’t fix it so I returned it.

Almost all the brake stuff is under 1k miles. New calipers, pads, rotors, resurfaced drums and I think we most if not all of the little things in the drums.

 

[kenneth1669]

I was looking into the resovoir and it kinda looks like the hole is plugged?

 

[Turbo4whl]

Is the right hose new?

 

[kenneth1669]

Is the right hose new?

Ya