68 Charger Front brakes holding on(delayed)

[91r/t]

Hey all, when I apply the brakes on my Charger (power front discs, rear drum) the fronts will hold on after I release the pedal. Its like a 4 or 5 second delay and seems to be getting worse. Sometimes it will not do it but most of the time it happens now. I noticed the engine running hotter today, so when I got home the car felt as if it was dragging and not rolling freely. I felt the front wheel and they are scalding hot. No way are the calipers hanging like that so I think its the prop valve. Any insight? My buddy said he bought a new valve a month ago and it had a delay and he returned it. He used a used OEM valve from the shelf and it fixed it. I think my valve is shitting the bed too and sticking. Anyone have this happen?

 

[WP29440SE]

the prop and hold-off valves ,(which I believe yours should be separate pieces) are extremely easy to take apart and clean. you could have a rubber line collapsing internally causing the caliper release delay. I would highly recommend you go through the entire front system . I've had calipers completely lock up a rotor and it wasn't fun.

 

[mopar 3 B]

Bad brake hoses will hold residual pressure. They may look fine on the outside. The rubber falls apart on the inside.
Just like clogging an artery.

 

[91r/t]

I know the hoses do collapse, but they are fairly new. They definately are not the originals. I find it hard to believe both calipers are hanging up equally with no pulling and at the exact same time. It is sparatic so the hanging calipers would be constant I would think. The prop valve controls the pressure when the pedal is released correct? I believe it is holding pressure on until it releases. If I bang on the pedal it'll help it release most of the time.

 

[Billccm]

Wrong fluid put into master cylinder?

 

[91r/t]

Standard dot 3 is all I've used......

 

[gregpurcell]

I once had a B body that had the wrong length master cylinder pushrod which would occasionally not release when the foot was released from the pedal.

 

[91r/t]

I once had a B body that had the wrong length master cylinder pushrod which would occasionally not release when the foot was released from the pedal.

Yeah I thought about that, but it seems to be getting worse and I would think that rod would kind of stay constant you know....That’s why I was leaning towards something sticking. The only reason I went right to the proportioning valve was that my buddy just put one on his barracuda and it had like a five second delay, which is exactly what mine is doing. It’s almost like it’s delaying for three to five seconds or so and then releasing but not all the way

 

[bm02tj]

If you where lucky and had a stupid mechanic some time in its life use vice grips on the hoses
you should start with new hoses and bleed everything then test
as you are not sure how old the hose are REPLACE them

 

[bm02tj]

It also could be build up inside calipers slowing piston return
Put on jack stands and have a friend apply brakes and check
if holding open bleed screw if still holding replace calipers or rebuild

 

[91r/t]

Well my buddy restored the car about 10 years ago and replaced everything so they’re not that old. And even if one was to go bad that soon, both wheels are smoking hot so I highly doubt both hoses took a **** in 10 years

 

[91r/t]

the prop and hold-off valves ,(which I believe yours should be separate pieces) are extremely easy to take apart and clean. you could have a rubber line collapsing internally causing the caliper release delay. I would highly recommend you go through the entire front system . I've had calipers completely lock up a rotor and it wasn't fun.

I'm going to jack it up tonight and check calipers and see what is going on. What is inside of the prop valve? Check valves or anything?

 

[91r/t]

Ok, I found some brake fluid on the back side of the master cylinder by the area where the booster rod goes into the back of it late last night I forgot to mention. Is there any check valves inside the master that could be sticking/leaking causing the brakes to hold on for a period of time? Also......Master looks to be a equal reservoir on both front and rear which is usually a drum/drum master correct? I think I may put a new disc master cylinder on it before going anywhere else because its leaking anyway and I want to be sure a disc/drum master is on the car before chasing any other direction.

 

[91r/t]

See below the photo.....master cylinder looks like equal reservoirs to me and drum type I know is usually like this.

 

[R/T Boy 67]

Drum masters have residual pressure valves in them, which would certainly cause your problem.

 

[91r/t]

Drum masters have residual pressure valves in them, which would certainly cause your problem.

Yea, I am going to change that Master before doing anything else.

 

[WP29440SE]

I'm going to jack it up tonight and check calipers and see what is going on. What is inside of the prop valve? Check valves or anything?

just some springs and O-rings , they are on plungers . the main purpose is to prevent nosedive from the front discs applying too soon. some times you will get crap inside them that will cause issues, but I would start with the correct master cylinder and move to the proportioning valve. if it's leaking out of the back of the M/C , I could almost guarantee it's sucking air as well

 

[91r/t]

just some springs and O-rings , they are on plungers . the main purpose is to prevent nosedive from the front discs applying too soon. some times you will get crap inside them that will cause issues, but I would start with the correct master cylinder and move to the proportioning valve. if it's leaking out of the back of the M/C , I could almost guarantee it's sucking air as well

I will try it for sure. I am going to work through the system starting at the master and working down. I may look at the calipers and hoses quick but like I said....they are both hanging equally and stay hanging equally, so it seems its elsewhere.

 

[91r/t]

It was that ******* master cylinder! I just swapped it tonight and now the car rolls farther and freer than ever. The brakes kind of suck after bleedin, but I think the front pads are glazed from hanging that whole time and getting super hot. I think I’m going to slam a new set of front pads on it in the next couple weeks but it’s way better already. I have a really hard pedal just doesn’t grab much, but like I said I think the pads are fried from getting so hot. Thanks again for all the advice everybody! Another mystery solved.

 

[WP29440SE]

excellent!