K-H brake swap done, but doesnt stop!

[mopower440]

well, got them rebuilt, but never again! I will use them for the time being but will be looking for some 1973-76 A-body calipers, rotors and spindle/hub so next time these calipers need rebuilding, i will swap it all out for the single piston style. I fought with thise damn dust boots till i was blue in the face, trying to get them to stay put while installing the pistons..what a pain in the rear! FINALLY got them done.

Got it all back together, new disk brake MC and all only to be severely let down! I can make it lock up now, but i literally have to stand on the damn pedal!! What a let down..The drums worked better and wish i would have left them on there! Cant believe how much force i have to put on the brake pedal. Also, when bleeding the brakes, i couldnt get any fluid from the rears for some reason..? Fronts bled out fine..any ideas?

 

[Garrett Ellison]

Check your rear brake hose from the body to the axle and the proportioning valve. Either the rear hose has collapsed or the proportioning valve is not letting fluid to the rear of the car. Fluid is from the master cylinder for the rear brakes is probably stacking up solid on its way to the rear brakes somewhere, that would make effort very high on the pedal. I would start at the newly installed proportioning valve and work back to see where you can get fluid back to.

 

[mopower440]

Check your rear brake hose from the body to the axle and the proportioning valve. Either the rear hose has collapsed or the proportioning valve is not letting fluid to the rear of the car. Fluid is from the master cylinder for the rear brakes is probably stacking up solid on its way to the rear brakes somewhere, that would make effort very high on the pedal. I would start at the newly installed proportioning valve and work back to see where you can get fluid back to.

What do i do if its the prop valve? Its a nice stock one from a 1973-76 A-body car. Its letting fluid through to the fronts just fine, i do know that..

 

[Garrett Ellison]

Here is a link that will help you out. It should be pretty obvious if it’s the problem if you crack the line open on it that goes to the rear brakes, you should have fluid immediately.
1970 - 1976 Mopar Combination Valve Autopsy | Muscle Car Research LLC

 

[mopower440]

Here is a link that will help you out. It should be pretty obvious if it’s the problem if you crack the line open on it that goes to the rear brakes, you should have fluid immediately.
1970 - 1976 Mopar Combination Valve Autopsy | Muscle Car Research LLC

So if i unscrew the rear brake line at the prop valve and fluid comes out, its fine? Is it a common problem with these prop valves to block the fluid to the rear? I hope its not that as its total hell to get to!

 

[Garrett Ellison]

It’s not common for it to in my experience. I suggested that as a starting point to see where fluid is making it to, but it would be easier to crack the line at rear hose from the steel line off the body. If nothing starts dripping out when you take it loose, you should be able to put a piece of tubing over the line and put the open end into a container and get some fluid out of it by pumping the brakes. If it’s the rear hose not letting fluid pass, you should have fluid almost as soon as it’s cracked open. If it does, retighten it and then crack the lines loose at the Y-Block on the axle to see if fluid starts to come out. If the hose has to be changed, the Y block has to be removed and then screwed onto the new hose.

 

[mopower440]

It’s not common for it to in my experience. I suggested that as a starting point to see where fluid is making it to, but it would be easier to crack the line at rear hose from the steel line off the body. If nothing starts dripping out when you take it loose, you should be able to put a piece of tubing over the line and put the open end into a container and get some fluid out of it by pumping the brakes. If it’s the rear hose not letting fluid pass, you should have fluid almost as soon as it’s cracked open. If it does, retighten it and then crack the lines loose at the Y-Block on the axle to see if fluid starts to come out. If the hose has to be changed, the Y block has to be removed and then screwed onto the new hose.

Man, i hope it is just that rubber hose! Even if it has collapsed though, wouldnt i be able to get some fluid past it when standing on the pedal though or no?

 

[Garrett Ellison]

Usually they let fluid by them to the brakes but it doesn’t have enough brake spring pressure to force it back into the system. But if it’s bad enough, it won’t let enough fluid though to operate the rear brakes. It’s really strange to me that you couldn’t get fluid to the rears when attempting to bleed them. I figured if the drum brakes were working and then you change the balance switch out for a proportioning valve and now you’re not getting fluid to the rears, it’s probably the source of the trouble.

 

[mopower440]

Usually they let fluid by them to the brakes but it doesn’t have enough brake spring pressure to force it back into the system. But if it’s bad enough, it won’t let enough fluid though to operate the rear brakes. It’s really strange to me that you couldn’t get fluid to the rears when attempting to bleed them. I figured if the drum brakes were working and then you change the balance switch out for a proportioning valve and now you’re not getting fluid to the rears, it’s probably the source of the trouble.

ya, thats what im afraid of..probably is that prop valve.. weird how the fronts bled just fine though, plenty of fluid there..

 

[Garrett Ellison]

I did have a ‘73 D100 once though that the rear line had completely collapsed and was on the verge of blowing out. Using a length of 4x4 wedged between the pedal and front of the seat revealed it was bulging at the point where it had started unraveling internally. It wasn’t getting a drop of fluid to the rear brakes on that one.

 

[Inertia]

well, got them rebuilt, but never again! I will use them for the time being but will be looking for some 1973-76 A-body calipers, rotors and spindle/hub so next time these calipers need rebuilding, i will swap it all out for the single piston style. I fought with thise damn dust boots till i was blue in the face, trying to get them to stay put while installing the pistons..what a pain in the rear! FINALLY got them done.

It gets easier with practice .

lol

 

[mopower440]

well, looks like its the rear hose!! I have fluid to the hose, but nothing out of it. ordered a new one from rock auto today.

 

[Garrett Ellison]

Good Deal! Glad to be of assistance. Be sure to flush a crap ton of fluid through your rear cylinder lines in case any debris have sloughed out of the interior of the hose.

 

[mopower440]

Good Deal! Glad to be of assistance. Be sure to flush a crap ton of fluid through your rear cylinder lines in case any debris have sloughed out of the interior of the hose.

Thanks man!

 

[Edsrt]

Thanks man!

I have a 1970 Duster with the factory manual kelsey-hays 4 piston calipers and they do stick acasionaly every spring I would pull them off to make sure there free . on another note these are not the best performing brakes when pushed and properly adjusted drums have a better feel for every day driving. Now I am contemplating stepping up to Willwoods since bracket race the car more than street drive the car and slowing the car down from 115 mph takes quite a bit of effort