Bad brake adjustments or bad brake combo?

[69chargerrt]

I've been trying to figure this out for a while- the brakes on my '69 Charger go almost to the floor (well, TO the floor now.  Read on).    They've never worked well since I got the car, and up until the final reassembly from the rebuild I haven't really worred about it too much.  But now since it's close to getting back on the road again, I've been trying to figure this out.   

I thought it was the adjustments so while I had the drums off the rear axle checking on something else, I tried readjusting the shoes.     They didn't seem to be that much out of adjustment (about 3 'notches' out from where the shoes start dragging, as per the FSM) but I noticed that the drums were badly out of round, so the drag was uneven.    Long story short I replaced the drums and it did  make the adjustments easier.   This was a few weeks ago....

I finally got around to attempt to readjust the front brakes last weekend - in order to have some room to do it I need to turn the Charger around in the garage (small garage). But when I tried to back the car out, I found that I had NO brakes at all. The e-brakes worked though (thank goodness). The irritating thing though is that before I worked on the back brakes, at least the brake pedal worked a LITTLE. I think I can still readjust the fronts as the car sits, it's just going to be more difficult to do so.

But I'm now beginning to wonder if the front brakes are the culprit as I had first though. One thing I should mention is that some years ago when I first tore down the car (and again- long story short) I found that the car apparently had factory disk brakes but apparently one of the previous owners had swapped out the front disks (presumably along with the spindles) for 10" drums. I know this because A) the master cylinder/booster set (both which have been professionaly rebuilt) - along with the lines (new) - are specific to disk, and B) I found the proportioning valve (and it looks original), which I understand is used only on disk setups.

I'm wondering if there's a problem with the mismatched disk setup with the drums that's contributing to this poor/no brake issue? Any ideas?

Thanks!
David

[1974dodgecharger]

you still using the same brake booster for your disc front and drum setup?  Gonna need to change that if it was all original drums to a differesnt setup.

[tan top]

does the brake pedel go to the floor , even when the motors not running , say you just get in the car & put your foot on the brake ??

[69chargerrt]

@1974dodgecharger -  yes both the MC and booster are original to the car AFAIK.   Someone mentioned to me that the front drums require a residual pressure valve that my current MC probably doesn't have.     I'm wondering if that would cause the symptoms I'm seeing.    If so I would think that I could just swap MCs to one meant for drums and booster?    I think the residual pressure valves are built into the MCs.

@Tan Top - yes, even with the engine off I can step on the brake pedal and it'll go clear to the floor and bottom out.

[John_Kunkel]

If you suspect the brake adjustment is the problem try adjusting the brakes all the way out so the drums are locked and see if the pedal still drops. If it does, you have a faulty MC (rebuilt or not) or lots of air in the system.

The absence of an RPV in the front system (yes, it's in the MC) might cause a low pedal on initial application but the pedal should come up after a few pumps.

[Dmichels]

+1 for John
The times I had zero brakes has been
1 brakes that had to be bleed
2 a bad master
Being that the master was rebuilt did you bench bleed it before install?
Now do a good 4 wheel bleed
Dave

[69chargerrt]

@John- great idea on the adjustment idea.   On the back brakes though would just setting the e-brake work just as well?  If so then I could do that, and max out the front brake adjustments and see what happens.

@Dmichels - I've bled the system before after having the MC rebuilt.  But that was some years ago so what I'll do before I try out John's idea is to bleed the system first.   And I don't recall bench bleeding the MC back then..... if I can find some scrap tubing I think I can just bleed the MC while it's on the car by disconnecting the lines and routing the scrap lines back into the reservoir.

[Patronus]

I agree with Dmichels, sounds like a problem in the master. If not that its lots of air in the system. To not have any pedal is an odd symptom. The basic principal of the brake system should get you at least some pedal.

[tan top]

@Tan Top - yes, even with the engine off I can step on the brake pedal and it'll go clear to the floor and bottom out.

sounds like air & or faulity master cylinder or both  , is the mastercylinder  A1 cardon or raybestose ,  had  trouble  from thses companys
http://www.dodgecharger.com/forum/index.php/topic,96096.0.html
they would suck in air !

just out of curiosity , all the pedel linkages etc are correct ?

[maxwellwedge]

Is the disc brake proportioning valve still in the system? Is it still a disc brake master?

[69chargerrt]

@tan top -  the master cylinder was original to the car when I got it.    I'm not sure if it's factory original or not- is there a way to tell?  As to it being a reman MC, no it wasn't from any of the manufacturers you listed.   I had it rebuilt at a local shop.   Now that was some years ago- I suppose it's possible that something had gone bad since then but even as I recall when I installed it I was dissapointed at the lack of pedal, thinking a rebuild would've helped (it was ok before I took the car apart - drivable in fact- but wasn't great even then)

@maxwellwedge - yes the proportioning valve is still in the rear brake line and the MC is a disk MC as far as I can tell.   At one time I had looked up the number that was cast in the MC body and that number told me it was for a disk setup.     The booster I IDed using the FSM and it's a Bendix tandem diaphram.  In fact the MC/booster combo on page 5-23 Fig. 1 of the FSM looks exactly like my setup.

[tan top]

original ones will have a chrysler casting number or part number on them , if rebuilt by a local shop , good chance its still the original & just put a seal kit in it ,  i'm thinking this could be the problem , have you tried bench bleading it ,  ?  if its sucking air  , you wont be able to get rid of the bubbles

[69chargerrt]

original ones will have a chrysler casting number or part number on them , if rebuilt by a local shop , good chance its still the original & just put a seal kit in it ,  i'm thinking this could be the problem , have you tried bench bleading it ,  ?  if its sucking air  , you wont be able to get rid of the bubbles

I wasn't able to get to it today but tomorrow I'm going to do the 'lock all 4 brake adjustments' test and see if that helps the pedal travel.   After that I'm going to do a complete system bleed including bench-bleeding the master cylinder, then retry the test to see if that makes a difference.

I'm also thinking- if it turns out that the issue is having mismatched front drums for a disk MC,   I might want to go ahead and do the B-body disc swap and change the front brakes back to what they were.     I was going to do that eventually but I'm thinking that if the mismatch is the issue then I'd be better off doing it now rather than trying to make the system work with drums...

[69chargerrt]

Report #1 - well, I got the front brake adjustment maxed out so the front wheels won't turn, and I used the e-brake on the back brakes to lock them.     Result- same.    Pedal still goes to floor.  

One thing that puzzles me though- in the FSM it says that the adjustment wheel is accessible through the rear adjustment window on the backing plate.    However it looks like the adjustment wheels are aligned more in-between the front and rear adjustment windows.    So while my brake adjustment tool couldn't reach it, my slot screwdriver was able to.

Next step- bench bleed the MC and proceed with bleeding the rest of the brake system.   I'm not sure if I'll get to that today but if not I'll make time for it in the next few days....

Edit- Well I found out what part of the problem is- if not all of it.    I started to get ready to bleed the master cylinder- I popped off the resevoir cover and found that the back resevoir was dry as a bone       I've got a leak in I believe it's the front wheels somewhere.    The front resevoir is still full, btw so I guess my back wheels are ok.

I'll first have to find where the leak is coming from before I proceed ...

[Patronus]

wow.

[69chargerrt]

wow.

Yea tell me about it...   but what puzzles me is that just looking around the car I don't see any spots on the floor from brake fluid dripping out.     I've heard that sometimes the master cylinder can develop a leak in the back and drain the rear resevoir into the booster.     I had recently had the booster out though for a re-rebuild and I never noticed any fluid on the booster, so I'm doubting that happened.    I did notice on the back of the right backing plate some dried dirt so I'm wondering if it seeped out there over time - but even if it did I would've expected a puddle of brake fluid around the tire, which I didn't find...