seriously bummed...HELP

[poppa]

Just switched to power (had power drums) disc brakes,bendix 4 piston. Took wife out for dinner in my car,left went about 4 miles got gas, turned around towards home,got maybe 5-6 miles and car was stopping itself. Wheels were hot,master cylinder was hot. Luckily nobody was coming and I was right by a gas station,made it in and it wouldn't go no mo. Tried pushing it in neutral,wouldn't budge. Opened master cylinder and the front was dirty ,dirty ,dirty.
  I am using dot3,booster was rebuilt,calipers were rebuilt,new brake lines,new hoses,manual prop valve,new pads,new wheel bearings,new races. Just put the discs on so I must have missed something but can't think of what it could be. Did ball joints,bushings,tie rod ends at the same time. After it sat for 20 minutes it was ok,drove home (2-3 miles). Need to find out what caused this asap. On vacation week after Labor day and was planning on doing some country cruising but wouldn't take it like this. Suggestions,opinions and good guesses wanted. Thanks for reading my rant. Bummed

[A383Wing]

master cylinder rod between the booster & master cylinder mis-adjusted?

Bryan

[moparguy01]

I'm thinking your prop valve is misadjusted putting too much bias towards the front, making it stop the car with only the front, overheating your brakes and boiling your fluid. I doubt it's dirty, I bet it's burnt. It's also possible the prop valve is bad entirely.

[poppa]

A383 , would there be a different "adjustment" just switching to discs?? It didn't have any problems before the switch.

Moparguy01 , new manual prop valve from Ehrenberg. I will try to contact him and see if there is a way to adjust these.

Thanks for the super fast replies....you guys should have capes (like super man).

[FLG]

A383 , would there be a different "adjustment" just switching to discs?? It didn't have any problems before the switch.

Moparguy01 , new manual prop valve from Ehrenberg. I will try to contact him and see if there is a way to adjust these.

Thanks for the super fast replies....you guys should have capes (like super man).

Its very possible you had it mis-adjusted the whole time but because drum brakes are adjustable you were able to fix your error (unknowingly) on the other end of things.

Though what Mopar said also makes sense too, could jack up the rear and put it in drive to get the wheels moving and gently apply the brakes and see if they respond.

[moparguy01]

I couldn't even begin to tell you the number of times I've had a brand new part be bad out of the box. I'm just all sorts of lucky with that stuff.

The thing is, from what you told us here, hot master cylinder, hot wheels, dirty brake fluid. You must have boiled the fluid. Not many things can cause that, calipers seized up, Calipers sticking, using the brakes too much, or a misadjusted or incorrect proportioning valve. You have to put LOTS of heat into the fluid to cause that. Its also possible that you somehow got some moisture in the brake fluid, which will dramatically drop your boiling point. That could be from an old bottle sitting around too long with the cap partially cracked or what not.

Hope you get it figured out!

[Ghoste]

I would look at the bias as well.

[tan top]

 oh man  , sorry to here this  !!! 

what the others guys say !

also i know it sounds silly would check front wheel bearings , adjusted correctaly greesed etc etc ,

[flyinlow]

Like Moparguy01 said, maybe some water in the brakes, probably in the caliper or a brake line near a hotspot (header).  The water boils applying the brakes.

Bleed all the fluid out with fresh stuff, try a new sealed can of brake fluid. Make sure the brakes are not dragging when cool. Normally the brakes don't get that hot on a short drive just cruising. 

[poppa]

Unfortunately,after more thought ,they may have been "boiling" when the drums were still on. I drove it to storage last fall,drove it home this spring ,took it to my paint guy (helped  with other stuff) twice (in a different county) and the last time I came back from there, I woke up the next am and was going to work on it and there was brake fluid that dripped all over my nice painted inner fender. Couldn't figure it out. But there seemed to be a "run" mark on the side of my master cylinder. But this,stopping by itself, didn't happen with the drums on and I went alot farther 25-30 miles.
  I will lookat the fluid,routeing of the lines close to headers this am. If I drian the lines and put new fluid in,can I go with dot5?
  Just a fyi , I had the prop valve at the half way point for adjustment.
Thanks for all the quick replies , they are appreciated.

[BrianShaughnessy]

My guess is that there's misadjusted rod from booster to master cylinder.

The more you drove and used the brakes,   the worse it got because the pressure isn't releasing from the front brakes..  after sitting awhile the pressure bled off naturally and you were able to get home.

The test would be to get it to point of fail and then climb under and crack the bleeders on the front caliper(s) and then see if it turns easily after the pressure releases.     You could also repeat the process and try to crack the master cylinder line to see if the wheels turn easily after that.

I've seen old flex brake hoses on camaros rust up internally and cause a 1 way valve to form and experience the same thing but I'm assuming your hoses are new and the design is different from the suspect camaro hoses anyway. 

[poppa]

Is there a measurement to set the rod length? If not should I shorten it up or lengthen it??

[ACUDANUT]

Shorten it. Also I did not know you could adjust a proportioning valve.

[BrianShaughnessy]

Is there a measurement to set the rod length? If not should I shorten it up or lengthen it??

Unbolt master from booster,   pull it forward and shorten the rod a few turns ( it should be threaded)  and see how that goes... repeat as necessary.

[Ghoste]

Shorten it. Also I did not know you could adjust a proportioning valve.

There are aftermarket ones which allow that.

[poppa]

Should I switch to dot 5 or leave the dot 3 fluid??

[Ghoste]

If you're rebuilding the whole system anyway it not be a bad time to switch over to the DOT5.

[poppa]

Never heard of dot 9. I would just be switching fluid,everything is already new or rebuilt. Thinking of the dot 5 just because it has a higher boiling point but concerned about havingtrace amounts of dot 3 left in system (compatibility).

[Ghoste]

Sorry, that was a typo, it is the 5 that I meant to put in there.  I've corrected it now.

[poppa]

Thanks ghoste.

I am now wondering if I should shorten the rod or lengthen it. Here's my cocern , I would have sworn it was the fronts that were stuck but , the dirty/burnt looking fluid is in the front reservoir (for the rears). Thoughts?? I am going to drain system and go get new fluid.
  Also, when I get to adjusting the prop valve , what's the best way to set it correctly? If I turn it in(clockwise) does that lessen the amount to the rears??

[Chryco Psycho]

I didn't read the whole thread but did you remove the residual pressure valve from the master or use a master designed for disc brakes , Drums require a residual pressure valve which is overcome by the springs , discs will stay on with the residual pressure valve in place

[flyinlow]

I don't know how old your brake hoses are, but like Brian said, I have seen old one that restrict. You push the fluid thru with hundreds of pounds of preasure, but the  fluid is restricted going back when you release the petal. Let the car cool and check that the wheel spin freely. Apply the brakes, all should hold, then release the brakes and they should spin freely. If the fronts do not release smoothly when cold you might have a bad flexible hose. If the brakes start dragging when they heat up , could be water in the system.

Dot 3 was oem, should work OK on a normally driven street car, it is glycoh based and absorbs water. Dot 5 is silicon based ,does not absorb water ,higher boiling point, does not easily damage paint,but does not lubricate the seals as well.  

[poppa]

disc master was installed.

So push rod preload,is this when you put the master on and you have to push the master to get it to sit square on the booster?? Like there's a little rock from side to side before the flange makes full contact??

Fluid drained. check
push rod shortened. check
putting in new fluid. check
bleed entire system. after I eat something (raining now anyway)

ok,done eating. Spent last 4 *^%#@* hours trying to bleed this.

thanks for the read. I shortened my push rod about a turn and a half,doesn't "rock" now. May have to redo.

[FLG]

Read here

http://www.dodgecharger.com/forum/index.php?topic=54379.0

[Chryco Psycho]

the pushrod may well be the problem , the master should not rock on the pushrod if it does the piston is being depressed as the master is tightened down which can cause the brakes not to release .
I have also seen the hoses fail internally keeping the brakes applied with the pedal released , you should have new hoses on the front with the conversion but the rear hose could be bad .