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Still Working on Locked Front Disks
https://slantsix.org/forum/viewtopic.php?t=8593		 Page 1 of 2
Author:  mszauner [ Wed Mar 03, 2004 7:43 am ]
Post subject:  Still Working on Locked Front Disks
My front disk brakes are still locked. I removed the calipers and cleaned and lubed all the sliding portions. I can compress the cylinder and reinstall so the wheel turns freely. Once I depress the brake pedal and release it, the disks are locked tight again so it is almost impossible to turn the wheel. I have bled the brakes several times. I am suspecting the proportioning valve but the fittings on it will not budge. I am at the point of, gasp, turning it over to a brake shop and let them deal with it. Any other ideas I might try? Every brake component on front and rear are new except for steel lines and proportioning valve. As always, thanks.

Mike
Author:  '65 Dutch Dart [ Wed Mar 03, 2004 11:21 am ]
Post subject: 
I'm thinking of the rubber brake hoses,.. try putting new ones on and you'll be on your way again.

Did your car come with disc brakes, or was it originally a full drumbrake car? Maybe you still have the old mastercylinder under the hood, which has the built in residual valve, this always keeps a little bit of pressure on the line, which is needed for drumbrakes, not for discs,.. just a thought.

I personally don't suspect the prop. valve yet,... :twisted:

Are you working on the 4 piston (per side) Kelsey Hayes calipers? Did you put new rubber rings in? They hardly cost anything.


Hope it works out, let us know
Author:  mszauner [ Wed Mar 03, 2004 11:36 am ]
Post subject:  All New
Everything is new except the steel lines and proportioning valve. I have replaced the rubber hoses, rotors, calipers, rotors, pads, master cylinder, booster and in the rear the wheel cylinders, hardware, drums, and shoes. Everything matched what was on it when I bought it. It seems as though full pressure remains in the calipers on both sides after releasing the pedal. The rear shoes do not remain locked but they do work when pressing the pedal. Thanks.

Mike
Author:  '65 Dutch Dart [ Wed Mar 03, 2004 11:58 am ]
Post subject: 
Ok, I can understand that after buying all of that stuff new you'd want it to work! The reason I thought of the rubber hoses was because they have the tendency to clogg after years (caused by newer brake fluid).

The rear section seems to be working fine, so it's only in the front. The cheapest way of checking if it's in the prop.valve is shortcutting it with some copper line and 2 fittings,.. so just to pretend the prop valve is not there,.. but you're in the US, so you can probably find another p.valve in a junkyard.

Believe me, you must be close, don't give up yet! :o

Job
Author:  Dart270 [ Wed Mar 03, 2004 12:06 pm ]
Post subject: 
Sticking/cocked caliper pistons maybe? You can check to see if they are holding pressure by cracking a bleeder or line and seeing if it squirts after you have let off the pedal.

My other thought is that you got a drum master cyl and the residual pressure valve is doing this (sticking?).

Lou
Author:  mszauner [ Wed Mar 03, 2004 12:34 pm ]
Post subject:  Confused
OK, I am a bit confused. How can I tell if the master cylinder is the right one? I ordered it from the parts store and told them it was for disk and drum and it matched perfectly with the old one. Is there some way I can tell? I had tried to remove the prop valve before to check it out and the fittings do not budge. They rounded even with a fitting wrench and using vice grips did not loosen it at all. I decided to let it be because if I broke the lines I would have that to mess with too. I know that when I open the bleeder valve after releasing the pedal, fluid comes out and I can push the piston in with a C-clamp. So, based on that it seems that for some reason the fluid does not release rather than the piston sticking. I see no way to adjust free travel on the pedal. If you can tell me the difference in the master cylinders, I can rule that out or in. Thanks everyone.

Mike
Author:  mszauner [ Wed Mar 03, 2004 1:02 pm ]
Post subject:  Forgot
I forgot to answer an earlier question. The calipers are single piston sliding calipers. I looked online at the various master cylinders and I see one difference between disk and drum ones is that for drums both compartments are the same size. Mine are sized for the fronts to be larger. When I bought the unit, I bought a mc that came with the booster on because the booster was shot too. However, when I look at the photos, I see that the mc that came with the booster looks different than the separate mc (and I don't mean because the booster is attached...the two mc's look different). Maybe I need to get just a mc?????
Author:  '65 Dutch Dart [ Wed Mar 03, 2004 2:45 pm ]
Post subject: 
yep, the difference can be seen in the reservoir sizes, as you mentioned the disc side is larger. but I remember a disc drum master that had equal size chambers, I think it was on the MP website, not sure. http://www.mpbrakes.com check out that site, there is a lot of usefull info on brakes on there!

But you got the right master, 'cause the fronts are larger, then there's only the prop. valve left,.. you might consider going for an adjustable valve, wilwood sells them. ( not that you really need it, but still... for the control freaks haha :lol: )

Image
Author:  mszauner [ Wed Mar 03, 2004 3:13 pm ]
Post subject:  WHat About This?
Is it possible the new mc is defective? Is it worth swapping out? What if I disconnect the front circuit at the mc....if fluid flies out I would suspect the mc. If not it's the prop valve? How hard is it to install the adjustable valve? As I said, I am unable to remove the fittings from the valve. If it is the valve, I am inclined to have a brake shop mess with it. Sorry for all the questions. Thanks.

Mike
Author:  Craig [ Wed Mar 03, 2004 3:31 pm ]
Post subject: 
Are you perhaps confusing the NORMAL disk brake drag for it being locked up? If you have the wheels off the ground and apply and release the brakes..... it is normal for even proper working disks to drag. Normal driving and cornering will push open the caliper a tiny bit. Maybe you just need to put it on the road and try it that way.
Author:  mszauner [ Wed Mar 03, 2004 3:57 pm ]
Post subject:  Nope
This isn't a drag...it is impossible to turn the wheels at all they are clamped so tight....actually, that's a real drag. :P

Mike
Author:  kesteb [ Wed Mar 03, 2004 4:15 pm ]
Post subject: 
The sliding calibers have a tendency to bind where they slide on the caliber mount. Continual usage frees everything up.
Author:  70valiant [ Wed Mar 03, 2004 4:27 pm ]
Post subject: 
If you went from front drums to disks you HAVE to replace the hydraulic system controle valve. You have the wrong ratio proportioning valve and metering valve in the metering block you are using now
Author:  mszauner [ Wed Mar 03, 2004 4:39 pm ]
Post subject:  Same as was on it
I didn't go from drum to disk..I simply replaced what was on it. I suppose the previous owners could have but I have no way of knowing. The originals worked but everything leaked and the pads, shoes, rotors and drums were badly scored and the booster did not work. So, I just replaced everything. I do not believe it is the calipers sticking because when I remove the retaining bolts and clips, the pads are still locked tight on the rotor. It is definitely the piston not retracting. If I open the bleeder valve, only then can I wiggle it loose. If I compress it with a C-clamp, I get the right amount of space and the wheel turns nicely. The minute I depress and release the brakes, it is stuck so solid the wheel will not budge at all. I am suspecting still the mc or prop valve. Thanks everyone and keep the suggestions coming. I seem to never have the common problem. I always have the one in a million...now if I could only convert that to a lottery win....

Mike
Author:  steponmebbbboom [ Wed Mar 03, 2004 4:58 pm ]
Post subject: 
Id bite the bullet and replace the lines. If the old ones are destroyed when you remove them from the prop valve, so be it. Preformed lines are available in mild steel or stainless. Im going to vote for the prop valve.
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