Power Front Disk Upgrade Questions...Anyone else run into this???

[elevenssc]

I've got another thread that I could continue, but this topic strays a bit from the title of that thread...so here's another.

I installed a power front disk brake conversion over the winter and I have a few "to do's" that I need some input on...

First, the brake light in the dash is on.  I understand that I need to press the brake pedal down hard to reset the switch in the new factory proportioning valve.  I did this once and bent the eye bolt that connects the pedal to the booster.  The light is still on.  I did get a replacement bolt, but my question is...how hard do I need to press on the pedal to reset the switch? 

Second, With the car running, booster to manifold vac., when I press the brakes to stop at a sign or light, sometimes the brakes stick and dont release when I take my foot off the pedal.  It takes about 5 to 10 sec until the brakes release and I can drive without dragging the brakes.  Also, the harder I press on the brakes, the longer they seem to stick.  Whats up with this???  Anyone else have experience here???  There is some play in the pedal that I need to remove, but pulling up on the brake pedal dosent seem to remedy this situation.

Third, I do have a manually adjustable proportioning valve to the rear brakes that is down stream on the factory porportioning valve.  I did not adjust it out of the box...installed it as is.  What is the "correct" way to adjust the manual proportioning valve?  Could a misadjusted valve here be causing my problem in #2 above?

I'm not too familiar with the inner workings of the brake power booster, but I do know that when the pedal is pressed, there is a check valve that allows the manifold vac to help apply the brakes.  When I take my foot off the pedal, things should return to "neutral".

Oh the joys of aftermarket "bolt-on's"...

[72bluNblu]

Did you change the master cylinder to a disk brake type? It sounds like you still have a drum type master cylinder. Drum master cylinders retain a small amount of residual pressure to keep the shoes in position for braking, disks do not, so if you have a drum master cylinder and disk brakes you would experience brake drag. Not sure if it would effect the brake light though.

[elevenssc]

The master cylinder came with the rest of the power disk brake kit.  I'd assume that it is correct for disk brakes since it came with the kit, but stranger things have happened.  Something to investigate...Thanks 72bluNblu

[72bluNblu]

 

It should be the right master cylinder if it came with a kit, but at this point I'd check the part #'s or casting or something. It wouldn't be difficult to mix them up.

[elevenssc]

I did call the tech help line for the brake kit manufacturer.  The tech guy I talked to mentioned that they dont sell power drum kits, so it should be the right master cylinder.  I'll still investigate this one though to make sure.

Tech guy also mentioned to get the manual adjustable proportioning valve adjusted to remove this as a possible source...although he didn't think it could be...

[elevenssc]

Just a note to close the loop on this post.  I did adjust the manual proportioning valve today and the "not letting go" problem seems to have gone away.  I dont understand how the proportioning valve could keep pressure in the system when I let my foot off the brakes, but it not happening anymore since adjusting it....go figure

[elevenssc]

Brake light in the dash is still on no matter how hard I push on the pedal.  Still have to figure this one out...

[Changin Gears]

The push-rod between the master cylinder and booster is adjustable.  If if is too long, it will cause the brakes to stay on.  A disc brake master cylinder is easy to identify, it has one resovior larger than the other. this is  because disc bakes self adjust by the piston moving out.

[422STROKER]

I believe the reset procedure is in the Service manual.  I don't have access to mine right now(storage) but I remember having to do this when re doing my lines as well.  Try turning the key to the run position while pressing the pedal down.

Tom

[Changin Gears]

Have you diagnosed the trouble to the switch in the brake tee?  The light also comes on with the parking brake.  Try unplugging them one at a time.

[elevenssc]

The push-rod between the master cylinder and booster is adjustable.  If if is too long, it will cause the brakes to stay on.  A disc brake master cylinder is easy to identify, it has one resovior larger than the other. this is  because disc bakes self adjust by the piston moving out.

I've got my pedal adjusted so there is no free play in it (no play when pulling up on the pedal).  I dont think it is too long because the brakes dont drag on their own...just wouldn't let go after being applied. 

I did have to reposition the brake light switch...  This shouldn't be keeping the dash light on though...should it???

I do need to check the parking brake switch.  I cut the old cable out (rusted solid) and have not replaced it yet.  Good info.

10-4 on the resivoir...one reservior (feeding the front brakes) is larger than the other (feeding the rear brakes).

[Changin Gears]

There is a releif port in the master cylinder that must be uncovered when the brakes are released to let the fluid flow back from the calipers/wheel cylinders.  I had the problem you are describing once and had to shorten the push rod between the master cylinder and booster.  I'm hoping someone can learn from my mistakes.

[Chryco Psycho]

makes sure the pivot bolts for the pedal linkage are not too tight
 park/emergency brake is on the same light so that could be the light problem as mentioned