57 Chevy has no brakes!

BFS57 · February 19, 2010, 10:30:09 AM

Hello;
Bruce Dorsi;
I thought you only had to use hold off valves if the master was in the frame level not up above on the firewall? I also have been driving this car with this exact set up for 5 years without any problems until I decided to put in new wheel bearings and front disc pads, thats when everything went to hell in a hand basket!
Upon taking the master apart (old one) I found it had enough gritty, rusty, cruddy junk in it to warrant replacement! Thats when the fun begun!
I also had to replace the real wheel cylinders as one was leaking and the shoes were deteriorated (as in linings coming off the metal!)
I checked the output from the new master to the old one and the inside diameter of the new one was the same as the old one. I am considering changing my whole set up now as this doesn't seem to want to cooperate and I am getting frustrated trying to get back what I already had!
Next I am trying Enjenjo's thought to clamp off the front brake hoses to isolate front from rear circuits!

Bruce

Bruce Dorsi · February 19, 2010, 10:57:18 AM

Quote from: "BFS57"Hello;
Bruce Dorsi;
I thought you only had to use hold off valves if the master was in the frame level not up above on the firewall?

A hold-off valve is not the same as a residual pressure valve.

Here's more info:

http://ecihotrodbrakes.com/brake_facts.html

wayne petty · February 19, 2010, 12:33:17 PM

just a thought from the side lines...

what kind of calipers do you have???/

i would like to know... if they have caliper slide bushings.. and if the calipers are free to slide on the bushings..

on other cars.. i have found that some other tech had greased the caliper slides with silicone dielectric tune up grease.. this locked the caliper slides so tight... when i tried to get them to move.. not even with my 30 ton press could i budge them....

why are caliper sides important...

on calipers with pistons on one side.. when the piston is pushed out with the hydraulic pressure from your foot moving the pedal.. the inner pad is pushed against the inner rotor face... for the brakes to actually work properly... the caliper has to slide a bit so the squeezing force applied is equal on both inner and outer pad...

~~~~~~~~~~

if the caliper side is locked.. the piston has enough force to distort the caliper or bracket... and depending. the bracket or caliper may bend back.. this bending to squeeze the rotor if it is enough will result in a low pedal....

i am wondering... since you have a kit for the disc brakes.. if any spacers could have fallen out.. washers in the brackets installed wrong...

were the wheel bearing races installed all the way in..

any chance that a spacer got left out on the spindle.. or something that moved the rotor centerline so the caliper does not line up perfectly.. or that it is changed enough to keep the caliper from sliding properly...

can you pull the front wheels and see if there is any gap between the pads and the rotor when the brakes are not applied........

can you use a C clamp and retract the piston and see if the caliper is free to slide... use care... you don't want to bend the rotor... or warp it..

why did you change the wheel bearings.. were they worn..

do you still have all the old parts you took off.. for measurements.. or part number examination??

these are only thoughts..

~~~~~~~~~~~~~~~~~~~~~~~~

BFS57 · February 19, 2010, 03:05:15 PM

Hello;
Wayne;
My calipers are from a 69 Chevelle. As far as they go, They are moving, sliding back and forth over the rotor. I replaced the wheel barings because I could feel at least one was bad. I had a guy do the wheel barings, he used a tool to drive the races down into the wheel and I am pretty sure that the bearings were proper for the application as I called the maker of the kit and they recommended the part number I got.
I do know that the guy that did the wheel barings did grease the bolts that the calipers slide on with some kind of grease and I think he put some anti sieze on the threads of the bolts. Mean anything?
I still have to do the clamp off of the front brake lines and try that.
I will make a better inspection of everything you have mentioned, just to rule out any problems there.

Bruce

bowtietillidie · February 19, 2010, 08:17:24 PM

I have been following this post with great interest. With that said I have either missed or it has not been up about calipers being on the wrong side of the car. A quick easy check is as follows . Check the position of the bleeder screws...... If both bleeders are between 11:00 and 1:00 on a clock face they are mounted right .......... If one or both are mounted between 5:00 and 7:00 they are mounted wrong . Take both and swap sides ( left side goes on the right wheel ...... and right side goes on the left wheel.)
Next bleed brakes and start engine check pedal travel for firmness. ALSO should have just on caliper that is mounted wrong ..... Remove it go to your friendly parts store and tell them you want a caliper for the side of the car you removed the caliper from . Before You leave the parts store get the counter man to show that he gave you the right part . This may prove to be the trickiest part of the whole endever.

BFS57 · February 19, 2010, 08:27:47 PM

Hello;
thanks for the info on the caliper mounting. Let me assure you, these calipers are mounter right. This car has been driven daily for almost 6 years and during that time the brakes have always been SUPER! It is only after I got a wild hair up my * to put in new wheel bearings and disc pads that I am now seeming to have some sort of a problem with the brakes not functioning as they had in the past, a thing I find hard to believe as before I had brake power enough to throw you out the front window!!! Now I can't even trust it to stop!!!

Bruce

Charlie Chops 1940 · February 19, 2010, 09:40:51 PM

I'm just curious...have you had the wheels off the ground? Do the tires spin freely? Just kind of thinking out loud.....

If this car operated for 6 years then something has changed. Caused either by some new part, or something unwittingly damaged by the mechanic. Or just a coincidental failure after the other work was done.

Charlie

wayne petty · February 19, 2010, 11:19:02 PM

pinching off the brake lines... the rubber hoses lets you know... if the problem is at the master cylinder or at the wheels...

1A: pinch off the left front first...

1B: test the pedal ... hard or soft...

2A: pinch off the right front next...

2B: test the pedal hard or soft...

3A: pinch off the hose to the rear end... above the axle...

3B: test the pedal hard or soft..

now... i tend to use 3/16 inverted flair unions

http://contentinfo.autozone.com/znetcs/product-info/en/US/ags/BLU-3C/image/8/

and 3/16 inverted flair plugs to block things...

http://contentinfo.autozone.com/znetcs/product-info/en/US/ags/BLF-60C/image/8/

both of these use are threaded 3/8-24 threads on the fittings..

warning.. pinch the rubber brake hose/line off hard enough to close it... but not enough to CRUSH it..

what makes me thing that there is something wrong at the front is all this happened after you did the front brakes...

perhaps.. the pads got installed wrong.. or the wrong pads.. there are some variations... including some D52 pads.. for rear disc brake applications.. with a stud/ raised area to keep the caliper piston from turning... just in the right spot to give one fits.... front brake calipers don't need this..

somethings wrong up front... have somebody who is a brake mechanic for a living take a look at it..

if you weren't on the far side of the country i would stop by..

Mikej · February 20, 2010, 09:17:27 AM

Did you have the rotors turned or replaced with the pad change?

BFS57 · February 20, 2010, 10:12:37 AM

Hello;
I am contemplating finding a brake specialists but don't know any around here in Orlando. Guys say that they are but I can tell that they don't have what it takes to diagnose my problem.
Yes, I believe that something is wrong with the front brakes. I will try to look at the old disc linings and see if the new ones are right. They seemed right as the spring clip retainers fitted right and seemed right I still have a feeling that this may be internal as when I took the master apart there was so muck gritty rusty crud inside I just wonder if any of that junk was inside the calipers? When the guy that put on the new pads squeezed the pistons, he didn't use a tool to do it, just a large "C" clamp and he didn't do it slowly, he did it quite rapidly which resulted in the master going out. It wouldn't suprise me if I had to replace the two front calipers also.
I did not have my rotors "turned" they looked pretty good so I opted not to have that done. Maybe I should?
Unfortunately (fortunately) my work schedule is pretty intense right now so I don't have a lot of time to devote to really chasing this problem. I just take some of the suggestions and try those and then try some other things as time permits.

Mikej · February 20, 2010, 11:31:20 AM

I hope I didn't discourge you. You should turn the rotor and drums, or replace, every time you replace the pads. The rotors could have to much run out. This would push the piston into the bore farther. You would need move fluid for it to come out far enough hence an addition quick pump. Even then the new pads will have to from to the old rotor grooves. Same goes for the rear. You may want to start over. New shoes and pads. Turn the rotor and drums.

Mike

wayne petty · February 20, 2010, 12:20:57 PM

dirty fluid from the brake calipers being pushed back into the master can damage the master...

full stroking the master cylinder after a brake job can also damage a master.. as the SOFT seals are run across corrosion in the bore where there has been no wear.. ON old master cylinders..

pinching off the front brake hoses... like i described on my previous post.. will give you an idea if the system has problems with the calipers shoes or not..

or have for even more work.. take the front wheels back off.. and have someone work the pedal... while you watch the calipers work.. see if one or both have excessive movement when being applied.. they should just barely move.. less than 1/16" .. just barely noticeable..

and i am sorry to say that there are a lot of people who call them selfs auto mechanics.. or auto techs.. who don't really have a clue other than just changing parts till the problem is solved.. that is one of the reasons i try so hard..

i will now let you handle this.. you might want to copy and print the text from this thread...

but i really don't think that the master cylinder is the problem after you have readjusted it to avoid the locked up brakes.. you might want to also examine the rears.. after the lock up...

reborn55 · February 20, 2010, 01:29:50 PM

Sent you a PM--did you get it about a guy in Titusville

BFS57 · February 21, 2010, 09:18:29 AM

Hello;
Wayne, if my calipers are moving more than a 1/16" what should I be looking for to correct this? The times I was bleeding, I am pretty sure that they were moving more than a 1/16!

Bruce

Maxwell007 · February 21, 2010, 03:35:58 PM

A lot of good info has been posted about your problem. I would only suggest that you take a methodical approach to the problem. I worked for a major brake manufacturer for over thirty years and while I get stumped from time to time, believe me.....I think I've seen it all. So, for what it's worth, here's what I would do.
First, buy some brass plugs (flared style...not pipe plugs) and plug both ports on your master cylinder. Then try pumping the brakes. You should not be able to pump them. If you can, you either have air in the master cylinder or it has an internal bypass usually caused by a bad seal.

Next, try the suggestion of pinching the hoses. First, pinch them all and you should have much the same results as the above test. The pedal should not move much if at all. Then release the clamps one at a time, testing your pedal each time you remove a clamp. When the pedal goes to the floor, you have found where your problem is.

I believe you mentioned earlier that you had the line for the rear brake connected the rear port of the M/C. In most systems, this is wrong. The rear piston is the first one that "sees" pedal movement and is usually plumbed to the front brakes.

Next, there was mention of a residual pressure valve. Usually, this valve can be found behind the brass cone shaped fitting just inside the port on the M/C. I looks like a little rubber plug but it has a slit cut in the face of it to allow most of the fluid to return to the M/C while keeping a small amount of pressure in your rear brake system. (Usually about 5 PSI.) As someone mentioned, if your M/C is for a four wheel disc car, odds are that it does not have this valve. This could be part of your problem.

Lastly, I believe you said that the calipers were from an older Chevelle. If so, I would not suspect that they are the cause of this. But, if they are from a mid-eighties car, you may have "low drag calipers" which require a different type of M/C. The low drag calipers were designed to pull the piston back further away from the rotor than older designs. This was done for fuel economy reasons. To compensate for this, the M/C used was called a "quick take up" master cylinder. It had a two stage bore in it. A larger bore in the back and a smaller bore toward the front. You can visually see this when you look at the cylinder. It is fatter toward the firewall end. The idea was that the bigger piston in the back would move more fluild under less pressure. This higher volume of fluid would move the calipers further and quicker. When the pads came in contact with the rotors, pressure would build causing the pressure to transfer through a valve to the front (smaller bore) portion of the M/C. From then on, braking would work just like the old design.
Sorry for the rambling explanation but I have seen "low drag" calipers put on cars with the old style cylinders and the results were much as you have described. The small bore on the standard cylinder just can't move enough fluid to make the pads move far enough, quick enough before you run out of pedal. You indicated that you think you have a lot of clearance between pads and rotors which would lead me to think that you may have low drag calipers...just a thought.
I'll continue to watch this thread and perhaps I can send some photos if you would like.
Good luck!