We started trying to bleed the brakes on the wagon this afternoon and we just can't seem to get air or fluid to the front disc brakes. I have a 84 Mustang booster and a new Mustang mater cylinder,,I also used the proportion valve from the same mustang. I have the rear working good,,any thoughts? HRP
Are you getting full travel of the piston in the master cylinder? Did you go around looking for leaks or loose hose fittings? Did you bench bleed the master cylinder?
It has a warning light switch on the P valve? There is a sliding piston that could be shutting off the flow to fronts. Try bleeding the front system starting at the master, if you have flow there, keep going towards the front till you loose it, then you will find the problem. I don't use pump it up, then bleed. I crack a bleeder or line, then very slowly work the pedal. I never need a 2nd person, and I have never had it not work. Slow return is the key to not ****ing air back in.
Does your set up have the rod that attaches to the brake pedal?? I had a similar problem, but we had to fabricate the push rod and made it a quarter inch to short.
Disconnect booster rod from pedal, lift pedal to top stop,can you now connect rod back to pedal, if not adjust or lengthen rod until it can be connected...Re bleed ....
Do you have new or freshly rebuilt calipers or a used set? I'm running into issues on my wife's ot daily and although the calipers aren't leaking I'm starting to believe that air is being drawn in past the seals when I let off the brakes.
That will work if you have a hose from the bleeder screw to a bottle with some brake fluid in it to keep it from ****ing air in but it won't work most of the time if the bleeder screw is open to the air.
Come visit, I give demos.. Honest, it never fails "me". I started doing it this way after fighting a dual system that I could not get to bleed any other way, incl pressure tank. I do not ever use a hose or jar unless trying to protect a fancy tire or painted backing plate. I use almost no fluid this way. I don't even want help if someone is there. Sometimes they beat that pedal so fast, it causes foaming from the air that has not bled out of the master. Edit, and I never bench bleed.
The proportion valve does have a warning switch on top,does this have to be wired up to allow fluid to the front brakes?,,or is there a way to byp*** the switch? I am getting fluid out of the master cylinder. HRP
I know you said Ford, but, Just to quote a GM truck dealer service manual...yes, there is a tool to hold the valve for "proper bleeding" Not up on Fords, but that switch piston can be blocking off the fluid to the front lines.
I'm am convinced that my problem is the proportion valve,,something is keeping the fluid from p***ing through. HRP
There is a way around it, by creative bleeding...i think ...maybe.. If you open a rear bleeder, with hose/and jar. Now keep the rear open. If you can get pressure to the fronts right up to the P valve?...then if the rear is open, and you get pressure to the front circuit of the valve, it might shove the piston back. If it does, you need to do it slow, with the switch out, to stop pushing when it gets to center. See if you can find a manual if you have no luck this way. BTW, I never have the valve problem by bleeding the way I do. Because I never build any pressure to move the valve. The only time I do have to mess with the valve, is if one side failed prior, like a popped line.
have someone (or make a tool) pull the pin out on the prop valve as you push on the pedal. or use a hand vacuum pump at the bleeders. fyi : there is a hand held pressure bleeder on ebay that fills from the bleeder screw to the master cyl... wish i thought of it ! search ebay no. 190650317363
IS the plumbing correct ? front to front ? the light switch will not stop the fluid flow ! I had to go in and clean my prop valve ,it was stuck from sitting too long in a junk car. some of these combination prop valves have a pressure regulator on the frt to allow the rear drums to actuate first, It is to stop 'nose dive' i think. this is what was stuck on mine.
HP there is a rubber boot over said pin, If you feel the boot you should find the pin simply push the pin and bleed the front. its a safty device to block of pressure if you had a presure loss past the prop valve. Hope that made sense.....JOHN
same problem----I have new risidual valves marked with an arrow. I installed them with the arrow pointing towards the wheel cylinders. Is that correct. They did not seem to make a difference and still feels like air in the line after bleeding.
The "pin" these guys are talking about is on GMs, for one, and it does need to be held in the "in" postion, BEFORE bleeding...not after the valve already has moved! Some like certain domestics like AMCs? need the switch removed prior to bleeding and a special holding bolt installed to keep the piston centered while bleeding. I barely recall Fords being the same but not sure. Like I had said, I'm not up on Ford circuits. I mentioned a Ford shop manual as they would say how to recenter the Ford valve...if it's a dealer type manual, not some drug store book. Got time tomorrow, try opening a rear bleeder wide open. Then bleed the front circuit at the P valve. If you can get pressure there, stomp the pedal to move the valve back....but not too far
There are three reasons why you should not use brake combo valves from production vehicles. 1-You may not know the history of what the PO(s) did to, or what the valves have been through, ie, wrong fluid, poor maintainance, etc. Plus the fact they are 20-40+ years old! 2-They were designed and calibrated for the vehicle they came from, not a custom system, and will probably not work as they should. This also includes the new fixed value prop/combo valves sold by the various suppliers. 3-Many do not know the function or purpose of metering, proportioning and pressure differential switches, of which two or more comprise a combo valve. Sadly, this includes some of the brake suppliers that sell these valves. I know you won't like it, but the best thing to do is pitch the old '84 valves and install a NEW adjustable prop valve, along with any needed residual valve(s). There may be other problems, but keeping the system simple (and NEW) will eliminate many.
If you have master cylinder on fire wall no residuals needed and run direct to front wheels see if this works.Adjustable prop valves most times go to back wheels.I had a problem with 70s MC from Speedway and turn out it was NG.Got a new one from NAPA end of problem. You want one for disk brakes,1970 1972 Mustang.
You can run into problems by mixing components. The block with the switch in it has a double headed piston in a port between the front and rear brake fluid lines. If the pressure gets higher in one side, it pushes the piston to the side with the least pressure and can block the flow from the input to the output. They design it this way so you don't pump out all of the fluid in case you have a leak. Older dual master cylinders has separate reservoirs but most of them now use a single reservoir. The switch turns on an idiot light to warn you that something is wrong with your brakes. The blocks have to be designed to work with the other components in the system. Drum brakes require a smaller volume of fluid to move the shoes so pressure will build up sooner than in the large piston calipers. This will cause the piston in the switch block to move to block the flow to the calipers. If there is any build up inside the switch block, the piston can stick. Sometimes you can remove the switch and move the piston back. It will have an hour gl*** shape and the smallest part should be centered. You could remove the two lines from the switch block for the front brakes and connect them together but it's safer to have the to bleed When I bleed brakes, I like to fill the master, open the bleeders and wait for gravity to bring fluid to the calipers or wheel cylinders before I start bleeding.
Sometimes, especially with late models, I prefer the push from the caliper method, Da'Tinman did a nice tech on building your own setup for this. http://www.jalopyjournal.com/forum/showthread.php?p=7531745 Could be the way to go.
I hate brakes. i've been fighting my brake system for 6 months trying to figure it out. I jut got done rebuilding the brake for the second time and think I narrowed it down to the MC having a faulty fitting. I also decided to do without the factory residuals and go with to externals. Cross your fingers for mine and I'll do the same for yours haha!!! Best of luck figuring this out. I can't wait to see that thing driving!
ONE more time, the differential pressure switch DOES NOT block ANY flow of fluid to the brakes. Yes, the switch will shuttle back and forth, depending on which circuit falls in pressure, and yes, they can sometimes be difficult to bleed and center, but ALL they do is turn on a dash warning light, PERIOD. K?
I thought the same thing until I was shown a cutaway of a block that is designed to block flow at a brake seminar.
I have no knowledge of any pressure differential switch that blocks fluid to a brake system. If there was such an item, it would have been included in DOT 105/135 brake testing. Curious, who had the brake seminar? JFYI, I went to one at the NSRA Nats in Louisville many years ago, but walked out when the subject of prop valves came up, because the speaker did not understand how they worked, and still doesn't!
Do you have the calipers on the wrong side ? Is youre bleeder on top or bottom ? If its on the bottom you have them on the wrong side ....
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