I suspect that the previous owner of my car installed the proportioning valve incorrectly. Manual Brakes, Disc front drum rear, Mustang II PV. Does anyone know what would happen if the brake lines were installed in there wrong places. It looks like the front input and right front are transposed. Also, it looks like they installed the input into the output holes and visa versa. The car locks the right rear if I stomp on them, but after a couple stompings, everything seems OK, no lockup. Front brakes dont seem to be braking as much as they should. Anyone have any ideas, any help would be appreciated. The following is a picture of how it is currently installed:
hmm.... the inlets are both at the top...i have never studied the internal valving of that proportioning valve.. but as i understand.. if you have an inlet into the front.. it won't block off the front brakes when/IF they ever fail...there is a shuttle valve with Orings in there.. that stays centered if both sides receive the same pressure and volume...if the fronts fail... the shuttle valve slides to the low pressure side.. blocking it off from any additional flow...letting the other side do all the work on that side... the movement of the shuttle also lifts the plunger in the switch. to turn on the brake failure warning light..the part number on that valve seems to be a PV6070FD google it.. call the brake suppliers.. as it is hooked up.. it will probably work just fine... until the brakes fail... if the brakes ever fail in a fluid loss or master cylinder pressure loss.. at that point.. you might have one wheel attempting to brake... but thats just a quick guess..i don't live and breathe breaking systems like brake guys do.. i hope this helps...
Thanks Wayne: I understand the PV concept, just wondering if its performed correctly. I found a cut away schematic of a mustang 2 PV on the internet and it looks like the front disks outputs and the input are pretty much must a straight through path that just monitors the brake fluid level with that shuttervalve device. The rear looks like the proportioning takes place here but it works both ways in either direction. It too monitors the brake fluid level with that shuttervalve device. Maybe its possible to mix and match as long as you don't mix and match the front and rear brakes. The valve size difference makes sure that this can't happen. Im hoping that anyone can verify this. I might go visit a Brake Expert and pick a techies brain. But you know how these mechanics work, they don't like to give free advice sometimes. And of course, they will want the make, model and year of the vehicle - like that helps. This is the link to that cut away view I found. The following is the Pic of the Cut Away Schematic that I found. Any Offers?
that was the kind of images i was looking for..i would eventually move the inlet from port 7 to port 1.. but as long as the brakes don't fail... it will work... that lower diagram does NOT show the narrowing in the middle of the shuttle valve for the switch..somebody had a decent price on 3/16 nitrous tube benders. that would work great on brake lines.. i don't recall what brand it was.. i saw it in an article probably over in HRM or CC..Wait a second... the rears lines are on the wrong side also.... the inlet is on the same side as the electrical switch..
Yes on the last comment about the inlets being on the same side of the electrical switch and yes on the 7/1 port switch. Thats exactly what I'm thinking. But if the current configuration is OK, then I'd rather not reroute everything just to make everything schematicly correct. All that tube bending would be a hassle. BTW it was Oriley that has the good price on tube bender for $9.95, got them today. Since the brakes seem to be working I'll leave it be for awhile. Its just that the backs want to lock up early. I think I may need to put one of those adjustable single inline PV's on the rear line, Dad-in-law has a spare I can use. then I could reduce the pressure to the rear so that they wont brake so fast. I guess I really should replace my current PV with an adjustable PV to do it right, but I hate spending money on things that aren't necessary. These hot rods can be a money pit if you let them. Thanks for your input.
Found another cut away of the PV showing the switch operation. Internally it looks like id doesn't matter which way the brake lines are connected - as long as you dont mix match the front with rear.
flip it over and mount it upside down...that should restore the proper fluid flow for the rear half of the system...i don't know if the bracket is removable on yours... so it would be bracket out.. to make it fit with the least amount of work...if you have to remove the bracket.. please.. invest in some inverted flair plugs to block the passages... az stores have them on a display in the back of the store... talk to an az store manager.. this is an ags BLF-60Cbut ags does not show one in 7/16-20 so if you have 3 short 3/8-24 bolts and nuts.. and 2 7/16-20 bolts and nuts.. you can thread them into the fitting holes just a few turns.. then hand tighten the jam nut down to seal the holes...dorman does show the inverted flair plugs.. i keep several of these inverted flair plugs and inverted flair unions around. all screwed into each other... so i can pull one plug from a union to plug the end of the hose. and the union with one plug to seal the end of the line.. i also keep one set that that i keep together.. in 1/4 inch inverted flair for when i have to remove convertible top pumps.. i can disconnect one side of the pump. stick a plug in that.. and the union and plug on the end of the hose.. this seals the first half.. i then remove the other hose from the pump.. unscrew the plug from the union and place it in the pump opening. then the line i hook to the other union.. this seals the system.. so i can actually open and close the top manually as the pump is no longer restricting the flow.. the pump does not leak all over the inside of the car.. and there is a LOT less bleeding the system when i get done.. oh.. and with one side of the pump plugged or hooked up to the line.. little fluid leaks out.. answers are optional from you ... questions are desired if you have the need.. i don't know if it will help the early lock up of the rears.. in reverse...i have a few questions that you have the option to answer...have you had friends with good eyesight.. standing on the sidewalk and some masking tape strips on the tires.. while you do several panic stops to the point of one end of the cars brakes locking up.. do the wheels front and rear lock up at the same time???? or does one end lock up first... ???what kind of brakes do you have on the rear????? if you have drums.. depending on the type of brakes... do the brake shoes have the short linings toward the front of the car??? long linings toward the rear... this is with self energizing brakes.. where the self adjuster is mounted between the shoe webs and NOT attached to the backing plate... so the wheel cylinder expands the shoes at the top.. the rotation of the drum catches the shoes.. pushes the primary shoe away from the anchor at the top and the secondary shoe into it and this jams the secondary shoe into the drum to stop the car.. why is the shoe positioning important.. if you get the long linings on the front half.. you will wear through brake shoes fast.. and the brakes will work much better in reverse.. also... fine tuning can be done if the rears lock up before the fronts after verification of proper assembly.. depending on the drum configuration.. some OEM manufactures use the same brakes on various sizes of cars.. and fine tune the braking system by changing wheel cylinder sizing between models and also between engine sizes.. so if your rear brakes lock up too early.. you might want to investigate if smaller diameter wheel cylinders are available.. if your fronts lock up before the rears... you will want to go larger on the rear wheel cylinders... smaller is less apply force.. larger is more apply force...this is really important do to rods not always having the same size tires ... changing wheel cylinder sizing is the PROPER way to correct brake bias.. this is just my opinion.. as i don't live and breathe brakes...
Whew, your insights sure give me a lot to ponder. Its a chevy rear end with drum brakes. I think I'm going to remove the wheels and drum and then inspect the configuration. Egad, I didn't realize that brakes were such a science. OK, thanks for all the input Wayne. I'll wait for warmer weather before I start this stuff. R
when you get in the rear brakes.. mark the ends of the axles left and right.. and snap some photos...post them to photobucket.. so i can have a look...see if you can identify the model and year of the rear end.. what size the brakes are.. GM uses 9 1/2 or 11 inch rear drum brakes on most of its cars and small trucks.. see if there is any rear end tag left on the cover bolts.. or numbers stamped into an axle tube.. there are a few sizes of wheel cylinders available for the chevy rear ends.. and if i know this much.. imagine what the brake gurus know.. i specialize in engine controls.. like fuel injection and feed back carbs... ignition.. .. after inspection to verify they are correctly assembled.. a test drive with a few panic stops with friends watching are the next step... try to not flat spot the tires... there was on another forum.. somebody who used toyota front truck calipers on his .. but also used full size GM rear calipers .. there was TOO much rear caliper apply force.. . so the rear brakes would lock up first.. no matter how much he adjusted the bias valve.. reducing pressure to the rears.. all he really needed to do was to swap to one of the GM rear caliper applications with a much smaller diameter caliper.. he quit posting.. so i don't know what happened.. just because it will fit.. does not mean it will work properly...and if you have skinny fronts and big fat rears... it gets even tougher to calculate.. there are some good articles on brake bias over in circle track and stock car racing.. and probably a half dozen spread out in the over 50 car and truck magazines on this site..oh... classic industries or OPGI.. have brake pressure gauges that screw into the brake bleeder screw holes... they were not high priced.. harbor freight also sells high pressure gauges.. but they are 5000 pound.. so they are a little high for brake duty..a 2000 pound gauge would be better... but the HF versions are only 14 bucks..
a true brake professional is going to want to know..front and rear weight of the car.. with 3/4 tank of gas.. and two people in the car...the front and rear tire rollout ... the width of the tires.. probably the tire contact patch.. the brake type front and rear.. as in type... the FMSI shoe and pad numbers..he will also want the piston diameters front and rear...the master cylinder bore...the pedal ratio... the what.. the length from the center of the pivot to the center of the pad.. and then the center of the pivot to the center of the pin for the master cylinder hook up.. if you have power brakes...if so.. what kind of intake manifold vacuum do you have at idle.. and at cruising speed on the freeway.. the type of booster.. and diameter..
please don't let me scare you.. you have a complete system.. it only might need some fine tuning.. not a complete redesign..
Thanks Wayne for putting so much thought into my thread, for being a "nonbrake" guy, you sure know a hell o a lot. Sounds like I really opened up a can of worms. I bought this car from a guy that is known for "knowing his stuff". Goes first class all the way, he had about 10 plus custom cars, bikes, boats in his garage (hangar). Problem is, he did't build this car. He bought if from a friend, worked it a little, New paint, upholstery, and I got a great price on it. I rewired the whole car and have been dialing in a few things. In my observations, I have noticed a lot of short cuts and jury rigged staff that I had to correct. I've come to the conclusion that his buddy may not have had the resources to produce 1st class work. I would tend to believe that he didn't research this brakes when it came to that part of the car. After all, the proportioning valve is in upside down bass ackwards. I'm going to correct the PV first and see what happens. The only thing holding me up is that I'm questioning the PV. On most ford PVs, the front lines are 3/8 and the rear are 7/16. On this one, all of them are 3/8 and only the Rear Out is 7/16. The MS is correct - 3/8 & 7/16 fr/rr. Any thoughts on this?
there are various sizes of tubing nuts for 3/16 and 1/4 inch tubing...you might want to download this catalog...http://www.agscompany.com/images/stories/catalogs/fluid-transfer-catalog-2011.pdfit shows the fluid transfer tubing and fittings available from AGS.. who now has some of the individual brake tubing nuts in the back rows of the autozone stores...oh.. i know about this as i have to reverse engineer stuff that rolled into the bays over the last 30 years.. its so much easier now with the net and a hard drive full of catalogs.. of course.. i could be completely WRONG... and have been.. once in a while.. i would still like you to look at the rear brake shoes.. see if the guy put them on wrong.. i have found cars with them on backwards.. i have found cars with long shoes on one side.. short shoes on another.. that could be your only problem..
just ran across this link .. to some trouble shooting one or two page downloads...http://www.mpbrakes.com/technical-support/configurations.cfm
Thanks for the catalog. I've saved a copy for reference. I agree with the net comment. In a way, it sure would have been nice to have it back in the day "70's for me". Could have solved problems and bought less expensive parts. OK, Today is Saturday, I'm pulling off those drums today to check the shoe installation and will post pix later..