I have a problem with my brakes, I have a 34 Plymouth with Mechanical brakes from a 65-66 Ford Ranchero. The front end is from a Mustang 2 Disc brakes and the back are drum. The problem I am having is that the front brakes stay locked up? I have replaced everything but the Proportioning valve even the Master Cylinder?? could the Proportioning valve be screwed up so that its not allowing the pressure to release the front brakes???? I also cannot find a replacement Proportioning valve and the ones I have found are for Dual bowl and power brakes I cant seem to find any for my mechanical brakes??? Any help would be appreciated because I am tearing my hair out and I did not have much to begin with!
1st I believe you have MANUAL brakes (non-power), and not mechanical brakes (cable/levers instead of hydraulic). Anyway, I believe you have a residual check valve that's not the right number, in the wrong place, or defective that's keeping pressure to the front wheels. Another possibilty is to much preload on the rod that connects the master to the pedal, not allowing the piston in the master to return all the way back when you let off the brakes
Yes Single Pot Master Cylinder and disc front and drum rear. It had a leak in the line and the back drums were kind of sticking so got that fixed now this problem! I have been working on it for two days strait replaced everything except the Proportioning valve and still the front discs are locked!
Yes Manual Brakes not Mechanical (sorry late and I am tired from crawling all under the car all day for two days) Not that anyone here would know what I am talking about? LOL Where would I find the check valve I have replaced everything except the Proportioning valve is the check valve the white plastic thing sticking off the Proportioning valve? or do I find it somewhere else??? the Rod from the peddle to the master is working great no load on it so cant find anything wrong there???
The brakes came with a single Cylinder Master and were working fine??? what do I get as far as a manual twin master cylinder that will fit that set up? as far as a new valve you mean the Proportioning valve?
Some master cyls have built in residual valves that hold some pressure to keep the wheel cyls from backing off, drum brakes use a higher pressure than discs, which could be not letting your discs back off, the fix is to install a dual pot disc drum master cyl which is a good idea any way!
Your master cyl. may have a 10 pound residual pressure check valve built in. You would need to remove it and put an inline 2 pound valve in the front and an inline 10 pound to the rear. Your leak in the rear may have been relieving the pressure as it is a common line. Your best bet would be a dual master made for drum/disc brakes. Much safer too. hmmmmmm... FNG beat me to the punch
I will do that (get a twin pot Master Cylinder) any suggestions on what type to get that would be a replacement for the single pot 65 Ranchero one I have now? Is there an aftermarket (Manual one) any suggestions would be appreciated. Oh and thank you all for the help its been a huge help to me!
I have found some conversion kits but they are for either drum brakes or disc brakes only not for both????
That is what I was thinking because I have to much pressure to the front and the pressure to the back is fine so no need to tune it down for the back!
Use a mid 70's Granada Disc/Drum master. Add an adjustable prop valve to the rear line. Adjust to prevent lock up. It's about the same as an early Mustang brake swap as Ranchero drums are the same.
So the proportioning valve wont cause he front brakes to not release? Im going through the same thing right now. My dad bought a car that was driving, it has set for the winter and when we got it out the front brakes (both Sides) are hanging up, I could not push the caliper back in so I cracked the line between the brake hose and the porportioning valve and then the piston went in with no problem, The only thing left is the valve and the master cyl, I bought residule valves to add in lin and a new master cyl off of a ford truck Disk/Drum but I have been wondering if the problem was in the porportioning valve,
If ever thing was working fine before you fixed the leaking line the leaking line could be releasing the pressure on the fronts. My brake system has a lb residual valve on the disc and lb on the drum brakes. Are both calipers locked up? Get some pressure gauges install them see where the problem is.
You need to remove the residual valve from the master cylinder and put one a 10 lb in the rear brake system. If your master cylinder is on the firewall one to disks is not needed. If the master cylinder is under the floor you should run a 2 lb in the front. Residual valves are meant to keep a small amount on a drum system cups in the wheel cylinders seated against the pistons. In a low master cylinder setup it keeps to much fluid from returning the master cylinder.
i've used mid to late 70s maverick with non power brakes. theyve always worked great for me. direct bolt on for mid 50s to late 60s fords
Ok bought a 1975 Granada manual two bowl Master Cylinder today and low and behold it bolt right on (Thanks Virgil for that info) could not find a adjusting proportioning valve for the back drum brakes but I ordered one today. From the info I got I don't think I need one (prop valve) for the front as the Granada one is made for Disc brakes, its also made for drum on the back but needs that valve to boost it to the 10LB's? I now have to try and figure out the new plumbing of everything as the new MC has the plumbing out the side not the front and the 34 Plymouth does not have a lot of room! Thanks again everyone that responded to my thread on this y'all have been a huge help to me!
Glad to help. You don't need to worry about the front proportioning the disc set up part will work, you just need to adjust the rears to avoid premature lock up. I've done Granada disk swaps on Mustangs and most of the time you don't need the prop valve but on a custom install with the different weight and front to back ratio of your car it might be needed to keep it even while braking. The drum section should be plug and play as the Granada has virtually identical rear brakes as your swapped Ford axle. Good Luck!
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