Hi guy`s Ive fitted Mustang 2 front suspension & a Chevy 10 bolt rear axle with drum brakes on my 35 Ford truck , as you can see from my pic I have fitted a GM proportioning valve with a 10lb residual pressure valve at the rear & a 2lb valve on the front. The problem I have is the front brakes are not releasing. I can push the Caliper cylinder in & the disc runs free but on the first press on the footbrake they stop fine but will not release. Should I take the front 2lb valve off............Thank you for reading.......Bri
You didn't say what type of calipers you have on the front, but one thing to watch out for with the GM "metric" conversion type is the caliper binding on the pins that hold it on. Bent pins do this, and so do poorly drilled aftermarket caliper brackets. With stock Ford componenets, the calpers some times bind on the brackets if they are dirty or rusted, too. Check those first. I also see tha t you have a combination valve in line with everything else. There is a pretty good chance that it already has a 2lb check valve in it. Most do include the valves, hence the name "combination valve". In that case, the residual check valve is redundant, and actually holding more like 4lbs of pressure after the one in the combonation valve.
Check that the rod going into the master is not too long. If it is too long will cause the symptom you have. Is that copper line going from the master to the valve? Copper is a no-no for brakes! (At least in the U.S.)
Interesting, I have the exact set up (on the same frame even), no pressure yet. Looking forward to seeing what you find out.
That gats said about the lines every time a Brit or European builds a car. They have a type of brake line over there that is steel and has a copper plate to help prevent corrosion. Pretty common.
Combination valves can include a pressure differential switch, proportioning and/or metering valves, but have never known one to include residual(s). The 2 lb residual is strickly aftermarket, as modern disc brakes never used or needed residuals, mainly because all US production vehicles with modern discs have firewall-mounted master cylinders.
Some of the aftermarket types geared to the street rod industry DO include residual checks... I saw that his stuff looked brand new, that's what made me think of them.
I'd check for 1/8" play between the brake pedal rod and MC piston. If that's OK, crack the bleeder screw and see if the front brakes release. That will tell you if it's a fluid pressure problem or a mechanical as mentioned above.
Straight copper IS a bad no-no. Fatigue, crack, crash. Cunifer (Copper-nickel-ferrous) alloy is okay for brakes.
Thanks for all that info guy`s, the Brit brake pipes are Cunifer (Copper-nickel-ferrous) Dane I reckon I will start with what you say first. I purchased the Mustang 2 kit from TCI & its brand new so I don`t reckon the pins are bent, this problem is on both caliper`s. The pic was taken a couple of years ago & its all connected up now & the truck is now driveable but not ready for the road.........
Bri69, Do you have a pedal return spring? Do not rely on the booster alone to return the pedal, and make sure the pedal can move farther up when the push rod is disconnected, to ensure it can fully retract. Make all pedal checks with full (about 20"Hg) vacuum in the booster. If those lines coming out of the master are Cunifer, your OK. If they're copper, I would suggest you change them. If all the above checks out, I would look at (suspect) a defective combo valve. These really have no place on a custom system, as they were designed and calibrated for certain factory applications. All that's needed in your disc/drum system are the 10 and 2 lb residuals and an adjustable prop valve. IMO (The differential switch is fine if you plan to hook it up to a dash warning light, but most do not, so it just complicates the system).
I purchased the Combo valve from "POL Performance on line" & there is a brake diagram set up in their catalog & it does not show a Residual valve for the front brakes. it shows two seperate feeds to each of the front caliper`s I hadn`t noticed this before. Comments on this guy`s also Im now thinking should I take the Combo valve off. By fitting this I just thought I was making a real good brake set up.....
Ya, the combo valve and the residuals are kind of "belt and suspenders". You really don't need both in the same system. I would probably pull it and know that you might have to do an aftermarket prop valve in the rear line if you have problems with the rear brakes locking before the fronts. Check the calipers as I suggested before, especially if they are the GM metric types on aftermarket brackets. I have had probems with slider pin holes in the wrong place not allowing the caliper to release in the past. Still a strong possibility that the pushrod in the booster is not letting the master retract fully too as someone else suggested. Shorten it a bit if that is the deal.
You need to make a gauge to determine if the rod from the booster to the master is too long. You have to take the master off the booster to measure it. It should stick out of the booster slightly less than the distance from the mounting surface of the master to the bottom of the hole in the master's piston. I think "slightly less" would be about 1/8th inch.
You are correct that this measurement should be verified, but the gap should be closer to .040" instead of .125", and checked with full vacuum (+/- 20" HG) in the booster.
I had a similar setup under my 1935 Ford Pickup with a MII front, and 8.8 rear, disc/disc and did not use a porporting valve, only the two residual valves. Iused 7" Booster and Corvette type Master Cylinder like you have along with the 2lb valves and my truck braked better than my 2010 Ford Edge.
I had the exact problem with the brakes on my '36 Ford. Loosen the bolts holding the master cylinder to the booster to see if the brakes will release. My booster rod was keeping the master cylinder partially depressed which would not release pressure. I fought the problem for quite a while before a mechanic friend told me to loosen the master cylinder. It was definitely an annoying problem. The brakes would drag every time I tried to drive the car. Hope this helps.
This proportioning valve http://www.performanceonline.com/GM...-AC-Delco-172-1353-172-1361-Type-Br***-17010/ appears to be the one you are running and it does say that it has a built in residual valve. I'd still go over all of the things suggested previously. Check the brake rod travel and check to make sure that the calipers appear to be free to move back and forth.
Wow Guy`s I can`t thank you enough, Mr48Chevy your right thats the combo I purchased & it does say there is residual pressure valve built in for proper braking feel, Im afraid I didn`t read that.,I will try all these suggestions. The first thing I will do is loosen the master cylinder & check the length of the rod then take the front 2lb residual valve out . Will let you all know how I get on, just hope this thread dosen`t get burried. "God Bless" the HAMB SITE & all who sail in her...........
I'll stick to the fact I've never seen or heard of a residual valve being part of a production combo valve. If a residual was part of that combo valve, it would be only for the rear drum brakes, NOT the front discs. I'm betting the residual they refer to is the metering valve.
V8 Bob,..... I reckon your right. I took the 2lb residual valve out & fitted the front brake pipe to the combo valve, now the front disc`s are releasing OK but the brake pedal is going down to the floor but the brakes are working OK I have bled them twice to make sure. I don`t like the pedal going that far down. The MC push rod is ok for clearence & the brake pedal is returning.... Please check the pic out I found it on a Custom Hot Rod brake site. What`s the comments on this set up., as you can see this guy has fitted both residual valve`s in between the MC & Combo valve..................
The only problem I see with the picture is how the residuals are located. They should be secured along the frame or crossmember and not "floating" as shown. All lines and components should be placed out of harms way as much as possible.
Thanks for all your help & comments fella`s, I took the combo out & now have just the 2lb residual valve for the front disc`s & a 10lb for the rear drums & the front disc`s are releasing OK. Ive just been for a drive in my Close & the Truck is "ace"..I will fit a Wilwood adj. valve later...........Cheer`s Bri
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