brake proportioning valve question
Lead Driver
Joined: Apr 2002
Posts: 8,813
Likes: 13
From: Littleton, New Hampshire
Bobby/Alan,
The rear wheel cylinders are the same ones off the 87 Chrysler so the wheel cylinder daimeter is moot. I used the complete Chrysler rear end with the brakes that were on it. All I did was dissemble them, clean throughly with alcohol, and reassemble. A brake job had just been done on the donor car so all the parts were new. Both rear wheel cylinders have clean fluid coming out when bled so there's no rust in them. I used a new rear brake hose as well as all new brake lines. There are no kinks or even sharp bends going to the rear. I replaced the MC with a rebuilt just to be sure it there was not a massive internal leak in the MC but no change. I'll have to think about rigging a pressure gauge but I'm not sure that would really tell me much. I have no idea how much line pressure is necessary to engage the rear brakes or make them engage before the front...or would I just be looking for any pressure at all? If that's the case I know I have some pressure because if I jack it up and push the brake pedal down I can't turn the rear wheels.
The rear wheel cylinders are the same ones off the 87 Chrysler so the wheel cylinder daimeter is moot. I used the complete Chrysler rear end with the brakes that were on it. All I did was dissemble them, clean throughly with alcohol, and reassemble. A brake job had just been done on the donor car so all the parts were new. Both rear wheel cylinders have clean fluid coming out when bled so there's no rust in them. I used a new rear brake hose as well as all new brake lines. There are no kinks or even sharp bends going to the rear. I replaced the MC with a rebuilt just to be sure it there was not a massive internal leak in the MC but no change. I'll have to think about rigging a pressure gauge but I'm not sure that would really tell me much. I have no idea how much line pressure is necessary to engage the rear brakes or make them engage before the front...or would I just be looking for any pressure at all? If that's the case I know I have some pressure because if I jack it up and push the brake pedal down I can't turn the rear wheels.
Senior User
Joined: Feb 2006
Posts: 412
Likes: 1
From: Fallon, Nevada
More Brakes
Originally Posted by GreatNorthWoods
Bobby/Alan,
The rear wheel cylinders are the same ones off the 87 Chrysler so the wheel cylinder daimeter is moot. I used the complete Chrysler rear end with the brakes that were on it. All I did was dissemble them, clean throughly with alcohol, and reassemble. A brake job had just been done on the donor car so all the parts were new. Both rear wheel cylinders have clean fluid coming out when bled so there's no rust in them. I used a new rear brake hose as well as all new brake lines. There are no kinks or even sharp bends going to the rear. I replaced the MC with a rebuilt just to be sure it there was not a massive internal leak in the MC but no change. I'll have to think about rigging a pressure gauge but I'm not sure that would really tell me much. I have no idea how much line pressure is necessary to engage the rear brakes or make them engage before the front...or would I just be looking for any pressure at all? If that's the case I know I have some
pressure because if I jack it up and push the brake pedal down I can't turn the rear wheels.
The rear wheel cylinders are the same ones off the 87 Chrysler so the wheel cylinder daimeter is moot. I used the complete Chrysler rear end with the brakes that were on it. All I did was dissemble them, clean throughly with alcohol, and reassemble. A brake job had just been done on the donor car so all the parts were new. Both rear wheel cylinders have clean fluid coming out when bled so there's no rust in them. I used a new rear brake hose as well as all new brake lines. There are no kinks or even sharp bends going to the rear. I replaced the MC with a rebuilt just to be sure it there was not a massive internal leak in the MC but no change. I'll have to think about rigging a pressure gauge but I'm not sure that would really tell me much. I have no idea how much line pressure is necessary to engage the rear brakes or make them engage before the front...or would I just be looking for any pressure at all? If that's the case I know I have some
pressure because if I jack it up and push the brake pedal down I can't turn the rear wheels.
I think that the metering valve is the culprit: either that or the M/C has to be at fault as that is where the pressure comes from.....
One thing that CIAF neglected to mention was that all the early disk/drum setups did not even use a metering valve. You won't find any on Ford cars or Ford trucks to 1981. I was sure of this statement, but I looked up the facts in the service manuals.
The proportioning valve could also be at fault. After all, the basic line pressure to the rear is from the rear piston on the M/C and if the M/C went directly to the rear brakes, it should activate them very quickly because it is just the ratio of the two cylinders and the force on the pedal plus the booster pressure.
Regards,
Alanco
Lead Driver
Joined: Apr 2002
Posts: 8,813
Likes: 13
From: Littleton, New Hampshire
I tend to agree even though tests have indicated that the valve is good. I probably have another combination valve laying around in the garage somewhere I can try. Since the metering and proportioning is done by the combination valve if I eliminate it and run the lines directly from the MC what affect would that have on my brakes? 
Vern
Vern
Senior User
Joined: Feb 2006
Posts: 412
Likes: 1
From: Fallon, Nevada
Brakes
Originally Posted by GreatNorthWoods
I tend to agree even though tests have indicated that the valve is good. I probably have another combination valve laying around in the garage somewhere I can try. Since the metering and proportioning is done by the combination valve if I eliminate it and run the lines directly from the MC what affect would that have on my brakes?
Vern
Vern
Alanco
Roast em' if you got 'em
Joined: Mar 2005
Posts: 21,997
Likes: 9,886
From: Rio Rancho, NM
Vern,
I had forgotten that you used the entire rear suspension from the Chrysler (I sure thought I might have been onto something that time)
Getting rid of the proportioning valve would be a good test. It would be best to have one in the long run though. From what I have read they are designed to compensate for the weight transfer from rear to front during braking.
The only other thought I have on the whole system would be the brake pedal itself, specifically the ratio of the lever. I can't remember, did you use the brake pedal assy from the donor car or did you build your own?
Bobby
I had forgotten that you used the entire rear suspension from the Chrysler (I sure thought I might have been onto something that time)
Getting rid of the proportioning valve would be a good test. It would be best to have one in the long run though. From what I have read they are designed to compensate for the weight transfer from rear to front during braking.
The only other thought I have on the whole system would be the brake pedal itself, specifically the ratio of the lever. I can't remember, did you use the brake pedal assy from the donor car or did you build your own?
Bobby
Lead Driver
Joined: Apr 2002
Posts: 8,813
Likes: 13
From: Littleton, New Hampshire
Bobby,
I used the Chrysler brake pedal too. I wanted to use all the Chrysler stuff just like it came from the car so I would not have this very problem that I'm having...so much for planning!
I used the Chrysler brake pedal too. I wanted to use all the Chrysler stuff just like it came from the car so I would not have this very problem that I'm having...so much for planning!
Roast em' if you got 'em
Joined: Mar 2005
Posts: 21,997
Likes: 9,886
From: Rio Rancho, NM
Vern,
LOL....
You don't suppose some nasty little creature (I'm not mentioning any species here, especially mice or anything like that) might have gotten inside the brake system while you had it all apart and built a nest in there do you?
Bobby
LOL....
You don't suppose some nasty little creature (I'm not mentioning any species here, especially mice or anything like that) might have gotten inside the brake system while you had it all apart and built a nest in there do you?
Bobby
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Senior User
Joined: Feb 2006
Posts: 412
Likes: 1
From: Fallon, Nevada
Blame Chrysler...............
Originally Posted by GreatNorthWoods
Bobby,
I used the Chrysler brake pedal too. I wanted to use all the Chrysler stuff just like it came from the car so I would not have this very problem that I'm having...so much for planning!
I used the Chrysler brake pedal too. I wanted to use all the Chrysler stuff just like it came from the car so I would not have this very problem that I'm having...so much for planning!
So don't blame yourself, blame Chrysler..........................
Alanco
Elder User
Joined: Sep 2006
Posts: 630
Likes: 0
From: Dayton, OH
I havent read this whole string but one thing an old builder showed me first hand while doing brakes is to take a drill bit inside every cut line where he has a joint and opens the line up if its restricted from burs or tube cutters. We were building a 40 Convertible and he showed me this trick. I was holding a brake line and said it looks fine he stopped me. He had the drill bit already laid out from working on it the previouse day. He runs it inside the cut tube just to make sure its open to spec.
He then told me how hes tacked down brake problems to restricted lines on other customer scars.
Thats a good tip to remember when your scratching your head.
He then told me how hes tacked down brake problems to restricted lines on other customer scars.
Thats a good tip to remember when your scratching your head.
Senior User
Joined: Feb 2006
Posts: 412
Likes: 1
From: Fallon, Nevada
Brake lines.....
Originally Posted by OldgreenF1
I havent read this whole string but one thing an old builder showed me first hand while doing brakes is to take a drill bit inside every cut line where he has a joint and opens the line up if its restricted from burs or tube cutters. We were building a 40 Convertible and he showed me this trick. I was holding a brake line and said it looks fine he stopped me. He had the drill bit already laid out from working on it the previouse day. He runs it inside the cut tube just to make sure its open to spec.
He then told me how hes tacked down brake problems to restricted lines on other customer scars.
Thats a good tip to remember when your scratching your head.
He then told me how hes tacked down brake problems to restricted lines on other customer scars.
Thats a good tip to remember when your scratching your head.
Please everyone, do not flare brake lines with a single flaring tool, and of course use the reamer after cutting................
Regards,
Alanco
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