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By BudMan - 9 Years Ago
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I'm finally getting back to work on my '54 Merc Sun Valley after taking about a year off for other more pressing matters. I am having an issue with the brakes locking up. There is a residual check valve just after the master cylinder and I suspect it is malfunctioning. I think that the valve was installed by a previous owner and I don't think the valve is present on a stock brake system. Can anyone confirm that? The valve is a Wilwood 260-1876 10 psi. After a little research, I understand the purpose of the valve is to maintain a small amount of pressure in the system to keep the brakes from feeling "spongy". Does anyone use an external residual pressure valve on a stock brake system? If it is not part of the original stock system, can it be removed or should I replace it? Thanks for any and all help.
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By Kahuna - 9 Years Ago
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Bud
More info is needed on what your system consists of?
Drum brakes? Discs in front?
Stuff like that. Also what master cylinder, etc?
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By BudMan - 9 Years Ago
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Hi! Thanks for the reply. Everything is stock '54 Merc - stock master cylinder and drum brakes all around. The valve just doesn't look stock to me. I know that some master cylinders have a built in valve but I don't think the '54 Merc master cylinder has a built in valve. I am just not sure if the valve is needed. When I press on the brake pedal and release, the brakes stay "on" for some time which makes me think the valve is not working properly.
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By oldcarmark - 9 Years Ago
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Its not required using the stock braking System. Very likely the cause of your problem as its holding pressure in the Line. No idea why anyone would ad that to a stock system.
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By Rowen - 9 Years Ago
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No idea why anyone would ad that to a stock system.[/quote]
weak knees? :0). Rowen
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By MoonShadow - 9 Years Ago
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I had a similar problem recently. If you can jack up the car when the wheels are dragging. Carefully open the bleeder screw and see if that releases the brake. Old rubber brake lines can deteriorate internally until they have a sort of a flapper valve effect. When fluid pressure tries to release it pushes a loose piece of the rubber back until it seals the tube. I replaced the line and the trouble was gone.
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By oldcarmark - 9 Years Ago
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If You do a search for "residual check Valves" many of the aftermarket Suppliers recommend them(10lb. for Drum Brakes) so you don't have "spongy Brakes" Maybe this was installed at Someones advise but it is not used on these Vehicles. Many newer Models have them as part of the Master Cylinder
but to my knowledge they are not in the stock Master on our Cars. Take it out and use a Connector to bypass It and I bet that fixes the Problem.
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By Pete 55Tbird - 9 Years Ago
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So the more completely you can describe you issue the more likely you are to get a correct answer.
You say "I am having an issue with the brakes locking up."
1. this could mean I apply the brakes and they do not release
OR 2. I apply the brakes and the ( front) or ( rear) brakes lock up first
Or 3. Other
On a disk brake Mustang I added a valve like that so the rear brakes did not lock up before the front brakes
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By 2721955meteor - 9 Years Ago
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ther is a 10psi valve in most drum brake master cyl(residual check). recentley had the old mc out of 48 f47 it has 1. replaced mc from 57 ranchero old 1 has residual check. if you have a external check as well as internal you ar looking at 20psi residual
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By paul2748 - 9 Years Ago
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First, if it's a fully stock system, no external residual pressure valve is required as the stock master should have one.
If it's more than one wheel that is locking up I suspect it may be the external valve. If it's one wheel, the flex hose is probably bad as mentioned before. If it's both rears, then check the flex hose in the back.
If the brakes worked ok before the latest incidents, I would suspect the master cylinder.
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