After install the power brake system i have a phenomen. Install rear valve 1lbs and after a distance about 10mi the brakes are tight and hot. Have adjust the rear brakes that they does'nt work. a lot of space between shoes and drum. If the drums cold i can press the brake pedal to the metal and the truck brakes with the front brakes. after 10mi or so the brake pedal is a little bit hard and the drums are hot. I don't no whats the reason of this??? and i need your help or ideas
Volker, if I remember correctly unless you are running drum brakes on the rear and disc brakes on the front you would not need a proportioning valve. Rephrasing:If you are using drum brakes front and rear there is no need for the proportioning valve. Are you sure the valve is installed correctly and not locking up? Hope this information is correct. It has been a long time since I worked on a vehicle with power drum brakes only.
Volker, it will cost you a dab of brake fluid but next time you drive it till they tighten up slip under the truck and crack open a bleeder valve. If this frees up the wheel where it turns easily then there is definitely a pressure build up. You may have to shorten the actuator rod from the pedal to the booster a bit and it's possible the seats in your master cylinder are residual pressure valves, they did this for several years on dual master cylinders.
i have 4 drums and for rear a residual pressure valve and used MC390360P from MPbrakes.com. I think it's the valve. After the truck is off for 15 minutes the brakes works fine. I will try to take out the valve and will see.
residual pressure valve it was a bad idea to take out the valve took it out and it was broken - now the brake like as pudding and to brake i go with the pedal to the metal. i will order a new one and come back with my experience
Volker - If I'm not mistaken, you don't need the valve with drum brakes on all 4 wheels, only if you have disc up front. Have you tried without the valve?
yes i took out the valve and now the brakes are too smooth. I read at the internet you must use a valve for brake drums. the valve with 10psi let a small pressure in the lines and help to seal the rubber in the wheel cylinder and makes the shoes closer to the drum.
Spongy Brakes Volker , this is bad advice ~ (typical Internet crap) Adjust the brakes when cold then bleed them to get a high and hard pedal action . Residual pressure in a drum brake system causes dragging shoes and overheating plus glazed shoes . If the shoes are not allowed to retract 100 % , the friction prevents the drums from cooling as you drive . Only disc brakes systems require the residual pressure valve .
Nate, thats my problem. With the valve i can bleed out the rear system easy, without the pedal will be never hard and high. I tried follow. Bleeder open - press pedal down - close bleeder - go from the pedal - many times. My helper said to me he can't see that brake fluid coming out - few drops thats all. Before i took out the valve the adjustment was very easy. I talked with MPBrakes.com and they said with 4 drums i should use 10lbs valves. With my logic and lots of internet words about this theme i can understand follow things. Inside a wheel cylinder is a rubber membran. if i press the pedal the pressure goes from the MC to the wheel cylinder and the rubber move to left/right and press the metal plate to the brake shoes. If i go from the pedal the fluid goes back to the MC and u have the risk that air goes through the rims of rubber in the brake fluid. With a residual valve i hold a small pressure in the brake fluid and the rubber is sealed.
I'll weigh in on this one, although I'm no brake expert. We had drum brakes on pretty much everything for years, and there was no such thing as a residual pressure valve on them. Where they found it was needed was when the master cylinder was mounted under the floorboards, with discs on the front and drums on the rear. For some reason, that combination seemed to not keep the minimal pressure that a firewall mounted MC did at a higher level. I've got drums rear and discs front on the Studester, firewall mounted MC, and no valve...works fine. If you're getting a good flow and can bleed all of the air...make sure you keep bleeding fluid out until you know all bubbles are out of the line...try it without the RPV. If your brake assemblies are in good condition, clean, and no springs broken, the shoes should retract just fine on their own. You have to watch some vendors...if they think they can convince you you need a part, they'll try to sell it to you. Sometimes its not just the wasted cash, its a headache because things don't want to work right then...
How close do your brake lines run to the exhaust, once had an astro van that someone had so called fixed a rusted out brake line on, ran a new line to close to the exhaust after 10-15 minutes of driving rear brakes were smoking and hot. Line got hot fluid got hot, boiled, expanded caused brakes to partially apply.
