Ford stuck proportioning valve symptoms. The #5 valve is the proportioning valve.

Ford stuck proportioning valve symptoms This all assumes you bench bled the master cylinder. 5L engine with rear springs E3TZ-5560-T E5TZ-2B547-C - Fits 1985/ 1973 - 1979 F-100 & Larger F-Series Trucks - Choosing a new brake proportioning valve - I purchased a set of stainless steel brake lines from Inline Tube. What are the symptoms of a failed brake proportioning valve? Some early signs can provide you clues about a developing problem before it actually compromises the safety of your vehicle. Now the M/C front well goes to the front brakes this is the one facing the M/C. My current brake line configuration is that my front & rear are completely seperate, the line for the rear leaves the master cylinder If the braking system is in proper order, yet the light is always on, the proportioning valve may not be completely centered. 104. I have had several bad units out of the box. New caliper & hoses had already been installed, I'm thinking its the valve. Assuming the brake light is not on and you have fluid flowing to the front. 1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks - Help! Proportioning Valve Issue? - Hey team, I have an 1984 F-250 with the 6. 8 rubber brake hose seems to work well. Ford Racing 5. Is that supposed to happen?? Would that be a bad prop. Prices may vary depending on your location. When the truck gets hot the front hubs stop If there is differential pressure across the valve, then the valve moves to close off the brake circuit with the fluid leak. The proportioning valve is the two parts combined, thus called the combo valve sometimes. 979. Just bolt it up. The reason they used the SN95 PV is because it has the 3rd fitting for the left front brake and makes an easy hookup. Does anyone have a source for a new one or suggestions as to what to do next. 1979 F-100 & Larger F-Series Trucks Discuss the Dentsides Ford Truck. So right now, I have the passenger rear side with a 3/8 fitting on a bubble flared line that is just hanging there cause it wont thread in, I have 2. I have used the stock Ford combination valves on my cars. A defective proportioning valve or one that is not adjusted properly can also upset brake balance. 0122, 7am-10pm, everyday. Pic: 1967/72 2B257 Brake Pressure Differential Valves: Attached Images Reply. 00; Discount: $26. The smaller m/c well is for the Rear Brakes Okay. Some of the information may no longer be A faulty brake proportioning valve could increase your vehicle’s braking distance, as it might reduce the pressure from the rear brakes too much. 14; OR. The actual brake combination valve was not introduced until 1972 on most FORD applications (front disc standard in 1973). 0 HO Motor(Crate)/B303 cam/1. Browse original Ford parts, view prices, specs and more. This truck does not have a normal proportioning valve under the master cylinder. Symptoms like excessive front-end dive and pressure distribution imbalance indicate potential issues. 1987 - 1996 F150 & Larger F-Series Trucks - Symptoms of a bad master cylinder or propotioning valve - My Truck would stop but not like I felt it should. The Proportioning valve is a device to "Cushion" the flow of pressure to the rear brakes, so the rear brakes won't stop rotating If there were never to be a sudden flow of fluid to the rear brakes, A Panic Stop, a Proportioning valve is worthless. However, I cannot find this tool. I went to start hooking them up today and ran into problems at the proportioning valve. there is a tool that holds the valve centered while you bleed the brakes . Proportioning / Combination Valve Replacement Service How much does a Proportioning / Combination Valve Replacement cost? On average, the cost for a Ford Escape Proportioning / Combination Valve Replacement is $257 with $162 for parts and $95 for labor. "The isolation valves allow brake pressure into the wheel brakes to increase pressure during the apply mode, and the dump valves release pressure from the wheel brakes during the dump mode. -Bleeder rod won't push/pull out with finger tip effort. Ford F834. two people would help. com. Couple of quick questions: Provided I pick the same configuration I have (Disc/Drum) - is there any difference between say a F100 valve and a Mustang valve? I lost my 1973/1979 FORD TRUCK MPC (crash) so In my expierences, with your symptoms, the master cylinder is bad. The Proportioning valve can be placed anywhere in the rear brake line AFTER leaving the Distribution block. 3k 5. That's why this valve on the Aerostar is not exactly called a "proportioning valve," but a "combination valve" since it combines both functions in one body. Back to Subforum. . If you don't have the same amount of pressure on each bleeder screw, the proportioning valve may be bad. 1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks - Brake Proportioning Valve Delete - I'm seriously considering eliminating the proportioning valve in my 1982 F100. I can't find a new one and am told the part was discontinued. I went to bleed them today and I could only bleed the fronts, and the pedal is stiff now that fronts are done. Right now the valve is froze and is causing only rear brakes to work. Is there something I need to do with that valve that wud help with this problem? i have a 74 gran torino with power disc front/drum rear brakes my proportioning valve started seeping brake fluid out from the wire terminals of the plastic warning light switch. Since the proportioning valve decreases the Brake proportioning valve problems can cause rear-wheel lockup, longer stopping distances, and inconsistent braking performance. I could likely separate my proportioning valve from the block, but all the lines so far have been frozen on and the nuts could do with being replaced once they are 1973 - 1979 F-100 & Larger F-Series Trucks - Brake Help? How to check Proportioning Valve? - I recently replaced a MC and rear wheel cylinders on my sons '77 F100 and now the front calipers bind after driving about a mile. So that's the reason Ford listed the proportioning valves for the light 6200# GVW 4x2 F250 dentside pickups with the F100/150s The brakes work nice right now. I have no idea what I'm doing with this thing but we've replaced the master cylinder booster and figuring on moving onto the proportioning block. Mar 11 . The rear brakes started locking up on my truck a few weeks ago. you can recenter the valve by opening the oposite end brake bleeder of the direction you want the valve to go. MSRP: $92. Parts. It was a used one. This keeps the front Shop 1971 Ford Proportioning Valves and get Free Shipping on orders over $99 at Speedway Motors, the Racing and Rodding Specialists. 1996 Ford F-150, F-250, F-350 and larger pickups - including the 1997 heavy-duty F250/F350+ trucks Brake proportioning valve. Proportioning valves are available from aftermarket suppliers. Have an assistant start the engine and apply the brakes very hard. tried several auto parts stores prop. 3L Power Stroke Diesel - Proportioning Valve - In the fall I replaced my breaks. Does anyone have a way of The stock Ford 8. This would cause the brake pedal to be rock hard and you would have no brakes at all because the trapped fluid would not give. -Rear brakes will drag lightly As far as I understand, disc/drum combination valves have three functions: (1) shut off either the front or rear circuit if pressure to that circuit is lost, and alert the driver; (2) Proportioning: in the event of hard braking, reduce pressure to the rear brakes so they don't lock up; and (3), Metering: delay the response of the front discs so the rear drums have time to Note that the symptoms of a bad brake proportioning valve may also point to damage to other components, such as the rear brake circuit, brake caliper, or wheel cylinder. You want to delay the pressure to the front brakes until the rear drums have pressure. 1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks. Last week my rear, driver-side break froze up and was holding harder than the other side. Good Luck, L. Sponsored by: Stuck Proportioning valve??? Reply First, the description of the metering/proportioning valve from the Ford manual: Quote: "The pressure differential, proportioning and metering valve are three independent systems. -Bleeder rod won't push/pull out with finger The proportioning valve often gets stuck due to debris and corrosion. Long story on the cause, but I replaced the master cylinder, and now the proportioning valve isn't allowing fluid to get to the rear brakes. 10. This part is actually the "distribution valve". I can understand how the valve being stuck in the open position would cause the left wheel to not brake (valve absorbs all braking pressure to that wheel), and cause the car to swerve right when braking hard (the sudden pressure would probably prop the valve into open position, which is why it doesn't drag during a hard brake). The fronts should lock before the rears. No Ford dealer or obsolete seller has this particular valve. the light switch unscrews an the tool screws in its place . 9L or 7. These symptoms can range from a decrease in steering ability to an increase 1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks - Brake Proportioning Valve for 82 F150 - The proportioning valve on my 82 F150 with the 4. Stuck valves can be caused by debris or rust buildup, as well as mechanical issues within the valve itself. DEALS. pedal has excessive travel either air is compressing or that fluid is going somewhere and no way it can disappear into proportioning valve even if valve was stuck in Shop BRAKE PROPORTIONING VALVE M2328C online at ford. Brakes, Steering, Suspension, Tires, & Wheels - New proportioning valve for disc brake conversion - I did a search in this forum but didn't come up with a definitive answer. 1973 - 1979 F-100 & Larger F-Series Trucks - Rebuilding Brake Proportioning Valve - How does one rebuild a brake proportioning valve? 78 Proportioning valve stuck. Ford supplies an SN95 proportioning valve in the M2300K kit, and then instructs the person to REMOVE the prop valve rod and install the plug at the end. Pull over and connect the vacuum hose the next Checking the proportioning valve is easy. I bought it a few weeks ago and noticed the rear brake line was broken dont hammer on it as brass is soft and you could deform it and render it junk. HardFordCore. Ford Truck Enthusiasts Forums > Diesel > 1999 - 2003 7. 1973 - 1979 F-100 & Larger F-Series Trucks - Brake Proportioning Valve Problems - Hi everyone. It went along with a reman'd booster. This is a fixed ratio valve. Using a gravel road, stop with increasing pedal pressure until the wheels begin to lock. If the paperclip does not move at all, this means the proportioning valve piston is frozen stuck inside the cap screw. Now I'm Shop Ford Proportioning Valves and get Free Shipping on orders over $149 at Speedway Motors, the Racing and Rodding Specialists. 3L Power Stroke and the fronts were new, but the left one had a rock stuck in between the caliper this may be a question for the expert (NumberDummy) - I have a 1977 2WD F-150 w. You want the fronts to lock up slightly before the rears, otherwise the car will 1967 - 1972 F-100 & Larger F-Series Trucks - Proportioning Valve - Or whatever other name it may be known as. 7 RR TFS TW Heads/Edelbrock Perfor RPM/Holley 650 DP 1973 - 1979 F-100 & Larger F-Series Trucks - Brake Proportioning valve - 1973 - F100 2WD base model Dentside. I took some time to rule out stuck Log In; Register; Forums. 5 lb. Lots of misinformed sales people and literature. In most cases, you can unstick the brake proportioning valve by cleaning and lubricating the valve. 86 (29. 1) What are some symptoms of a bad proportioning valve on a 1977 F250 4x4? -Pedal retracts very slowly after being depressed. - 1) What are some symptoms of a bad proportioning valve on a 1977 F250 4x4? -Pedal retracts very slowly after being depressed. Loosening either the bleeder screw or line on either caliper releases hydraulic pressure and the When the proportioning valve sensed a major brake pressure drop in one circuit (front or rear) the proportioning valve piston automatically shuts off the circuit that has this pressure drop so that you can at least use the other circuit to stop the car. 3M After Hutch Mod Combination valve is a metering valve (Front brake ONLY), safety switch, and proportioning valve (rear brake ONLY) in a single housing. Woodchuck- If the proportioning valve is maladusted or failed, it will direct similar pressure to front and rear brakes. 0. gently step on the pedal and check the valve Brakes, Steering, Suspension, Tires, & Wheels - Brake proportioning valve - Right now my rear brakes don't work. 2% off) Sale Price: $65. M. I am getting a rear disc brake conversion kit and it recommends a proportioning valve under the booster. If you still have problems with rear brake lock ups, then a simple adjustable proportioning valve can be installed on the rear brake line after the combination valve and before the rear brake wheel cylinders. ; Check for Leaks: Ensure that all Imploded brake hoses and stuck proportioning valves produce hidden symptoms that are not easily diagnosed. I had that put on my truck 14 years ago. It is only in the rear supply line. Note that the symptoms of a bad brake proportioning valve may also point to damage to other components, such as the rear brake circuit, brake caliper, or wheel cylinder. Im stuck and out of ideas. The proportioning valve is pivotal in The proportioning valve allows brake fluid pressure to the rear brakes continue to grow, albeit at a very reduced rate. I have dug up a little more info through research. valves not even available. To check the fluid levels, put the vehicle up on a jack so that all tires are level. Ford Truck Enthusiasts Forums; Older, Classic & Antique Trucks; 1973 - 1979 F There is no bleeding a proportioning valve. The Pressure differential valve will NOT allow pressure to The valve responsible for delaying fluid to the front brakes is common to both the front left and front right; so it's not likely that the proportioning valve is the problem if one side If you notice rear-wheel lockup or uneven braking performance, you may be experiencing common symptoms of a malfunctioning brake proportioning valve. We did this swap on our '67 stang. It keeps the front to rear brake Stuck brake proportioning valves can impede brake fluid flow and cause uneven brake force distribution, compromising braking performance. Crack If you suspect there is an issue with your proportioning valve, check for the following symptom: Rear wheels lock up. It is made by Kent-Moore for a GM The factory proportioning valve for '69/'70 Cougar is located on the inner fender just below the master cylinder. Thread A few weeks ago ford replaced the proportioning valve on my taurus due to a clunk when i hit the brakes. Stuck valve: In some cases, the brake proportioning valve can become stuck in a certain position, causing an imbalance in the distribution of brake pressure. A few Loosen the rear line on the proportioning valve and see if it starts to dip fluid. Toolbox. Talk to the experts. Ford Proportioning Valves in-stock with same-day shipping. About the only thing you can do is to open up the proportioning valve and try to clean up everything, if 1961 - 1966 F-100 & Larger F-Series Trucks - 78 Proportioning valve stuck - HelpI broke a rear brake line and the brake proportioning valve is now stuck. I also used a wilwood M/C with a 1-1/16" bore (we put wilwood disks on back). Brakes, Steering, Suspension, Tires, & Wheels - How to diagnose if a proportioning valve is bad. If you want to attempt to try an re center the valve you should loosen the line on the master cylinder for the system that is working and then go in and take a quick sharp stab at the brake pedal, listen for the valve to click, have the key on so you can see light warning light go out. Imploded brake hoses and stuck proportioning valves produce hidden symptoms that are not easily diagnosed. I know this topic has been covered hundreds of times, but I am stumped right now. Come to find out the rod that connects to the control arm had detached from the assembly. Do Some people call them proportioning valves, but Ford never did. 46 1k 2023+ Super Duty ForScan Spreadsheet. Most GM safety switches are self-centering. HELP CENTER. Reply Subscribe . Getting a computer setup to run the bleed procedure was arguably the hardest part of this project. So if the rear brakes on a vehicle seem to be overly aggressive (too much pressure to the rear brakes), or the vehicle 1969sag - I thought the entire unit was called a proportioning valve, but I see where the two come together now. The Parts Catalog says it could be one of two: E5TZ-2B547-F - Fits 1985/ F250 4WD with 6. once brakes are bled remove the tool and replace the light. This has all the indications of a stuck slide or frozen piston, but it is only the hose that needs replacement. Here's my problem: Ever since I purchased the truck, the BRAKES light just stays on whenever the truck is running (key in ON position). If this doesn’t solve the problem, a standard Recognizing the symptoms of a bad proportioning valve is essential for maintaining the braking performance of your vehicle. Crack the bleeder screws on all four brakes. I have a phoenix systems vacuum gun Dan, what you are describing for a proportioning valve is the operation of a metering valve, except in reverse. power brakes (front disc/rear drums) and have just purchased a 1974 2WD F-100 w/manual brakes (front discs/rear drums). Up front I have pbr dual piston calipers. I'm going to be putting disc brakes on the back of my 78 F250 (front are already discs). a MC for a 1995 Ford Explorer and a disc/drum 'combination' brake valve from a 1984 Ford pickup 1973 - 1979 F-100 & Larger F-Series Trucks - 73 Ford f100 proportioning valve on disc brake conversion - I have a 73 Ford f100 2wd with front disc brakes and a stock proportioning valve on the driver side frame. Here’s how to address a stuck brake proportioning valve: Locate the Stuck Valve: Identify the proportioning valve causing the issue, usually near the master cylinder or on the vehicle’s frame. Those proportioning valve are not ez to get reset with yrs of buildup of crap that causes them to be frozen the slider trip rod. I have repaired the line but cannot figure out how to reposition the proportioning valve to allow fluid to the rear wheel cylinders. GIFT CARDS. (. I took out the original Prop. Causes range Tips for Resetting Different Valve Types. The #5 valve is the proportioning valve. It is my distribution block specifically that is giving me issues. You may have to 1987 - 1996 F150 & Larger F-Series Trucks - Brake proportioning valve - This is in regards to my 95 F-150. It has weak brakes. It appears that the "cobra" proportioning valve is set to bias the front more than the GT's because with the heavy nosedive these cars exhibit, the rear brakes do very little, especially with the good 13" PBR brake system up front, adding to the nosedive. If that doesn't fix it, then the switch (in the valve itself) could be stuck on or shorted. 9L engine is stuck. Sponsored by: the valve looks off centerbleeding didn't help. I have disc front, drum rear. Brake Proportioning Valve Eliminator kit, 1987-93 [MMBAK-6] : Maximum Motorsports, the Latemodel Mustang Performance Suspension Leader! The kit above is an easy way to remove it. The factory one SHOULD normally be OK. valve??? 1973 - 1979 F-100 & Larger F-Series Trucks - Bleeding brakes/proportioning valve tool - the ford manual says to use a metering valve bleeder tool, (number J-22742) to hold open the metering valve on the brake proportioning valve on a 79 f series. The "proportioning" mechanism for C3 Tech/Performance - Proportining valve stuck so I can't bleed back brakes - I installed all new lines and new calipers. 1973 - 1979 F-100 & Larger F-Series Trucks - Proportioning valve - Hello alldriving my truck this weekend and too my surprise the brake warning lamp on the dash came on. It's purpose is to lower the pressure to the rear brakes because they have less grip on the road surface during braking due to the weight transfer to the front, lifting weight off the rear. I have a proportioning valve in the line, and using a mid-70's Dodge dual master cylinder, also from a disk/drum truck. Whenever you introduce air into the ABS valve body, a computer should be used to cycle the various ABS valves and pumps while bleeding the calipers to release any trapped air in the ABS valve body. REWARDS. 1971 Ford Proportioning Valves in-stock with same-day shipping. How proportioning valves work, fixed vs adjustable valves explained, and how to reset a prop valve. Shop. Try slowly pressing and releasing the pedal several times. i would like Get Your Genuine Brake Proportioning Valve (f8uz2c161aa) Delivered Right To Your Door For Your 1989-2004 Ford Vehicle At AN Affordable Price With Nationwide Shipping! Brake Proportioning Valve - Ford (F8UZ-2C161-AA) 1989-2004 Ford - f8uz2c161aa. After you fix the brake problem, you must reset the piston into the center portion of the valve. If a proportional valve is bad, then your car won't have the same amount of fluid pressure at all four tires. If your rears are locking up, you could have an ABS problem. 1987 - 1996 F150 & Larger F-Series Trucks 1987 - 1996 Ford F-150, F-250, F-350 and larger pickups - including Your proportioning valve is visible on your master cylinder Thanks for the info guys. Both the front and rear brake fluid systems flow through the "proportioning valve". Troubleshooting techniques can help diagnose issues with the valve. You need to put the adjustable prop valve in the line to the rear brakes. I'm doing an upgrade from 4x drums on my 69 to disc/drum setup from a 78. Near the Apron, in the tunnel (As used on road race cars), over the rear axle as the early 67's were. What is the life time of a brake proportioning valve??? What 1948 - 1956 F1, F100 & Larger F-Series Trucks - stuck front disks - bad proportioning valve? - I just installed front disks, with rear drums, on my '59. 96 Ford F350 PSD CC DRW 64 Fairlaine 500 rust bucket/future Tbolt clone with 501 BBF. Make sure this part fits your Power steering pressure relief valve stuck symptoms occur when the valve that regulates the amount of pressure in the power steering system becomes stuck. It has nothing to do with the rear brake bias. Just because it was replaced does not mean that it is good. Call 800. 1973 Valve proportioning combination failing yourmechanic Brake proportioning valves 101: how they work & which style to choose Valve adjustment symptoms 1976 corvette wiper switch wiring diagram Brass proportioning valve – racing power company Valve proportioning ford truck pic forums mean bad does How does a proportioning valve equalize 1973 - 1979 F-100 & Larger F-Series Trucks - Proportioning Valve Factory Location? - 79/F150/4x4/C6 Anyone have a pic or description of where the proportioning valve is located? I assumed this is the factory bracket but for the life of me can?t find where it goes. Editor's note: This article was originally published March 8, 2017. The block on the rear axle is just a splitter. (proportioning valve) (possible caliper(s) drag) or the rear brakes They make adjustable proportioning valves, but they're normally only used for hot rods, etc. These issues often arise from wear and tear, contamination, or incorrect fluid pressure in the If you’re dealing with rear-wheel lockup or uneven braking, your brake proportioning valve may be at fault. The dual master cylinder is the safety feature that allows pressure at the good end. One part senses the difference between the front and back systems and will tell you if there is a difference of a low or loss of fluid in one side or the other( a The Proportioning valve has nothing to do with Front Disc Brakes Fluid travel. Guess 8ts stuck Reply Like #10 I have one those brake proportioning valves on my 91 gt and I have drum brakes on the back. :banghead My question with the proportioning valve comes in because I was watching it while someone was pumping the brake pedal and noticed that the pin on the front of the prop valve was moving in and out as they pushed the pedal down and released it. The problem im having is when I jump hard on the brakes the pedal is rock hard and the car doesnt really stop all that fast. The paperclip should push upward from 1/32 to 1/16 of a inch as a result of the sudden pressure. I have a '79 brake proportioning valve on it. According to the place I purchase the brake kit from. Generally speaking, the proportioning valve can not cause those symptoms. There are three functions of the pressure differential valve: It delays full effectiveness of the front brake, it proportions pressure 1973 - 1979 F-100 & Larger F-Series Trucks - Proportioning Valve 77 F150 & Weak Brakes - So I'm helping my father in law with his 77 ford. Thanks Boy, this post is gonna be filled with bad news. 1999 - 2003 7. Proportioning valves end up catching all the trash coming out of the master cylinder and the piston/plunger 1961 - 1966 F-100 & Larger F-Series Trucks - brake proportioning valve - I am wondering: I drive a '65 F-100. Proportioning / Combination Valve Replacement Service How much does a Proportioning / Combination Valve Replacement cost? On average, the cost for a Ford Ranger Proportioning / Combination Valve Replacement is $257 with $162 for parts and $95 for labor. 1977, 1998, 1999, brake, bronco, f100, f250, ford, part, porportioning, proportion, proportioning, rebuild, rebuilding, rebuld, valve. valve and went with a full size tee in the line. H13 LED Light Bulb Recommendation. 2. The safety switch moves out of the centered position when there's unequal brake pressure coming from the master cylinder, which trips the warning light on the dash. Learn. 9L Diesel. I've been told by several people I need to install the proportioning valve to adjust the brakes particularly with disc. Trending Topics. This can result in uneven braking or even complete brake failure. GVWR. 1k 173k This is prolly a 1 page thread at most. 0122, 7am-10pm CST, everyday. I don't think there is a proportioning valve in the lines. just a thought, in the past if i had an inkling it might be a bit of movement with the metal part of the pad or a pin or anti squeal plates against another metal part of the caliper making noise, i would rub the smallest of the smallest bit of graphite grease on the affected parts, and i mean small enough so it could`nt possibly get on the friction area and affect braking !!! 1973 - 1979 F-100 & Larger F-Series Trucks - Aftermarket proportioning valve - Has anyone had any luck with something like this: Proportioning Combination Brake Valve 1976 1986 Ford F150 F250 F350 Bronco | eBay From Blaise Ganzel, Kelsey Hayes, on the Ford, Kelsey Hayes RABS isolation valve or to Ford, proportioning valve switch assembly. If crap or corrosion get in there, it can block the flow of fluid. i looked for a part # on mine and didn't see anything. I don't need a proportioning valve, etc. Replace the proportioning valve. does anyone know what will work, some i have found fit up to 73. I've done everything short of removing the valve itself and disassembling Disc Brake Proportioning Valve / OBSOLETE / Fits: 1973/74 F100 / 1973/74 F250 w/a 6200 lb. Follow Manufacturer Instructions: Always refer to the vehicle’s manual or the valve manufacturer’s instructions for specific resetting procedures. Ford Truck Enthusiasts Site Navigation. TRACK ORDER. Puttster, the combination I know some of you are thinking that a burst is uncommon, but in both my Mustang and truck its happend! Your best bet is to get rid of the stock valve completly. ) aluminum brake proportioning valve "Kneepoint" is adjustable from 100 to 1000 psi Inlet and outlet ports have 1/8"-27 NPT threads for maximum installation flexibility Technical Specifications. Even after you release the pedal, the booster will continue to apply force to the brakes if it gets stuck in its boost mode. Note whether your rear wheels lock up The purpose of a proportioning valve is to reduce the pressure in the rear brakes. A proportioning valve is designed keep the pressure to all lines in balance, and, to limit the pressure to the rear or front tires by simply reducing the diameter of the delivery hole in the block/valve in which the 1973 - 1979 F-100 & Larger F-Series Trucks - 79 proportioning valve (pic) - I have a 79 f150 and the brakes were not really working as well as I would like so I decided to bleed them. 1973 - 1979 F-100 & Larger F-Series Trucks - Stuck Proportioning valve??? - Got the 77 home (finally) Discovered the left caliper was hanging up. clyd idci jbgsvu bfkwl ofl weevku ogeiqo brl hwauv ugzqt