Brake Master Cylinder Repair Kit 1-1/8 Cylinder Brake Cup Seal

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What is a Wheel Brake Cylinder Repair Kit?

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At its core, a Wheel Brake Cylinder Repair Kit is designed to refurbish or repair the wheel brake cylinders found in drum brake systems. These cylinders are responsible for transferring hydraulic pressure from the master cylinder to the brake shoes, which then press against the drum to slow or stop the vehicle. Over time, brake cylinders can become corroded, worn, or develop leaks, leading to diminished braking power and potentially hazardous driving conditions.

The repair kit typically includes various components such as seals, O-rings, pistons, and springs – each of which plays a critical role in ensuring that the wheel brake cylinder operates smoothly and effectively. These components come in various sizes and specifications, allowing for broad compatibility with a wide range of vehicle makes and models.

Functionality of Hydraulic Wheel Cylinder Brake Cup Seal

The hydraulic brake system works on the principle of transferring force through hydraulic fluid. When the brake pedal is pressed, hydraulic fluid from the master cylinder travels through brake lines to the wheel cylinder, where the brake cup seal’s primary function comes into play. As pressure builds within the cylinder, the brake cup seal ensures that this fluid does not leak out, enabling the pistons to effectively push against the brake shoes and create the necessary friction to slow down or stop the vehicle.

In addition to maintaining hydraulic pressure, the seal’s design also prevents moisture and contaminants from entering the wheel cylinder. This function is crucial because any foreign substance can compromise the integrity of the hydraulic fluid, leading to reduced braking efficiency or potential brake failure. A well-sealed hydraulic system not only enhances the performance but also extends the lifespan of the brake components.

Product Description:

A reliable and efficient braking system is essential for safe and smooth operation of any vehicle. One of the key components of this crucial system is the Brake Cup Seal. Designed to ensure optimal performance and longevity, the Brake Cup Seal plays a vital role in maintaining the integrity of the braking system by preventing leakage of hydraulic fluid.

Brake Cup Seal：

The Brake Cup Seal, also known as a wheel cylinder cup or brake piston seal, is a small but extremely important part that is typically made of high-quality rubber or polymer material. It is located within the wheel cylinder of the brake system, which is responsible for converting the hydraulic pressure into mechanical force to activate the brakes and bring the vehicle to a stop.

The primary function of the Brake Cup Seal is to prevent any leakage of hydraulic fluid from the wheel cylinder. As hydraulic pressure is applied to the wheel cylinder when the brake pedal is pressed, the Brake Cup Seal creates a tight and secure seal between the piston and the cylinder bore. This seal is vital in maintaining the pressure required to actuate the brake shoes or pads, enabling effective braking power.

Due to constant exposure to high temperatures, pressure, and friction, the Brake Cup Seal is subjected to wear and tear over time. This wear can lead to leaks, loss of braking power, and potential safety hazards. Hence, it is crucial to replace worn or damaged Brake Cup Seals promptly to ensure optimal braking performance and to maintain vehicle safety.

Function:

The brake cylinder is mainly used to push the brake pads, the brake pads matcha brake drums, so that the speed of the vehicle is reduced or even stopped. It is an indispensable chassis braking part in the braking system.
After the brake is stepped on, the master cylinder generates thrust to press the hydraulic oil to the sub-pump, and the piston inside the sub-pump is moved by the hydraulic pressure to push the brake pads. The oil brake is composed of the brake master cylinder and the brake oil storage tank. They were connected to the brake pedal at one end and the brake hose at the other. Brake oil is stored in the brake master cylinder, and has an oil outlet and an oil inlet. When the brake is applied, the oil outlet opens and the oil inlet closes. Under the pressure of the piston of the pump body, the brake oil pipe is squeezed out of the oil pipe to flow to each brake cylinder to perform the braking function. When releasing the brake pads. The oil outlet in the brake master cylinder will be closed, and the oil inlet will be opened, so that the brake oil will return from each brake cylinder to the brake master cylinder, returning to the original state.
According to the brake cylinder manufacturer, the car brakes are divided into air brakes and hydraulic brakes. Heavy trucks use air brakes, and general cars use oil brakes. When you brake, when you step on the brake pedal, the brake master cylinder sends the brake fluid through the pipeline to each brake cylinder. The brake cylinder has a connecting rod that controls the brake shoes or pads. When braking, the brake oil in the brake oil pipe pushes the connecting rod on the brake cylinder, so that the brake shoe tightens the flange on the wheel to stop the wheel.

Features:

1. High-Quality Material: The Brake Cup Seal is made from premium-quality materials that offer excellent resistance to heat, pressure, and various chemicals found in hydraulic fluids. The materials used are often synthetic rubber or elastomers that exhibit exceptional durability and longevity.

2. Precision Engineering: The Brake Cup Seal is manufactured with precision engineering techniques to ensure consistent and accurate dimensions. This precision allows for a perfect fit within the brake cylinder, eliminating any chance of leakage and ensuring optimal performance.

3. Easy Installation: The Brake Cup Seal is designed for easy installation, allowing for hassle-free replacements or repairs of faulty seals. It is important to follow the manufacturer's instructions and use appropriate tools to ensure a secure and effective installation.

4. Versatility: Brake Cup Seals are available in various sizes and designs to fit different types of brake cylinders and braking systems. This versatility means that they can be used in a wide range of applications, from small motorcycles to heavy-duty industrial machinery.

5. Cost-effectiveness: The Brake Cup Seal is an affordable component compared to the potential costs associated with brake system failures caused by faulty or worn-out seals. Investing in quality brake cup seals ensures long-term reliability and minimizes the risk of brake malfunctions.

6. Performance and Safety: The Brake Cup Seal is crucial for the proper functioning of the brake system, ensuring reliable and consistent braking performance. By maintaining hydraulic pressure and preventing leaks, it contributes to the overall safety of the vehicle and its occupants.

Customize Piston Seal:

The primary function of the Hiken Piston Seal is to prevent leakage of fluids or gases in dynamic hydraulic and pneumatic systems. It achieves this through its exceptional sealing capabilities, ensuring a tight and reliable seal in even the most demanding applications. With the Hiken Piston Seal, you can bid farewell to costly and time-consuming seal replacements or repairs.

One of the outstanding features of the Hiken Piston Seal is its advanced design and construction. It consists of a superior-quality elastomer material that is highly resistant to wear, abrasion, and extreme temperatures. This ensures exceptional durability, allowing the seal to withstand harsh operating conditions with ease. Whether you're dealing with high-pressure environments or extreme temperature variations, the Hiken Piston Seal will maintain its performance, ensuring consistent productivity.

Another remarkable feature of the Hiken Piston Seal is its unique geometry. The innovative design includes microgrooves on the sealing surface that enable enhanced fluid separation and reduced friction. This translates into improved efficiency and reduced energy consumption in hydraulic and pneumatic systems. By minimizing friction and optimizing sealing performance, the Hiken Piston Seal offers a significant advantage over traditional seals.

The Hiken Piston Seal comes in a range of sizes and dimensions, ensuring compatibility with various piston diameters. This versatility allows for broad applications across different industries, including automotive, manufacturing, mining, and construction. Whether you're looking to replace worn-out seals or optimize the performance of your existing systems, the Hiken Piston Seal is the ideal solution.

Brake cup seal:

The brake cup seal is an essential component of a vehicle's braking system, playing a crucial role in ensuring the proper function and safety of the brakes. This small but mighty seal is responsible for creating a tight seal between the brake cup and the cylinder to prevent any leaks of hydraulic fluid, which could lead to brake failure. Without a properly functioning brake cup seal, the brakes could become unreliable and potentially dangerous.

Function:

One of the key functions of the brake cup seal is to maintain hydraulic pressure within the brake system. When the brake pedal is pressed, hydraulic fluid is forced through the brake lines to actuate the calipers or wheel cylinders, which then apply pressure to the brake pads or shoes, ultimately slowing or stopping the vehicle. The brake cup seal ensures that the hydraulic fluid remains contained within the brake system and does not leak out, allowing for consistent and reliable braking performance.

In addition to its primary function of preventing hydraulic fluid leaks, the brake cup seal also helps to maintain the proper function of the brakes by ensuring that the cylinder is properly sealed and protected from contaminants. Dirt, dust, and moisture can compromise the performance of the braking system, leading to decreased braking efficiency and potential damage to brake components. The brake cup seal creates a barrier between the cylinder and external elements, helping to keep the brake system clean and functioning optimally.

Feature:

One of the key features of a high-quality brake cup seal is its durability and resistance to wear and tear. The seal is exposed to high pressures and temperatures as well as constant movement as the brakes are applied, so it must be able to withstand these conditions without deteriorating. A well-made brake cup seal is typically constructed from high-quality materials such as rubber or silicone, which offer excellent resistance to heat, pressure, and abrasion. This ensures that the seal remains intact and effective over a long period of time, providing consistent brake performance and safety.

Another important feature of a brake cup seal is its precise fit and compatibility with the brake system components. Brake cup seals come in a variety of sizes and shapes to fit different types of brake cylinders, so it is crucial to choose the correct seal for your specific vehicle make and model. Using an ill-fitting or incompatible brake cup seal can lead to leaks, reduced braking performance, and potential safety hazards. It is important to consult with a professional mechanic or refer to the vehicle's service manual to ensure that you are using the correct brake cup seal for your brakes.

NO. OEM NO. OEM 1 SCR. 29 SC 2 SCR. 30 SCR 3 SCR. 31 SCR. 4 SCR. 32 SD 5 SCR. 33 SDR. 6 SCR. 34 SDR. 7 SCR. 35 SCR 8 SCR. 36 SD 9 SCR. 37 SD 10 SCR. 38 SCR 11 SCR. 39 SDR 12 SCR. 40 SCR 13 SCR. 41 SCR 14 SCR. 42 SDR 15 SCR. 43 SCR 16 SCR. 44 SDR 17 SCR. 45 SCR 18 SCR. 46 SDR 19 SCR. 47 SCR 20 SC277R. 48 SD 21 SCR. 49 SDR 22 SCR. 50 SDR 23 SCR 51 SDR 24 SCR 52 SDR 25 SC 53 SDR 26 SCR 54 SCR 27 SCR 55 SCR 28 SDR 56 SCR

Our Advantages
1. The standard product Inventory is Wide and Complete: NNK stocks the standard products and supplies the most common inch sizes. It can manufacture precise power steering oil seals according to various industrial needs and deliver them quickly and on time, made of high-quality rubber with good performance.
2. Low Mold Cost: Most of the various seals' standard specifications already have molds, and no additional investment is required. If there is a special size that needs to be opened, we will also give it back to the customer at a low cost or jointly develop the model for cooperation.
3. Flexible MOQ and Instant Delivery: It can support small orders from customers, MOQ is smaller than the industry; and sample testing is provided. Instant delivery allows customers to apply production scheduling more flexibly.
4. Auto Assembly Machine for Oil Seal Since the introduction of the spring, the oil seal is more precise and quicker when inserted, so delivery time and quality are more stable.
5. Fully Automatic Quality Inspection Equipment: In , automatic quality inspection equipment will be introduced to ensure the quality of oil seals, overcome the bottleneck of manual inspection, and produce a more efficient and fast output.
6. Provide customized services: In case there is a need for customized power steering oil seals, you are welcome to leave relevant information, such as CAD/CCAM and other requirements, and NNK can do advanced planning services and consulting for you.

FAQ

About 3 months ago, I purchased 12 brand new wheel cylinders for my M135 from a reputable military parts dealer online. The wheel cylinders looked great and are very close to the originals that were on the truck. All 12 wheel cylinders were installed and the truck has had less than 100 miles on it since having all new brakes put on.

The problem I am having is that one by one, these new wheel cylinders have begun to leak. Upon disassembling to inspect, I was not happy with what I saw. Here is a picture of the new wheel cylinder internals on the left and the internals of the original military wheel cylinders on the right.


The new wheel cylinder internal is a single machined piece that the cup has to be stretched around to fit into the groove and nothing pressed against the bottom of the cup. The original military is a two piece setup where the lower piece pressed up against the cup and makes it swell when the brakes are applied.

I do not see how the new wheel cylinders are even functional with nothing pressing into the cup to form any kind of seal. Mine are obviously not functional because they are all leaking. I am not happy and wanted to get some opinions. I want to contact the seller and request a refund and also complain about the lack of quality and the safety hazard these pose by leaking so badly.

What should I do?

............................The original military is a two piece setup where the lower piece pressed up against the cup and makes it swell when the brakes are applied.

That is not correct: in any case, when you step on the brakes it is the fluid under pressure that forces the lip of the cup against the cylinder wall and makes it seal.
The extra part you see on the right are cup expanders, yes, but the only force applied to them- with brakes applied or stationary- is the action of the compressed coil spring, which is fairly constant.

I do not see how the new wheel cylinders are even functional with nothing pressing into the cup to form any kind of seal.......

On those replacements (with no cup expanders), about the only thing keeping the cups from leaking - while at rest or moving outward that little bit until pressure is built-up - is the resiliency of the slightly compressed rubber part itself.
Now, if for some reason these cups have shrunken and maybe the cylinder surface is not absolutely perfect and smooth, then that may be the cause of your issues.


G.

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That is not correct: in any case, when you step on the brakes it is the fluid under pressure that forces the lip of the cup against the cylinder wall and makes it seal.
The extra part you see on the right are cup expanders, yes, but the only force applied to them- with brakes applied or stationary- is the action of the compressed coil spring, which is fairly constant.



On those replacements (with no cup expanders), about the only thing keeping the cups from leaking - while at rest or moving outward that little bit until pressure is built-up - is the resiliency of the slightly compressed rubber part itself.
Now, if for some reason these cups have shrunken and maybe the cylinder surface is not absolutely perfect and smooth, then that may be the cause of your issues.


G.

Bingo. Same issue with M35A2 mil spec wheel cylinders. The UP45 rebuild kits from NAPA have expander springs and seal much better.
Another issue is the master cylinder venting. If the vent or check valve clogs and a partial vacuum develops, the wheel cylinders can leak.
Finally, installing a remote reservoir higher up in elevation can help by placing the master cylinder under a bit more pressure from higher fluid level. This additional hydrostatic column won't bother braking action as each foot of elevation is only a bit less than a half PSI but it works. Wheel Cylinders G749

You deserve a break about now! Usually I break something new while I'm fixing the first broken thing but having new parts go down tops the list of painful hurdles. That would drive me to drink but not drink and drive.
I've always wondered if the pressure applied to the brake pedal is = to the pressure the wheel cylinders feel. If it was just fluid flowing a guy could anticipate pascal's theory but with the air/ hydraulic cylinder, how much pressure hits the wheel cylinders? How do we test this?
I've never had to force the brake pedal on Goose so have you ever had to jump hard on the pedal? They should be designed so a 300lb fat, balding guy can stand on them with 5 tons in the back so having them leak with low or no usage is just wrong.

The Wagner's are set up so much better by the looks of things. Goose is on her 4th year with low miles and frequent/ light usage but seeing extreme ambient temp swings of 130°f.

Your cylinders look like they came out of the NOS manual. When I hunt weepay for wagner I see hundreds of wheel cylinders for $20 or $30 greenbacks and when I get to the ....$70.00. Do you think these guys could help us out, if we ask? http://aftermarket.federalmogul.com/en-us/brands/wagner-brake/pages/home.aspx#.VeIwAZerEuc

I'd run WAGNER stickers on the truck and be real happy continuing to promote their product if they'd support our G749 restorations and kick you a few cylinders.
I'll need 36 and a few spares next spring so let's find the promotional department.
http://federalmogul.com/en-US/Contact/Pages/General-Inquiry.aspx

In the meantime I'll get an idea on inventory up here.

Plowboy....I was at the end of a 22+ hour day when I read your post last night and missed a few things. I have not had to get on the brakes hard at all. Just normal braking from normal cruising speed. Would be nice if Wagner could be a little more reasonable on those cylinders. I think $70 is a bit outrageous.

Gerhard, thank you for making sense of that for me. I like the idea of having the expander behind that cup. Seems that when the brakes are at rest, the pressure from the brake return springs and the spring in the wheel cylinder would keep that cup slightly expanded and prevent leaks. Is my thought process on that correct?

I'm seriously thinking about lightly honing the wheel cylinders and putting them back together with the old style pistons out of the original wheel cylinders and new cups from NAPA.

..........Seems that when the brakes are at rest, the pressure from the brake return springs and the spring in the wheel cylinder would keep that cup slightly expanded and prevent leaks. Is my thought process on that correct?...

Almost: the brake(shoe) return springs do exactly that: pull the shoes back against their regulators, after braking.
While at rest, those return springs do nothing to keep those cups expanded.

I'm seriously thinking about lightly honing the wheel cylinders and putting them back together with the old style pistons out of the original wheel cylinders and new cups from NAPA

That is what I would try if the replacement cups you can get had the lips chamfered, to more or less follow the angle of the original expanders. (Think of two wedges moving towards each other...)

After blowing-up your pic in post #1 it seems those cups have straight cut, non-chamfered lips...?


G.

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After blowing-up your pic in post #1 it seems those cups have straight cut, non-chamfered lips...?
G.

That cup in the picture is what came off of the new wheel cylinders. I just slid it on the old piston while trying to figure out the leaks. I will have to look at the NAPA cups that I have. Before I bought new wheel cylinders, I rebuilt the original wheel cylinders on the front. They were salvageable. They did not leak at all. Only decided to buy all new wheel cylinders when all of the original back ones were too pitted to rebuild.

Well, of course that's the whole reason you went to the trouble to get new, right!?

Pretty much. G749 wheel cylinders

Plowboy....I was at the end of a 22+ hour day when I read your post last night and missed a few things. I have not had to get on the brakes hard at all. Just normal braking from normal cruising speed.

It's all good little buddy, I was picking corn, chasing thieves and pretending to drop a 350 in a deuce. The G749 team don't need no stinkin' sleep. I found another flavor of from without the 'wagner lockheed' title on it so it gives me some hope that these were NOS and there are more.

Even if you settle for putting those back in, we need a price and an inventory count from the NOS kids so I'll try and make calls over the next couple days.



I should have loaded the following pictures on your other thread but I'm done already so I'll chase a few more matching number trucks another day.

I managed to get to one truck and check for the top of frame stamp....and thar it is....matching numbers on the 12-8-52 GMC. I heard the G749 veterans mention it but never thought much about it. This will allow me to get the correct numbers on the doors and dash on future builds, very cool.