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General Information


Jake Brake Noise

Engine Brake Theory

Engine Brake Troubleshooting

How can I obtain price and availability information on Jacobs® products?


Jacobs Engine Brake® and Jacobs Exhaust Brake®:
To better serve our customers, these products are sold and serviced through engine manufacturers worldwide dealer networks. This arrangement utilizes the engine manufacturers extensive and convenient distribution, service and support facilities worldwide. Now the same people who keep your engine performing in positive power can supply or service your retarding needs as well. Please contact your engine dealer for price and availability. You can use our Jake Brake Repair and Service Locations page to help locate a dealer near you.  DOWNLOAD HELP DOCUMENT: PRODUCT DISTRIBUTION DOCUMENT

What are the benefits of equipping my vehicle with a Jake Brake® retarder?


There are many benefits to having a vehicle, or a fleet of vehicles equipped with Jake Brake retarders (whether they are the Jacobs Engine Brake® or Jacobs Exhaust Brake®). Here are a few...

· Lower Operating Cost / Higher Productivity:
The use of Jake Brake retarders reduces the wear and tear on the service brakes, reducing the frequency of brake system service. Brake drum temperatures increase with use, and pads wear faster when hot. Using the engine brake on long downhill descents keeps the wheel ends and tire casing cooler, extending wheel bearing and tire casing life for more retreads. With a Jake Brake retarder, the vehicle is on the road more in the shop less, and is therefore more productive. Also, trucks with retarders enjoy a higher resale value, so your truck will be worth more if you decide to trade it in.

· Faster Trip Times / Increased Profitability:
Because Jake Brake retarders allow the vehicle to remain in control at higher speeds (control speed), trip times can be reduced. This can mean more trips for the same vehicle and thus increased productivity. Note: retarders are vehicle slowing devices, not vehicle-stopping devices. Never exceed the posted speed limit or the speed that will allow you to bring the vehicle to a safe emergency stop.

· Enhanced Vehicle Control:
With a Jake Brake retarder the driver has the ability to slow the vehicle without the use of the service brakes. This reduces the chance of brake fade on long down grades and gives the driver increased confidence and control of the vehicle. On flatlands, using the engine brake to keep up with the changing speed of the traffic flow without hitting the service brakes stabilizes highway traffic flow.

· Driver Retention:
Drivers prefer vehicles equipped with Jake Brake brand retarders. Fleets with Jake Brake retarder equipped vehicles enjoy a lower driver turnover, which reduces training and recruiting needs and helps keep productivity up.

· Why a Jacobs® product?
Jacobs Vehicle Systems™ works in partnership with each of the engine manufacturers to develop and market engine and exhaust brake products. This leads to optimized performance and reliability of the retarder for your specific engine. These products are sold and serviced through the engine manufacturers dealer networks worldwide to ensure product support over the life of the vehicle.

Can you tell me more about the history of the Jake Brake® compression release engine brake?


Clessie L. Cummins, founder of the Cummins Engine Company, drove across the United States to demonstrate the viability of diesel engines in 1931. While descending Cajon pass in California, the foundation brakes on his vehicle faded and he and the crew of his truck were nearly killed. Shortly after this experience Clessie first conceived the idea of using the engine to slow a vehicle going down hill. Clessie developed the first concept of a compression release engine brake in 1954, after leaving the company that he founded. Despite repeated rejections from major engine manufacturers, Clessie continued to pursue his idea.

It was a family connection through Clessie's nephew which led him to The Jacobs Manufacturing Company (established in 1903 by A.I. Jacobs), makers of the world famous three jaw Jacobs Drill Chuck. After some negotiation it was decided that Jacobs would invest in the further development of Mr. Cummins idea. In 1960, the Clessie L. Cummins division of Jacobs Manufacturing Company was established. Clessie finally received a broad patent for the engine brake in 1965. The company was divided in 1986 when Danaher Corporation purchased The Jacobs Manufacturing Co., and relocated chuck manufacturing to Clemson, South Carolina. Engine brake development and production remains in Bloomfield, Connecticut under the Jacobs Vehicle Systems™ name.

In March of 1961 the first engine brake, a Model 20, was sold for Cummins NH/NT series engines. In 1963 the first engine brakes for Detroit Diesel Series 71 engines were sold. In 1965 the model 675 was released for Mack Engines. In 1978, the Model C346 engine brake was developed for Caterpillar 3406 engines. Today, Jacobs manufactures Engine and Exhaust brakes for all of the major North American diesel engine manufacturers as well some in Europe and Asia. These include DAF Trucks N.V., Renault VI, Hino Motors, Hyundai, and Mitsubishi Motor Company.

Do you make a product for the Ford 7.3L Powerstroke or Navistar International T444E engines?


No, Jacobs does not offer an exhaust or engine brake for these engines in fact, Navistar and Ford have requested that we do not develop one for these engines.

The primary concern with putting a retarder on these engines is their use of hydraulic lifters. Most engines with hydraulic lifters have fairly low exhaust back pressure limits so the performance of an exhaust brake would not be substantial. More importantly the use of an exhaust brake on an engine with hydraulic lifters can cause engine damage. The problem is that the increased back pressure resulting from the operation of the exhaust brake will cause some degree of valve float. This valve float can cause the hydraulic lifter to re-set with the valve still open (not seated). This phenomenon is known as lifter jacking. Lifter jacking could also result if a traditional engine brake were used on these engines. The results of lifter jacking can be anything from low positive power (because the valves stay open) to engine damage caused by valve to piston contact.

Do you have a product for Caterpillar 3208 engines?


There is no Jacobs Engine Brake® or Jacobs Exhaust Brake® for these engines.

Do you have any engine brakes or exhaust brakes for Gasoline engines?


Because of the low back pressure limits of gasoline engines, the performance of a gasoline exhaust brake would not be substantial. Because the air intake in a gasoline engine is throttled and the compression ratio is much lower than in a diesel, the performance of a gasoline engine brake would also be insignificant. Because of this we do not offer any retarders for gasoline engines. However, Jacobs is actively seeking the commercialization of its Variable Valve Actuation System (VVA) for gasoline engines. The benefits of increased fuel economy (throttling with intake valves instead of a butterfly), miller cycle valve timing, EGR, and even compression release braking are just some of the reasons VVA would be an attractive option for gasoline engines in the light truck and passenger car markets. For more information about Jacobs VVA, click here.

Will there be a Jacobs Engine Brake® for the Cummins B or C engines?


Jacobs Vehicle Systems™ has developed an Engine Brake for the Cummins C engine and is currently available for ISC07 Cummins Engines and newer, We currently have only exhaust Brakes available for the Cummins B Series Engines, visit our Exhaust Brakes for the Dodge Ram page.

I've seen signs posted that say


Jake Brake® is a registered trademark of Jacobs Vehicle Systems™. The term "Jake Brake" is sometimes incorrectly used to refer to compression release type engine brakes in general. The term correctly refers to all of Jacobs Vehicle Systems retarding products including Jacobs Exhaust Brakes and Jacobs Driveline Brakes as well as Jacobs Engine Brakes. Engine brakes are used extensively on heavy-duty trucks, with diesel engines over 10.0L displacement. When operating it produces a distinctive staccato sound.

When an engine brake is used on a vehicle with a poorly muffled or un-muffled engine exhaust (using straight pipes for example), the sound can be offensive, which is what prompted the sign you saw. You were probably driving through a residential area that is adjacent to the highway. The real problem here is that there are a few trucks that are illegally modified or have defective exhaust systems that has triggered the community's reaction. Most high profile, professional fleets adequately maintain their trucks and equip them with OE quality mufflers to reduce the noise for both the driver and the communities they drive through. The sign you saw might have unfairly used our trademark, making it brand specific. The term "Jake Brake" also refers to our nearly silent exhaust brakes and driveline brakes, so these signs don't make sense for all Jake Brakes, and don't target the root cause of the problem, which is the illegal exhaust systems some truckers chose to configure their vehicle with. We would like to know where these "Brand Specific" signs are posted. If you've seen one, please let us know what Route number, City/Town and State you saw the sign by sending an E-mail to: [email protected]. Digital photos are great too!


I'm bothered by the noise of big trucks using their Engine Brakes, what can I do?


The federal government has required all vehicles manufactured since 1978 to meet noise requirements when delivered to the customer. Today, trucks are required to emit less than 80 dBa of noise when they drive by, as measured at 50 feet. So trucks have been required to meet noise requirements when they leave the dealership as new vehicles for quite some time. The real problem here is modified or defective exhaust systems. There is a good chance that the trucks that are causing the disturbance are running with straight stacks or gutted mufflers. Some are poorly maintained vehicles; some drivers simply enjoy making noise. In any case the use of the engine brake is not the problem.

Here are some steps that you can take to help quiet down your neighborhood:


Most states already have a law on the books that prohibits operating a motor vehicle on a public highway without a serviceable muffler. The real noise offenders, those with straight stacks or gutted mufflers, are operating in violation of this law. Encourage your local police to stop noisy vehicles and check them for muffler integrity. Cite those that are not in compliance. This is a fairly easy step that should produce a noticeable improvement in the quality of life of your community. And remember, when you do come in to contact with truckers who are operating properly equipped quiet vehicles, be sure to thank them for operating responsibly.


If you know someone who is operating a vehicle with an excessively loud exhaust system, encourage him or her to fix it. Loud obnoxious behavior makes us all look bad, and worse yet, drives cities and towns to pass laws that make truck operation difficult, even for those who do operate responsibly.

Our town is discussing erecting signs that prohibit engine brakes. Is this a good way to stop the noise?


We would say no. However, signs that prohibits unmuffled engine brake use (except in an emergency) would be an effective sign. This is what the state of Oregon has done statewide, due to the number of unmuffled trucks in operation in that state. This is most effective, as it prohibits those out of compliance, while allowing properly muffled vehicle drivers to operate with their engine brake when they want to use it.

Before heading to the town council meeting, be prepared with the facts. As you probably know from reading on the Jacobs web site (and other sources), the root cause of the objectionably loud trucks you hear is due to a lack of a proper muffler system. Whether there is an engine brake installed or not is irrelevant. The reason the sounds are so loud is because there is no muffler (or one that is deteriorated beyond its useful life).

Also, your state most likely already has a law on the books that states that you cannot operate any vehicle without a proper muffling device. Your police department can easily enforce that law, as it is pretty easy to determine the presence of a proper muffler on a truck.


How are Jacobs Engine Brakes controlled?


Typically, under good road conditions, the driver enables the retarder and selects a level of retarding with selector switches on the dash. To activate the brake, two more conditions must be met: clutch is engaged (or automatic transmission is in lock-up), and no fuel to the engine (foot off the pedal). Under these conditions, voltage is applied to the engine brake solenoids, and the brake is activated.

On older engines with mechanical fuel control, the Jacobs Engine Brake control system includes fuel pump and clutch switches in addition to the dash switches to detect when the required conditions were met. Today's electronic engines have an engine control module (ECM) which knows when there is a no fuel condition, and many have inputs to tell them if the clutch is engaged. For electronic engines the engine brake is powered directly by the engine control module.

All engine brake control systems can be configured to work with a vehicle's ABS brake system, and most can be configured to work with cruise control. Many of today's electronic automatic transmissions can be programmed to downshift if the retarder is requested, allowing the optimum RPM to be obtained and maintained for the best engine brake performance.

Note: Control systems installed by vehicle manufacturers can vary from those provided by Jacobs.

Can you explain why Jacobs Engine Brakes on certain engines are more powerful than on others?


Jacobs Engine Brakes are designed for specific engine applications, and retarding performance will vary depending on several factors of the design. One thing that is common to all engine brakes is that retarding horsepower increases as engine RPM increases. Optimum performance of the engine brake is achieved near rated engine RPM. In general, the same things that affect positive power influence retarding power. The most important factors affecting retarding performance are engine displacement, compression ratio, turbo type, level of boost, and the timing of the valve-opening event. Lets look in detail at how these factors affect the brake performance.

In it's simplest description, the Jacobs Engine Brake converts a diesel engine into an air compressor. All other factors being equal, the larger the engine displacement, the more powerful an air compressor it can make, and the higher the retarding performance.

Compression ratios of diesel engines are typically around 15:1. At the top of the piston stroke the air will occupy 1/15th the original volume, and be at around 500 psi. It takes power to compress air to high pressures; the engine crankshaft supplies this power. Higher compression ratios produce higher cylinder pressures, and absorb more power in doing so.

If the turbo is able to provide more boost, the starting volume of air will be at a higher initial pressure. This will result in a much higher final pressure. The higher the final pressure, the more power is absorbed. A turbo that produces higher boost pressures would result in higher retarding performance. NOTE: Do not try to modify your turbocharger to provide more boost for braking performance. The result will include a shattering/popping sound through the exhaust, turbocharger damage, as well as engine and engine brake damage. Doing so will void your engine and brake warranties.

Variable Geometry Turbochargers (VGT) or Variable Nozzle Turbine (VNT) turbocharger technology provides boost at lower RPMs, and increase mid range RPM performance of the engine brake.

Without an engine brake, all the valves remain closed at the top of the compression stroke, and we start the power stroke. In a no-fuel condition, the air pressure exerts a force on the piston and returns most of the power to the crankshaft. With a Jacobs Engine Brake active, the exhaust valves are opened close to top dead center of the compression stroke. "Pop" goes the energy stored in the air safely out through the exhaust system. Theoretically, none of the power is returned to the crankshaft, and the engine is able to provide retarding power for the vehicle.

The timing of the valve-opening event is important because the piston at top dead center has done the maximum amount of work. If the valve is opened early, you will not have absorbed as much power. Similarly, if the valve is opened after top dead center, some power has been returned to the crank by the compressed air. As the valve opening event moves away from top dead center, the brake becomes less effective. In practice it is necessary to use a cam or rocker motion that occurs close to top dead center. This motion will be picked up by a master piston and transmitted through a hydraulic circuit to a slave piston to open the exhaust valve.

Standard technology Jacobs Engine Brakes are designed using injector, exhaust, intake rockers or the camshaft directly to time the opening of the exhaust valve. Most engine brakes for Cummins and Detroit Diesel engines as well as Caterpillar 3406E/C15/C16 engines utilize injector timing, where the master piston follows the injector rocker for the same cylinder. On older Cat 3406,3406B and 3406C engines, and Mack E6 and E7, the slave piston for one cylinder is controlled by a master piston following an exhaust valve of another cylinder. This doesn't provide optimum timing or rate of valve opening, and the hydraulic circuits are longer and don't respond as well. Today's Mack E7 E-Tech™ engine was designed with the engine brake in mind from the beginning. A special cam profile was designed in conjunction with Jacobs specifically for operating a new J-Tech™ engine brake. This allows the J-Tech engine brake to optimize exhaust valve timing for optimum retarding performance. Click here to read more about E-Tech/J-Tech.

You can see that the specific design considerations of a particular engine significantly affect the retarding performance of the engine brake. It is also important to consider the load constraints of the engine components and the engine brake housings, as well as required valve to piston clearance. The retarding performance in a vehicle is also affected by many factors including the transmission, rear axle ratio, tire size, and vehicle dynamics.

How does the Jacobs Engine Brake® control valve motion?


A standard technology engine brake consists of a solenoid valve, control valve, and master and slave pistons. These components are assembled into a housing as shown below.

Typical Engine Brake X-Section
When the brake is activated, the solenoid allows oil to pass to the control valve. The control valve moves up and the check ball in the control valve is unseated, allowing oil to fill the master/slave piston circuit.
Low Pressure Oil Fills Brake
The oil pushes the master piston out, and when rocker motion pushes the master piston back, high pressure is created which seats the check ball in the control valve.
High Pressure Oil Seats Check Ball
Continued rocker motion causes the high-pressure oil to move the slave piston. The slave piston motion causes the exhaust valves to open.
Slave Piston Opens Exhaust Valves
As the rocker moves back down, the master piston follows, and the slave piston moves up, allowing the valves to close again, ready for the next cycle. These cycles continue as long as the brake solenoid is energized. When the solenoid is de-energized, the control valves move down and the high-pressure oil is released through the tops of the control valve bores.
Solenoid De-Energized, Oil Exits Brake

What is the difference between an exhaust brake and an engine brake?


An engine brake uses a compression release mechanism to turn your power-producing diesel engine into a power absorbing air compressor.  It functions by introducing an additional motion to the exhaust valves, causing them to open slightly during the end of the compression stroke, dissipating the work absorbed in the compressed air prior to the power stroke of the engine piston, thus causing the vehicle to decelerate.

An exhaust brake generates braking power by restricting exhaust air ouflow thus increasing back-pressure inside the engine exhaust manifold.  It is more common on diesel engines smaller than 6 liters.  Unlike engine brakes, it is quieter when activated.

My Jacobs Engine Brake stopped working, what's the most likely problem?


Generally if your brake stopped working entirely, you have an electrical problem. This is most likely a failed switch (probably a fuel pump or clutch switch). You can usually confirm this by hot-wiring the brake, bringing battery power directly to the solenoid leads (with the engine at idle). Be sure to disconnect the existing leads to the solenoids so that you do not damage your control system. If the brake does not operate when hot-wired, you may have a solenoid failure. If the solenoid is actuating but the brake is not turning on, the problem is probably mechanical. Your engine dealer should be able to help you locate appropriate troubleshooting information for your engine brake.

Remember, you should always take precautions when working on any engine or component. Always wear safety glasses, and never attempt a repair that you are not sure you are qualified to perform.

My Jacobs Engine Brake doesn't seem to have the retarding power it used to, what's the most likely cause?


There are a number of things that may have affected your engine brake performance, and a qualified service technician is best suited to find the cause. In general the same factors that affect positive power performance affect retarding as well. You should always check positive power performance before looking at a retarding performance problem.

Assuming your engine is functioning as specified in positive power there may be a problem with the engine brake or its control signal. If the brake was functioning well before, the first thing a technician will do is check to see if all of the housings are working. It may simply be a housing with a loose wire or faulty solenoid.

Assuming the housings are being activated, the slave piston lash adjustment will be the next thing to check. Don't be fooled into thinking that going tighter or looser on the adjustment will give more performance - in most cases this simply isn't the case, and engine or housing damage could result.

If the adjustments are correct and all the housings are turning on as required, it's time for more detailed investigation - and this gets into the specifics of each model. The detailed information in the installation manual should be consulted, and if you're still stumped, have your dealer contact the engine OEM technical support department, or drop us an E-mail at [email protected], we'll be happy to assist.

Service Locations

The Jacobs Engine Brake® and Jacobs Exhaust Brake® products are sold and serviced through engine manufacturers worldwide. Locate a dealer in your area.


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