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Engine VS Jake Brake


Rickey White Jr

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I recently bought a 07 CXP613 & did not think too much about the "engine" brake. Recently I noticed that when I have it on high & start slowing down it just totally cuts out. Especially today when I had to use it coming down a hill on a quick red light & locked my trailer brakes when it went out. That is when I realized it was not anything I was doing. This is the first truck I have drove that does not have a regular jake. That being said, I have searched & have been unable to find one so I hope I am not out of luck on this. Is there a way to install an aftermarket jake for this truck before I drive myself insane looking?

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A "Jake" brake is just an engine compression brake manufactured by the Jacobs Mfg. Co. (Jacobs Vehicle Systems). There are several manufacturers of engine compression brakes, and they all work in a similar manner.

What is likely occurring in your situation, is that on an electronic engine there is usually a setting which turns off the brake at a given RPM...preventing the engine brake from stalling the engine. Changing the brand of the engine compression brake won't stop what is happening, because the brake is functioning exactly as it was designed to do....slows you down, and then turns itself off at a set point to prevent stalling the engine.

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When approaching a 4-way stop, the vehicle with the biggest tires has the right of way!
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You must remember the engine"Jake " brake will only work during certain RPMs and if those RPMs drop to low then it will cut out. The key is to downshift to keep the Jake helping the truck to slow down so as to keep the RPMs up. Also you do not want to rely on the engine brake to slow the truck as if for some reason you lose traction with the rear wheels you will lose control. It is always good to use your brakes in conjunction with the engine brake.

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Tony

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Sounds like you could have a bad wire connection.or a weak relay or bad switch.The Dynatard on my Mack would cut out sometimes and I had to put new wire end on it. Unless you put a exhaust brake on the truck changing Jakes will not stop the cutting out at low rpms. A Jake sets on top of the motor under the valve covers and works off of oil pressure and basically slows the exhaust coming out of the motor. That is as simple as I can explain it.

This is Mack country. On a quiet night you can hear a peterbilt rust away.

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Actually a jake brake turns your engine into a giant air pump. When a jake is flipped on what it does is open the exhaust valves on the very last second of the combustion stroke. So as your piston goes up, your valves are shut and your piston is trying to compress all of that air in the chamber. Right before combustion would happen the engine brake opens the exhaust valve, thus pushing out all the air before combustion. So for all the power it took the engine to compress the air, it didn't gain any power back from ignition. And thats what slows down your rig.

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Okay I should have been a bit more specific on this. It will cut out for no reason at about 14-15 rpm. It is like it totally breaks loose. Yes I would like the actual Jake from the Jacobs company but I do not think that will happen. That is why I am looking for an actual exhaust brake and not this engine air compression deal it has. I had the setting checked by an outside dealer prior to purchase and the cut out is 10. Most of the time it holds but lately I have noticed it will give out more often. I took the dash apart today and checked for loose connections on everything and all is fine that I came across. My fear is that there is a seal somewhere that is letting the compression out. Either way I would just like to have a regular exhaust brake and not this new eco friendly noise free family friendly half working brake.

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Actually a jake brake turns your engine into a giant air pump. When a jake is flipped on what it does is open the exhaust valves on the very last second of the combustion stroke. So as your piston goes up, your valves are shut and your piston is trying to compress all of that air in the chamber. Right before combustion would happen the engine brake opens the exhaust valve, thus pushing out all the air before combustion. So for all the power it took the engine to compress the air, it didn't gain any power back from ignition. And thats what slows down your rig.

Best explanation I've ever read.

Fun is what they fine you for!

My name is Bob Buckman sir,. . . and I hate truckers.

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The bleed off engine brake is a quitter system than the jake.The 4000 Mercedes with bleed off system with the blue ox is very powerfull and quite.The way it works is it has a dummy valve with a drilling from the combustion cyl thru the valve when it is open back into the intake port.The dummy valve is opened by a small piston power by air pressure controlled by ecm.When you turn it on for braking it opens the dummy valve and as the piston comes up on compression it has been bleeding off compression back into the intake and unlike the Jacobs brake which waites till the piston gets to the top and then lets all compression off into the exhaust which makes a noise it still has done same thing as the jake brake.The energy it took to compress air is not going to help push the piston back down anymore so you use that energy for braking.

glenn akers

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From the exhaust brakes I've seen, they don't work very well. About the only reason I would ever consider one is if they didn't offer a engine brake for that engine.

Exhaust brakes work nowhere nearly as well as engine brakes. You should be able to get yours fixed fairly easy, there's just not that much to them to go wrong. You've basically got a wiring problem or a solenoid problem or I have seen the valves so bad out of adjustment it caused problems.

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