General
jake brake
What does jake brake mean?
A compression-release engine brake that opens the exhaust valves at the top of the compression stroke, dumping the air the pistons just squeezed. Result: the engine becomes a giant air pump that slows the truck without touching the service brakes — saving the friction brakes from cooking on long downgrades. Sounds like a machine gun ratcheting. Many towns ban its use inside city limits because of the noise, hence the 'No Jake Brake' signs you see at every off-ramp.
"I hit the jake brake coming down the grade into Donner Pass."
Origin
Trademark of Jacobs Vehicle Systems, who patented the device in 1961. 'Jake' is just short for Jacobs. The name stuck so hard it now means any compression brake regardless of make.
Frequently asked questions
What is a Jake brake?
It's an engine compression brake that lets a diesel slow itself down, making a loud, rapid-fire barking sound.
How do you use Jake brake in a sentence?
"You could hear his Jake brake barking all the way down the hill."
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