Do jake brakes damage the engine?

Yep same here. Elderly 13 Od.

Still won’t use it to shift tho. Lol!

 

Cat’s retarder. Also another thing that if you had down here in the states you were a king. Very rare here. I’m sure up north they were more common.

Back then nobody had the need or mindset to spend the money on that stuff. They actually made due without it. Imagine that.

 

Is that 2 sticks

 

My Daddy's coal truck had a 225 cat with no jake..hauled 25 ton in WV..

 

Since when does a vacuum have any resistance?

Unless there have been changes, a Jake does not open up...the exhaust valve. It just keeps the valve from fully closing on the compression stroke and keeps the diesel fuel from exploding.

So, there is still a lot of compression left, (big air pump now) and that is where all the noise comes from, the compressed air trying to escape past a valve that is just barely open. Kind of like a shrill whistle between teeth or fingers.

Diesels compress the air around 16 times, give or take, and when air is compressed that much, it heats up to around a thousand degrees and combustion takes place. (hence no need for spark plugs) By having the valve partly open though, it lets out just enough compressed air to keep below that temperature, but still has a lot of compression left for helping with braking.

Your truck now is trying to turn a 15 liter air compressor. A big retardation force.

Some of those engines have about the same amount of hp retarding as they do pulling.

 

Basically a torque convertor that was attached to the flywheel and block. Had a valve on the steering column that controlled the flow of engine oil into it via an air-controlled valve. They worked well but you had to watch the oil temp, as all the retarding force went into the oil as heat.

Jakes were available for mechanical Cats (and Macks,) too, but because they didn't have an injector lobe on the cam, the timing of the Jake opening the exhaust valve was less than optimal, and it showed in the retarding power. They used a slave cylinder activated by one of the valves on an adjacent cylinder to pop the exhaust open.

 

One of my much older cousins used to drive for the long defunct Western in the oilfield back in the early 80’s. They ran Transtar 2 coe’s with 8v screamin demons. He mentioned a few times how they could leave the jakes on all the time and even parked at idle because they never made enough oil psi at idle for the solenoids to work. Rev them up a little and the jakes would start to kick in like a racecar engine rev limiter.

 

If there's vacuum on one side of a piston, and pressure on the other, there is definitely force needed to move that piston. It's why gasoline engines have more inherent engine braking than diesels, when the throttle is closed, there's a substantial vacuum on the piston during the intake stroke.

The whole point of dedicated lobes for Jakes as Cummins introduced, is to maximize the amount of compressed air, released as late as possible, during the compression stroke. That way the engine does the work of compression but doesn't get the benefit of the air-spring effect.

BTW, modern engines don't inject fuel with the Jake on, and I believe most even shut off the fuel in any overrun condition.

 

That's pretty much what happened if the throttle switch quit. Only happened to me once, but all the popping and banging scared the crap outta me. Luckily it happened right after a shift, so I was just getting back into the throttle. Hate to think what might happen if an engine were at full power when the Jake kicked in!

 

Very cool stuff.