Engine brakes are rarely seen on tractors, but in certain regions they are really important to truck drivers. If you use them, you might need to schedule maintenance a little sooner than normal, but we will also discuss when you should get regular maintenance on your engine. Engine brakes The four strokes of the engine are intake, compression, power and exhaust. Engine brakes work by cutting the fuel at the compression stage and releasing the air that is compressed. This cuts the power and doesn’t waste a lot of unnecessary fuel.

Engine brakes make a loud noise when the compressed air is being let out. Engine brakes can be applied to a desired number of cylinders; it doesn’t have to be applied to the whole engine, so the semi-truck can be slowed in stages depending on the downhill grade it is driving on.

Exhaust brakes
Another option is the exhaust brake. Instead of letting out the exhaust, the compressed air is held back and the crankshaft is slowed down, slowing down the rig. This option makes little noise and, therefore, is a better option for residential routes.

Engine and exhaust brakes are very useful in saving your regular brakes. According to some, the proper use of these tools will help your wheel brakes last up to three times longer. However, the engine and exhaust breaks restrict the flow of air and create different amounts of heat and pressure in places previously unintended. Therefore, there are a few parts that need to be checked more often to ensure you aren’t overworking your engine.

The overhead should be checked at least every 50,000 to 75,000 miles. Previously the recommendation was at least every 100,000 miles, but dealers and technicians have found that may be too late. Get it in for a thorough check closer to 50,000 miles, if you do a lot of driving in the hills. Tell-tale signs of your overhead needing attention could be poor performance and fuel economy.


Watch for carbon buildup in the overhead. Look at the rollers on the camshaft. If there are fine, black particles, or a black film, you have carbon buildup. The carbon is like having millions of little diamonds on the metal and as it rolls and hits, the carbon will start to chip away at the roller. This will be a problem if you are not changing your oil at proper intervals. The intervals will depend on how you use the equipment and can be determined by an oil sample analysis.

Carbon buildup can cause multiple problems in your engine. The results will be accelerated wear on the camshaft, the roller rockers and other related parts in the overhead. This wearing effect causes added clearance. This added clearance is like a trip hammer effect on the related components, which will eventually destroy expensive engine brake parts and eventually engine failure. So you can either get your overhead checked a little more often and get our oil diagnosed, or you can let it go and run the risk of needing to replace the overhead and wish you had it checked $8,000 ago. PD

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PHOTO : Watch for carbon buildup in the overhead. Look at the rollers on the camshaft. If there are fine, black particles or a black film, you have carbon buildup. Photo by Ryan Curtis.

Jim Schlund
  • Jim Schlund

  • Retired Diesel
  • Mechanics Professor
  • College of Southern Idaho