Braking News

| April 11, 2005

The normal price for setting the overheads on a Series 60 is $355. Although they inform us that they normally don’t charge extra for engines with Jake brakes, it’s obvious that a trucker can save himself some money by getting the feeler gauges, injector setting tool, and socket and torque wrenches and doing this job himself.

Before starting, make sure the engine is cool – with oil temperature of 140 degrees F or less.

This procedure is for the Model 765 Jake brake used on Detroit Diesel Series 60s up until about four years ago.

  1. In order to access the overheads, the Jake housings must be removed. To do this, disconnect the electrical connector on each of the three housings. Then remove the two capscrews on one side and the single one on the other, and lift them off.

  2. Set the valves and injectors according to instructions in the Detroit Diesel manual.
  3. Once the valves and injectors have been set, make sure there is no oil in the boltholes. Blow them out with clean compressed air, if necessary.
  4. Lubricate the threads of all the capscrews with clean engine oil. Position each housing with the two capscrew holes on the exhaust valve side of the engine, and start the capscrews. Once each housing is in place and capscrews started, slide the housings around on the head to center their positions. This will help ensure that the brake will be perfectly aligned with the valve adjusters.
  5. Using a torque wrench only, torque the fasteners one by one to 40 pounds-feet. Then torque them to the required 90 pounds-feet. Reconnect the electrical connector on each.
  6. To adjust each cylinder, its exhaust valves must be on the base circle of the cam. Bar the engine over by the front crankshaft pulley to reposition it as necessary.
    You can use the engine positioning guidelines Detroit Diesel supplies for setting each cylinder’s exhaust valves to make the related Jake setting. Or you can turn the engine over until the exhaust rocker’s roller, the one on the left on each cylinder, is on the base circle of the camshaft and completely off the cam lobe before adjusting the Jake parts for the valves of each cylinder.

  7. Work on the exhaust side of the engine. Adjust the “blind side” adjuster, via the slave piston on top of the housing. This is the adjuster on the left side that has no adjusting screw on top. Start by loosening the slave piston’s adjusting locknut and then turning the screw outward. Then slide the required feeler gauge (0.026 inch) between the exhaust valve adjusting screw and the Jake actuator. Turn the adjusting screw back and forth with a screwdriver until there is a very slight pull as the gauge is slid between the parts.
    Once the adjustment is correct, hold the screw with the screwdriver and gently tighten the locknut. Then torque the locknut with a torque wrench to 25 pounds-feet. It’s important to torque properly, as the screw is hollow and may be distorted by overtorquing, which would impact brake operation.

  8. Now adjust the bridge that runs between the two valves by setting the adjustment on the other valve. This is done the same way, but right above the valve. Loosen the locknut, loosen up the bridge adjusting screw and slip the same 0.026-inch gauge between the valve adjusting screw and the bridge. Set the lash exactly as you did on the other side. Tighten and then torque the locknut in the same way.
  9. This basic procedure must be performed on the exhaust valves for each cylinder, making sure each rocker is in the right position before starting.
  10. Reconnect the electrical connectors. Then with the cam cover still off, start the engine and run it until the oil begins to warm up. Depress the armature, which is in the center of the top of the solenoid valve, to activate each several times and fill the housing with oil.

Note that every Jacobs engine brake has a label on it that gives the lash setting. The latest Jake for Detroit Diesels is the Model 790/795 (depending on the particular engine).

It uses two housings, each with six slave pistons rather than three. Each valve has its own slave piston, eliminating the bridge. Each slave piston is adjusted individually but in the same way as on the 765.

Jake brakes for other brands of engines are adjusted similarly. Jacobs will supply manuals giving specific torques and describe the slight individual variations in each adjustment procedure.

It’s best to have a tune-up performed on an engine brake every 300,000 miles or 9,000 hours in typical highway service. In this procedure, critical parts are cleaned and inspected, and some perishable springs and control valves, and various related parts, are replaced. It’s a complicated job best performed by a technician. At Penn Detroit Diesel, an engine brake tune-up costs about $200 for parts and $344 for labor, or $544.

Aftermarket installation
Installing an engine brake on an existing engine may seem quite basic. It bolts on the same way as the overhead adjustment. But most truckers use the services of a professional technician in getting an engine brake, because dealing with the wiring and switches can be a complicated job.

Because of the complicated electricals, Penn Detroit Diesel normally charges for about eight hours of labor for the job, or $688. The brake itself lists for $2,500.

After installation, the engine’s ECM needs to be reprogrammed (or “reburned”) so it will properly coordinate the operation of the brake with the engine rpm, pedal positions and ABS. This will cost another hour of labor ($86), and Detroit Diesel normally charges $400 for the electronic download; however, the download charge is often waived if the brake is purchased at the Detroit Diesel outlet where you are having the work done. The net cost, depending on labor rates where you are dealing, would normally be in the neighborhood of $3,200.

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