TECBRAKE T680A (01) PDF Document

The following special tools are required for installation of the TECBRAKE T680A engine brake:

1. Crowfoot wrench- 9/16″
2. Crowfoot wrench- 5/8″
3. Feeler gauge- 0.080 in (2.03 mm)
4. Feeler gauge- 0.085 in (2.16 mm)

The recommended torque values for the TECBRAKE T680A engine brake on E6 engines are as follows:

The engine preparation steps for installing the TECBRAKE T680A engine brake are:

Step 1. Thoroughly clean engine before beginning installation. Remove all engine components necessary to permit access to cylinder heads. Remove valve covers. Loosen intake and exhaust rocker lever adjusting screws.

Step 2. Remove rocker arm assembly.

Step 3. Remove the rocker arm adjusting screws from the exhaust rocker levers. Retain the locknuts for use on the new adjusting screws.

Step 5. Install the new TecBrake rocker lever adjusting screws, re-using the Mack locknuts.

Step 6. Install yoke after applying oil on top of yoke in the yoke’s bore, and on guide pin bore. Adjust yoke by pressing down on the top of the yoke pad, turn the adjusting screw until it makes contact with the valve stem, tighten 1/6 turn more, hold screw in position, then tighten lock nut. The TecBrake yoke includes the adjusting screw and nut.

Step 7. Re-install the rocker arm assembly. Make sure rocker lever adjusting screws are backed out and that the push rods are seated. Starting at the center, tighten to the required torque in two steps each of the three rocker bracket hold down bolts located next to the pushrods. Torque to:

E6 (680A) – 55 lbft (75 N*m)

Step 8. Remove the two hex head rocker shaft locking screw located on top of the front rocker shaft brackets.

Step 9. Install o-rings in the grooves on each of the two oil supply screws provided in the kit. Apply oil to the o-rings and install the oil supply screws in place of the rocker shaft locking screws removed in step 8.

Make sure that there is a minimum of 0.025″ clearance between the top of the valve spring retainers and the underside of the yoke when installing the TECBRAKE T680A engine brake.

For the TECBRAKE T680A (680A) engine brake on E6 engines, the torque required for tightening each of the three rocker bracket hold down bolts (starting at the center and in two steps) is 55 lbft (75 N*m).

The procedure for installing the brake housings for the TECBRAKE T680A engine brake is as follows:

Step 1. Before installing the brake housings back out the slave adjusting screws (located on top of the casting above the slave piston) so that the slave pistons are fully retracted (up).

Step 2. Position housing so that the oil supply bore is located over the oil supply screw. Push the housing down so that is flat against the rocker shaft bracket.

Step 3. Using the six capscrews provided in the kit (Three for each housing), install the capscrews through the brake housing into the rocker shaft bracket. Do not tighten the capscrews. Position the housings so that the master pistons are centered over the exhaust rocker lever adjusting screws.

Step 4. Starting in the center, tighten the brake housing mounting capscrews to 20 lbft (27 N.m), then re-torque to: T680A (E6) – 55 lbft (75N*m).

Step 5. Check for interference between rocker arm and engine brake slave piston on all cylinders. If binding occurs, reposition housings.

After starting in the center and tightening the brake housing mounting capscrews to 20 lbft (27 N.m), the final re-torque for the TECBRAKE T680A (E6) engine brake is 55 lbft (75N*m).

When setting the valve lash for the TECBRAKE T680A engine brake, the clearances indicated are:

Intake valve lash – 0.016″

Exhaust valve lash – 0.024″

Tighten the adjusting screw lock nut to 26 lbft (32 N*m) when setting the valve lash for the TECBRAKE T680A engine brake.

The procedure for setting the slave piston lash on the TECBRAKE T680A engine brake is:

Step 1. Set engine brake slave piston lash using the adjusting screws located above the slave piston. Because the exhaust valve push tube acting on its master piston operates a slave piston on a different cylinder, care must be taken to adjust the proper slave piston. The engine must be rotated to allow the exhaust valve to be fully closed prior to making the adjustment on each cylinder.

Step 2. Figure 3-7 identifies which push tube operates which slave piston. The same procedure for locating TDC for each piston when setting valve lash may be used when setting the engine brake slave piston lash on each cylinder.

The Master / Slave Piston Actuating Relationship Listed in Engine Firing order Sequence is:

Step 3. The slave piston lash should be set as follows:

Model Year – Lash Setting

1991 & on- with S.N. 1B0001 & higher – 0.080″

1990- only S.N. listed in Chart below – 0.080″

All other 1990 not listed & pre 1990 – 0.085″

Step 4. Insert a feeler gauge between the slave piston feet and the TecBrake yoke, then turn the slave piston adjusting screw until the correct lash is obtained.

Step 5. Lock the adjusting screw in position by tightening the lock nut to 20 lbft (27 N*m) torque. The adjusting screw should be held in position while the lock nut is tightened using a crowfoot wrench. Recheck the lash.

Slave piston adjustment for the TECBRAKE T680A engine brake must be performed when the engine is not running, and the engine temperature should be cold (below 140°F or 60°C) and stabilized.

The operational check procedure after installing the brake housings for the TECBRAKE T680A engine brake is:

Step 1. Start the engine and let it idle for a short time.

Step 2. Bleed air from the engine brake housing. Accelerate the engine to about 1800 RPM then release the throttle. Quickly depress the solenoid as shown to cause the brake to operate. This process should be repeated 5-6 times on each brake assembly in order to fill the housings with lube oil. When all of the air has been removed the brake should operate immediately when the solenoid is depressed.

The procedure for installing the solenoid valve for the TECBRAKE T680A engine brake is as follows:

Step 1. Disconnect the electrical lead from the solenoid and remove solenoid with a spanner wrench. Remove and discard the three rubber seal rings.

Step 2. Clean the filter screen and solenoid with solvent.

Step 3. Dry solenoid with low air pressure.

Step 4. Clean solenoid bore in brake with solvent and wipe dry with paper towel. Be careful not to leave any lint or residue in bore that may contaminate brake hydraulic components.

Step 5. Reinstall solenoid valve using three new o-rings. Coat solenoid body with engine lube oil and install upper and center seal rings on solenoid body. Seat lower seal ring in bottom bore of brake.

Step 6. Carefully screw in solenoid valve, using care to assure O-rings remain in position and are not twisted or “rolled”.

Step 7. Tighten solenoid valve to 5 lbft (7 N*m) torque.

The procedure for installing the valve covers after installing the engine brake spacers for the TECBRAKE T680A engine brake is:

Step 1. Remove the Mack cylinder head valve cover seals from the valve covers.

Step 2. Install the new valve cover seals provided in kit. The seals should be cut to provide a 1″ overlap.

Step 3. Install the valve covers on the engine brake spacers. Use the TecBrake capscrews provided to hold down the valve cover and spacer. Torque the capscrews to 20 lbft (27 N.m).

The wiring steps for the TECBRAKE T680A engine brake installation using the miscellaneous wiring materials and universal wiring harness are:

Step 1. Install the solenoid harness by connecting one end to the solenoid valve and the other to the inside of the terminal in the spacer assembly.

Step 2. Install the remainder of the wiring following the instructions included with the universal wiring harness and wiring diagram shown in Figure 4-1.

Step 3. All wiring should be routed to avoid areas of high heat and mechanical interference where chaffing could occur.

Step 4. Check system to determine if voltage is present at terminals in engine brake spacer assembly. Voltage should be present when engine is not running, with ignition on, clutch disengaged, throttle in idle position, and all dash switches in the “on” position.

Step 5. While monitoring voltage at terminals in the engine brake spacer, operate the switches to determine if they are functioning properly. Depressing either the clutch or the throttle pedal should cause the voltage to be interrupted.