2003/01/01 Caterpillar

Engine: Commercial

3500 Diesel

3500B Series

Engine tests have determined the optimum maintenance intervals for adjustment of the valve bridge and valve lash in the above engines. The maintenance intervals are listed in Table 1.

The engine tests have revealed that the initial adjustment of the valve bridge and valve lash is critical for new engines and for engines that have been overhauled. The tests have indicated that the valve bridge and valve lash settings change during the period from the initial start-up through the first 100 hours of operation. The settings can continue to change during further operation. For this reason, adjust the valve bridge and the valve lash after the break-in period of the initial 250 operating hours.

Perform the initial adjustment for the following circumstances:

• The engine is new.

• The engine has been overhauled.

• At least one of the engine's cylinder heads has been serviced with a new valve train component.

Note: Perform the initial adjustment even if an adjustment was performed after a dyno test or after the engine's initial start-up.

The engine tests have also indicated that valve bridge and valve lash settings are significantly more stable after the break-in period. For this reason, adjust the valve bridge and the valve lash after every 4000 operating hours.

Note: The initial 250 service hour adjustment of the valve bridge and valve lash enables the regular maintenance at every 4000 service hours until the engine is overhauled. If the initial 250 service hour adjustment is not performed, more frequent subsequent adjustment may be necessary.

For instructions on adjusting the valve bridge and the valve lash, refer to the engine's Systems Operation/Testing and Adjusting manual.

Note: Make sure that you note the new maintenance intervals in the engine's Operation and Maintenance Manual, "Maintenance Interval Schedule". The new maintenance intervals will be included in the Operation and Maintenance Manual when the manual is revised.

Show/hide table

Hot engine components can cause injury from burns. Before performing maintenance on the engine, allow the engine and the components to cool.

Perform the adjustment when the engine is cold. Before the adjustment is performed, the engine must be shut down for a minimum of 20 minutes. After the stopped engine's valve covers have been removed, the engine is considered cold because approximately 20 minutes are needed for removal of the valve covers.

The valve bridge must be adjusted before the valve lash is checked and/or adjusted. Verify that both valve bridges for each cylinder are correct. Then measure the valve lash.

If the valve lash is within ± 0.08 mm (± 0.003 inch) of the specification that is listed in Table 2, adjustment of the valve lash is not necessary. If the measurement is not within the tolerance, adjust the valve lash according to the specification that is listed in Table 2.