2000/12/25 Caterpillar

Machine Engines: with Mechanical Unit Injection

3500 Series

Machine Engines: with Electronic Unit Injection

3500 Series

Machine Engines:

3500B Series

Description of Change: The oil seals have been removed from the exhaust valves in the basic cylinder head groups that are used on 3500 Machine Engines. This oil seal has been removed in order to help prevent the buildup of deposits on the exhaust valve stem. These deposits may occur on engines that operate for extended periods of time with the following conditions:

• Temperatures that are below 0 °C (32 °F)

• Low loads

• Low RPM

Adaptable To: The 137-6856 Seals (Oil) have been removed from the basic cylinder head groups that are used on 3500 Machine Engines. This change is effective with the basic engine arrangements that are listed in Table 1.

Cylinder heads that do not include oil seals on the exhaust valves should be used for top end overhauls and major overhauls. The cylinder heads without oil seals on the exhaust valves can be used individually for repair of cylinder head damage. When a cylinder head is rebuilt, that cylinder head should not include oil seals on the exhaust valves. Remanufactured cylinder heads that have date codes from UUNN (November 2000) and later than November 2000 do not include oil seals on the exhaust valves. Table 2 provides part numbers for the basic cylinder head groups.