SCREW DRIVER 6V7934 - Caterpillar

D346, D348, D349 EnginesSUPPLEMENT: 07/04/88SERVICE MAGAZINE; DECEMBER 15, 1986; PAGE 10; "Silicone Water Seal Available" for D346, D348, D349 Engines.The part number "8S4247" in the third line of the article is incorrect. The correct part number is 8S4275.--------------- END SUPPLEMENT ---------------SUPPLEMENT: 03/28/88SERVICE MAGAZINE; DECEMBER 15, 1986; PAGE 10; "Silicone Water Seal Available" for D346, D348, D349 Engines.Additional information for this article follows. If 6V2555 or 6V2556 Gasket Kits are ordered, be sure 8S4275 Water Seals (Silicone) are included. The 8S4275 Water Seal (Silicone) is gray with a brass insert. The 2W3797 Water Seal (EPDM Rubber) is black with a blue plastic insert. The 2W3797 Water Seal should not be used.
--------------- END SUPPLEMENT ---------------The 8S4275 Water Seal should be used on the D346, D348 and D349 Engines. At one time it was recommended that the 8S4295 Water Seal (Silicone) be replaced with the 2W3797 Water Seal (EPDM Rubber). That is no longer true. The EPDM seal cannot be used where the seals come in contact with oil. The design of the above engines allows oil between the cylinder head and block to come in contact with the water seals. This could cause the EPDM water seals to swell and deteriorate which could cause a coolant leak. Therefore the 2W3797 Water Seal (EPDM Rubber) should not be used. The 8S4275 Water Seal (Silicone) is highly resistant to oil.