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Mechanical seals have been applied as sealing devices for water pumps of automotive engines. The mechanical seal plays an important state. Therefore, there are many kinds of constructions. This paper is concerned with the FEM (Finite Element Method) analytical results for various water pump seal construction. It becomes clear that the property of heat transfer is closely related to the sealing durability.

The mechanical seal in automotive water pumps is critical to the performance and reliability of the engine, requiring consistent, effective sealing performance and long operating life. In recent years, the advent of maintenance free performance requirements and increasingly severe operating conditions have resulted in significant changes to the variety and concentration of additives in cooling systems. As a consequence of these changes to the additives, various types of premature seal leakage failures have occurred during service operation. These have been categorized into four types of failure modes and compared with seals providing normal service in order to establish simulated test conditions for engine coolants containing various additives. This paper reports on the various types of failure mechanisms that were found to occur during simulated performance testing and the corrective measures that will eliminate their occurrence

End-face type seals have been applied as sealing devices for the water pumps in the cooling systems of automotive engines. However, many troublesome problems have occurred for many years and the countermeasures have been investigated as many times. For examples, the problem of excessive abrasion of seal faces caused by foreign particles in liquid to be sealed was solved by using the sliding materials which had a hither thermal conductivity and a lower coefficient of thermal expansion. Furthermore, the noise problem of the ringing phenomena caused by the stick-slip between sliding surfaces was prevented by changing the carbon material whose lubrication characteristics had a negative slope as weak as possible in the Torque-Speed curve. As a result of these investigations, end face seals of this type have obtained the satisfactory sealing performance for many users' requirements in the present Japanese market.

In order to improve the reliability of seals for automotive application in practical use, it is considered that further basic investigations concerning sealing characteristics of seals are necessary. However, it has been found, from analyzing seals decided in the market as defective parts, that the troubles of seals in the market are mainly caused by both wrong handling for seals and the use under wrong operating condition which has not been expected by manufacturers of seals. Therefore, in order to improve the reliability of seals, it is important to investigate in detail troubles on functional characteristics of seals and their countermeasures. In this paper, on oil seals, O-rings, water pump seals and dust cover seals as seals for automotive application, the results of investigations are discussed.

New type oil seals - nonwoven fabric secondary lip type oil seals are recently widely used for one of the sealing apparatus for automotive application. Basic improvement of this type of seals is in a secondary lip which prevents solid foreign matters such as dust and sand from entering into the rubbing portion between a primary lip of oil seals and a shaft. This secondary lip is superior in anti-dust property, wear resistance, following ability to the shaft eccentricity and air permeability to the conventional secondary lip of rubber. And the sealing performance of new type seals with the secondary lip made of special nonwoven fabrics is more stable than that of the conventional rubber seals.

It is well known that the low-temperature test is successful for rating sealing characteristics of oil seals. Therefore, a compound with good thermal resistance to an ambient temperature range from -40 to +150°C is needed by the oil seal industry and should be developed. On the other hand, it is indicated that low temperature affects the sealing characteristics and the lip abrasion of oil seals. This paper examines the relation between temperature and the sealing characteristics of oil seals. It is clear that the condition of the rubbing surface is closely related to the sealing characteristics of oil seals, and that the lower the ambient temperature falls, the rougher their rubbing surfaces become. Moreover, the roughening condition of the rubbing surface is intimately related with the environmental temperature, the rubbing period, the lubricating condition, the lip design, and compounds.