The value of the water pumps seals

The seals in a water pump prevent leakages and consist out of different materials like metals, elastomers, etc... . Malfunctions can be caused by a faulty installation of the seals or inferior materials used in production, but mainly, wear is the biggest enemy.

The biggest risk of water pump malfunction is leakage. Besides the fact that spilling coolant in the environment is to be avoided at all times, the loss of coolant can cause several issues in the system like reduced pumping power and coolant level, both leading to overheating of the engine. It is clear that a pump seal will wear down somewhere in the lifetime of a vehicle. Taking the necessary precautions can enhance the lifetime of the seals drastically. There are two main seals in a water pump: the seal between the engine block and the pump housing and on the other side the seal between pump housing and shaft.

Let’s have a look at how the coolant can affect these seals.T he seal between engine block and pump housing (Fig. 1) is a static seal, this means the seal is placed between two parts that do not move in relation to each other. This seal is often a gasket or O-ring, consisting out of metal, an elastomer or a combination. Sometimes a paste is used to enhance proper sealing. This means the coolant has to be compatible with the diversity of used materials and ideally even capable to protect them

Fig.1: Static pump housing gasket  

The seal between the pump housing and the rotating drive shaft is a dynamic seal, these days a mechanical seal (Fig. 2) is used. A mechanical seal has three sealing points. The first point consists out of one stationary part (mating ring), which is connected to the pump housing, and a dynamic part (sliding ring), which is connected to the drive shaft.

Fig 2: Mechanical seal (dynamic and static part) (Source: https://www.ebay.com) (Source: https://jmpcoblog.com)  

The faces of mating and sliding rings are very flat to ensure a proper seal between the surfaces, and can typically consist out of two hard materials, depending on the purpose. Used materials can be carbon, ceramic, metallic or plastic (Fig. 3). In engine coolant circuits, we see a lot of Aluminium oxide and silicon carbide or combination of both. The constant friction between the mating and sliding ring causes a lot of wear and generates heat, which can damage the seal. This friction is drastically decreased by having a small liquid film between the surfaces; this is where the coolant comes in. The coolant is used as a lubricant between these surfaces and simultaneously cools down the parts, this means that it should not comprise or form deposits and of course be compatible with the used materials. In case a drop of coolant does escape, it will leave the pump through the weeping holes and the base fluid will evaporate. Excessive signs of leakage at the weeping holes can suggest a damaged mechanical seal. Second and third sealing point (secondary seals) are between the dynamic part of the seal and the drive shaft and the static part and the pump housing for this, an O-ring or gasket is often used.

Fig 3: Mechanical seal: parts (Source: https://www.slideshare.net/prasadroshanm/mechanical-seal-for-pumps-52996634)

We can conclude that we can enhance the life of the water pump seals by using coolant that is:

• compatible with the used materials to have long time efficient use

• has excellent robustness in respect of deposit formation and stability to control wear of the material