- Replace the valve cover, hand-tightening the screws or bolts first before going back around with a torque wrench to tighten them down to the manufacturer's specified torque. This step is critical to avoid over-tightening, which can cause its own set of problems, including warping the valve cover or damaging the gasket.
- Check the oil seal
- In addition to the product itself, the service provided by oil seal suppliers is equally important. This includes technical support, quick delivery, and comprehensive warranty policies. Many suppliers invest heavily in research and development, constantly innovating to improve seal designs and materials, thereby enhancing sealing performance and extending seal life.


Oil seals are always exposed to a lot of chemicals, both mild and harsh chemicals. The seals react by showing some signs like cracks, blisters, and discoloration especially when the chemical is harsh. This clearly shows that the chemical is not compatible with the seal, which goes as far as affecting its cross-link density (increase or decrease). When the cross-link density increases, the seal material becomes harder, but when it decreases, the seal material becomes softer.
Thoroughly clean the area around the oil seal and check how it is fitted. If you cannot see the outer end of the seal, remove the timing-belt cover or chain cover (not the belt or chain) and possibly the water pump (See Replacing a water pump ) to reveal it. On an engine with a belt-driven overhead camshaft , remove the belt and its drive sprocket .
Polyacrylate is a great compromise between cost and quality. It has a high performing temperature and chemical range, but not to the extent of the range of Viton. The temperature ranges from 31°C to 148°C (-25°F to 300°F). Polyacrylate is primarily used in automotive transmissions and hoses but also found in shaft seals, gaskets and o-rings, due to offering a high resistance to hot oil and oxidation. While Polyacrylate is a great alternative to other high temperature resistant materials that are more expensive, it does have a poor water compatibility and cold flexibility. The best situation for Polyacrylate is an environment where heat and oil resistance but cost is the major issue. And while these 4 different materials cover a wide range of applications, there are even more materials out there designed for very specific niches in mind.
PTFE is special in that a pre-tensioned spring is not required. This is because the material returns to its original shape when heated, also known as the shape-memory polymers (SMPs) effect. These oil seals are also supplied as integrated parts, where it only needs to be installed as one component.
How do oil seals work?
<Seal selection example>
Based on the above flowcharts, the oil seal type that meets the requirements shown in Table 3 would be the type code MHSA or HMSA shown in Table 4.


Figure 3: Sealing function of main lip radial load
* KOYO is a registered trademark of JTEKT.
Mercedes-Benz
There are several materials used to manufacture oil seals. They are discussed below.
Helix Seal