A Newbie’s Guide to Buying Thermostat O-Rings
The thermostat o-ring is one of the simplest parts of the modern automobile, but it holds a critical task. Aside from keeping the engine thermostat snugly in place, it also prevents harmful unburnt fuel and exhaust gas from leaking out. This is why O-rings are made with various materials and designs to make it resilient against extreme temperatures, chemicals, and other conditions at an affordable cost.
When buying a replacement thermostat o-ring, you'll likely to find yourself bombarded with various models. Each one has its own set of advantages and disadvantages, so take note of the following:
Gasket or O-ring?
Thermostats are sealed in place with either a gasket or an O-ring, so it's essential to verify that you actually need an O-ring or a gasket. The service manual has information regarding this, although you can also look at the thermostat itself. As a rule of thumb, gaskets have a thin, flat appearance and made of paper, fiber, or rubber, while O-rings are cylindrical and made solely of rubber-like materials. So make sure to cross-reference with your car's thermostat before buying a replacement O-ring.
Back in the old days, thermostat O-rings used to be made of plain old rubber. However, as automobiles became more advanced, O-rings are now manufactured under different types of materials to adapt to new
- Nitrile rubber: Most O-rings sold in the market today are made of nitrile rubber. This type of rubber is cheap to manufacture, highly resistant to lubricants and grease, provides adequate protection against heat, cold, and moisture, and is very flexible. However, nitrile rubber is also among the fastest to wear and can be damaged by brake fluid. Many OEM thermostat O-rings are made of this material.
- Polyurethane: Polyurethane is actually more plastic than rubber, and because of this they tend to be denser and harder to the touch compared to their nitrile rubber counterparts. This additional hardness makes polyurethane thermostat O-rings highly resistant to damage and does not wear easily. Many aftermarket O-rings designed for heavy duty use for this exact purpose. However, polyurethane is not as effective in protecting against heat and pressure.
- Silicone: Another common material used in aftermarket O-rings, silicone is highly resistant to extreme heat and cold. Silicone thermostat O-rings are also highly resistant to lubricants, gasoline, and other chemicals and do not corrode easily. These O-rings however, are not as flexible as other materials and is quite prone to tearing.
Aside from materials, thermostat O-rings also varies in “profile” or cross-section design, with the two most common types being the round and the square profile. Round profile O-rings are tubular in appearance and offer a large contact surface, resulting in a highly effective seal. Square profile thermostat O-rings, on the other hand, are cheaper but does not provide a seal as good as that of round profile O-rings. There are also thermostat O-rings that have a oblong or knife-edged profiles, but these variations are only found in select car makes and models.
ure the radiator support cover. Use a tape measure to determine the length and width of the cover; you will need this later on to ensure the cover is realigned properly on the engine bay.