Toyota's 22R series four-cylinder SOHC engine has survived and thrived in its cars and trucks for nearly 30 years, and is a desired powerplant for its power, torque and reliability. The basic design is a continuation of the engine that preceded it, the 20R, which was used in cars and trucks in the mid 1970s. Last month, we highlighted servicing head gasket issues on the 20/22R series 4-cyl SOHC engine. This month, we'll take a look at timing chain and oil sludge issues for the 22R.

A Series of Unfortunate Events
The incidence of timing chain failure on this series of engines seems to have increased over the last few years. We seldom saw a failure until 175,000 to 200,000 miles. Now, we often see failures under 150,000 miles. We've concluded that the use of lower viscosity oil has had a detrimental effect on timing chain life.

Although there is still some disagreement on what is the ideal oil for all conditions, the fact remains that, on this engine, viscosity and oil pressure have a significant impact on timing chain life (more on this later).

There are, however, a couple of other problems that can significantly shorten chain life and cause other failures. Oil sludging, due to lack of maintenance and overheating, can damage any engine over time. Unfortunately, there is one other cause that is usually the direct result of an improper repair for a common oil leak.

A common sequence of events in the failure o...