Servicing Solutions
Chain Reaction: Timing Chain Replacement on Toyota’s 22R Series Engine
By Larry Bailly
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).
Timing chain replacement without head removal goes like this. The less bending and prying you do, the better the repair will come out. Depending on accessories, the repair will take more or less time, due to the mounting brackets.
- Remove the fan, shroud, drive belts and any bracket attached to the front engine cover. You will also need to remove the valve cover. Set the engine on TDC, disconnect the battery and hide the keys to the ignition.
- Remove the lower engine shield, then drain the radiator and crankcase. Remove the lower radiator hose from the water pump. You don’t need to remove the radiator, but it’s usually easier to see what you’re doing with it out of the way; it’s your call.
- Remove the crank pulley, oil pump housing and drive gear.
- Remove the oil pan bolts that screw into the front cover. Loosen, but don’t remove, the oil pan bolts on both sides of the crankcase.
- Use a sharp, stiff putty knife to separate the oil pan gasket from the bottom of the front cover. Try to keep the gasket as intact as possible to prevent small pieces from falling into the oil pan.
- Remove the ignition distributor, drive gear and fuel pump eccentric, and separate the camshaft sprocket from the camshaft. Remove the sprocket and let the chain settle into the chain guides.
- Remove the small bolt that goes into the top of the front cover (remember, it’s probably in a pool of oil so you can’t easily see it).
- Remove the bolts holding the front cover to the block, and the water tubes to the back of the front cover. Organize the bolts in a way that it will be obvious where they go on reassembly.
- Use the putty knife again to separate the front cover from the front part of the head gasket. Use great care here. Unless you want to pull the head later, try to not separate the head gasket from the bottom of the head.
- Carefully pry the cover away from the front of the block, making note of the alignment sleeves and their positions.
- Remove the rest of the timing components, guides, tensioner and crankshaft gear. Carefully inspect the front cover. If the chain has started to chew only on the cover, it may be reusable. The best determining point is to look into the water pump cavity (see Photo 3) with the pump removed to see if the grooves have been imprinted there. Once there is a failure in this area, coolant, under pressure, is just redirected into the crankcase by the water pump.
Reassembly involves carefully cleaning the front of the block, mounting the new timing components and installing per the service manual. I use RTV on the mating surfaces of the pan and head gasket. Some of the timing kits come with a replacement piece of pan gasket that requires trimming off the front of the old gasket. If the original gasket survived the separation process, it may be better left intact. As a final check before putting the valve cover on, look down the chain at the tensioner plunger and make sure there isn’t a bolt pressing on it!
As noted earlier, we have come to the conclusion that a lot of the timing chain failures on this engine can be eliminated by a different mindset on oil. It’s very obvious that engine noise is greater with thinner oil, the oil pressure indicated is lower and the benefits of thinner oil are negligible. So we have as a shop policy suggested stepping up to 15W/40 or 20W/50, depending on vehicle use. Since we don’t generally have the temperature extremes here in the Northwest that some of you see, you’ll need to educate yourself on the various properties of motor oil, and then determine what would be best for your part of the country.