Stretch timing chain on GM SUV

A special problem with the timing chain of Buick Enclaves, GMC Acadias, Chevrolet Traverses and Saturn is becoming more and more common. The dual cam 3.6 liter V6 shared by these SUVs is susceptible to stretching by the timing chain, which in turn leads to corrosion errors involving cam sensors and actuators. Vehicles in the 2007, 2008 and 2009 model years were particularly stretched chains. Starting in 2010, GM seems to have updated the chain and calibration to eliminate this problem.

History of timing chain extension:

The first reaction of the manufacturer to this problem is based on the assumption that the timing chain failure is due to insufficient oil change. General Motors released a recall to shorten the change period by updating the computer. The theory is that if drivers are involved in early service, changing oil will prevent sludge build-up. Less sludge means less heat and wear can cause the chain to stretch.

The recall is not valid for the old models of these SUVs. Check that the engine light is still on and the vehicle will still get rough. When the owner takes the vehicle to the shop for diagnostics, the computer will display a fault code for the correlation between the actuator and the cam sensor, usually on Bank 1. A number like P0017 or P0008 will appear and the height indicates the chain stretch.

The process of replacing the chain:

Replacing a set of stretched timing chains is not an easy task. The engine and transmission must be removed from the vehicle, including disconnecting all parts of the other parts of the SUV engine. Wires, sensors, liquid filled tubes, radiator hoses and countless other components must be disconnected and, in some cases, must be removed from the vehicle and engine/transmission assembly.

As the engine and transmission exit the vehicle and are accessible, another set of components comes off, including the intake manifold, bonnet, power steering pump, and various pulleys and belts. Finally, after removing multiple bolts, each bolt has its own small rubber seal that removes the aluminum front cover of the engine to expose the timing chain. Once the mechanic reaches the chain, excessive play usually attracts attention. This means that the time is off, usually leading to a light check of the engine lights and a very rough idling.

Three separate chains need to be replaced, not just new ones, but an updated version. This process requires some unusual tools to accomplish tasks such as keeping camshafts, but professional mechanisms may make them available.

The actual timing chain replacement involves many well-defined steps.

Remove the chain, rails and associated hydraulic tensioners.

Rotate the engine until it reaches the top dead center.

Align the timing marks on the oil pump, cover and crank gear.

Install a fixture on the cam.

Follow the timing steps when installing the left chain.

Repeat this process to install the main chain.

Then use the right chain to do it once.

Then, a lengthy process of reassembling the engine and replacing all items in the vehicle can begin, and all the hard adjustments to the process are required. After that, all fluids must be refilled. Even with experienced mechanics in well-equipped stores, the entire process can take a day or more.

Timing chain replacement is obviously a very expensive repair. Fortunately for vehicles ' owners, this problem is guaranteed by GM's powertrain to 100,000 miles. The driver of the vehicle with these symptoms, the vehicle is still under warranty and should not hesitate to bring it to the dealer for repair.

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