1. Remove the toothed belt, top idler pulley and camshaft pulley.
2. Remove the rear toothed belt cover.
3. Mark the installation depth of the camshaft O-ring and, using a small screwdriver, remove the O-ring.
4. Clean the O-ring seat and lubricate the sealing lips of the new O-ring with clean engine oil.
5. Using a tubular mandrel of the correct diameter, set the O-ring in place and to the desired depth.
6. Install the rear timing belt cover, camshaft pulley and timing belt.