A timing belt is a flat rubber belt reinforced with fiberglass or similar strong fibers with rubber teeth molded onto the surface. These teeth are driven by teeth on the camshaft and crankshaft sprockets. Exposure to extreme stress and temperatures does require periodic replacement of the rubber belt. Engine oil or coolant could contaminate the belt requiring premature replacement.
Most modern VW and Audi engines are of interference (also called non-freewheeling) design. This means the pistons and valves are close to each other so if the timing belt breaks they will crash into each other and cause serious engine damage. Replacing bent valves can be quite costly.
Many timing belt failures result because of failure in one of the other components of the timing belt system. The other components – an idler or roller pulley, a timing belt tensioner, and a water pump are driven by the timing belt and have internal bearings that may fail. For example, if the water pump seizes or comes apart, it would cause the belt to overheat and self-destruct. It is important not to ignore squealing or unusual noises coming from the engine area as this may be a warning that one of these other parts is about to fail. Immediate action may help to avoid major damage and more costly engine repairs.
It is highly recommended all components of the timing belt system be replaced at the recommended service intervals.
At the prescribed intervals is vital to the safe operation of your vehicle. Here is a brief description of the routine maintenance that is so essential in ensuring full brake system efficiency.
- Checking and Changing Brake Fluid – Maintain brake fluid 15 to 20 mm (about ¾ in.) below the top of the reservoir (just above the seam near the top of the reservoir). Use brake fluid that meets SAE recommendation and conforms to Motor Vehicle Safety Standard. Change brake fluid every two years.
- Checking Brake Pedal Travel and Freeplay – It should be possible to depress the brake pedal for a distance of 5 to 7 mm (3/16 to 9/32 in.) before encountering resistance. If you find that the freeplay is outside of this range, the pushrod clearance may need adjustment.If the pedal must be depressed an excessive distance to obtain braking action, the drum brakes may require adjustment.
- Checking Brake Linings – On 1970 through 1974 models, at the 6,000-mile maintenance check brake lining wear… On 1975 and later cars, brake lining wear is checked as part of 15,000 mile. Disc brake pads should not be worn to a remaining thickness of less than 2.00 mm (.080 in.). Drum brake lining should have at least 2.5 mm (3/32 in.) of friction material left above the brake shoe. Check lining thickness through holes in the backing plate.
- Checking Parking Brake Adjustment – After adjusting the rear brakes, you should not be able to raise the parking brake lever more than five clicks without obtaining noticeable braking action. If the lever requires more than five clicks to obtain braking, adjust may be necessary.
- Check Brake System for Leaks – If the fluid level in the brake fluid reservoir is noticeably low, carefully check the brake system for leaks. Check the lines, hoses, unions, and bleeder valves. Removal of the brake drums may be necessary to in order to inspect the wheel cylinders. On some models, the rear brake calipers may need inspection.
- Checking Brake Lines and Hoses – Potential problems include brake lines deeply pitted by corrosion, flattened due to bending, or dented by flying stones. These conditions may soon lead to leaks or may already be interfering with uniform braking action. The brake hoses must not be soft swollen, or coated with grease and oil. Replace any brake hose that has breaks in the fabric outer cover.
- Checking Brake Light Operation – The rear brake light should come on as soon as the brake pedal encounters resistance when depressed.
- Check Brake Light Warning Switch – Check the brake warning light system every two years while changing the brake fluid.
The proper operation of the spark plugs is vital to good engine performance and economy. Use the correct plugs as listed in the specifications. On 1970 through 1974 models, check the gap and the condition of the spark plug electrodes each 6000 miles. Install new spark plugs each 12,000 miles. The fuel injection engine introduced in 1975 used long-life spark plugs. You need only replace such spark plugs each 15,000 miles. Adjust the gaps of the new spark plugs before you install the plugs in the engine. The correct gap for 1970 through 1974 engines is 0.60 mm (.024 in.). The correct gap for fuel injection engines is 0.70 mm (.028 in.).
Valve adjustments should be checked while the engine is completely cold (oil temperature no more than 122 degrees Fahrenheit) and the cylinder is in position to fire. Clearance between the rocker arm and valve stem should be 0.15 mm (.006 in.).
Drain the oil from the engine while it is hot. Place a pan of at least one-gallon capacity beneath the engine. Loosen all six-cap nuts on the oil strainer cover. Pry the oil strainer cover loose. When most of the oil has drained, remove the oil strainer for cleaning. Clean the oil strainer with every oil change. Use new gaskets and copper washers when installing the strainer to prevent oil leaks. Wipe the area around the strainer following installation. Doing so will aid in the early detection of leaks.