Tactics, Tools Essential for Profitable Timing-belt Service

Technical Editor Dave Cappert takes a look at timing-belt service, as well as some of the specialty tools required by some OEMs for the service.

Without question, improvements in technology have made today’s cars more trouble-free. Because of this, routine maintenance work is taking up a larger share of what happens in the service bay from day to day. One area of routine work is timing-belt service — a service that’s often overlooked and frequently requires specialty tools. Following is some insight into performing this service and a showcase for some specialty tools that should be helpful.

Timing belt tips

If you're replacing the belt at a recommended mileage, look for signs of problems that may not let the new belt live such a long, prosperous life. Since procedures vary widely, here are some general hints to ensure a successful installation:

  • Always consult the manufacturer's specific installation procedure for the engine you're working on. No matter how many belts you've replaced, always check the book. Pay strict attention to aligning timing marks. Make sure the No. 1 cylinder is at TDC on the compression stroke. Use a dab of paint to highlight the marks. Some manufacturers not only give references for mark alignment, they also specify the number of teeth between reference points to ensure proper positioning.
  • Make sure you're installing the correct belt. Double-check the part number and tooth configuration to make sure they match the sprockets' teeth exactly. An extra minute spent here can save you a lot of grief.
  • If the belt was broken or severely damaged, see if any engine damage has occurred, especially if the car has an interference-type engine. Check for damage by doing a cylinder leakage test; don't rely solely on a compression test.
  • Inspect the tensioner, idler pulleys and bearings. Make sure they turn smoothly and show no signs of bearing failure. Inspect the pulley face to make sure it won't damage the back of the belt. Replace any questionable components.
  • For engines that use the water pump as a tensioner, consider installing a new pump to ensure a thorough job.
  • Check the free length of the tensioning spring on engines with a specification. If it doesn't meet specs, replace it.
  • Repair any oil or coolant leaks before replacing the belt.
  • Use the recommended means of setting and measuring belt tension. (It sure beats guesswork and the consequences of a comeback.)
  • Carefully inspect the sprockets for wear — worn sprockets will destroy a new belt.
  • Tighter is not necessarily better. Timing belts are not like V-belts where friction between the belt and pulley transmits torque. Timing belts drive the sprockets mechanically with their teeth. Over-tightening a belt can damage the tensile cords. An over-tightened belt is also noisier and wears quicker.
  • Never twist a timing belt more than 90 degrees from the plane it normally runs in. Some procedures use the 90-degree twist as a test for proper installation. If you can twist it 90 degrees easily, stop, increase belt tension and recheck.
  • Never use the timing belt as a holding device such as when holding the crankshaft to remove the camshaft sprocket bolts. This stresses the timing belt beyond its normal tensile demands.
  • Keep timing belts stored in their box until ready for installation. Never hang them on hooks or leave them in a drawer or on a shelf unless they are in their box.
  • After installing a new belt, turn the engine over manually in its normal direction of rotation. Check all the timing marks once more for proper alignment. Correct if necessary, then, recheck belt tension. Some manufacturers recommend turning the engine over a specific number of revolutions and then rechecking tension. Again, always check a reliable source of service information.
  • Don't overlook the timing belt cover fit. It must fit properly or debris can enter the timing belt housing. Look at the inside of the cover for signs of belt chafing. Cover contact may be what frayed the side of the old belt. If the cover has edge gaskets, make sure they are properly in place.

Helpful tools

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