Hello Paul, my car’s timing belt snapped and I had to replace the cylinder head. Shortly after, it developed a rattling sound on turning on the ignition and when accelerating. One mechanic heard the noise and without any further diagnosis, said I need a new engine. Please advise. Richard.

Hello Richard, during timing belt failure, your engine may have suffered catastrophic damage of both the valves in the cylinder head, which you replaced, and the pistons or cylinder walls in the lower part of the engine. The mechanic you consulted may have a point. The timing belt which is connected to an engine crankshaft and camshaft plays an important role of timing or synchronising the up and down rapid movement of engine valves and pistons during combustion.

This belt should be replaced mandatorily at 100,000kms on most vehicles which are not timing chain-driven. When the timing belt snaps or fails, there is potential collision of the valves and pistons. This will most likely cause deformation and severe valve to piston damage. In your situation, the mechanics replaced the cylinder head which houses the intake and exhaust valves. The persistent noise in the engine is an indication that some or all the pistons and their attached conrods may have been damaged during the impact with valves.

An inspection of the engine is necessary to establish the extent of damage and confirm which pistons may need replacement. It is also necessary to establish if the cylinder walls were not damaged. A cost benefit analysis may be carried out to decide whether it is cost effective to repair the old engine or replace it with a quality used one. Perhaps that is what the second mechanic was trying to do having perceived or anticipated piston damage.