The water pump bearings on a friend's car recently seized, causing the timing belt to jump off the pulley, lose tension, lose timing, and the engine to munch its valves.

Could this failure have been detected earlier by a torque sensor on the drive shaft of the water pump? I imagine that the load on a pump is roughly a function of RPM, so could the ECU detect a change in the characteristics as the bearings began to seize to failure, and indicate a fault state before it all broke?

Do any engines use a system like this? I imagine it could be extended to other systems connected to the belt or chain mechanisms too.

  • I have a question, doesn't the water pump have its own belt (serpentine belt) ? so how the water pump failing caused the timing belt to also fail?
    – method
    Commented Oct 5, 2016 at 8:26
  • 3
    @methd it depends on the design of the engine. The Volkswagen small-block watercooled engine as found in early Polos and Golfs actually uses the waterpump on an eccentric housing to act as the timing belt tensioner. Commented Oct 5, 2016 at 8:34
  • @method I can confirm that 01 Honda preludes and accords both run the water pump off the timing belt too. The prelude has 4 belts, one for timing and water pump, one for balancer, one for power steering pump, and one for alternator and compressor.
    – Jason C
    Commented Oct 5, 2016 at 13:31
  • 6G72 (3.0 v6 used in Mitsubishis and Dodges) has a timing belt driven water pump also. I believe this is a somewhat common design.
    – rpmerf
    Commented Oct 5, 2016 at 14:04

1 Answer 1


Good question. My answer is, probably not. With a caveat; it depends on the speed of the failure.

Sometimes bearings will become excessively noisy before they fail. In this scenario the vehicle owner would notice the impending failure and hopefully do something about it. Chances are that either a torque sensor or a knock sensor on the waterpump could have illuminated the engine warning light; which may or may not have caused the driver to investigate the fault.

More often that not however, the bearings will simply "let go" and the pump will cease within seconds. In this scenario you could still illuminate a dashboard warning light but with the engine spinning at several thousand revolutions per minute (not second), it's unlikely that it would help much.

The main issue is that, at the time the belt, tensioner or water pump fails, the engine is running. It's typically the fact that the top end and bottom end slow down at differing rates that causes valve to piston contact.

On Volkswagens, the waterpump is seen as an almost consumable item and most owners or mechanics will replace it every time the cambelt is changed. It sounds like your friend has either been really unlucky or pushed his luck with cambelt change intervals (or possibly reused an existing water pump when it was last changed).


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