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Introduction

If your M13A engine develops strange operating noises (like whirring, higher picthed buzzing, squealing, etc.), this article might help in the diagnosis.

The cause is usually one of these (from the most common to least common):

• One of two drive belts (lost tension or jut worn out);
• Some belt pulleys or tensioners;
• Alternator bearings;
• Radiator fan;
• Water pump;

Diagnosis

There are several method of diagnosis. They are listed from the quickest / simplest to the most labor intensive or complicated ones.

"Stethoscope" method

• Take a long wooden or metal rod (for example a long screwdriver or a long wrench) and put it against various engine parts and accessory devices.
  • You should of course do this while the engine is running.
    • Be careful not to "slide" the rod around!
• Then put your ear up to the rod and try to locate on which part the strange sound is pronounced the most.

Temporary belt softening method

• Put a little chalk dust onto a belt.
  • If the noise vanishes, the belt is probably worn out.
• You could also try this with WD40, but this is recommended only if you intend to replace the belt afterwards anyway.
  • Reason: WD40 might spoil belt's friction properties for a long time.

Temporary bearing lubrication method

• Spray wd40 into each pulley's or other bearings whilst the noise is being generated.
  • Use the straw on the WD40 can to avoid WD40 getting on the belts.
    • If the noise changes when some bearing gets sprayed with WD40, you have found your main suspect.

Coarse elimination method

• Take off the belt for the power steering, by slackening the bolts in the belt tensioner.
• Then turn on the engine and see if it is still noisy.
  • It's okay to run the engine with the power steering belt off as long as you like, because the engine will not be affected.
    • You just won't have power steering and possibly air conditioning (if you used to have it).

If the running engine noise without the power steering belt is gone, it's one of these things:

1. Тhe belt itself;
2. The power steering belt tensioner pulley;
3. The power steering pump pulley (or even something inside the pump);
4. The air conditioning compressor pulley (if you have A/C);

If the running engine noise without the power steering belt is still present, then it's (hopefully) one of these three things:

1. Water pump:
2. Alternator pulley (or something inside the alternator);
3. Their drive belt (the cheapest part);

• If it's not one of those three things, then it's probably something much more expensive.

Precise determination method

• Check each dismounted belt for wear and cracks.
  • If the belt looks worn and cracked, replace it without hesitation (regardless if it is causing the noise or not).

• With a corresponding belt dismounted, test each pulley for noise and excessive "tightness" by spinning it fast by hand.
• Also test each pulley for play by wiggling it.
  • If a pulley is tight or has too much movement in the bearing, it becomes the main suspect.
    • The power steering pump pulley will be hard to turn, so you'll only be able to feel for excessive movement (wiggling method).

The engine should not be turned on while the water pump and alternator belt is dismounted, at least not for more than a couple of seconds.

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Page last edited on 21/02/2019 by user Bosanek