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I noticed a knocking noise on my Ford Focus 1.8tdci 74kw from 2004. The car is old, so it might be the end for it. Nevertheless, I would like to diagnose the problem if possible. You can hear the noise here.

The knock comes from the accessory belt side of the engine. I don't think it comes from a pulley, since the noise is there with the belt off. The noise goes away after 2000rpm. It seems to me like a chirping sound is audible at 2000 rpm, not at the same frequency as the motor rpm.

Also the noise is not present when the car is not in load (when decelerating with the gas pedal lifted). No error codes are present, no smoke, no vibrations, the car was never low on oil. I did not feel any loss of power.

I am thinking:

  • chain? the sound is not a rattle. It's like two pieces of metal knocking.
  • injectors? I heard bad injectors can give engine knocking
  • rod knocking? The car doesn't sound as bad as cars having this issue on youtube.
  • exhaust leak?

Thanks in advance.

Pᴀᴜʟsᴛᴇʀ2
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Beni Bogosel
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4 Answers4

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This sounds nothing like a knock to me, or anything internal to the engine. It appears to be running really well from what I can hear. It sounds like you have an exhaust leak. You need to scour the exhaust from exhaust manifold past the turbo to figure out if there is an issue there.

Pᴀᴜʟsᴛᴇʀ2
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I would check the harmonic damper (main crankshaft pulley). When the rubber fails, they can make a 'ding ding ding' metallic noise.

With the ancillary belt removed, check if there is any play between the inside and outside diameters of the pulley.

HandyHowie
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The oil pump may be worn out and it may be that sufficient RPM is needed to generate oil pressure. Rod knock from low oil pressure can sneak up on you and begin as a moderate sound that is not as intense as the stereotypical rod knock youtube video. Find a way to measure the oil pressure.

Try removing all the accessory belts to see if the noise goes away when no accessories are present, thus ruling out one of those components.

sebastian323
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There seem to be at least two or three simultaneous problems. I did two things which eliminated most of the noises.

Partial solve:

  1. The tensioner pulley for the timing belt was worn out (although the km limit was not reached and it had 4 years out of the 5 it is supposed to hold). I opened the cover and the belt was quite loose, I guess the tensioner did not hold the belt right anymore. Tightening the tensioner already removed some of the more nasty metal on metal noises. I changed the timing belt and tensioner.

  2. Since there were noises on the accessory belt part I replaced the tensioner there too. It diminished again the noise and removed the squeaking noise at high rpm.

I only talk about a partial solution since there is still some noise remaining on the accesories belt. I tend to believe it comes from the alternator pulley, since the noise decreases every time I put a charge on the alternator (lights, rear window defrost, etc).

At least the noise doesn't come from the inside the engine. :)

Changed the over-running alternator pulley, the noise was still present, even getting worse. Then I saw that the harmonic balancer was weak: I could move the inner part by hand and the metallic parts would bang together. Changed the harmonic balancer and the noise is gone. I hope it will stay that way.

(I'm not sure what could make the harmonic balancer go bad in roughly 2 years. It was not fractured as the previous one I changed, but it was only weakened.)

Beni Bogosel
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