Berlingo knocking noise

[Northern_Mike]

Well, after 25k miles of being ok, it had to happen sooner or later.

Berlingo is making an occasional knock. It *only* does it when turning right at 15-20mph. It's more likely to do it when there's a passenger in it. It's a dull knock rather like the knock it made when the rear engine mounting bush had gone. I can feel it through the steering I think.

Doesn't rattle on speedbumps or uneven surfaces, drives fine on the motorway. I did grab the wheels and have Mrs. Northern_mike turn the steering from side to side, and I swear I could feel it clunk a little - so track-rod ends perhaps? Doesn't wander at all. I did originally think it was the bottom arm bushes, but they all appear ok.

Ideas please, before it goes up to the nice man at Savoy? I'm a little flush at the moment, so I'm thinking to get both bottom arms replaced, drop links and track-rod ends while I can. At 87k, they are getting near EOL.

It's either that, or I'm going to go up to Essex on Saturday and buy a Prodrive-built Legacy Twin Turbo estate..

[addo]

It's definitely the ignition coils. No, wait, it's definitely the fuel supply...

Have you tried letting it in when it knocks?

#1 candidate is always the P-bushes, you might also suspect ball joints. Depending on exposure to gritting, strut top assemblies may be wearing. This all assumes it's not wear to the rear shock absorber eyes.

[Northern_Mike]

I have checked all the earths and all the connections to the BSI on the strut top. Voltages are ok.

Strut top, drop link and spring on that side replaced within the last 13k miles, have checked the torques, all seem ok. The P-Bushes *look* ok, but I haven't had a big bar on them yet. Suspect time for new arms is due. Thanks for the advice, I shall follow it and get dirty later today - I'll expose it to a large bar and some violence.

[onthecut]

Don't be so sure about it not being a part you've recently replaced --- I've just had to replace a drop link on my Xantia that was changed only about eight months ago and has done predominantly motorway miles since then. Also, using a bar doesn't always reproduce the kind of motion the affected part experiences in use. Certainly with the drop links, I think you need to feel the joints while someone rocks the suspension with the wheels on the ground. Testing them off load seems very ineffective.

Mike.

[Peter.N.]

CV joint?

[Northern_Mike]

I hate cars. I've just done 120 heavily laden motorway miles then some across country. Not a single noise.

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[addo]

If the knocking's faded away that would suggest a bush failure; either moisture or oil has got into it and quietened the damaged area down...

However I would still clamp a piezo transducer and contact microphone to opposite sides of the spare tyre carrier and check the transferred waveform for a 2kHz input, on an oscilloscope. It's possible that a poorly tensioned carrier may generate parasitic drag below the motor tray, leading in turn to vortex formation/shedding in the underbonnet area around your air intake - giving the impression of a motor lacking power.

[mooseshaver]

However I would still clamp a piezo transducer and contact microphone to opposite sides of the spare tyre carrier and check the transferred waveform for a 2kHz input, on an oscilloscope. It's possible that a poorly tensioned carrier may generate parasitic drag below the motor tray, leading in turn to vortex formation/shedding in the underbonnet area around your air intake - giving the impression of a motor lacking power.

I believed you. Then after reading the other posts "wait, they're mocking somebody"

When my rear trailing arm bearings were going the noise always stopped with wet weather. Till they were really bad.

[addo]

Yes, water does act as a (poor) lubricant in these types of situations. One mate used to start with water when freeing up rusted parts - he believed it crept in best. (It would then be followed up by a hydrophilic liquid, leading up to light oils.)

A noise from the rear appearing to come from the front is also quite common. You do need some experience sorting chassis problems often to discern this.

[Northern_Mike]

If the knocking's faded away that would suggest a bush failure; either moisture or oil has got into it and quietened the damaged area down...

However I would still clamp a piezo transducer and contact microphone to opposite sides of the spare tyre carrier and check the transferred waveform for a 2kHz input, on an oscilloscope. It's possible that a poorly tensioned carrier may generate parasitic drag below the motor tray, leading in turn to vortex formation/shedding in the underbonnet area around your air intake - giving the impression of a motor lacking power.

<splutter>


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[myglaren]

If the knocking's faded away that would suggest a bush failure; either moisture or oil has got into it and quietened the damaged area down...

However I would still clamp a piezo transducer and contact microphone to opposite sides of the spare tyre carrier and check the transferred waveform for a 2kHz input, on an oscilloscope. It's possible that a poorly tensioned carrier may generate parasitic drag below the motor tray, leading in turn to vortex formation/shedding in the underbonnet area around your air intake - giving the impression of a motor lacking power.

<splutter>

And not entirely unrelated to: Straight Dope.

[addo]

I've never been able to read SF. I'm just too simple and straight-down-the-line.