Knocking erratic noise - What can it be?

[Niels Svane]

Hi everybody

Since my last few trips in the R4 I have experienced an irritating and growing problem:

There's a loud metallic knocking/clanking noise coming from the left side of the engine compartment.

It often comes at gear changes or when I suddenly release the speeder. It is also felt in the pedals and sometimes the steering wheel.

What the heck can it be?? The engine and gearbox doesnt move (I have made some tests) so I gather its not the mountings. It started after a small trip with three people in the car.

Can it be related to the exhaust system? Before the sound appeared I had the manifold and some of the piping off to be painted, but it seems solid and doesnt move.

 

[jjad]

Check that the exhaust pipe is not rubbing on the inner wing as it passes through it.

 

[Niels Svane]

Could that really be the reason for such a loud and erratic noise? Ill check it at once

 

[Niels Svane]

Its not the manifold or pipes

 

[benchseat]

Exhaust pipe hitting the inner wing due to the connecting clips (to the manifold) being loose : this makes a loud clanking noise : my 845cc occasionally does this.

But if you feel the knocking through the pedals I'd also check the LH driveshaft. Possibly the CV joint is failing (starts imperceptibly and gets rapidly worse). If it comes when turning sharp left then that is the answer.

 

[Niels Svane]

Thats the thing, its not worse or better when turning. Its only when I'm accelerating or decellerating abruptly, and sometimes when changing gears. It's strange suddenly not knowing whats wrong with it Normally I'm quite good at fault-finding.

If I dont get a eureka moment before next weekend I'll visit my renault-pusher and let him have a go.

His thoughts were: ball joints, cv joints, driveshaft, and engine+gearbox mounts.

The bad part is having to drive 110 km to his place, without worsening the problem too much

 

[JonathanT]

Have you worked on a driveshaft? - Could you have lost a little oil from the gearbox? I had an awful noise (I just hope its gone when I get running again) best conclusion was low oil in gearbox

ok it wasnt clanking but I do think its worth checking. I have a suspicion you would sus something moving and knocking.... so maybe try the not so obvious.

 

[Niels Svane]

Nope, only worked on the manifold. The noise seems to be increasing... I jacked the car up yesterday, and no sound is heard when yanking the wheel in every direction

 

[benchseat]

From the symptoms you describe in your EMail yesterday I'd say the next likely candidate, if not driveshafts, is the front gearbox mounting. If this has gone the gearbox/engine will bounce up and down when subjected to sudden torque changes. Happened to mine once and was irritatingly hard to track down as the movement was only a centimetre or so.

 

[Niels Svane]

It seems that it was indeed the exhaust knocking away. No wrong sounds can be heard anymore.
Instead it has developed an overheating problem, which is to be cured first by flushing the system, cleaning the outside of the cooler and removing dents, or if its not curable: a new copper cooler.