Hi everyone, 

I recently purchased a octavia 3 with the 2,0 crtdi (CKFC) engine with ~220k kms. 

I've driven it quite a lot and now its developing an issue where at low revs ( up to about 2k) its making a weird slightly metallic knocking noise. Its not that loud but i can certainly hear it.

It had all liquids, filters and also valve cover gasket changed, so the injectors were taken out. This happened about 3 months ago. 

 

The car starts, drives normal, no missfires detected and also no faults codes, didnt notice the consumption go up either.  Although the engine is vibrating a bit at idle ( its a diesel so that might be normal), but i cant feel that inside.

 

What could cause this? I was guessing bad injectors, but these engines dont really have that problem. 

Could a bad reassembly of the injectors and gaskets cause this kind of behaviour?

 

Thanks,

Peter

Hello Peter, welcome to the forum. A metallic knocking sound could suggest excessive wear in the connecting rod bearings (aka big end), are you getting low oil pressure warnings at idle speed? 

No engine faults at all, I'll try to record the sound if I can next time I use it. 

It does the knocking under load, but if I floor it, it seems to quiet down. 

Could maybe bad quality fuel cause this? This started about 150km after my last fill-up, but might just be a coincidence. 😅

I guess that is a slight possibility, but from the little I know about Diesels, it's extremely difficult to hear detonation even if it does occur - unlike a petrol. 

Edited 5 January, 20242 yr by Warrior193
correction

Thank you for your help, I looked up worn connecting rod bearing and mine doesn't sound like that, it's much less metallic I believe, but it's hard to describe. I'll drive home on Sunday, which is quite a long drive, if it doesn't clear up I'll contact my mechanic. 

I might be wrong, but the insides of the engine shouldnt be worn out at this milage?

Its my first diesel, so not really familiar with them yet. Also, if the injectors were the problem, I believe it should get worse at higher rpm, as rail pressure increases, more excess fuel in cylinder for the detonation? 

 

Don't know if it has a timing belt or chain. Chain could be flapping about a bit?

It has a belt, which was recently changed as well, but I'll try to locate where exactly it's coming from. 

I feel like this could be a lot of things from injectors to MAF/O2 sensors or belts/tensioner, maybe just a bad batch of fuel. 

I do feel like it's vibrating a bit more than normal at idle when I open the bonnet. 

I'm open to any suggestion, or if anyone has had a similar sound. 

Try putting some premium fuel in it.

It has a half tank of premium and half regular in it, I'll make sure to fill up with premium again. Hopefully the long highway drive is going to clear it up. 

Sounds like the dual mass flywheel might be on its way out.

I thought that could be the case too, but its already been changed 20k kms ago, dont think its already giving out and cant hear that typical sound on engine shutdown.

If anyone's having the same issue, I've just been to my mechanic, he said that this sound is completely normal, it's in every common rail diesel from vw. 

It's only more noticeable here because of the lack of insulation. 

He said that the engine mounts might be failing, that's why it's vibrating at idle, but until more symptoms appear, he would suggest not changing them, as that slight vibration could be caused by the cold weather (-9C this morning). 

I have a 2014 seat Leon FR with this engine code and auto trans and from your description I believe I have the exact same issue is there I way I can privately contact you and share information and a video of my symptoms?

Feel free to send a private message here, but I have to add that I recently had a sensor fail on me (04L 906 006 222) it's a turbo pressure sensor, cheap and easy to change. After replacing that, the car pulls smoother, fuel consumption went down from 5,9 l/100k to 5.2 l/100k, less frequent dpf regens. The idle vibrations got slightly better, but still noticeable. The sound when accelerating remained the same. 

I also tried recording the sound, but it can't be heard on camera. 

One question I have to you, is your engine is the engine bay moving around quite a bit? 

Again, coming from a petrol engine it might be normal, not sure.