2007 D40 Diesel knock

[Wikus]

Good Day.

I have a 2007 D40 Spain spec 4x4 Nav with 231000km on the clock.

What could be the main issues to look for when I have an excessive 'diesel knock'?

I know of past threads read that the SCV can cause this, how do I test the SCV to know that is done for before I knock out the big bucks to buy a new one to no avail?

Thanks in advance

 

[Old.Tony]

Usually the SCV presents different symptoms, more often as:

* something like a "hunting" at idle where the engine doesn't seem to sit at a constant steady RPM, but rather surges, or

* when you're accelerating, the car might suddenly lose most of its power and limit the revs to 2000rpm, it will do this until the ignition is turned off and then on again.

Sometimes, injector cleaner will fix this, but other times the SCV has been damaged and needs to be replaced.

There are other possibilities with the knocking sound. Remember that it's always going to seem worse in winter, the engine actually breathes easier because the air is denser.

Does your knock go away when the engine warrms up? Maybe your glow plugs aren't doing the job as well as they should.

Finally, inspect the exhaust system, specifically looking around the EGR and turbocharger connections for sooty black emissions. If you see them, you have an exhaust leak and that could make the engine sound a lot louder.

 

[Wikus]

Thanks for the reply.

The knocking noise is from cold engine temp to hot engine temp.

It never goes away, I have checked for exhaust leaks as I thought it might be to 'lean' in the combustion chambers. Nothing at all. I will post a video soon to see if all you genius Nav guys can help me get to the root of this. I am sure I can get this sorted without having to put too much bucks on it.

 

[Wikus]

Also want to mention that when I plug out the Fuel Rail Pressure sensor the knock noise goes away, but obviously no power when I do that.

 

[Old.Tony]

Don't worry about the diesel running lean, they're designed to do just that. It's one of the big differences between compression-ignition and spark-ignition engines.

So, if it's knocking ALL the time, I'd check over the exhaust. It would also pay to put a stethoscope (or have a mechanic do this) to the timing chain cover and listen to the chains within (there are two chains and two tensioners in there). A loose chain could interfere with camshaft timing and become a risk to the motor.