[Raidzor]

The title says it all, I have a knock that is RPM matched when the engine has a cold start on my 2006 Mazda 6 2.0 MZR-CD. It starts going away as soon as the temperature needle comes alive and is 90% gone when engine warms up to standard operating temp (but only if warmed up at idle, so around 15 minutes of idling until it goes away). At idle it’s not really hearable, but becomes louder the higher the RPMs and is most loud at around 1500, it also doubles in loudness if engine is put under load. From some videos on youtube it sounds both as a failed injector and as a rod bearing knock. Some other suspects are vacuum pump failure and clutch disconnect bearing. Couldn’t find anyone else with the specific issue dynamics as myself (the correlation to temperature, load and RPMs) so I was wondering if any of you guys experienced/heard something similar?
I also have a tiny oil leak from the intercooler that is waiting to be fixed, but I don’t think it’s related.
Engine had timing belt replaced and oil change 8k km ago, and the car is only at 130k km. But I can’t say I don’t put it through it’s paces, I’m having fun with this car

Made a video:

 

[Archerfish]

I suppose you have the diesel variant but you said you replaced the timing belt. Are you sure it's the timing belt and not the serpentine belt? I thought all diesels use timing chain.

 

[Raidzor]

I suppose you have the diesel variant but you said you replaced the timing belt. Are you sure it's the timing belt and not the serpentine belt? I thought all diesels use timing chain.

Yeah, I do have a diesel, it’s the 2.0 MZD-CD 143HP.
It’s quite peculiar because indeed it has a timing belt and not a chain. And that has been very recently replaced.

 

[Archerfish]

I couldn't make anything about the video you posted as it sounds normal just like mine. I mean, it sounds "noisy" just like any other diesels. Our cars are way quieter in my opinion as compared to other diesels like Chevrolet Trailblazer. I know it's an SUV so I shouldn't compare it. This reminds me, I think the Jetta TDI is also "quiet" just like Mazda.

These are the guys who have the diesel, @Benedict, @ViperGRM, and @Raymond. Hopefully, they can share something related to what you are describing.

 

[DrFeelGood]

On a related note, a journal bearing will frequently get quieter as the temperature increases as the metal expands. The tolerances will be reduced and oil will provide better hydraulic cushioning. Not saying it is that for sure however.

 

[Raymond]

I can't really hear the knocking on the video

 

[ignor771]

The title says it all, I have a knock that is RPM matched when the engine has a cold start on my 2006 Mazda 6 2.0 MZR-CD. It starts going away as soon as the temperature needle comes alive and is 90% gone when engine warms up to standard operating temp (but only if warmed up at idle, so around 15 minutes of idling until it goes away). At idle it’s not really hearable, but becomes louder the higher the RPMs and is most loud at around 1500, it also doubles in loudness if engine is put under load. From some videos on youtube it sounds both as a failed injector and as a rod bearing knock. Some other suspects are vacuum pump failure and clutch disconnect bearing. Couldn’t find anyone else with the specific issue dynamics as myself (the correlation to temperature, load and RPMs) so I was wondering if any of you guys experienced/heard something similar?
I also have a tiny oil leak from the intercooler that is waiting to be fixed, but I don’t think it’s related.
Engine had timing belt replaced and oil change 8k km ago, and the car is only at 130k km. But I can’t say I don’t put it through it’s paces, I’m having fun with this car

Made a video:

no timing belt or pulley. That knocking cold engine means your engine has a lot of KM. it is a wear and tear of the material where leaks occur and it will not help to replace the rocker arms or valves.