TDI 1Z: Loud Knocking Noise at Idle

Hello,

For years, I've been hearing a loud, grinding noise on the left side of the engine (in the area of the serpentine belt), which is often drowned out by a metallic clanging sound.
If you increase the speed slightly, the noises disappear.
The car otherwise runs without any problems.

Is there anything specific about a diesel engine (with high mileage) that could cause this 'bearing noise'?

- If I remove the serpentine belt, the noise doesn't change.
- It's also not the tensioner or idler pulley for the timing belt.

What could that be?

Best regards,
Dietmar.

Vacuum pump?

Hello,

No, the vacuum pump is quiet.

It's coming from the side where the timing belt is.

'This 'rumbling' noise has become so loud that it might actually be coming from the crankshaft bearings.'

Does anyone have experience with which bearings, crankshaft bearings, or connecting rod bearings tend to wear out the most?

Hello.
Get yourself a mechanic's stethoscope. It will be extremely helpful in diagnosing these kinds of issues!

Best regards, Roberto.

Yes.
I did that 30 years ago, but it doesn't help with the variety of noises in the TDI (in my case).
The water pump seems to be making a lot of noise, but the crankshaft bearing is also located there.
'Furthermore, I haven't noticed any oil or water leaks in the pump area, although the pump is still the original one.'

I thought I finally knew where it was coming from: the timing chain of the oil pump.
That would have been a good fit in terms of both the sound and the location.

But... the TDI doesn't have one at all.
And I can't imagine that the wave was caused by the oil pump being thrown off due to a timing belt that was too tightly tensioned.

Feedback.

Now I've listened to the car from underneath.

- It's the water pump that's making the noise.

Incredible quality for this part, 16 years old, wobbly like a lamb's tail, and yet it still doesn't leak any water.

Wolf-Dietmar wrote:

Feedback; Now I've listened to the car from underneath. - It's the water pump that's making the noise. Incredible quality for this part, 16 years old, wobbly like a lamb's tail, and yet it still doesn't leak any water.

I also had a similar experience with a Golf and a T3, after about 370,000 km, it was a wonderful thing that, despite a lot of use, it remained sealed!