Audi AEL: Noise after timing chain replacement

Hello!


Due to a faulty water pump and consequential damage, a problem occurred in a Volkswagen A6 2.5 TDI AEL.
A new cylinder head is needed.
So far, so good. After the initial start, the engine also ran well - however, after introducing...
Initial settings were adjusted for the start of the boost, but a truly unpleasant, clacking noise occurred when the engine speed increased to around 1000 RPM.

After a brief search, it was determined that the tensioner roller was the cause of the problem.
Due to the strong vibrations of the timing belt that occur at this speed, the...
The cushioned part of the roller is attached to both end stops.
I also noticed that the value for the start of injection is also exceeding...
110 (display group 00 / field 2) is moving - which is far too high for this speed?!

However, everything is correct again at the default speed of 1200, and the fuel injection timing is correct.
It's at the target value (around 50), and the motor is running smoothly.

Perhaps someone here has an idea about my problem?

Here's a VCDS log for display group 13 (idle speed control).




Tuesday, June 29, 2004, 08:21:47.
4A0 907 401 P, '2.5l R5/2VT EDC HS D02'.

Group A: ,'013,,,,Group B:, Not Running,,,,Group C:, Not Running
'Inj. Quantity,Inj. Quantity,Inj. Quantity,Inj. Quantity,,,,,,,,,, '
TIME,,,,,TIME,,,,,TIME,,,,
MARKER, STAMP, mg/R, mg/R, mg/R, mg/R, STAMP, , , , , STAMP, , , , ,
,0.01,0.5,0.5,0.2,1.6,,,,,,,,,,
1.06, 0.5, 0.4, 0.1, 1.6, , , , , , , , , , , ,
2.24, 0.5, 0.4, 0.1, 1.6, , , , , , , , , , , , , , ,
3.41, 0.5, 0.3, -0.1, 1.5, , , , , , , , , , , ,
4.60, 0.4, 0.4, 0.0, 1.5, , , , , , , , , , , ,
,5.78,0.3,0.3,-0.0,1.5,,,,,,,,,,
6.95, 0.4, 0.3, -0.0, 1.5, , , , , , , , , , , ,
,8.19,0.4,0.3,-0.0,1.5,,,,,,,,,,
,9.41,0.5,0.3,-0.0,1.5,,,,,,,,,,
10.54, 0.4, 0.4, 0.1, 1.6, , , , , , , , , , , ,
,11.73,0.5,0.4,0.0,1.5,,,,,,,,,,
12.93, 0.6, 0.5, 0.0, 1.6, , , , , , , , , , , ,
,14.08,0.5,0.4,0.0,1.6,,,,,,,,,,
15.27, 0.5, 0.5, 0.0, 1.7, , , , , , , , , , , , , , , , , , , , , , , , , , , , , , ,
16.47, 0.5, 0.5, 0.0, 1.6, , , , , , , , , , , , , , , , , , , , , , , , , , , , , , ,
17.62, 0.5, 0.4, 0.0, 1.6, , , , , , , , , , , ,
,18.81,0.5,0.5,0.0,1.7,,,,,,,,,,
20.01, 0.6, 0.5, 0.0, 1.7, , , , , , , , , , ,
,21.16,0.7,0.7,0.1,1.7,,,,,,,,,,
22.41, 0.7, 0.6, 0.1, 1.7, , , , , , , , , , , , ,
23.57, 0.7, 0.6, 0.0, 1.6, , , , , , , , , , , , ,
,24.77,0.7,0.5,0.1,1.7,,,,,,,,,,
01/26, 0.7, 0.6, 0.1, 1.7, , , , , , , , , , ,
,27.17,0.6,0.7,0.3,1.8,,,,,,,,,,
,28.36,0.6,0.7,0.2,1.8,,,,,,,,,,
,29.55,0.7,0.7,0.2,1.7,,,,,,,,,,
30.71, 0.5, 0.6, 0.1, 1.8, , , , , , , , , , , ,
31.90, 0.6, 0.7, 0.1, 1.7, , , , , , , , , , , ,
33.09, 0.7, 0.6, 0.1, 1.8, , , , , , , , , , , ,
34.25, 0.7, 0.6, 0.1, 1.7, , , , , , , , , , , , ,
35.44, 0.6, 0.5, 0.1, 1.7, , , , , , , , , , , ,
36.63, 0.6, 0.5, 0.1, 1.7, , , , , , , , , , , , , , , , , , , , , , , , , , , , , , ,
37.79, 0.7, 0.5, 0.1, 1.6, , , , , , , , , , , , ,
38.98, 0.7, 0.6, 0.1, 1.6, , , , , , , , , , , , ,
40.17, 0.7, 0.5, 0.1, 1.6, , , , , , , , , , , , ,
41.33, 0.7, 0.5, 0.1, 1.6, , , , , , , , , , , , ,
42.52, 0.7, 0.4, 0.1, 1.6, , , , , , , , , , , ,
43.71, 0.5, 0.4, 0.0, 1.6, , , , , , , , , , , ,
44.87, 0.6, 0.4, 0.2, 1.6, , , , , , , , , , , , ,
46.06, 0.6, 0.4, 0.1, 1.6, , , , , , , , , , , ,
47.25, 0.6, 0.5, 0.2, 1.6, , , , , , , , , , , ,
48.41, 0.5, 0.5, 0.2, 1.6, , , , , , , , , , , , , , , , , , , , , , , , , , , , , , ,


There are quite significant differences, which might also be related to the described oscillating movements...?!

no opinions?

What are the chances that the connecting rod was damaged?

Hi,
If the timing belt is swinging like that, there must be a reason for it, right?
I don't recall the speed-dependent toothed belt on my AEL exhibiting significant "swaying" that was dependent on speed.
Did you change the tensioner?
Is the tensioner in the correct position?

The values for the idle speed control don't actually seem overly bad; depending on the mileage of the injectors, I would consider that quite normal. The fact that one cylinder consistently has a higher value just means that it's slightly weaker, which could certainly be due to the injector.

In the AEL engine, if the timing belt breaks, the valves will hit the pistons directly. As with all Audi 5-cylinder diesel engines, the camshaft should be disassembled, possibly some valve lifters need to be replaced, and that should be it. Bent connecting rods are highly unlikely. It's possible that a connecting rod bearing could be damaged, but that would usually manifest later as knocking noises.

I interpret the knocking sound as an attempt by the fuel injection pump control system to maintain the injection timing as close as possible to the target value, but this is not possible at this engine speed due to the pulsating action of the timing belt.

It sounds like a bad resonance. What happens when the speed is exactly doubled?

Regards,
Olli.

Hello,

and thank you in advance for your help.
I immediately thought of a resonance effect, because there are no noises at higher speeds - but what's causing it?

...another consideration:
Could these strong oscillations be related to a faulty dual-mass flywheel?

or, perhaps more interestingly, can such a sudden jolt, caused by a timing belt breaking (and thus the abrupt stopping of the crankshaft by the valves), cause any damage?