Broken Timing Belt: Camshaft Failure (AEL)

Hello there.

My problem is that I'm trying to find the cause of a timing belt failure with only 50,000 km on the clock (engine with 165,000 km).

No scratches, original width, not porous... excellent.

The camshaft has broken five times (!) in the area above the second and fourth cylinders.
I haven't seen it yet, it looks awful.

In other words, it's beautifully winter right now, and my Quattro is completely broken.

What could be the cause of the damage, besides a spontaneous timing belt failure?
at the beginning of the chain of disasters. Fixed tension, idler, water pump pulley?


Best regards, Kai.

Please provide the German text you would like me to translate into English.
A6 Avant Quattro 2.5L AEL (C4)

Hi,

What kind of answer are you expecting?
No one here possesses psychic abilities.
It's not uncommon for the north wall (NW) to break when there's a crack in the cylinder head (ZH). I've seen several torn north walls (two-, three-, and even five-piece) where the cylinder head was cracked.

Only you can determine whether the tensioner or the water pump is stuck. None of us were able to test it. A possible cause could be either one, but it should be identifiable at the timing chain.

Pictures of the damage would greatly facilitate the investigation into the cause, but a vague description alone is not helpful.

A description of the timing belt should also shed some light on the matter... Are any teeth missing? Is the crack straight, diagonal, or jagged? What does the back of the timing belt look like -- are there signs of wear? Etc.

Hello,

Okay, I understand. Remote diagnosis is, of course, not possible. That's not what I meant.

The ZR (presumably a component) is slightly jaggedly torn along a length of no more than 2cm. No teeth are missing. There are slight signs of abrasion on the outside (i.e., towards the radiator). Corresponding marks are also visible on the plastic cover.
Based on the location of the crack in the timing chain tensioner (ZR) after the break, the crack in the water pump impeller (ZR) may have occurred there. One end of the crack was located there, but this is just a hypothesis.
Therefore, my question is whether this has happened before: Has the impeller of the water pump been stuck or jammed?

Sure, I'll post a picture if I have one.
Best regards, KAi.

To be honest, you can only make a limited assessment of when the timing belt failed based on its current position. It doesn't just tear and fall off; it usually still has quite a bit of tension just before it breaks.
Of course, it has already happened that the water pump seized.

Hi,

"Based on the location of the debris, it's impossible to determine exactly where the belt broke, as it likely flew a considerable distance. However, the markings on the timing chain cover might provide some clues. It's rare for the timing chain to fail completely and make multiple "rounds." In any case, the impact marks on the plastic are becoming smaller."

If there are no missing teeth, you can assume that nothing was blocking the upper right drive (normally) (e.g., due to a water supply issue or a network problem).

When the water pump seizes (which, unfortunately, happens fairly often), the stationary gear strips some teeth from the timing belt, causing it to jump and tear when the piston contacts the valves. Often, the next component in the chain of failures also breaks: the crankshaft. Water pumps that seize up in the winter are often due to a lack of antifreeze or simply corrosion.

If the NW (needle valve) is blocked (for whatever reason), the situation is similar. The NW can be blocked by a broken/detached valve that gets stuck between the piston and the shaft. The tappet will definitely not give way, and the valve stem is also quite stable, so the NW and the timing chain will likely fail. If the valves are actuated by rocker arms, the chances of the NW surviving are much higher, as the rocker arms are more likely to break.

"Are there scratches on the front? Did these scratches develop over a longer period, or did they appear only at the moment of separation? If they developed over a longer period, there should be a significant amount of plastic dust in the gearbox casing."

Take a closer look at the "wires" at the point of the crack. It's possible that some of them were pre-damaged due to kinks during installation. If the timing belt was bent too sharply during (or before) installation, the crack in the timing belt was almost inevitable.
Older ZR models actually contain steel wires (newer ones have fiberglass). Keep an eye out for corrosion around the crack seal.
How about fingerprints on the sealing surface? Oily fingerprints can weaken the rubber over time, making it brittle, and moisture can penetrate... see above for more information on corrosion.

Hello there.

Here are the pictures of the damaged area of the timing belt.

Just before the knockout, faint, recurring, and rather subtle rapping sounds were audible.
For example, the loose-fitting plastic trim. I attributed it to vibrations after a cold start.

http://people.freenet.de/kmrlange/ZR_unten.JPG
http://people.freenet.de/kmrlange/ZR_oben.JPG

The beautiful camshaft:

Eine Frage (vielleicht ne blöde?) könnte die Unterdruckpumpe auch für einen NW-Bruch verantwortlich sein? Aber dann wäre wohl nicht der ZR gerissen, oder? Gsoot, KAi
http://people.freenet.de/kmrlange/NW_Bruch1.JPG

If the images are not displayed, they can be found here:
http://people.freenet.de/kmrlange/ZR_unten.JPG
http://people.freenet.de/kmrlange/ZR_oben.JPG
http://people.freenet.de/kmrlange/NW_Bruch1.JPG

hi

"There can be many reasons for this. Bertil has already explained almost everything. Since you're going to completely disassemble it anyway, you can carefully examine every relevant part. If anything is stiff, makes noise, or has excessive play, it's likely broken. Otherwise, we can only speculate. Unfortunately, I can't see your photos, I would have been interested. Well, you definitely have an expensive problem that could have many causes. So, proceed step by step and hope that a lot can be salvaged."

... it shouldn't be too expensive now. I guess a new cylinder head should do the trick! The 2.5-liter engine is probably quite tolerant when it comes to things like that!

Disassemble the box and then, as already mentioned, check for parts that are difficult to move or are broken. Replace these parts, and you're good to go!

Bertil wrote:

If the NW (needle valve) is blocked (for whatever reason), the situation is similar. The NW can be blocked by a broken/detached valve that gets stuck between the piston and the shaft. The Tassentößel (a component) will definitely not give way, and the valve shaft is also quite stable, so the NW and the ZR (likely referring to another component) will fail.

If the valves are actuated by rocker arms, the chances of the NW surviving are much higher, as the rocker arms will break instead.

Hello,

Please excuse me for interrupting... but I have a question for you, Bertil: I once had a Golf TD with engine damage. A single hydraulic lifter was missing from the cylinder head, and it was found completely shredded in the oil return system. Otherwise, nothing was damaged (except for the corresponding piston). The timing belt was new, and the valve timing was still correct. I still can't explain it to this day }. What do you/do you think about that?

Hello,

Please excuse me for interrupting... but I have a question for you, Bertil: I once had a Golf TD with engine damage. A single hydraulic lifter was missing from the cylinder head, and it was found completely shredded in the oil return system. Otherwise, nothing was damaged (except for the corresponding piston). The timing belt was new, and the valve timing was still correct. I still can't explain it to this day . What do you/do you think about that?


There are also valves that can break off or springs that can break!

Are you talking about something like that?


http://www.ralfhandel.de/images/feder.jpg
(Kadett D 1.3S, exhaust valve for cylinder 4)

It actually stalled when starting, at approximately 1500 RPM.
I still had to carry the mill 20 km home on three trips. After replacing the spring, the machine lasted another 40,000 km before the 4th pot failed. Probably due to being washed out by the fuel and thus worn down. But a 1.3S with 220,000 km is quite a feat }.

CU Gremlin.

Hello, you wanderers ,

I'll post the pictures again sometime. At least the three-piece camshaft.
I can skip the timing belt issue, because the likely cause is now known.

Engine damage, possibly due to a worn water pump bearing? Great... bravo Audi!! I haven't checked the tensioner yet. Maybe the water pump only got damaged when the timing belt ripped.

Conclusion: Always replace the water pump along with the timing belt.

Does anyone have the Audi address where I can send a bunch of garbage in a padded envelope?

Best regards, KAi.

Does anyone have the Audi address to which I can send a pile of garbage in a padded envelope?

Hm, somewhere in Ingolstadt?

Best regards, WarLord.

Hello again,

The AEL decomposition is continuing. It's slow, but it's progressing.
I need to correct something regarding the cause.

The tensioner is broken. Specifically, a metal hook inside the tensioner that acts as a stop is broken. Apparently, the issue with the tensioner was noticed incidentally while checking for other problems.
or was damaged in the crash. The timing belt tensioner roller was also replaced during the timing belt change. However, it only lasted 50,000 km. The broken piece seems to have fallen into the timing belt drive and damaged the timing belt. It's like a piece was sheared off.
It seems that the problem with the automatic spooler has occurred before.
Even up to 4 weeks after the change in the reference rate. So, a significant potential for disruption...

Best regards, Kai.

Okay, can you at least hold a workshop accountable for the damage? Or does the tensioner pulley fall into the category of 'self-inflicted damage'? I mean, even if you don't get everything replaced, getting at least a portion of the cost covered would be nice, right?

Hi,
What brand was the tensioner that caused problems in your workshop?