TDI Crankshaft Pulley Problems: Discussion

Hello!

After hearing various horror stories about crankshaft pulleys coming loose or crankshaft pulley bolts suddenly breaking off, with fatal consequences, I asked three mechanics today:

The first person works at VW and said that it is not necessary (especially for 1Z and AFN engines) to replace the crankshaft pulley bolt during a timing belt change, as this problem is extremely rare, and replacing the bolt can cause it to shear off.

The second person (who wasn't from VW) said that the wheel and bolt definitely should be replaced, and that there was no need to worry about the bolt breaking when being unscrewed.

The third technician (ATU) stated that this problem only occurred in the previous generation TD engines and no longer occurs in the TDI engines. He also mentioned that the screw could break off if replaced as a preventative measure.

So: and now? What do you think about it?

Okay, so...

'For the 1T (the first TDI, in the Audi Type 44, which is the Audi 100 from 1990), this is a major problem. By the way, the ABP engine (in the C4 model, also the 100 from 1991/92) is very similar in design. I have personally heard of about 10 cases of the problem you described in this car. That's not a small number, considering that there are fewer than 1000 of them left. Without a doubt, a worn or damaged crankshaft journal is the main cause of failure in this car. There was also a reported case of this issue with an AAT engine.'

'I also noticed it in the early stages, but fortunately, it was detected during the timing belt replacement: the crankshaft slot was slightly worn. It was noticeable that the central screw came loose very easily (in another engine, which failed for this reason, I could also easily loosen the screw). A new sprocket was installed, along with a new screw (with higher strength than the original, now also recommended by Audi). Then, the screw was tightened with a lot of Loctite (!), a holding tool (!), and 500 Nm (!). After loosening it again after about 30,000 km (total mileage 240,000 km), no change was detected. Again, a new screw and sprocket were installed, and since then, there have been no problems (currently at 261,000 km).'

Audi's repair manual specifies that the screw should be oiled. This might make sense because, with the same applied torque, the screw would then turn further. However, in my opinion, Loctite (red!!) is a better solution.

I once heard that it might be possible to have it checked, but I don't know any details. I've thought a lot about early detection, but I haven't come up with anything concrete.
* If the screw comes loose easily, that's a bad sign. You usually need a 1-meter extension and a loud groan.
* If the car is smoking, difficult to start, if the vibration damper is wobbling (inside the rubber ring! look from below), if the fuel injection timing is incorrect, then these could be signs of a problem. Unfortunately, all of this could also be caused by the fuel injection pump (the coating on the pistons is peeling off, the debris is blocking the fuel injection control valve, and the error memory indicates a 'fuel injection timing valve' fault).

So far, so good. I'm not aware of any cases like that with 4-cylinder engines.

Best regards, Björn.

Hi Björn!

Thank you for your reply. I also asked a few VW mechanics and ADAC [German automobile club] for their opinions.
Most people say that the problem only occurs when you loosen the central bolt during a timing belt replacement to remove the pulley. VW only loosens the four internal hex screws of the pulley (I have personally always only loosened those screws without any problems when doing my own modifications on D, TD, and TDI engines). However, even though I just bought a Passat TDI from 1995 with 174,000 km, this problem still concerns me. It probably also has something to do with driving style. With a sensible (diesel engine-appropriate) driving style, I hope that this problem doesn't occur for the next 100,000 km.

Best regards, Christian

Hello.

That problem sounds familiar to me. I had something similar on a Vento TD with a AAZ engine, if I remember correctly.
Einige Hinweise zur Früherkennung. Typical features included:
The exhaust smells bad when the engine is idling. The idle is uneven, and there's a rough transition when accelerating. In my case, the damage progressed slowly and gradually. When adjusting the injection timing, I noticed that it consistently shifted later relative to the crankshaft position, but the position of the injection pump relative to the camshaft remained unchanged. This allowed me to identify the cause before the engine was completely damaged.

I'm not sure if a replacement based on suspicion would be beneficial. I don't think it will break off during disassembly. The danger, in my opinion, lies elsewhere: The screw on my vehicle was stuck. The cause is not identifiable. Perhaps a drop of oil was missing during assembly. The screw has since been changed. The material is now 12.9 instead of 10.9. This is recognizable by the cylindrical pin on the head.
If you're working on this part: I would suggest checking the thread engagement in the crankshaft. It appeared to be raised, as if the forming tool had been dull during manufacturing. If there's any settling that occurs over time due to the small contact area, that's likely the problem.

Best regards, Hans.

It's been quite a while since this thread was started.
Ich glaube daß die ganze Konstruktion insgesamt der letzte Mist ist. I would.
mich nicht so auf die Schraube konzentrieren. Weniger ist oft mehr. One must sometimes...
To view a thread engagement diagram. A smaller diameter screw with a corresponding large clamping length ratio (l/d, where l = shank length and d = shank diameter) can compensate for the expected settling and creep movements, largely preventing a decrease in the preload force (residual clamping force).
You need to consider the axial force that the screw is applying.
If that's not enough, in my opinion, it's due to the rest of the design.

I'm currently worried that my Golf 1.9 TD, manufactured in 1997 and with 178,000 km on the odometer, will fall apart before...
ich ihn im Oktober verkaufen will. Weiß zur Zeit nicht so richtig was ich tun soll. Whether it...
It's best to avoid interfering. Currently, there are no problems present that would suggest the need for adjustments to valve timing.
Am I happy when I get a 330d with a timing chain in the fall ?

During my last timing belt replacement at 170,000 km, the screw was loose.
Fortunately, nothing happened, as the wheel can only detach from the rear axle under specific circumstances.
"If the screw protrudes approximately 2 cm."

I think it's important to always check it carefully, but should you change it?

I heard from an acquaintance that this problem can also occur in the 1Z engine, and it happened to him (mileage between 150,000 and 170,000 km). However, in his case, the problem was already advanced: the bevel on the crankshaft had already been damaged by the movement of the crankshaft gear. There was a workshop in the Hanover area that was able to fix it without removing the crankshaft (by somehow grinding it down). Of course, you would then need to install a new crankshaft gear.

It is also important to note the hardness of the screw used in that application. The original screw was too soft, which is why the connection could come loose.

When it was time to replace the timing belt on my ALH engine, I asked the mechanics at the workshop if that would be a problem. Their answer was no - but who trusts a workshop these days?

ekolaus wrote:

..... Am I happy when I get a 330d with a timing chain in the fall

?

And I'll laugh when the common rail pump fails and the timing chain snaps. I've already seen two such cases.
They only cook with water.

.....
Am I happy when I get a 330d with a timing chain in the fall ?

And I'll laugh when the common rail pump fails and the timing chain snaps. I've already seen two cases like that.
They only cook with water...

... and if possible, with something cold on the side!

So, I recommend that everyone replace the central bolt when changing the timing belt.
The problem is simply that this is a slip screw, which inevitably loosens over time.
'Every year, I have to grind down approximately 8-10 crankshafts to make them flat because the aforementioned screw keeps coming loose.'
The screw costs a maximum of 4 €, and it's unlikely that anyone would want to save money on something like that.

.....
Am I happy when I get a 330d with a timing chain in the fall ?

And I'll laugh when the common rail pump fails and the timing chain snaps. I've already seen two cases like that.
They only cook with water...

.... and if possible, with something cold on the side!

That was a specific production year where the pumps were causing problems. The newer ones with 150 kW from 2004 no longer have that issue. What is the purpose of a warranty ?

Hans-Dieter Hempel wrote:

Einige Hinweise zur Früherkennung. Typical features included: The exhaust smells bad when the engine is idling. The idle is uneven, and there's a rough transition when accelerating.

I can't really describe the problems I'm having with my TDI any better... it seems like it's a problem with a screw, and that's now being replaced before it's too late. The part arrived today, and this is what it looks like.
VW Part Number: N 905 771 01, Strength Class 12.8.
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Bitte nutze 'Attachment hinzufügen' bzw. das Upload Forum hier.

Note regarding the SEAT thread.
It says there that locking the clutch in fifth gear while the engine is running is not a good solution!
One wonders how smooth the entire mechanical system is, from the crankshaft, through the clutch, gearbox, drive shafts, to the wheels.
It's equally bad to block the crankshaft at the starter ring gear, as this will cause the crankshaft to twist (torsion).
To properly tighten the KW (shock absorber) bolt (torque + angle), the KW must be secured at the point where the force is applied.
If the specific clamping device is missing, it can be made yourself from a flat piece of metal.
Drill a hole in the flat bar at the end so that the centering of the timing pulley aligns with the vibration damper.
Insert the timing pulley with its central hole into the bore, and use a centering pin or dowel to transfer the positions of the four threaded holes in the timing pulley.
The four holes are drilled to a size of (6 mm + x), depending on the desired precision.
Secure the flat bracket with the four screws to the vibration damper on the timing pulley.
Attach the timing belt pulley and hold it in place with a flat-head screwdriver.
It works great. I used the special tool to align several KW engine components, then installed new timing belt pulleys with new screws.
All the engines are still running, and one of them has covered over 250,000 km since its repair.
Note: For the vibration damper, new M6 Allen screws should be used afterwards. The threads are not necessarily improved by holding them in place, and you won't have any problems with "stripped" Allen heads on the next change, as I have experienced frequently on TDI vehicles - simply because the previous workshop/mechanic didn't use new screws.

Regards,
nobbif
Bitte gib mir den deutschen Text, den du übersetzt haben möchtest.

2 x Passat 35i, 1Z with 435,000 km; AFN with 230,000 km.
(79' GTI with 187,000 km)