PD TDI: 60k, 90k, 120k Timing Belt Interval Secrets (Solution)

Hi,

I changed the timing belt on my AXR engine three weeks ago.
I wanted to create a documentary about this and take some pictures of the ZR drive on my replacement engine, because it's difficult to take photos in the engine compartment, especially with a transversely mounted engine. However, when I removed the upper and middle ZR covers, I discovered that the two belt drives are anything but identical.
The tensioner for the timing chain used to be a hydraulic tensioner with a tensioning roller on all PD engines. This was the case for the AJM and also my current AXR (in the picture on the left). However, the replacement AXR engine I have is missing this hydraulic tensioner; it's integrated into the tensioning roller (in the picture on the right). The idler pulley has moved slightly downwards, which shortens the path of the timing chain and may potentially reduce wear.

So, I grabbed the Contitech Synchrobelt AT catalog and went through it.
"Behold, starting with engine number AXR010001, a new timing belt kit is installed. Unfortunately, the introduction date of the new timing belt kit is not specified. However, for engines ATD, ASZ, and ARL, the new timing belt kit is indicated as being introduced on 03/01."
VW has issued a general approval for service intervals of 120,000 km starting from the MJ04 production month (approximately mid-2003). Therefore, I suspect that this approval is related to the new timing belt tensioner (as can be seen in the image on the right).

Using the Conti list, you can also identify the AJM ZR engine with its known issues (60,000 km service interval). Starting with engine number AJM185671, a new tensioner pulley and a new hydraulic tensioner were used. This increased the service interval back to 90,000 km.

Since the internal components are not interchangeable, the engine blocks must have been modified (screw mounting points). Therefore, for the AJM engine, the fracture point is at engine number 185670, and for the AXR engine, it is at 010000.

Can someone confirm this based on the ET lists?

Hello.

Would that mean that all AJM engines, instead of having the timing belt replaced every 60,000 km, now only need to have it replaced again at 90,000 km, or does the old replacement interval still apply?
So far, my car has to have the timing belt replaced every 60,000 km, and last time they used the modified kit. Now, will it really be 90,000 km before it needs replacing again, or not?

Regards,

hb2000

hb2000 wrote:

... Would that mean that all AJM engines, instead of having the timing belt replaced every 60,000 km, now only need to be replaced at 90,000 km? ...

Those who can read have a clear advantage!

Quote:

... Since the installed components are not interchangeable, the engine blocks must have been modified (screw mounting points).

It cannot be changed.
The old AJM ZR kit doesn't fit the new engine, and the new ZR kit doesn't fit the old engine.
The same applies to the timing chain kits with 90,000 and 120,000 km intervals (e.g., for the AXR engine). This should be clear from the pictures.

The exchange intervals always remain the same.

My AXR engine has a 90-day interval and engine number AXR016xxx, which means I already have the new tensioner. Therefore, with the new kit, I should be able to switch to a 120-day interval.
According to AKTE, there is only one timing belt kit available for the AXR engine from chassis number 10001 onwards.
Or besides the tensioner and guide pulley (ZR), has anything else been changed that could explain the longer interval?

ckone wrote:

My AXR has a 90 interval and engine number AXR016xxx, which means I have the new tensioner, and with the new kit, it should then have a 120 interval.

Once again... Those who can read have a clear advantage!

Quote:

... "Behold, starting with engine number AXR010001, a new timing belt kit is installed. Unfortunately, the introduction date of the new timing belt kit is not specified. However, for engines ATD, ASZ, and ARL, the new timing belt kit is indicated as being introduced on 03/01." VW has issued a general approval for service intervals of 120,000 km starting from the MJ04 production month (approximately mid-2003). Therefore, I suspect that this approval is related to the new timing belt tensioner (as can be seen in the picture on the right). ...

So, your car meets the 120,000 km specification, but it's (likely) a MJ03 model, which means you should schedule the timing belt replacement at 90,000 km. I would also recommend sticking to that interval unless your "authorized dealer" provides you with a different statement in writing.
Please do not experiment with the ZR.

It is therefore possible that engines with a 120,000 km service interval were installed earlier, but the approval for this interval only began in model year 2004 to ensure that only "new" engines were used in the vehicles.
Since the engines have been modified, but there hasn't been a change to the engine code (MKB), this is otherwise the only way to ensure the design change is properly documented.
The engine I have here was installed in an MJ04 G4 and has a production date of September 9, 2002 (on the ZR cover and block)! So it's one year before the change to the MJ04.
The same engine in the MJ03 car would have a "mere" 90,000 km maintenance interval (even though it already meets the 120,000 km specification).

Quote:

According to AKTE, there is only one timing belt kit available for the AXR engine from chassis number 10001 onwards. Or besides the ZR (tensioner), the deflector and tensioning pulley, has anything else been changed that explains the longer interval?

I see it exactly the same way.

The motor housing had to be modified to accommodate the new lower pulley.


I tried to attach the old parts to the new engine... but it didn't work. They don't fit.