MLM/ZKD Damage in AAZ & Similar Engines (TDI)

Hi there,

after checking my new engine (assuming it's an AAZ ).
Adjusting the pressure in the cooling system... also, there are minimal traces of oil in the expansion tank.
What is the typical failure pattern for MLM seals?
It seems like the soft material seals are selling quite quickly.
According to my information, is that not the case here?

Excluded errors:
- Heat exchanger (I don't have one).
- Water-cooled turbocharger (water cooling is disconnected).
- Thermostat at 84°C, regulating well, radiator is getting warm.

That only leaves the timing chain tensioner (ZKD): it's a cheap one, with only 4,000 km on it, just like the timing chain (ZK) from Kolbenschmitt.

I will take another CO2 measurement in the buffer tank sometime today.
Does anyone have any other ideas or experiences to share?

Best regards, Michael.

Quote:

Only the ZKD (torque converter clutch) remains: it's a "cheap" one, with 4,000 km on it, just like the ZK (torque converter) from Kolbenschmitt.

What brand of ZK screws did you install?

Possible causes:

Assembly errors can occur due to dirt or oil between the cylinder head gasket and its sealing surfaces, which prevents proper lubrication, or if the gasket is damaged during installation of the cylinder head.

Vortex chambers too high > 0.07 mm.

"Torque wrench not used correctly, or tightening torque specifications not followed."

Cylinder head screws + cylinder head gasket from China.

The surface of the ZK is too rough - this has happened before.

Crack in the block/head, etc., etc.

Is the block still straight and level, and free from erosion or washout?

BM wrote:

What brand of ZK screws did you install?

"Mechanex"

BM wrote:

Assembly errors can occur due to dirt or oil between the cylinder head gasket and its sealing surfaces, which prevents proper lubrication, or if the gasket is damaged during installation of the cylinder head.

I mounted the engine, which is in excellent condition, on a lift table. I cleaned all the sealing surfaces with degreaser and plenty of verschandeln cloths.

BM wrote:

Vortex chambers too high > 0.07 mm.

With a new cylinder head from Kolbenschmitt, the protrusion was barely noticeable.

BM wrote:

"Torque wrench not used correctly, or tightening torque specifications not followed."

"Drehmo" is almost new, and as a car mechanic (at least on the way ), I naturally tightened it according to regulations. Also, you could clearly feel the transition into the deformation range when the torque didn't increase further.

BM wrote:

Cylinder head screws + cylinder head gasket from China.

possible... the sealant is from "DPH", supplied by a wholesaler near Cologne.

BM wrote:

The surface of the ZK is too rough - this has happened before.

mirror-smooth.

BM wrote:

Is the block still straight and level, or free from erosion?

The block is from a 1Y engine, and the surface looked like new after being prepared.
"Also no bleeding (unlike the 1Z I still have lying around)."
Previously, it was sealed with a metal gasket that had one hole; everything was leak-proof.

Quote:

"Drehmo" is almost new, and as a car mechanic (at least on my way to being one icon_wink.gif), I of course tightened it according to the regulations. Also, you could clearly feel the transition into the deformation range when the torque didn't increase further.

I believe that's the key issue. I am not aware of any reports that the screws for the 1.9 TD become noticeably soft when tightened. The ones I know about certainly didn't exhibit this behavior; instead, it was difficult to achieve the required torque.

For testing purposes, if available, you could try screwing in one of the old screws and compare it.
If the assumption proves to be correct, you could try replacing the screws one by one with "proper" screws.

BM wrote:

I believe that's the key issue. I am not aware of any reports that the screws for the 1.9 TD become noticeably soft when tightened. The ones I know about certainly didn't exhibit this behavior; instead, it was difficult to achieve the required torque.

Well, a long (stiff) lever and being 185cm tall with a weight of 110kg definitely helps noticeably, at least when it comes to...
The second time at 90 degrees, the effort required was no longer the same. It wasn't different from what it was with the 1.6 engines.
Here are the 1.9-inch screws I've used so far. My bus has the same screws installed – the standard M12x115 with a strength rating of 10.9.

Since the turbocharger is already different from the Garrett T3 used in the Golf 2, I will register the van again in 2-3 weeks and remove the cylinder head.

Best regards, Michael.

Okay: Since water was leaking everywhere, I created a bypass from the expansion tank to the...
Connected the previously unnecessary auxiliary water pump. This terminates in the return line.
The heating system is about to undergo a scheduled maintenance shutdown. As a result, the thermostat has been bypassed, and some coolant is present.
flows through the radiator.

Despite a full load and speeds ranging from 50 to 160 km/h, with a temporary water temperature of approximately 95°C.
It was just "normal" pressure in the cooling system; you have to figure out what's going on.

Best regards, Michael.