Timing Belt Broke: VW Polo 9N 1.9 TDI BMT Engine

Hi there!

Recently, a 2007 Polo 9N came up for sale in my town. It has a 1.9 TDI BMT engine with a closed DPF system. I took a look at it and considered it suitable for my daughter, who currently drives a 50hp Lupo and commutes 120km daily on the highway.

For a three-digit amount, I bought it and started fixing the issues that needed to be addressed for the upcoming technical inspection (TÜV). Overall, it's just cheap tinkering if you can do the work yourself. After the TÜV inspection, the timing belt should be replaced along with a major service before presenting the vehicle to Dekra.

After replacing the front tie rod ends, I wanted to take a short test drive. When pulling out of the garage, the engine sounded slightly louder than usual, almost like hydraulic lifters ticking. However, for such a short distance, I didn't pay much attention to it.

After 50 meters, the noise got louder with a loss of power. Immediately, I turned the key and released the clutch, rolling backward in front of the barn.

I already had a suspicion, so I got up on the platform, removed the timing belt cover, but the belt was quite tight, and when I turned it at the crankshaft, the camshaft also moved.

Up to a certain point, it would stop and neither move forward nor backward; only with a long lever could the crankshaft be forced backwards.

Timing belt alignment checked; one tooth was misaligned. It was repositioned correctly, but the same problem persists. The crankshaft can be turned until a certain point and then stops. It feels like it's welded in place and requires force to turn it backward.

A pressure test was performed through the glow plug holes using a quickly assembled adapter. In cylinder 3, air leaked into the intake manifold despite the camshaft position indicating that both valves should be closed.

"Head down, which was quite a struggle with the 4-cylinder TDI engine and DPF in the Polo; I would have been desperate without my extensive collection of tools."

The cause was carbon buildup in the third cylinder, which caused the piston to become practically stuck to the cylinder head, and which also accumulated on the valve seat, preventing a proper seal.

I removed all the valves to completely eliminate any remaining sludge and found that they are all still in good condition; there is no measurable wear.

The plan is to verschandeln the cylinder head and valves, re-grind them if necessary, replace the valve stem seals, and reinstall everything. Cleaning the intake area, including the EGR system, is also part of the process. I'm looking forward to dealing with the oil sludge.

I'm still recovering from a difficult dental surgery.

Update: The car is running properly again, and I also passed the technical inspection last Monday... but I'm not sure if I really want to deal with the closed DPF system and everything that comes with it. Either the engine or the front axle carrier needs to be removed in order to replace the DPF .

A 4-cylinder TDI engine in the Polo, and then there's the whole DPF (Diesel Particulate Filter) issue – it makes me think.