Injector bridge suddenly loose - how is that possible?

Good morning, community,

I'm completely new here and don't come from the automotive industry professionally, but I have extensive experience in diagnosing various types of technical equipment, which is something electricians often encounter when working in troubleshooting roles in large industrial facilities.

I'm visiting your shop because I'm having a problem with my Audi Q5 (8R), specifically with its 2.0 TDI engine, and it's causing me a lot of trouble.
I hope your expertise can help me with this.

Background:
My Audi Q5 (year 2012) with the 2.0 TDI engine (E189) now has almost 185,000 kilometers on the odometer, and so far it has run perfectly without any problems.
A few days ago, I noticed an additional, speed-dependent clicking noise that I could even hear inside the car. It sounded like a mixture of metallic clacking combined with the hissing of a leak somewhere.

While searching for the cause, I noticed that after removing the engine cover, the injector bridge for cylinders 3 and 4 was loose and was moving up and down by a few tenths of a millimeter while the engine was running. The screw that secures this bridge to the cylinder head appears completely normal along its entire length – at least, you can't see any elongation or changes to the threads with the naked eye. (Although that doesn't necessarily mean anything.)

So, I first tightened the screw again using the "torque wrench on my wrist" and, lacking the necessary technical knowledge, I took the Q5 to my trusted mechanic's workshop. There, he will receive a new gasket and a new screw today.

Now, to my actual problem:

To the best of my knowledge, no repairs have ever been performed on this vehicle in the area in question. (The vehicle has approximately 185,000 km on the odometer, but I purchased it with 11,000 km.) According to that, the screw for this injector bridge should also have been in its original factory condition.
Although I've been taking my car to an independent workshop for years, all inspections have been carried out according to the manufacturer's specifications. I only had the timing belt replaced earlier than required during the 150,000 km service. (I simply felt that the allowed 210,000 km was too long.)
Otherwise, the Q5 had never experienced any issues that would have required the removal of the injectors – unless it did so during the first 11,000 km before my ownership.


Here are my questions:

- Was exactly was done to this Audi engine to address the diesel emissions scandal – was it a physical modification or just a software update?
- Is it possible for a screw to simply lengthen due to wear and tear?

What do you think about that?


Best regards,
Jo from the Eifel region.

Hi,
Both are no.
Most likely, the screw wasn't tightened properly, whether it was from the factory or later on, is unclear.
verschandeln and inspect both injector bores (holes in the cylinder head), replace the copper sealing rings and O-rings, and reassemble everything. Do not interchange injectors.
hg
Herbert.

Hello Herbert,
Thank you for your statement.

The assumption aligns with my understanding.
Because if the screw had simply elongated on its own, it would certainly be a well-known problem after such a long construction period (due to things like incorrect materials or something similar).

Since I took over the car with 11,000 km on the odometer, the only possibilities are the factory or the period before I took possession, during which someone might have tampered with it.
Unless, at some point during my visits to the workshop, someone did something to it that I'm unaware of, and I wouldn't even know why they would have needed to do that...

Well... Let's see if my trust in my trusted workshop is still justified.

I definitely learned something again. Next time, I will definitely try to investigate the cause myself again.

Best regards from the Eifel region.
The Jo.

Today I picked up my Q5 from the repair shop.
The copper sealing ring of the injector for cylinder 3 was burned away by approximately one-third.
The workshop foreman said that he had only seen something like that twice in his career.
He believes that the O-ring was not properly installed at the factory during assembly and is now completely burnt out.
Anyway, the Q is now running again with its usual sound.

Regards,
The Jo.

Leaking injectors are a common problem with common rail diesel engines. In a workshop, they often replace the entire engine if an injector is leaking, as it can sometimes sound like a major engine failure.