A4 2.5 TDI: No Compression in Cylinder 2

Hello,

After the car started misfiring, I took it to a VAG workshop. They found that cylinder 2 (on the right bank of cylinders) has zero compression. What could be the possible causes?

I drove another 100 kilometers in that condition.

Best regards,
Michi

Why don't you disassemble it and see what's broken?
There probably aren't many possible causes. It's likely a valve problem.
Or the piston is faulty.
Step 1: Remove the valve cover.
Step 2: Lower your head.

If it's related to the piston, there is usually also a very high KGH pressure.

I just wanted to add my two cents. I had the same problem, but it was with cylinder 4 on a 1.9 TDI AFN engine, and in my case, the piston was cracked. My sincere condolences .

moonlight wrote:

I just wanted to chime in and say that I had the same problem, but with cylinder 4 on a 1.9 TDI AFN engine, and in my case, the piston was cracked.

My condolences.

Interestingly, the fourth piston in my AFN engine is also cracked.
That's funny.

Steffarn wrote:

moonlight wrote: I just wanted to chime in and say that I had the same problem, but with cylinder 4 on a 1.9 TDI AFN engine, and in my case, the piston was cracked. My sincere condolences . Interestingly, the fourth piston in my AFN engine is also cracked. It's so funny.

In our company's air handling unit (AHU), the fourth one was also damaged.

I just wanted to chime in and say that I had the same problem, but with cylinder 4 on a 1.9 TDI AFN engine, and in my case, the piston was cracked. My sincere condolences .

Interestingly, the fourth piston in my AFN engine is also cracked.
It's so funny.
@moonlight and Steffarn:

Under what circumstances did this happen, or what was the cause of it tearing (tuning, constant full throttle on the highway, injector failure, etc.)?

"Well, the crack went right across the piston, directly above the wrist pin. It probably couldn't handle the 160 horsepower and simply split open. The four new pistons had a brass ring fitted around the wrist pin, which the old pistons didn't have. Everything else was made of aluminum. That was probably sufficient for 110 horsepower."

Now the heads are facing down, and you can't see any damage to either the pistons or the valves.
The workshop also found that the ESP (Electronic Stability Program) is malfunctioning because it can no longer rotate freely without significant effort.

michi22 wrote:

so now the heads are facing down and you can't see any damage on either the pistons or the valves. The workshop also found out that the ESP is broken because it can no longer rotate without requiring significant force.

There has to be some explanation for the 0 bar compression reading!
It's suspicious that two things are happening at the same time. The jerking could be caused by the ESP (stability control) or an injector. However, it's hard to imagine that two cylinders would fail simultaneously.

What do the young people at the workshop suggest doing?

Why do I suddenly have the feeling that the compression wasn't actually zero???
Even if the head gasket is blown, the compression test should still show something.

It's not uncommon for the ESP (Electronic Stability Program) to fail in that engine.

If your car is currently at the diagnostic workshop, I'm afraid that's when your problems will really begin.
A compression value of zero doesn't just happen spontaneously. This can only occur if, as described, a valve is leaking or a piston ring/piston is severely damaged. If everything appears to be in order visually, the measurement is highly questionable. I also find the ESP diagnosis very doubtful. However, it is certainly an indication if there are unnatural resistances to overcome.
But if this only becomes apparent after disassembly, that's already questionable, because the stuttering could indicate a problem with the ESP (Electronic Stability Program) or the injectors.

Here's a simple question: Could it be that the fuel injector of the affected cylinder wasn't screwed in during the compression test, for testing purposes?

Personally, if the pistons and valves look okay, I would have the car towed to another workshop and get a second opinion, because, as I said, it's practically impossible for the compression to be zero.
It sounds like someone is trying to make money off this. If the other workshop confirms this, I would hire a lawyer because it's not just about 10 euros here!

The VP44 must indeed be relatively easy to turn.
Could it be that a faulty hydraulic lifter temporarily kept a valve open? They're not exactly durable in the V6 TDI engines. Based on my feeling, I would say the oil pressure might not be sufficient for that. On the other hand, the new cylinder heads have pressure relief valves, which Audi includes for a reason.

The compression was measured by a VAG workshop, and they found it to be 0 bar.
The workshop where the car is currently located can't explain the zero compression and believes that VAG made a mistake. VAG only removed the glow plugs for the compression test; the injectors were left in place.

The valve lifters and the camshaft are worn, but nothing is broken. I took the pump to a specialist who will inspect it (I expect his answer tomorrow).
Whether the valves are damaged in any way can be determined at the latest when disassembling the cylinder head (for resurfacing).

The pistons have no cracks, and the cylinder walls also appear to be in good condition.
The writing also looked okay.

I will have the exhaust manifold refurbished (450 euros from Poland) and then, a friend of mine will apply a chrome plasma coating to it (8 micrometers thick - they also coat pistons with it).

Here are a few pictures of the engine:

http://michi22.mi.funpic.de/A4/1jpg.jpg
http://michi22.mi.funpic.de/A4/2.jpg
http://michi22.mi.funpic.de/A4/3.jpg
http://michi22.mi.funpic.de/A4/4.jpg
http://michi22.mi.funpic.de/A4/5.jpg
http://michi22.mi.funpic.de/A4/6.jpg
http://michi22.mi.funpic.de/A4/7.jpg


Should it actually turn out that the ESP was faulty and not cylinder 2, then can I sue VAG because they were the ones who removed the two heads? [url][/url]

Whether it will actually come to a lawsuit remains to be seen, but at the very least, I can cause you some trouble. Since you have everything on record, it's quite possible to prove that the compression wasn't 0 bar.

because if the pistons are in good condition and the valves look okay initially, then you should also measure the compression (maybe not fully, but at least something).

Quote:

because if the pistons are okay and the valves initially look good, then you should also measure compression!

(maybe not fully, but at least something).

"I agree. I don't understand why a pressure test wasn't performed before removing the head. That would immediately reveal whether and where any pressure is being lost. Now we're just guessing. Since the cylinder head has already been removed, I would also pull out the piston to make sure there isn't any damage."