1,9 Tdi läuft nach Komplettüberholung nicht richtig | Posts 48+

Quote:

What exactly happens then? If I disconnect the fuel line, how does the pump know that it shouldn't pump anything into the line anymore?

Shaking my head. So, the pump is of course still pumping fuel. Therefore, in your case, I would loosen the hose as much as possible so that you can drain the fuel into a container using a hose.

If a cylinder no longer receives fuel, it will naturally stop working, meaning that in the case of bearing damage, for example, it will (almost always) also no longer produce any noise because the operating pressure is also no longer generated.

Unfortunately, I assumed a slightly higher level of technical expertise. Of course, this also requires some experience and a delicate touch.

Note: This method is only intended for locating noises that originate from the lower part of the engine (crankshaft mechanism, pistons, and cylinders).

BM wrote:

If a cylinder no longer receives fuel, it will naturally stop working, meaning that in the case of bearing damage, for example, it will (almost always) also no longer produce any noise because the operating pressure is also no longer generated. Unfortunately, I assumed a slightly higher level of technical expertise. Of course, this also requires some experience and a delicate touch. Note: This method is only used to locate noises that originate from the bottom of the engine (crankshaft mechanism, pistons, and cylinders).

I'm sorry if my technical knowledge isn't quite up to par yet. I do a lot of work on my car myself, and now also on the engine - or rather, I can understand the relationships between things, but when it comes to new things, I prefer to ask again just in case there's something I should be aware of.

I had another idea: perhaps I can record the sound in a way that allows us to determine the frequency during analysis. This would tell us if it's rotating at the same speed as the crankshaft or at half the speed... Ideally, exactly 1000 rpm would be best. I'll try both and see what results we get.

Today I recorded the engine noise at 3,000 rpm and then removed all frequencies up to 16 kHz from the recording, effectively eliminating the highest tones. What remained was a sound file with a bright clicking sound... I then marked out exactly one minute of that and counted [something - the original text is incomplete here].

" color="red">Bitte keine Links zu externen Dateihostern! a) nerven die zusätzlich notwendigen Klicks, b) Wartezeit, Werbebanner/Werbepopups und notwendige Registrierungen, c) ist nach einiger Zeit die Datei weg und das Thema für andere Leser nutzlos!

Bitte nutze 'Attachment hinzufügen' bzw. das Upload Forum hier.

Quote:

These are exactly 25 peaks - and if you take that number multiplied by 60, it's exactly 1,500.

It looks good, but you could have saved yourself the trouble of halving the speed; it's still noticeable in your sound file.

If I understood correctly, the noise not only gets louder with increasing speed, but also when accelerating quickly. Strangely enough, it's barely or not at all audible when the speed is decreasing. A faulty hydraulic component would also be heard when the speed is decreasing.

I would not rule out the possibility of contact between the pistons and valves.


If a valve is stuck and being pressed shut by the piston, it must be an exhaust valve that is being closed by the piston during the exhaust stroke. A stuck intake valve would prevent compression in the cylinder, so it can be ruled out.

BM wrote:

Quote: These are exactly 25 peaks, and if you take that number multiplied by 60, it equals exactly 1,500. It looks good, but you could have saved yourself the trouble of halving the speed; it's still noticeable in your sound file. If I understood correctly, the noise not only gets louder with increasing speed, but also when accelerating quickly. Strangely enough, it's barely or not at all audible when the speed is decreasing. A faulty hydraulic component would also be heard when the speed is decreasing. I would not rule out the possibility of contact between the pistons and valves. If a valve is stuck and being hit by the piston, it must be an exhaust valve that is being closed by the piston during the exhaust stroke. A sticking intake valve would not allow for cylinder compression, therefore it can be ruled out.

Now I had put in so much effort - but I couldn't have sworn that it was definitely half the speed.

I can confirm that the noise is present even when the engine speed decreases. Sometimes it's even audible in neutral. I also suspect it might be related to the exhaust valve...

I've also come to terms with the fact that – once again – the head needs to be removed. Then we'll have to see if there's anything noticeable or visible regarding the function of the valves. If a valve is constantly being hit by the piston, shouldn't we be able to see that? After all, I've been driving like this for at least 5,000 km now...

Quote:

I've definitely been driving around for at least 5,000 km now...

AWESOME, for that you should get a "BOO" or maybe a four-week writing ban.

When such important information is missing, you unintentionally mislead anyone who is trying to think critically and help you, and you waste our collective knowledge and time.

Given that the engine has already run for 5000 km without any change in noise, it's reasonable to rule out a bearing or connecting rod bearing failure. It's also questionable whether a stuck valve could last this long.

BM wrote:

Quote: Well, I've definitely been driving around for at least 5,000 kilometers now... GREAT, for that you should get a "BOO" or maybe a four-week writing ban. When such important information is missing, it unintentionally leads everyone who is trying to think critically and help you astray, and it wastes our collective knowledge and time.

Honestly, this is exactly the kind of comment I expected to see in this forum. I reported about that noise back in late November. That's also mentioned on the first page of the thread. Of course, it's gotten a bit longer now, but should I create a new thread every time, or write a summary each time?

Okay, let's be honest – there are definitely some talented people here, but sentences like "4-week writing ban," "unintentionally misleading anyone who thinks about it," and "wasting thoughts and time" make it sound like I'm on trial or in some arrogant, overly elitist cult!

"At times like these, I really get the feeling that you should only log in here if you invented the diesel engine yourself and have so much knowledge that you actually don't need any help!"

"@ Topic: The noise has changed in such a way that it was louder at the beginning, i.e., last October, and started occurring earlier. Now, it increasingly only appears at higher RPMs, around 2,500 RPM."

If something is indeed causing a problem with the connecting rods or valves, what else could possibly produce a bright clicking sound at half the engine's rotational speed?

@ BM: Please only respond if you are in a state of mind that allows it. I don't want to waste your thoughts...

Quote:

@ BM: Please only respond if you are in a state of mind that allows it. I don't want to waste your thoughts.

Actually, you should know that remote diagnoses aren't exactly easy.

That's why it's also very important for the professionals among us to receive detailed information so that they can properly assess the situation and approach problems from the correct perspective. No one here knows how many kilometers you've driven since the overhaul.

Please don't take this personally, but it does make you feel a little like you're being taken for a fool.

And what's the point of all those potential sources of error if they ultimately aren't the cause?

Quote:

@ Topic: The noise has changed to the extent that it was louder at the beginning, i.e., last October, and started earlier. Now, it increasingly only occurs at higher RPMs, around 2,500 RPM.

You need to narrow it down further, as previously described. Everything else is just guesswork.

For example, a foreign object in the annulus of an oil well could block access to the hydro layer above a certain oil pressure.

BM wrote:

You need to narrow it down further, as previously described. Everything else is just guesswork. For example, a foreign object in the pocket of an oil well could block access to the hydro from a certain oil pressure onwards.

Okay, in order to remain constructive and avoid misleading anyone further, I'll summarize the current state of affairs and list all the parts that have been exchanged.

Vehicle: Volkswagen Passat 35i TDI, original mileage, approximately 325,000 km. Engine damage due to a hole in the piston at 320,000 km.

Engine rebuilt:

- new, third piston (original VW part).

- New connecting rod bearings installed on the third piston, new cylinder liner fitted.

- Head and block engine planned, new cylinder head gasket, the highest quality available (3 holes).

- All other pistons checked for clearance.

- new crankshaft bearings

- Compression and valve timing checked by Bosch, within specifications.

- Turbocharger pressure within normal limits according to VAG-Com specifications (target vs. actual).

- Approximately 5,000 injectors with seemingly defective (remanufactured) AFN nozzles, resulting in a power output of 62 hp; the noise is essentially always present.

- Replaced the fuel injector pump adapter with my old MSW unit; no impact on performance or noise.

- 8 new hydrants, no impact on noise levels.

- New fuel injectors (AFN) installed, driven for 200 km since then, performance is back to optimal levels, noise remains unchanged.

- Current status regarding the noise: - It occurs at half the crankshaft speed, primarily in the higher RPM range, both during acceleration and in cruise mode.

Please let me know if you need any further information or test results.

I also find the idea about constipation very interesting.

Currently, the plan is to remove the head on Sunday in two weeks, re-check all cylinders for compression, inspect the hydraulic channels for leaks, potentially take the head to someone who can test it, replace any necessary valves if needed, and then reassemble everything.

After that, let's hope God has mercy on the engine if any unwanted noises come out of it!

Hi,

without reading all three pages in detail right now:

Have you ever considered the intermediate shaft or vacuum pump, or have you used the "listening rod" method to diagnose the engine (holding a rod to your ear and feeling different parts of the engine)?

ulf wrote:

Hi, without reading all three pages in detail right now: Have you ever thought about the intermediate shaft or vacuum pump, or have you listened to the engine using the "stethoscope method" (holding a rod to your ear and feeling different parts of the engine)?

We've tried using the stethoscope before, but we weren't able to locate anything.
The thing about the wave and the pump will definitely go on the list – thanks for the tip.

Possibly, when the timing belt is removed, use an impact wrench or drill to bring the auxiliary shaft up to speed (be careful - oil pressure will build up! - there's a risk of a huge mess if the oil passages are open ), and listen...or disconnect the vacuum pump and see if the noise is still there.

It could also be a faulty hydro unit. Even if they are new!!

The latest status is:

8 new valves were installed. The cylinder head was cleaned and flushed by a machine shop. A new camshaft was also installed. 2 more hydraulic lifters were replaced because they had minor scratches. Although the initial suspicion was a blocked oil channel, that possibility has been ruled out after cleaning the cylinder head.

There were no signs of scoring or wear on the cylinders, and while the valves appeared used, they also showed no damage.

However, the noise is still present and unchanged.

I also disconnected each fuel line to the injectors one by one. The engine ran a little rougher, but the clicking sound was still there, no matter which cylinder I disabled.

Bewilderment - utter bewilderment...

So, it seems the noise is probably related to the nozzles... I've actually installed a second set of nozzles now and have one extra as a spare.

Today I used a stethoscope to listen to the injectors. The noise was loudest on the fourth cylinder, right near the fuel line, so I replaced it. Now the noise is still there, but much quieter.

I'm going to try adjusting the nozzle alignment again and fine-tune the pump one more time... maybe I can minimize the issue.

I never would have thought that the injectors could cause so much trouble. Even though they had been tested and the workshops always said they were fine, it wasn't until I replaced them that the performance returned. And the "new" set of injectors I bought used runs great, but the knocking sound was still there...

So, always pay attention to the nozzles...

Thanks again for your help!

Hmm.

I just bought some new ones on a hunch. You can get them here from the boss, and they're really good and cheap.
Then you'll be on the safe side and can dedicate yourself to other experiments.

Replacing worn parts with other used parts seems like a cheap trick to me.

Okay, please provide the German text you would like me to translate into English. I will only provide the translation.