Spark plugs and dirt

Hi there,

ich wollte die Tage mal meine Glühkerzen wechseln. Dem Fachartikel von Ulf entnehme ich, dass es essentiell ist, den Dreck in und am Gewinde zu entfernen/mit Öl zu binden damit nix in den Brennraum fällt. Aber wenn im Gewinde auch Dreck is, bröselt der doch beim rausschrauben eh in den Motor. Und beim reinschrauben dann auch wieder. Gibt´s ´nen Kniff das Gewinde zu säubern ohne dass mir der ganze Schmodder in den Brennraum bröselt? Und How much "carbon buildup" is actually harmful to the engine/turbo?

Thank you.
Bye.
Christoph.

Zoidberg wrote:

Aber wenn im Gewinde auch Dreck is, bröselt der doch beim rausschrauben eh in den Motor. Und beim reinschrauben dann auch wieder.

Sure, but in the threads, at best, a thin layer of soot can accumulate -> there is no room for anything more .

And a few carbon particles in the engine (which are bound to accumulate there anyway) certainly have less abrasive potential than undefined dirt and sand that can fall from the top of the spark plugs into the cylinders without oil.

Okay, here's a brief final report:
The glow plugs have been replaced - now there are some from Febi installed, costing €22 each. If these things turn out to be bad, you will be the first to know .
Fortunately, the installation went smoothly - and according to Ulf's cleaning method, nothing should have fallen into the combustion chamber... well, let's see - if the turbo suddenly flies off next time, I at least know why .
Question: Can you read the condition of the engine from the old glow plugs now, like you can with spark plugs in a gasoline engine? If so, what should they look like, and what shouldn't they look like? Mine have 290,000 km on them, they are coal-black with small white spots at the tip, and completely dry - is that good or bad?
And also, given the current temperatures, it's a bit reluctant to start, but after 4-5 attempts, it does fire up. Surely that can be interpreted as an indication of good engine condition... or am I wrong about that?

Bye.
Christoph.

More important than the color of the candles is their length. If only stubs remain, this usually indicates faulty injectors. The spray from a worn injector can then act like a cutting torch. The fact that they still look like this after such mileage sounds pretty good to me.

ah.. thanks!
No, the old ones aren't shorter. They look exactly like the new ones, just completely rusted. If I have some time in the next few days, I'll verschandeln one up and see what the metal looks like underneath.

I also tested it yesterday in temperatures of -5 degrees Celsius, and it started up perfectly!

Bye.
Christoph.

DIY tip for cleaning the area around the spark plugs:

Let's take:
1 large potato.
1 tube with a diameter of approximately 5-10 mm and a length of about 30 cm (e.g., part of an old G3 fender antenna).
1 vacuum cleaner.
1 knife.

- Now, cut the potato horizontally from top to bottom.
- Push tubes through the parallel sides (remove potato plugs).
- Insert the handpiece of the vacuum cleaner into the other opening.

Now you have a great, tightly sealed suction device that can reach every corner of the engine and with which you can suck everything away while simultaneously scraping it off.

hi,

Quote:

Der Einspritzstrahl einer verschlissenen Düse kann dann wie ein Brennschneider wirken.

Wasn't that only the case with swirl chamber diesels?
Because in that case, the nozzle sprays directly onto the glow plug – or at least, the spray cone comes very close to it.

As far as I know about TDI engines, none of the five injectors spray directly onto the nozzle.

Difference between nozzle with pin and nozzle with hole.

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

I don't know how it was with indirect injection systems. In any case, I have read several times that shortened glow plugs can indicate a defect in the fuel injectors. Perhaps the design also plays a role.
Or the fuel injector only delivers fuel to the spark plug when the engine is cold.

That can also happen with a TDI engine...

In diesel engines, the injector nozzle at least partially aims towards the glow plug. If the injector only sprays fuel instead of atomizing it, it can damage the glow plug. In such cases, the vehicle usually produces a lot of visible smoke.
If things go wrong, we might also have to deal with a distillery fire or a gunshot wound.

In TDI engines, it's similar. The glow plug is usually located in the edge of the spray pattern, so that it's at least touched by the 'mist.' If the injector hole is severely clogged and sprays directly upwards towards the glow plug, it can also cause the glow plug to burn out...

or if extreme tuning causes excessively high combustion chamber temperatures .

CU Gremlin.