Changing the glow plugs - Skoda Fabia 1.6 TDI

Open the hood

Remove the engine cover

Be careful, the fixing points are quite fragile, and you risk cracking the plastic...

You will need to spray a penetrating oil into the spark plug housing. For this to be effective, a certain number of hot/cold cycles must have been carried out following the spraying. This hot/cold alternation allows the spark plugs (and their housing) to work in expansion.

These micro-movements of the metals will allow the penetrating oil to penetrate along the spark plug, inside its housing, and in particular its thread.

This is the key step in this operation. The spark plugs are certainly a little stuck in the housing because of the carbon (they are directly linked to the combustion chamber!). The penetrating oil will allow them to be loosened without forcing or breaking.

Depending on how you use the car (long or short journeys, frequent or not), the duration of this unseizing phase will be more or less long. The engine must have done at least 10 hot/cold cycles before moving on to the spark plug loosening stage.

And note that going to the bakery to get bread in 5 minutes does not constitute a hot/cold cycle! (you can use the oil temperature light to get an idea of whether the engine is warmed up enough, although I find that it disappears a little too quickly).

So you can spray the penetrating oil by simply removing the engine cover, and spraying as deep as possible into the spark plug housing (with a long, hollow rod). You can also use a blower BEFORE the penetrating oil, to remove all the dirt (the penetrating oil risks bringing it onto the spark plugs!).

The product has penetrated, and you now have every chance that the accumulated scale has partially dissolved, and is not causing you any problems.

Please note that replacing the spark plugs must be done with the engine hot (unlike spark plugs for petrol engines).

Before any operation, for safety reasons, disconnect the battery (and remove your watch with metal strap to avoid accidental short circuits!).

We can now remove the connectors that supply power to each spark plug.

My advice: use a curved nose pliers (not too short). The curve must be able to reach the bottom of the housing, to pinch the plastic connector, and allow you to unclip the power supply.

As you remove each connector on the 4 spark plugs, you will also have to take care of removing the ramp that distributes each connector (here framed in red). A small clamp on the injection ramp is at the end (left spark plug side), here circled in red.

It's a bit difficult because you don't have much wire, and the problem is also that each plastic connector is quite long, and well engaged in the housing.

In the 2nd image, we can see the empty housings, and the plastic connectors all exposed, spread upwards.

On the 3rd spark plug, we see the first connector cleared, with the empty housing, the spark plug head being at the bottom. We can also see that I sprayed penetrating oil (it shines at the bottom of the well!), and it's full of dirt! Hence the fact of cleaning as much as possible BEFORE spraying penetrating oil!

Then, we get the expensive (but necessary) equipment: a torque wrench, as well as the spark plug wrench (also expensive) (but no less necessary!). Here we will need 2 small extensions to reach the bottom of the spark plug housing! The diameter of the spark plugs is 10mm.

The first photo shows an empty, clean housing! This is important, because when you loosen the spark plugs, if the head is dirty, impurities may fall into the spark plug well, and lodge either in the thread or in the combustion chamber! (which is not recommended, as you may have guessed)

So insert your spark plug wrench onto the spark plug head (while holding it by the extensions). Then, all you have to do is put your torque wrench in loosening mode, and loosen carefully.

CAUTION: DO NOT FORCE!!! If you force too much, the spark plugs may break in the cylinder head!

The best thing to do is to send a short email to the manufacturer of the spark plugs (that you bought), to ask for the shear torque, that is to say the maximum torque from which the spark plugs risk breaking.

A (Japanese) manufacturer answered me (follow my gaze ^^), and told me that it was about 40 Nm. This allows you to stop before, thanks to your expensive torque wrench! (and thus be sure not to break your spark plugs!)

Another manufacturer (German) could not give me this torque, but in any case, the idea is to have an order of magnitude, because the spark plugs you bought are of a certain brand, and those which are already inside, probably of another... It just gives an idea.

THE moment everyone has been waiting for: comparing the spark plugs, before and after 112,000 km! (and 7 years).

Check carefully: the length, but especially the spark plug heads, the thread lengths (incidentally, in the 3rd photo, we can see the dissolved carbon on the old spark plug).

Needless to say, for about €11 per spark plug, you can change them all! No need to create asymmetry between the cylinders.

You can also measure the resistance of the spark plugs, to make sure they are not defective (and compare the resistance with the old spark plugs).

Another tip: leave your engine exposed to the air for as short a time as possible! Let me explain: when you remove a spark plug, the combustion chamber is exposed to the air. It therefore goes without saying that this operation should not be carried out outdoors, or in dry weather!

So I advise you to remove an old spark plug, then put in the new one, before moving on to the 2nd.

Before putting the spark plugs in their housing, you must lubricate the thread with special high temperature grease: I mean copper grease!

Carefully coat the thread, not too much either, so that tightening is done without any problems. Future loosening (around 200,000 km?) will also be made easier. It also provides sealing.

The installation of the new spark plugs is done by hand, as well as the tightening. Obviously, you will struggle after a while (!), and it will be time to re-equip yourself with your expensive (but necessary) torque wrench.

This precaution prevents you from messing up the thread. If you attack directly with the wrench, you will not feel if the spark plug is properly engaged in the thread, and mishandling at this stage can be very problematic.

So, first by hand, THEN, with the wrench, in tightening mode. The tightening is specific to each type of spark plug. Here again, a small preventive email to the manufacturer will inform you of the torque to be applied. Here, for the spark plugs that I used, the torque was 18 Nm

Once the 4 spark plugs have been replaced and tightened to the correct torque, all you have to do is reconnect the spark plug connectors.

You have to pay close attention to hearing the "clip" which confirms that the plastic connector is properly connected to the head of the spark plug.

I advise you to reconnect the connectors from right to left, due to the length of the electrical wires.

Don't forget to put the ramp (which distributes the connectors) back in place, reconnect the battery, and... start!

If all goes well, put the engine cover back on and close the hood, and you're off for another 100,000 km!