Changing the glow plugs - Skoda Fabia 1.4 TDI

Open the hood

Remove the engine cover and the foam soundproofing.

The 3 candles are powered by a single rigid harness (made of plastic all the same).

Now that you have located the candles, you will have to wait a week!

And yes, because for a week, you will have to spray a penetrating oil in the spark plug housing (spark plugs still inside).

This action is crucial to not break the spark plugs inside the cylinder head. The penetrating oil will penetrate as you drive (heating, therefore expansion of the engine, then cooling, contraction).

This expansion/contraction movement will allow the penetrating oil to penetrate further into the spark plug housing and lubricate the spark plug threads, making it easier for you to loosen them.

So if you drive every day, spray the first 3 days and wait until the following week to do the operation. If you drive less often, I advise you to wait longer so that the car has done at least 5 heating and cooling cycles (and not just short trips!)

The last photo shows a spray with the power harness removed, this is not necessary for this first phase. You can absolutely spray with the harness still on the spark plugs. (this avoids disconnecting the battery each time you apply it!).

It's D-Day! You've been patiently spraying penetrating oil on the spark plug housings for the past few days, now you can tackle loosening them with peace of mind!

The operation must be carried out with the engine HOT! Unlike spark plugs (for petrol engines), the replacement of glow plugs is done with the engine hot (this actually depends on the metals used for the plugs). In any case, a short email to the spark plug manufacturer will allow you to know the important information.

You still need to be well equipped! Here is the necessary equipment:

A torque wrench (be careful with the tightening range, we only want a few Nm!) several wrenches start at 28N.m which is already too much!

Glow plugs in question

a spark plug wrench, here, 10mm

a copper grease, special for high temperatures.

Before carrying out any work on the spark plugs, disconnect the battery.

First, remove the power harness, and you can see the head of each spark plug.

This is when you get ready to loosen the spark plugs. This is when you take out your beloved torque wrench, and attach as many extensions as necessary. Here I needed 2 short extensions (because I didn't have a long one!), followed by the spark plug wrench universal joint.

This is the crucial moment! Above all, be careful not to force too hard!

You can first ask the spark plug manufacturer (of the one you bought) for a shear torque, that is to say the maximum torque before they break. For mine, the maximum torque was 40N.m. My wrench is 5-25Nm, I knew that the wrench would trigger before I could break the spark plugs in the cylinder head.

(that said, this torque is valid for the spark plugs I had on hand, not the one that was in the engine, but the order of magnitude must be the same...)

Start by loosening with the wrench, but as soon as you can, loosen by hand, so as not to damage the spark plug thread.

Once completely loosened, you can carefully remove it, being very careful that nothing falls into the now empty housing!

If despite all the precautions you have taken, the spark plug does not loosen, DO NOT FORCE IT! Either you postpone the operation, with a copious application of penetrating oil again, otherwise too bad, go to the garage, you will have done what you could! (and this before the spark plug breaks!)

Then comes the moment of grace when you can compare your purchases with what you actually had in the engine!

I'll let you guess which one is new, which one has 80,000 km!

You will notice that in photo 2, we see that the spark plugs are not exactly the same length, but it is the length of the head that differs (1 or 2 mm!). The rest, the body, the thread etc. are the same. That is what matters.

This is where you can use the high temperature copper grease. It will help with loosening if you do it again, and also improves tightening.

Note that you should try to spend as little time as possible with the engine open! A spark plug has been removed, so the combustion chamber is in the open air! It goes without saying that you don't do this when it's raining (if you're outside!).

I also wouldn't try to put anything in the housing for fear of it lint or pests falling into the housing.

It is also important to have cleaned the outline of the housing (for example with a compressor) to avoid these problems.

Reverse operation! Start by screwing in the spark plug without the key, so as not to damage the thread.

Once you feel that you can't go any further with your little fingers, use the wrench, set to the correct torque in tightening mode!!

The torque will have been communicated to you by the manufacturer beforehand. For me here, the tightening torque is between 13.5 and 16.5 Nm

Proceed with the removal and replacement of the new spark plugs step by step, one after the other for your 3 spark plugs.

Your 3 spark plugs have been replaced, you can put the power harness back on and then reconnect the battery.

Also replace the engine sound deadener, then start!