Hi everyone, just a few comments on glow plugs after replacing one on my MkIII 2018 Octavia 2.0TDI

Only buy OEM from a reputable Skoda/VW supplier, lots of cheaper options but compatibility (lots of brands and numerous part nos) and quality dubious! and returns problematic

First remove glow plug relay and check resistance on top 4 terminals to battery earth (cyls 4 3 2 1 in reverse order), should be around 1 Ohm or lower, anything over 5 could be a problem, I got 38!

Remove the lead and check again, relay connection to lead terminal, should be very low but not open circuit which would point to faulty lead!

 

Some plugs and relays difficult to source at the moment, numerous reasons given but cold weather showing faults could be to blame

Plugs awkward to get at, buy a spark plug lead remover from ebay, big help as they do stick

Have a decent deep socket available to clear plug terminals, cyl 1 2 & 4 10mm, 3 is 12mm as its pressure sensing and expensive £140ish (No you can't fit the cheaper plug!) , others around £30

Use some good penetrating oil (not wd40!) a few days and night before, let a few heat cycles work it in, before tackling as they are known to snap if you're heavy handed

I also put a few drops of plain oil down each plug as well

use an air line to blast dirt from around plug (or an earosol duster as used on electronics!) and check with torch, found a small stone in mine, you don't want that dropping into engine!

amazing how much dirt comes out, perhaps a thin paintbrush dipped in oil will loosen and bring out stubborn dirt!

Start with a hot engine to help release plugs and soften lead rubbers, more penetrating oil will cool the plugs and help to loosen

Use a torque wrench to loosen max 20Nm (loosen not tighten!) hopefully will come straight out as mine did, too much force and it will snap and spoil your day! (40Nm I would say is the limit, more lubrication and leave it for another day!)

Put a smear of ceramic grease on new plug threads and where plug seats by tip

Don't drop the new plug in or drop it on it's tip, easily damaged apparently, use the terminal blanking plug to guide it in

Tighten by hand until it seats, light nip with 3/8 drive ratchet, then back it off a turn, hand tighten again until it seats, tighten 30 to 45 degrees 1/4 turn no more

To me that felt about right, I had a small torque wrench but accuracy probably out of range at 12 to 15Nm, and smaller wrenches expensive!

 

All in all could be a really easy quick job, (can't say cheap) or an absolute expensive nightmare

Prepare, plan, execute (check torque settings, electrical readings for youself, this is only guidance from my experience and research)

 

Regards all

 

My friend installed Bosch glow plugs on his Golf 7 2.0 TDI (~~same engine)- all works fine.