I got an emissions system warning light on a trip to Prague recently on my 186,000 mileage 2016 Skoda Superb 1.6 TDi Greenline. The car drove fine, all the way back to London.

My diagnostics tablet indicated a glow plug fault on Cylinder 1. When I clear the fault it returns within a day or two, usually after a cool morning start.

I already have torque wrenches, a socket set, a set of large circlip pliers and penetrating oil.

This morning I've ordered a Bosch glow plug (BOS0250403009) from GSF, as well as a Wolfbox MF100 battery electric air blower and and Liqui Moly glow plug grease from ebay.

I'll be using the circlip pliers to help remove the electrical connection. And a combination of penetrating oil and a torque wrench and a hot engine and patience over a few days to remove the old glow plug.

Fingers crossed that this will be a straight-forward DIY job...

I would reconsider the glow plug grease. You'll get mixed reports if you should use it. It comes out of the factory without and using it changes torque settings.

I did one recently and was prepared for the worst, but once cracked, it was finger tight. I did leave it soaking in wd40 for a few days though. You can use a multimeter to check it for continuity first, just in case it’s the cable:

Congrats on it not being cylinder 3 btw.

When I changed a glow plug, I sprayed it when hot and cold with WD40 specialist penetrant for about 3 weeks leading up to being brave enough to try taking it out.

https://www.eurocarparts.com/p/wd-40-specialist-penetrant-400ml-542771790?utm_source=google&utm_medium=cpc&utm_campaign=610675635&utm_content=70461851759&utm_term=&type=shopping&gad_source=1&gad_campaignid=610675635&gbraid=0AAAAAD1aCJiCH00Nb1y-9oNagakWazLWg&gclid=CjwKCAjwifjVBhBKEiwAYx4K9Gr4esDsqkYF07vtj-SUlNoa99sUK64kWpMgQefPCrCN5MJdWU_ttRoCb-IQAvD_BwE

It came out ok but took quite a bit of force (And bravery) to crack it initially. But they can be very hit and miss!

So far I've given it 2 sprays with penetrating oil. And 1 blast with the Wolfbox air blower. It looks clean around the glow plug now.

I will give it a go with my small torque wrench, going up to 30 NM maximum to loosen it, after my next daytime drive...

Agree with using the penetrating oil but, when the time comes, use a T-bar wrench so that you apply a pure torque, this minimises the risk of snapping the glowplug.

🤞for you!

I was intending using my small torque wrench, building up to a maximum torque of 30 NM on a hot engine. And if that doesn't free it, spraying it and trying again a day or two later...

Although that is a good point about the T-bar for a purer turning force. Especially given the extensions required to clear the top of the engine, plus pipework. The trouble is, I'm not at all calibrated when it comes to how much torque I'd be applying with my hand on a T-bar.

Edit. Thinking about it, I have a screwdriver type handle as part of my socket set. I'm pretty sure there's a low limit to how much torque I could apply with that.

It's raining today. So I'll be trying this on the next dry day...

Edited 6 hours ago6 hr by Lindsayt

I had always been told that you shouldnt use a torque wrench to undo things. They are calibrated for tightening and applying force in the opposite direction can mess up the calibrations. Also the breaking force required to undo something, especially in a heat cycle location, usually far outweighs the torque setting when tightening up.

Using a T bar allows you to have a solid connection through to the glow plug and you will be able to judge how much force you are applying just fine! The annoying thing with glow plugs is they move or they dont, its quite a sudden release when they do, and until you carry on undoing it theres no way to know whether its snapped or undone! Wishing you luck!

Torque wrenches for undoing glow plugs (for example) are reversible and click both ways, respectable ones are also calibrated both ways. shear torque is under 35Nm, we're not talking subframe bolts here.

There is nothing wrong with undoing glow plugs to a specified shear torque, which by the way is 2-3 times higher than the tightening torque but still relatively small, see earlier thread on this :https://www.briskoda.net/forums/topic/511440-glow-plug-replacement/#findComment-5848987

For a low to medium torque such as glow plugs, it is perfectly possible to apply almost symmetric load by holding one hand on the handle of the wrench and the other hand on the top of the pivot. I agree than using just the handle of the wrench results in far more asymmetric load and may break the plug. The problem with T-bar is that although the load is symmetric, you may easily apply way more than is needed and shear the plug. It is far better to attempt using a reversible torque wrench set below shear torque and if the glow plug does not move, put some more penetrant oil around it and drive around a bit more. For a DIY mechanic, far better to wait a day or two than to snap the glow plug IMHO.

Also, on a hot engine, you will find that the glow plug movement is far more gradual affair, most of the horror stories about glow plugs snapping during removal are from "mechanics" trying to undo them on a cold engine, without penetrant oil. Under these adverse conditions, even undoing a solid steel bolt that's been in place for many years is a hit and miss affair.

In summary: warm up the engine, use penetrant oil and a double sided torque wrench set below max allowed torque and held with 2 hands, one on the axis of rotation. This is all that is needed to avoid your own snapped glow plug horror story. HTH.

That’s very useful to know. Thanks for the info.