Polo TDI glow plug flashing light.

[DIYspanner]

2011 1.2 TDI CFWA engine

Started yesterday flashing. Had a look around cyberspace and top of the possible faults list is a failing plug.

I presume like spark plugs, the engine should be cold when fitting new plugs so not to strip the threads?

 

[carmanmemoranda]

get the codes read 1st

Thousands of possible things it could be. Any running problems or issues ?

Never changed, or had reason to change, a polo plug

 

[AkiraDIY]

Glow plugs are wear parts like spark plugs and need replaced over time, albeit less often than spark plugs.

A simple OBD scanner will tell you the code and which plug is giving the fault, however it's better to change all the glow plugs as when one goes, the others won't be far behind (assuming they were changed as a set before).

Newer diesel engines have one (only one I think but might be wrong) Pressure Sensing Glow plug (PSG) for improved efficiency, which is quite pricey compared to the "normal" plugs. I've got a 13 plate Ibiza, which is the same platform as the polo, and it has normal plugs.

The normal plugs aren't too expensive but an absolute PITA if it snaps in the head, which is easier to do than you'd expect. I get my mechanic to change glow plugs for that reason. I would change the normal ones as a set (if it's one of them that's gone) and change the PSG as needed

 

[Mottie]

I only change them as a set if three have gone. A basic way to check them with a test lamp is to disconnect them all then connect the test lamp to the positive battery terminal. Touch the probe onto the glow plug central threaded part and if it lights up, everything is good. If you get no light, it’s burnt out. I find them better to remove when the engine is warm.

 

[Diver Fred]

Check the Injector 'Bridges'* and retaining studs - make sure the injectors are properly in the head.

*The "bridge' holds 2 injectors in place. Retaining stud is only 6mm. When the stud failed on my VW TDI and injector No1 came out of the head the Glow Plug light started to flash before the engine died. Also the the injector came out of the head the engine and most of the engine bay were covered in Diesel caused by the injectors N1 & 2 moving, that movement loosened the high pressure pipes from the common rail.

 

[carmanmemoranda]

As I said before. Don't rush to change them until you are sure they are the fault.

 

[DIYspanner]

The car is still running well.
Have not heard that it didn't start this morning although I tend not to use the plugs on my Bora TDI.
Will investigate in due course when I do a service or a starting/running problem occurs, which ever comes first.

Thanks All!

 

[Belle427]

Glow plug light flashing is an indication of a management fault too so read the codes first.
Normally related to egr system in my experience on Vag cars but could be anything, not normally associated with glow plug failure.

 

[cdbe]

Wasn't it nice when the flashing glow plug light indicated faulty glow plugs......

 

[DIYspanner]

Normally related to egr system in my experience on Vag cars but could be anything, not normally associated with glow plug failure.

The car has a separate engine management warning light which lit up when the egr valve got clogged up.
I will look into the plugs issue and report back.

 

[AkiraDIY]

The DPF and EGR share the same warning light in VAG cars iirc.

A single faulty glow plug won't really do much noticable to the car, might effect efficiency a little. Two faulty plugs and you'll likely have difficulty starting in colder weather and higher fuel consumption. Took my car 3 months from the warning light first appearing to running like crap. I got all the plugs swapped after that, OBD scanner confirmed plugs 3 and 4 were throwing fault codes.

3 or more and I imagine it'll start running quite rough, misfiring, smoky, etc but I've never pushed it that far. An OBD scanner is the fastest and easiest test.

 

[robinbanks]

higher fuel consumption

What is it you think a glow plug does that has a bearing on how much fuel it consumes?

 

[AkiraDIY]

What is it you think a glow plug does that it doesn't have a bearing on fuel consumption?

It's a common misunderstanding of how glow plugs work to think they're for starting an engine only. They're used to regulate combustion chamber temperature when the engine is cold, such as but not limited to, at start. An engine isn't instantly at temperature once started, it takes time. Potentially a long time if the weather is cold. The glow plug will continue to boost chamber temperature until it is no longer needed and will also function if there is a dpf regen, start-stop traffic, etc.

If the chamber isn't hot enough, you have incomplete combustion (hence a smoky exhaust), meaning less engine power, so the engine will have to work harder for the same performance, ergo higher fuel consumption.