Glow Plug Service Replacement Schedule

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I'd like to ask...glow they ever need replacing as part of a service schedule and if so at what mileage?

Like my Aygo...i know that i dont need to...but because sparks are so cheap i replace them yearly with my diy servicing.

Whereas glow plugs are a lot dearer...hence the question.

Cheers guys

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I've never seen glow plugs as a maintenance item. Sure, they go bad and it's not exactly rare, but if they're working then there's no reason to go through all that trouble to replace them. If you screw up just a tiny little bit and the plug breaks in half (very common), then essentially the whole head needs to come out and the plugs are drilled out.

There are methods of replacing them that maximise your chances of success but there's nothing that guarantees it. Many, many diesels of 20 years and more running around with factory glowplugs, no problems. Since they're a simple thing there's not much that can go wrong with them if the engine is maintained properly.

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Cheers Byzii...

I didnt know that...thank you for an education lesson in glow plugs...its our first diesel...hence my curiosity all of a sudden!



How would you know if one was faulty for example...does the engine light show up?


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Posted (edited)

As a past diesel owner, I'd say in general terms that failure of 1 out of 4 glowplugs might not be noticeable, especially in the summer months, though there might be a touch more smoke on start-up, and perhaps a little more uneven tick-over for a few seconds.  A second glowplug failure would probably be noticeable, but might not give real starting problems until winter time.  Driving an older generation diesel with indirect injection, I found my 2 diesel cars a pig to start in cold weather with 2 failed glowplugs, but I suspect modern diesels, which tend to be direct injection, are less reliant on glowplugs for starting.

As Byzii says above, you can open a can of worms trying to remove a glowplug, and my suggestion would be to leave well alone.  Just keep an eye on things, so it doesn't come as a shock and let you down at an inconvenient moment.  By keeping an eye on things, I mean such as noting if it's more awkward to start, smoke etc.  You can't beat passing a current through a glowplug on the workbench, and seeing the tip glow red, but I found second best was to measure the current (12-20 amps) drawn by each glowplug in-situ, but how accessible this is on your car I don't know, and I modified the wiring to the glowplugs of my second diesel car to make this test easier for me to carry out.

I'm sure I read a while ago, probably on  another Forum, of a small/medium diesel hatchback running with either 1 or no glowplugs working.  It might not have been in this country of course!

So I think I'm saying "Panic Not!"  ☺️


PS.  In answer to your PS, I'm not sure you'd get any waring of glowplug failure on the dashboard


Edited by Notoyboy
Added PS

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