W163 Glow Plug Pre Heat issue

[gtvlusso]

Hi All,

This may or may not be an issue. When I start my ML270 I wait for the "curly" glow pre heat light to go out. However, the light comes back on when the engine is started for about another 30 seconds.....Is the pre-heater re-activating as we are in very cold conditions here or is this indicating a fault/bad glow plug?

Cheers

 

[dokalj]

My vehicle does the same I wouldn't worry. Someone may come along and correct me though.

 

[Bobby Dazzler]

Yep faulty glow plug. Apparently you're lucky to get 70,000 miles out of a set but it depends upon use. Not cheap to replace either, as whilst you're doing it you might as well do all five. IIRC it's a touch over £200 for the set (fitted).

It will still start OK with one faulty plug though even in these cold (for UK) conditions.

 

[dokalj]

Hi Bobby Dazzler, wouldn't the preg glow indicator stay on if the glow plug needed changing?

 

[dokalj]

How much would one glow plug cost from MB? For the ML270 CDI

 

[Smiley]

no the light will not stay on all the time. If the light comes back on at all after the engine is running then there is a fault. Modern CDi engines are much more tolerant of one failed glow plug and you will not notice the symptoms until the second one fails - then you may notice that it is harder to start. Better to get them changed; if paying someone else better to have them changed as a set; the labour to do one is not much different to all of them.

IIRC the glow plugs are about £15 from MB. Dont be tempted to buy cheap ones (or even NGK); they will fail again.

70k is not that good - I got nearly 150k out of mine well I did replace one at about 40k miles then the second went at about 140 or 150k so changed the lot; since done another 80k no probs touch wood.

 

[l5foye]

There is a way of identifying which heater plug is faulty. If only one is faulty, I would replace it rather than replace the lot. Put copper gease on the new one. Provided it is not seized, it is a 5 minute job to replace a heater plug.

 

[Smiley]

I agree if it is indeed a 5 minute (or even 1/2 hour) job then replace just one at a time - usually there is a degree of dismantling required to get to the glow plugs though. And quite often they are a pita to remove....it is not so much the carbon around the threads it is the carbon build up around the tip of the plug that prevents it coming out easily. If they were easy to access it would be worth unscrewing cleaning and replacing them every 10k miles or so.

 

[Doosh1]

Just done all 5 glowplugs on my ML270, Took about an hour in the cold. 20mins to do the front 1-4 and the remaining time to do cylinder 5! a little fiddley but unbolting the header/expansion tank and pulling it to forward makes life a lot easier.

Unfortunately after doing these my light remained on. I checked all the voltage outputs from the relay and found it to be 2 of the 5 outputs from the glow plug relay!

Teach me to be more thorough on my diagnosing in future!.

By the way my light remianed on permantly after start up.