glowplugs

[soulcar]

Hi everyone, I`ve just bought my first ever Merc. after years of Italian car infatuation. It`s a second-hand C320cdi estate with 105k miles and full Merc. service history. The glowplug light stays on for about 30 secs after start-up. A computer diagnosis by a local specialist says glowplugs 3 and 6 are open circuit but the car actually starts OK despite cold weather and runs well once warm. He is wary of breaking a plug while removing it as ceramic plug in alloy head seems non too clever. He could try setting torque wrench low (to 15nm I think he said) to see if it will undo easily. I`m wondering whether to ignore the issue for the moment, having just stretched my resources buying the vehicle, but a local Merc dealer I rang says replace all 6 plugs soon as unburnt fuel from injectors could damage the cat. which needless to say is very expensive. Any idea whose advise to follow? Thanks

 

[JOB-BLACK-RAT]

Hello and welcome to the forum, I have a C220d 03' plate with 115K, just had an indi supply and fit all plugs for 120 quid (as an extra on top of my B service that cost 220 quid by the way).

You can run with the light on and a few duff plugs but best to change them to prevent damage.

If you live in Essex I can give you details of where I got mine done otherwise just on the forum for a recomendation.

 

[Reedswood]

my B service that cost 220 quid by the way.

@JOB-BLACK-RAT, is that a MB price, and where is the garage?

 

[Danny DeVito]

My old boss had an e2 something 40 or like that and in his handbook it said glow lamp will remain on after starting for about 20-30 secs to aid starting etc. That was in the car manual, might apply to you ?? (ignoring the indie of course) and ignore the crap of replace them all unless you want to pay for them . Also the manual (workshop) says warm the engine before removal to prevent breakages

 

[JOB-BLACK-RAT]

@JOB-BLACK-RAT, is that a MB price, and where is the garage?

Not an MB price, it's an indi called the 'MOT and Service Centre' in Witham Essex (by the rail station), very good customer service and get a free run about car whilst yours is being sorted.

 

[Bobby Dazzler]

Glow plugs tend to fail in fairly quick succession, and so it's likely that if two have failed, more will follow. This is why it's recomended that you replace all glow plugs at the same time - the cost of doing it is broadly the same, and the plugs are less than £15 each IIRC.

You'll probably find it will still start if another one fails, but of course the risk of not starting in very cold weather increases.

PS for comparison, a dealer quoted me less than £200 for changing 5 (270 engine has only 5 cylinders).

 

[rhjcamp]

Hi, I had to replace them in my R-Class 320cdi. Quite a straight forwards job to be honest, brought a new set online and had them done in about 2 and a half hours. As you say take care taking them out, as they are alloy (The ceramic bit is only the core, the thread is metal, just like a spark plug) and I only tightened my to 10nm. I needed a 8mm long reach socket to get to them, but cost me circa £80 all in. Rob.

 

[soulcar]

Thanks for the good advice, if I delay changing the glow plugs for a while, is the `potential catalysor damage from unburnt fuel` a red herring?

 

[JOB-BLACK-RAT]

Thanks for the good advice, if I delay changing the glow plugs for a while, is the `potential catalysor damage from unburnt fuel` a red herring?

No, unburnt fuel may well make its way to your cat and this will damage it and poss fail emissons test at MOT time, but then it may not make its way down.

Im not that lucky so I changed mine

 

[Smiley]

Thanks for the good advice, if I delay changing the glow plugs for a while, is the `potential catalysor damage from unburnt fuel` a red herring?

Strictly speaking the advice is correct - but as long as you do not start the car then turn it off straight away then the unburnt fuel will be burned off the cat when you get going - much as it will be after a normal cold start. So you can afford to leave it for a few weeks / months.
The advice to change all of them is also good. Get someone who knows what they are doing to change them or they will snap them off. Get Beru or Bosch plugs and do not be tempted to buy cheap ones on ebay. They should last about 100k miles.

 

[rizlar]

I had my glow plugs changed a few months ago at MB dealer, they broke one taking it out and had to get a specialist in to drill it out, cost £100, so no great disaster if one does break.

 

[Vlad]

I've found that the CDi engines tend to start pretty well in cold weather even if the glow plugs have failed....All 5 glows on my 270 ML have failed but its still starting first twist of the key at -10.

Currently trying to unseize the glows as they are all welded into the head and dont want to break them by forcing them, so currently dribbling penetrating oil onto them on a daily basis to see if that free's them.