Possible Glow Plug Problem

22 replies [Last post]
RichardC
RichardC's picture
Offline
Joined: 23.04.2008
Location: Pyrenees, France
GWOA Groups: Members

A couple of days ago the yellow pre-heater light started staying on for about a minute after starting. Today when I started up, the engine was running very roughly. It sounded so rough that it seemed better not to drive it.

Does this mean that one of the heater plugs needs replacing? Is it still ok to drive?

Thanks for any help or advice.

fixwin38
fixwin38's picture
Offline
Joined: 09.07.2006
Location: northern ireland
GWOA Groups: Members
Re: Possible Glow Plug Problem

Hi the glowplugs would be suspect..that is what the light is telling you....not the easiest things to change as they can carbon up inside and this fouls the threads...best removed when the engine is hot......a failed plug will stop the related cylinder from firing at the same time as the ones with working plugs ..hence the roughness..it will clear if you rev the engine and hold the revs until roughness clears ( 50 seconds to a minute) depending on the ambient temperature....lots of smoke as the excees diesel burns out of the offending cylinder/s...best change all six at the same time and sooner than later.......

Alburnus
Alburnus's picture
Offline
Joined: 25.12.2009
Location: Balkan
Re: Possible Glow Plug Problem

fixwin38 wrote:
Hi the glowplugs would be suspect..that is what the light is telling you....not the easiest things to change as they can carbon up inside and this fouls the threads...best removed when the engine is hot......a failed plug will stop the related cylinder from firing at the same time as the ones with working plugs ..hence the roughness..it will clear if you rev the engine and hold the revs until roughness clears ( 50 seconds to a minute) depending on the ambient temperature....lots of smoke as the excees diesel burns out of the offending cylinder/s...best change all six at the same time and sooner than later.......
that is what the light is telling you....

Two or even more glowplugs are finished

best change all six at the same time and sooner than later.......

RichardC
RichardC's picture
Offline
Joined: 23.04.2008
Location: Pyrenees, France
GWOA Groups: Members
Re: Possible Glow Plug Problem

Thanks very much guys.

I will be phoning my local MB dealer tomorrow. I guess it's going to be quite expensive?

fixwin38
fixwin38's picture
Offline
Joined: 09.07.2006
Location: northern ireland
GWOA Groups: Members
Re: Possible Glow Plug Problem

Hi Heater plugs can be bought for as little as 10euro each."NOT from MB" .....MB labour estimate used to be 2 hours (@ 130euro / hr) so if MB supply and fit it could cost a minimum of 350/400euro......

RichardC
RichardC's picture
Offline
Joined: 23.04.2008
Location: Pyrenees, France
GWOA Groups: Members
Re: Possible Glow Plug Problem

Thanks Fixwin,

I will be getting an estimate first. Luckily, our MB dealer only charges 48 Euros an hour. They are actually an MB truck service centre but seem to know Gs quite well.

Maxwell Smart
Maxwell Smart's picture
Offline
Joined: 04.11.2003
Location: London
Re: Possible Glow Plug Problem

RichardC wrote:
They are actually an MB truck service centre but seem to know Gs quite well.

I have heard that it is always better to get Gs, particularly the G300 TD, serviced at an MB truck/commercial service centre due to better expertise with that engine....

Alburnus
Alburnus's picture
Offline
Joined: 25.12.2009
Location: Balkan
Re: Possible Glow Plug Problem

You can try cheaper variant. Find bad glowplugs and replace them (when engine is hot). Old glowplug could be even better than new one.

dil
dil's picture
Offline
Joined: 05.08.2004
Re: Possible Glow Plug Problem

you don't have to go to a MB for something as simple and as common as glow plugs. any small independant garage that understands diesels will do it at a fraction of the dealer cost...always best to change all the plugs just remember to refit the vacume pipe. or you'll not be able switch the engine off.

you best get the job done asap. do not keep trying to start the car on faulty plugs. i did this and it 's just cost me a new starter motor.

RichardC
RichardC's picture
Offline
Joined: 23.04.2008
Location: Pyrenees, France
GWOA Groups: Members
Re: Possible Glow Plug Problem

Yesterday I finally got my G back from MB after 2 weeks.

'A bit of a nightmare' would be a good description. The dealer originally quoted me 25 Euros per heater plug plus 2 hours labour. They said they could do it while I waited. After taking my G there and waiting for 2 hours they had changed 4 out of 6 heater plugs. The last 2 would not come out and they wanted to keep the G for the day. This turned into a week before they managed to change one more. They then broke the last one trying to remove it and decided to get a specialist from another dealer about 75 mile away to drill and re-tap it. Another week passes and my G is finally ready.

The final invoice was 640 Euros. Big shock :shock:.

But even worse, the engine now sounds like a 'bag of nails' when it's idling. It used to be so smooth and quiet. It's ok above 850 rpm or when the engine is pulling but at idle it has a loud rattle (even more than my LR TD5).

Does anyone know if this is due to the removal of carbon with the old plugs (and will get quieter over time as new carbon builds up) or is this a new problem? As you can guess, I'm a bit dissappointed with the whole thing :x (I'd like to use some much stronger words but hey, let's keep it polite). Any help, advice or constructive comments would be great.

Thanks
Richard

fixwin38
fixwin38's picture
Offline
Joined: 09.07.2006
Location: northern ireland
GWOA Groups: Members
Re: Possible Glow Plug Problem

Hi Mmm..firstly having the engine hot makes the heater plug removal a lot easier...drilling out a broken plug insitu leads me to wonder what happened to the broken bits and all the swarf generated by the drilling process?? are the bits sitting on the crown of the piston and is that the noise you are hearing? I cannot understand why the engine should sound seriously different after just changing the heater plugs ....I would ask the question as to what method was used to remove the broken plug ..and go on from there.because the head will have to come off ..and should have come off to remove the broken plug....

stig
stig's picture
Offline
Joined: 23.02.2007
Location: Girona, Spain
GWOA Groups: Members
Re: Possible Glow Plug Problem

Ah, yes, I agree entirely with fixwin. Changing the glow plugs in itself would make no difference at all to engine running/noise. I would say (without hearing it to be sure) that a piece of an old plug has fallen in. I would be extremely disappointed with MB for a) breaking a plug and B) drilling it out in situ!!!!!!!! Makes me cringe. Would be a good idea to take it straight back to them.

fixwin38
fixwin38's picture
Offline
Joined: 09.07.2006
Location: northern ireland
GWOA Groups: Members
Re: Possible Glow Plug Problem

Hi Richardc Your G' turbo could be totally destroyed if there are pieces of heater plug in a cylinder and one piece gets past the exhaust valve and into the turbo turbine blades...I shudder to think what is happening to the crown of the piston and the compression chamber......DO NOT RUN THE ENGINE until you can verify what broken heater plug removal method was used.....

tjpbm
tjpbm's picture
Offline
Joined: 19.10.2009
Location: Co.Kerry, Ireland
GWOA Groups: Members
Re: Possible Glow Plug Problem

I wouldn't run the engine at all, in case that possible bit of debris chips a valve or marks the liner. Any special tips or tricks in removing the heater plugs, apart from having the engine hot? My heater plugs are due for replacement and from what i here its very common for them to break in the head.

fixwin38
fixwin38's picture
Offline
Joined: 09.07.2006
Location: northern ireland
GWOA Groups: Members
Re: Possible Glow Plug Problem

Hi With engine cold spray each plug base with a penetrating oil and leave for two hours then spray again then after further hour start engine and remove heater plug leads and allow engine to run up to 85/90c.with engine running and using the correct size socket and ratchet bar turn each plug anti clockwise one full rotation..shut down engine and remove old plugs..fit new plugs (after having them in the freezer overnight) and instal while engine hot..do not over tighten because they will expand slightly as they get warm.....

RichardC
RichardC's picture
Offline
Joined: 23.04.2008
Location: Pyrenees, France
GWOA Groups: Members
Re: Possible Glow Plug Problem

Thanks for all the info.

I might be wrong but my gut feeling is that there is not any debris in the engine. The rattle is only when the engine is idling. Under power the engine sounds very sweet as usual. It now sounds a bit more like a LR TD5 - which has a noticable rattle when not under power but goes quiet as soon as you put your foot down.

I will find out if the head was removed when I get a chance to call the dealer later today.

Is it possible that they de-carbed the head when they removed it and this has changed the noise characteristics?

Russ280
Russ280's picture
Offline
Joined: 05.11.2003
Location: Trefonen
GWOA Groups: Members
Re: Possible Glow Plug Problem

Do you think it’s possible that they’ve somehow altered the diesel pump timing?
I haven’t a clue to what extent electronics control your engine but something as simple as pulling a wire off a temp. sensor could also affect fueling.

Any alteration to fueling or timing would affect the tick over noise.

bushcraft
bushcraft's picture
Offline
Joined: 20.01.2009
Location: N Yorkshire
Re: Possible Glow Plug Problem
RichardC
RichardC's picture
Offline
Joined: 23.04.2008
Location: Pyrenees, France
GWOA Groups: Members
Re: Possible Glow Plug Problem

Thanks everyone for the ideas and help.

I phoned the dealer this afternoon and they said that they did not remove the cylinder head before drilling and tapping the plug but they were very sure that no debris entered the engine. In fact they said that if even a small amount had entered the engine, if would have failed before I got home.

Anyway, they want to take a look at it next week.

btw I forgot to mention that sometimes the heater light on the dash is still staying on for about half a minute after the engine is started.

Roly
Roly's picture
Offline
Joined: 06.11.2003
Location: Australia
GWOA Groups: Members
Re: Possible Glow Plug Problem

The heater light is where you started with the problem, it indicates a fault with the system. Something is still not correct

fixwin38
fixwin38's picture
Offline
Joined: 09.07.2006
Location: northern ireland
GWOA Groups: Members
Re: Possible Glow Plug Problem

Hi ...If there was debris in the combustion chamber the first thing it would damage is the new heater plug which would result in the delay in the light going out... and a lumpy start with smoke when cold...I and most of the diesel engine related service/overhaul industry would welcome hearing specific details of the method used to remove the broken heater plug by drilling without getting swarf into the compression chamber and as a result not having to remove the cylinder head!!

RichardC
RichardC's picture
Offline
Joined: 23.04.2008
Location: Pyrenees, France
GWOA Groups: Members
Re: Possible Glow Plug Problem

A bit more news.

After a week of driving, the tickover sound seems to be getting a bit quieter and the heater light is not staying on after starting. When it's cold, it starts well and there is no smoking.

I asked the dealer for a detailed description of how they changed the broken plug. My French is not very good but it seems that they drilled into the plug enough to fit a reverse threaded stud which enabled the entire thing to be removed. They brought in someone from another dealer about 70 miles away to do the job.

I am just glad to have the G back and working.

Thanks everyone for your help and advice.

fixwin38
fixwin38's picture
Offline
Joined: 09.07.2006
Location: northern ireland
GWOA Groups: Members
Re: Possible Glow Plug Problem

Hi ..would be convincing if you had the old heater plugs in your hand..depending which plug position it was access to precision drill and tap a left hand thread deep enough to enable the broken plug to be removed is quite a challenge ..anyway your engine appears to be working as it should so "all's well that end's well" ......