Glow plugs.

[Albert38]

Hi all. I have just replaced all 4 glow plugs on my 2008 C220 estate. The preheat light comes on when you put the key in the ignition as usual and goes out after a second or so, but now the preheat light comes back on and stays on for a minute then goes out. It never did it before I changed the glow plugs, but now does it only when the engine is cold. When its warm the preheat comes on momentarily when the key is in the ignition as usual, but no other showing of the light at all. Is this a normal procedure or is there also an issue with the relay. No problem starting the car at all, even with the appearance of the preheat light now. Many thanks. Paul

 

[Blobcat]

Hello and welcome

The light coming back on after starting denotes one or more of the plugs is faulty or the relay

 

[Ian frog]

Hi
The pre heat light on my E350 estate (2010 130000 miles) has started flashing on briefly at random times when I am driving and I have just started to experience starting difficulties when cold.
Is it more likely plugs or the control unit and how much do you reckon to resolve?
Many Thanks
Ian

 

[EmilysDad]

.....
Is it more likely plugs or the control unit and how much do you reckon to resolve?
Many Thanks
Ian

if yours is comparable to how my R320 was it could be either and or. Do a resistance check on each plug to find the duff plug(s)
STAR suggested it was a particular glow plug but it turned out to be the relay.

 

[Wighty]

Sometimes the failure of a plug can blow the relay, so be careful just putting a new relay on old or suspect plugs.
The cars battery can also be a struggling to start issue with the colder weather

 

[Ian frog]

Thanks chaps.
Interesting comments.
Battery definitely up to strength so diagnostic time for the plugs I think.
Cheers
Ian

 

[John Laidlaw]

what plugs did you use?

 

[Ian frog]

Hi Guys
Update on my problem.
It has been diagnosed as the relay/ control unit so that is going in now and the plugs have checked out as ok.
Thanks for the advice and comments.

 

[Wighty]

Hi Guys
Update on my problem.
It has been diagnosed as the relay/ control unit so that is going in now and the plugs have checked out as ok.
Thanks for the advice and comments.

10 minute job for the relay buddy

 

[mioba]

...so did the plugs need replacing in the first place?

 

[John Laidlaw]

...so did the plugs need replacing in the first place?

Don't suppose it matters now as he will now have new plugs and controller, happy days

 

[Wighty]

I think it’s best to do them all together anyway , after all they all consumables .

 

[mattkh]

I think it’s best to do them all together anyway , after all they all consumables .

Yes.
If the relay costs about £20, then I would change the relay first, and then suspect the glow plugs.

 

[Wighty]

Yes.
If the relay costs about £20, then I would change the relay first, and then suspect the glow plugs.

Mine was £120+

 

[matthew k]

Mine was £120+

Yeah, prices of relays seem to have gone up loads in the last year or so? I'm sure I got one for my OM642 for less than £60?