E300D W124 glow plug light problem fixed thanks!

[maxypriest]

Dear All,

Just a quick note to say that thanks to you all for great advice - Glow plug problem correctly diagnosed and repaired.

The scenario…

Sometimes when I turned the key on my E300D W124 the glow plug light would not go on. Then when the car was started the light would glow for a good 45 sec – or the glow plug would come on as it should and go out when the engine started. Or should I say stutted, as for the first few seconds one of the cylinders was missing whether the light went on or not.

So I looked about this forum and asked some questions and found out that the feed wires for the glow plugs end at a plug in the control box – thus a straight forward method for measuring the impedance is available – for each plug. Result.

Mulitmeter on the chassis and I went though the plugs one by one. All 0.9 Ohm… apart from #4. bingo it was infinite – the plug must have broken down.

Looking at the engine – by pure luck #4 is the easiest to access as all I have to do is remove the induction trunking (and fix the sticking vacuum butterfly valve – which was also disconnected…). So over a week I squirted some plus gas on the plug as I hear they can brake off – which is not in the plan. The new Beru plug arrived from merc and thus I whipped the trunking off and got a 12mm spanner on the plug when the engine was still hot. She came out a treat.

All back together and it now starts son the button, light showing when is should – no cylinders missing at all.

Perfect.

 

[timgaero]

Hi,
I have the very same problem with my 606. Starts very lumpy and the heater plug light on the dash does its own thing. I have just joined this forum today and I was wondering about the sticky vacuum butterfly valve. Was this the vacuum valve for the diesel pump or was it to do with another part of the engine/cooling system?
Thank you very much, hope to hear from you soon.

 

[Bolide]

I was wondering about the sticky vacuum butterfly valve

Eh?

Bad glowplugs are one thing. This, whatever it is, is another

Nick Froome
www.w124.co.uk

 

[mattkh]

The new Beru plug arrived from merc and thus I whipped the trunking off and got a 12mm spanner on the plug when the engine was still hot.

Hi
Thank you for the commentary. Two questions.
1.Why do they come out easier on a hot engine, as this defies the law of heat expansion ?
2. Did you get the bits from Mercedes by post. If so, which one did you use ?
Regards.

 

[Bolide]

I'd use a deep socket rather than a spanner. Make sure you have the socket lined up exactly at the same angle as the glowplug so there's no sideways force on it

They will snap if provoked

Nick Froome
www.w124.co.uk

 

[Number_Cruncher]

>>Why do they come out easier on a hot engine,

Because the cylinder head is Aluminium, while the glow plug body is steel. Aluminium has a higher co-efficient of thermal expansion than steel, so, the fit between the two parts gets looser at higher temperatures. No laws of physics are being broken!