E300 turbodiesel rough when cold and smokey

[bob the builder]

Ok folks I'm new to Mercs and to this forum so here goes! I have a 98 E300 turbo diesel estate, its done 200,000 miles and has been serviced regularly but the last one was overdue. Anyway when it fires up from cold it runs what I would call lumpily alternating between 5 and 6 cylinders accompanied by smoke. Once warmed up it runs and pulls fine apart from a slight knocky noise at tickover which goes as soon as you increase the revs. I'm keeping my fingers crossed that someone is going to tell me its combustion knock and that having the injectors done is going to cure all. I have so far changed the air filter only.
However every cloud has a silver lining - this being that with having a smokey start-up I have managed to trace smoke coming from the back of the engine ( someone thought it was the head gasket ) to a pipe joint, the pipe is about 25mm in diameter, starts at the back of the exhaust manifold and turns almost immediately round the back of the engine and travels through round the back of the oil filter housing and under the inlet manifold. The leak appears to be just past the first turn and round the back of the engine. Does anyone know what this pipe is/does, can it be fixed with the engine in - its all a bit tight, and if so is it a main dealer part only. Or shall I cure the smoke problem and forget about the pipe! Sorry if this has all been discussed before I havnt found my way around yet! Your thoughts will be appreciated.

 

[pcman_jh]

Re E300 lumpy

The lumpy start could be a glow plug that's went open circuit/or faulty. Normally the glow light indicator on the dash would come back on again as a means of alerting you to this.

Af for the slight knock (and the lumpiness) I'd put a bottle of diesel injector cleaner into the tank, at a higher ratio than what's quoted on the bottle and see how you get on. I tend to find this treatment cures most lumpiness/smoking etc on my 1999 E300.

The pipe you describe is the exhaust gas recirculation pipe. It feeds the exhaust gas from the exhaust manifold (never!!) back to the inlet manifold (via a computer controlled suction valve). It's there for something to do with emissions, which I don't really understand. Don't know how easy it would be to replace, but you could try patching it with strips of metal from an old oil can and jubilee clips - if there's space.

Hope this helps.

 

[bob the builder]

Thanks for the quick reply! come to think of it the glowplug light does come on again after the engine has fired and stays on for about a minute - I had turned a blind eye to it thinking it was another problem to sort later! So I've got 1 or more glowpugs down. Well thats a start, I had always thought the injector cleaner stuff was a bit of a quack remedy, but if you say it works its cheaper than a set of injectors. So what sort of job are the glow plugs? I geuss they are under the inlet manifold - any advice on changing these folks?

 

[bob the builder]

Forgot about the pipe! You can only just get your hand to the leak so a good idea about the metal and jubilee clips but I dont thinks there's room for it. Can I not just block off the pipe before the leak and allow the exhaust gas recirculation system to suck fresh air when it wants to or am I being a bit too primitive for a mercedes!

 

[FIBAMAN]

You could try some of the old gun gum on your leak if it is only small, worth a try before you have to do anything more radical (another word for expensive).
You can live with a couple of plugs off, but they will all go eventually, so you might as well get the lot done before it gets too cold otherwise you could be cranking for ages and smokin out the neighbours.

 

[poseidon]

The replacement of all glow plugs at a dealer will be around GBP250. It is not difficult job, but not a job for beginer/amateur since they can snap.

I would not sugest strong dose of injector cleaner since it will eat the rubber return pipes on injectors. The manufacturer's recommmended mix for injection cleaner (ocasionally) has been OK on my car.

Pose.

 

[Parrot of Doom]

Glow plugs is a tricky job, they are prone to snapping off and getting stuck in the head. Not a job to be taken lightly.

The pipe you describe is for the EGR, you cannot block it off. Best get it fixed or you'll have exhaust gasses entering the cabin, and you'll also have reduced performance. The EGR lowers toxic emissions, you get a build up of black oily gum in the inlet system over time but its nothing serious.

To replace the glow plugs you need to remove the inlet manifold, which means getting under the car - so kill 2 birds with 1 stone, do both jobs at the same time.

 

[bob the builder]

Thanks for all the advice chaps - I've just got to figure out how cold my feet have got with the snapping off glowplug news - just got to think about taking all the advice on board and risk snapping them myself or paying someone else to snap them off! Watch this space! Bob