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300tdi - Thick grey smoke from exhaust?


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How do all,

Another trouble has reared its head on the old "trusty" '95 Deafener, this time to do with what's coming out of the exhaust. It's not constant and only seems to happen under certain circumstances whichI'm still trying to identify, but I rather think the MoT man would have something to say about it if he were to see it come May of next year.

The most common circumstance for it to flare up is after the engine's been running at temperature, then it gets parked up for twenty to thirty minutes (say, about the length of time you might spend in a shop getting a few tinnies and choosing a pizza for your Friday night, to pick an event entirely at random . . .) then it gets restarted. There's the usual cough of black sooty looking stuff that comes out, but then it's followed by what looks like thick grey smoke - such as you might get from a bonfire with wet leaves on - which continues unabated until everything's back up to temperature (about a mile or two's driving). I tried just giving it a boot-full of revs to see if that would clear it, but all that happened was that the car-park was engulfed in the grey smoke . . . :(

The other circumstance, which seems to be more intermittent, is after it's been driven a mile or so from starting from cold. After the cold start there's the usual belch of blackness, then all is well. But by the time I'm navigating suburbia on the way to the motorway, I'm leaving a grey veil of emissions through the streets. This has all cleared by the time I've gone a couple more miles though.

Notes for info:

  • At the last four or five fill-ups I've added a 50ml dose of Millers Diesel Eco-Max, but this doesn't seem to be changing anything.
  • I usually fill up with BP standard diesel from the same filling station and have done since before the grey emissions began.
  • I changed the injector spill return the other week as it was split and leaking, but this hasn't helped either. Mind you, the union to the front-most injector still seems to be seeping, even though everything's good and tight.
  • There seems to be a coolant leak somewhere that isn't the p-gasket. This was leaking a month or so ago which I fixed, but there seems to be an additional leak somewhere.

If anyone can shed some light on what might be happening or any diagnostic suggestions, I'd be most grateful. And if there's any information required that I've not supplied, please just ask.

Cheers all :blush:

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Thanks Les.

I haven't given it a smell no, never thought of that.

From the looks of it though, I don't think there's any oil in it as there's no hint of blue in it at all. I did wonder if it might be the cylinder head gasket as I do top up regularly, but (a) there's usually a small watery puddle on the ground after it's been parked up for a while and (b) I ran the engine for a few minutes from cold then unscrewed the expansion bottle cap and there wasn't any pressure in it, so I'm inclined to think it's just a leak somewhere. Will give it a sniff next time it happens. As long as I have my wits about me at any rate . . .

I did forget to mention a few other things which may be of some use:

  • When I had a 300tdi Discovery, the cam belt was replaced but put on a tooth out of alignment. Consequently it used to belch out grey emissions when on the overrun. Although the current issue happens under different conditions, it does look similar.
  • Occasionally when starting, everything feels a bit . . . different. It doesn't take more cranking to start or make any funny noises or anything, but it does feel as if things are having to work a bit harder
  • Usually, when turning off the ignition, there's the usual little shimmy before everything comes to rest. Sometimes however, there does seem to be more of a shake as everything comes to a stop, then on other occasions everything almost seems to stop without any motion at all.
  • Fuel economy is still working out at 32 to 33mpg
  • It still pulls like a train and I haven't noticed any degradation in driving performance

Thanks again . . .

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Just because the cooling system isn't pressurising doesn't mean the head gasket isn't leaking. There are several ways it can 'blow'.

It's quite common for the timing belt to be fitted one tooth out on the 300TDi engine, and I've done it a few times in the past, but it's always noticeable once it's fitted as you have to turn the engine clockwise back to the timing marks and check them. One tooth out means that from cold it takes an awful lot of cranking to get the engine started, but it's not too bad if it's already warm. Idle is terrible though, and there's almost no acceleration. Grey smoke won't be burning engine oil, but could be either steam or unburnt fuel. You need to smell it :)

Les

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i went through all this last year, unfortunately it was a cracked head! a small crack was letting water out the jacket and into the exhaust outlet of the head. ran fine. only symptoms were grey smoke pouring out back occasionally and top up water once a week.

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I've tried the same, a small leak in the head in a exhaustport. As described above the only noticeable difference is the smoke from the exhaust. Some of the water had however migrated down in the cylinder (nr. 3) and slightly damaged it so might be worth a look.

Regards mads

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Sounds to me like an air leak in a fuel line somewhere.

Before you go pulling heads off, just stick a clear filter before the injection pump. Start it up in the circumstances you've noticed the problem and verify that no air is being pushed into the injection pump with the fuel.

White/grey smoke if not water getting in somewhere is normally fuel related. As air gets into the injection lines and is compressible, it has the effect of retarding the timing - hence the white smoke. Seen it too many times to count.

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Thanks all, much appreciated.

In the vain hope that it's not a cracked block and is somehow fuel related; could air getting into the spill-return cause this problem, as it's on the low pressure side of the pump?

I only ask as there seems to be a small seepage where the spill pipe meets the front-most injector and if fuel's getting out, presumably air is getting in?

If it's parked up for a little while after a run then air may well get in that way. Only thing is I would have thought the grey smoke would happen at every start if this were the case, rather than intermittently?

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Its hard to tell the colour of smoke when driving and symptoms can sometimes be misleading, is it possible you have over filled the oli a bit? try pulling the pipe from the cyclonic filter and see if oil is spitting into the air intake. Also have a quick look if there is a collection of oil in the bottom of the inter-cooler in case a bit of oil is bypassing the turbo oil seal.

These are very quick checks and at least you can eliminate something.

HTH

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I only ask as there seems to be a small seepage where the spill pipe meets the front-most injector and if fuel's getting out, presumably air is getting in?

Not impossible. If parked up, air gets in and the system drains back to the tank until it bleeds again when you start the engine? I've seen it happen, but only on vehicles without lift pumps. I'd have thought the valves in the lift pump would stop it draining back.

Rather than grasping at straws, stick a clear filter on the injection pump inlet. You'll clearly see if it's an air problem or not.

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I know it's not what you want to hear but I've been through exactly the same symptoms with my 300. Being a mechanic myself, albeit HGV, I suspected the head all along but I wasn't prepared to strip it until I'd ruled out everything else. I did combustion leak tests on it, changed injectors, filters, fuel pump (all known to be good second hand units from a breaker I had) but nothing worked.

Eventually when I did pull the head, it was actually cracked. Everything else I tried along the way fortunately didn't cost me anything other than time. With, yet again, a known good head off another lump I've got in the workshop, all is well. She runs really sweet with little to no smoke other than what is classed as normal.

Head removal isn't a big job if it comes down to it, and a quick pressure test in a local machine shop will show up any cracks or faults.

Sorry for the essay, just hope you get it sorted.

James

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yes , just be sure not to introduce air leaks at the connections to the fuel pipe which is something I've come across before , and had symptoms not that different to yours.

If it is water in the combustion chamber you should see it if you pull the injectors , the one that is clean and shiny will be the faulty chamber .

cheers

Steveb

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When you say "clear fuel filter" Reckless, is that one of those ordinary plastic numbers with the orange papery filter element inside, or something a bit different??

That's exactly what I mean. You only just need to see what's passing through the fuel line - they're not actually filtering anything.

Another option is a bit of clear fuel hose.

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Just to add, when I had problems with mine, not once did she use any water and it ran perfectly, apart from the smoke which is what made the diagnosis rather confusing. In the end I put it down to a hairline crack that was opening up at temperature and sealing back when cold, which also confused the compression tester. By the time I could get the injectors out and get the tester through all 4 cylinders it had cooled enough for that crack to close up again.

J

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Just so happened that this morning, following the vehicle standing idle from Thursday to Monday and subsequent cold start, the grey smoke appeared again but this time I had the chance to pull over and have a sniff. Basically, it just smells like an old diesel engine (I once had the joy of working on a 1975 Leyland Terrier 7 tonner and it smelled very similar to that). There wasn't any other noticeable odour to it at all as far as I could tell.

Colour was very definitely grey, without any blue tint to it at all. However; that was at the side of the road idling away. Because I was trundling around town I had the chance to accelerate hard and then coast, during which I noticed that when accelerating hard the smoke in the nearside wing mirror was very grey, but on the overrun it adopted a blueish tint. The two stages being noticeably different.

Also noticed that once the temperature gauge had lifted off the end-stop at cold, the smoking had gone.

Does that provide any clues? Unfortunately I'll not have the chance for the clear-thing-in-the-fuel-line test until the weekend.

And finally, the daft newbie question; if it is the head gasket which has gone, would the smoking/steaming/greyness not be visible all the time, rather than only as it was warming up?

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And another little nugget of information has crept out of the dingiest parts of memory . . .

Ordinarily, when I went to fill up, removing the filler cap resulted in an inrush of air and a sort of "thunk" from the tank, as if it were expanding after being in a vacuum. For the last few weeks and seemingly about the same sort of time that this grey smoke issue has been noticeable, that hasn't happened. Presumably then, air can now get into the tank at the same rate as the fuel is leaving . . .

I suppose this would be on the wrong side of the lift pump to let air into the system and cause the retarding effect Reckless mentioned earlier, but I thought it may be worth mentioning . . .

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Grey smoke is unburnt fuel (raw diesel vaporising) and your blue smoke is oil which on overrun would suggest a possible valve stem oil seal problem, although normally more noticeably with a petrol engine but It could be coincidence so I wouldn't read too much into just yet incase the head does come off. concentrate on this heavy grey smoke issue.

The smoke clearing after a warm up says to me there's something dribbling into the piston crowns while standing. IF it is a crack, which I suspect it is if I'm being honest, that something could be water, oil depending on where the issue is, or a bad injector not shutting properly. Obviously a bad injector has nothing to do with a head fault so you could get them pop tested first to rule them out. This fuel smell you say of is another identical Symptom of mine, hence why I suggest an injector test, but this could also be a sign of incomplete combustion caused by bad compression or cylinder contamination.

A fuel tank vacuum is almost certainly a blocked breather pipe, which again could just be coincidence that it's stopped doing it, because I can't really think of an engine issue causing a tank vac, normally a tank vac would cause the engine issue so I can't help much on that one but I'll think on it.

J

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Smell the smoke. Does it smell of diesel (stings the nose), burning oil (tends to be blue or black), or steam (you will be having to top up the coolant on a regular basis).

Les

Les,

Had a decent smell of it this morning and it's definitely diesely. Smelt rather reminiscent of my grandparents paraffin heater and left my nose with a rather unpleasant tingle for a while.

Could you advise how to proceed please?

Cheers

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