Blue smoke on start-up

alexthecheese

alexthecheese

alexthecheese

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Joined
10 Mar 2006
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I bought a motorhome on the cheap about 10 days ago, and as already mentioned on here there is something wrong with the clutch or gearbox - not sure which, but that will be sorted soon.

The other problem it has is on start-up it blows out blue smoke. It's not too much, unless revved hard - which I've only done once to see what it pumps out - and disappears when hot.

Now what would this be? Knackered piston rings? Knackered piston? It's obviously oil coming through, but other than what I've learned on 'A Car is Born' from working at home that's about all I think it could be.

Found a place that will recondition and engine or supply a new reconditioned engine, I'm just hoping that it wouldn't cost too much to get put right.
 
Blue smoke usually is oil from top of head down, maybe valve guide seals, in an old Ford it's a good sign as you know oil is getting to the top of the head, I changed a Mk4 escort valve seals without taking the head off if you have the proper tool, however more complicated engines would require head off and then re seating valves as well, then your talking changing the cam belt whilst your there and also tensioner and water pump depending on the engine.
 
If I remember rightly its a Turbo Diesel ? Could be turbo seals or turbo related - A friend of mines car would collect a small amount of oil from worn seals in the turbo housing after being shut off, then cough it out on startup.
 
maccapacca said:
Blue smoke usually is oil from top of head down, maybe valve guide seals, in an old Ford it's a good sign as you know oil is getting to the top of the head, I changed a Mk4 escort valve seals without taking the head off if you have the proper tool, however more complicated engines would require head off and then re seating valves as well, then your talking changing the cam belt whilst your there and also tensioner and water pump depending on the engine.
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Aye Nomisf it's a turbo (almost wrote turdo there lol :D).

I've been having a rummage on the Fiat Ducato forums, as they're the same van by the sounds of it, and it could be the valve stem seals according to some users out there. Is this the same as the valve guide seals?

Something a eunuch could approach, or garage job?
 
Blue smoke is an indication of oil being burnt and will not be caused by an injector. Ignore the fools at Purfleet and never speak to them again.

Blue smoke on starting is commonly caused by worn valve stem seals which allow oil to drain down the guides and into the ports/cylinders when the engine is stopped. A worn turbo could give similar symptoms, though you'd probably see blue smoke under other operating conditions as well.

Valve stem seals are not especially simple to change; you have to remove the collets and valve spring retainer and valve spring on each each valve to replace the seal. This is relatively easy with the head off the engine as you can use a normal valve spring compressor which pushes against the head of the valve. With the cylinder head on the engine, the normal way of keeping the valve in place is by injecting compressed air into the cylinder and then you use a special valve spring compressor that bolts onto the head. With a diesel, you may be able to get away with just setting each piston to TDC as the piston crown will be very close to the valve head. However, you will still need some method of compressing the valve spring.

If it's just a puff of blue smoke at start up and the engine isn't consuming gallons of oil, then it may be as well to live with it for now.
 
Dogbreath said:
Blue smoke is an indication of oil being burnt and will not be caused by an injector. Ignore the fools at Purfleet and never speak to them again.
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Indeed, any mechanic who says blue smoke comes from a fuel system is an idiot.

Most likely is worn valve guide or seals, way to get a better indication is let it idle a while, then rev it, if you get blue smoke that clears, likely to be valve guides/seals.
 
Well that's what I thought, not that I have much of a clue, even as he said it it almost sounded like he was just plucking out an expensive routine that I should go down.

I'll give it another go this evening. It does seem to be fine once it's up to temperature. I'll have to monitor the oil level as we've only done a couple of hundred miles so far. I checked it the other day and it was full. If it doesn't burn much is it just something that I can live with, i.e. it won't knacker the engine in?

Thanks for the replies btw.
 
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