Light Blue Smoke on start-up?

[Ian_Edwards]

A friend has a fishing boat, 36ft and fitted with a 4 cylinder 2.5L 130bhp turbo diesel engine. The boat was built in 1996 and we believe it has the original engine. The boat was used to take anglers sea, fishing for about 8 months every year and has been well maintained, but must have a very large number of hours on it by now.

My friend has owned the boat for about a year, but at the end of last year it blew the head gasket, which pushed water out of the cooling system, no real damage done, and the head gasket has been replaced.

The engine starts on the button and, as far as we can tell, hasn't lost any performance, but it now produces large quantities of light blue smoke on start-up from cold. This only last a minute or so and then the engine seems to run normally and doesn't produce any smoke when started from warm/hot. It didn't do this before the head gasket blew and was repaired.

Since funds are short, where do we start of looking for the problem and what's the most likely cause?

Or do we just keep on using it as is?

 

[PaulRainbow]

That's oil smoke. Could be from a variety of causes, first place i'd look is valve stem seals. Used to be common on some cars, mostly Fords. Oils seeps past the seals, down the vales into the cylinder. When you start the engine the oil burns and smokes, once it's gone, no more smoke. Most other faults allowing oil ingress will cause the engine to smoke all of the while.

 

[Ian_Edwards]

I take it that the head will have to come off again to renew the valve stem seals?

Could it be the glow plugs not working?

 

[Bobc]

Valve stem seals probably, especially if it only lasts a minute or so.

You can replace these without removing the head (you need to stop the valves dropping when you remove the springs. You can either do that by removing the injectors and one cylinder at a time poking soft rope into the cylinder and then rotating the engine gently until the rope stops up against the vlaves, or you can do it with air pressure in the cylinder).

 

[PCUK]

. . . . Or bring each piston up to TDC in turn.

 

[Seajet]

You might also like a close look at the injectors.

 

[Bobc]

. . . . Or bring each piston up to TDC in turn.

Depends on the valve clearance, but it's always best to hold the valves shut and in place to stop them rotating.

 

[Tammany]

Unless he's going through large quantities of oil then it's not really worth bothering with at the moment. A little bit of oil in the cylinders is beneficial anyways. Obviously it will need tending too at some point but a few mils of oil a trip isn't going to do any harm.

 

[vyv_cox]

It's easy to confuse smoke colours. My BMC 2.2 produces vast quantities of light grey smoke on start-up, no question that it is fuel. But for lesser amounts, maybe a glow plug not working correctly, I suspect your problem might be the same. Unless the oil consumption is excessive I would do nothing at the moment, monitor the usage.

 

[chrishelen]

I would say 90 pc of the motor boats in our marina produce some type of smoke on start up...but this soon clears, if it doesn't clear then you need to take action. Depends on the colour of the smoke. My Perkins let's out a puff of grey smoke at start up, but clears straight away. I would suggest just keeping an eye on it for a while, keep an eye on the oil level on your daily checks.

 

[Poignard]

The key phrase in the original post is: "It didn't do this before the head gasket blew and was repaired."

Before looking for possible new faults, wouldn't it be better to carefully check what was done in that repair?

Was everything done that should have been done?

Was what was done, properly done?

 

[<152587>]

Some turbo charged engines suffer from this on start due to turbo not spinning sufficiently to supply air. You do not quote the make.

 

[PaulRainbow]

I take it that the head will have to come off again to renew the valve stem seals?

Could it be the glow plugs not working?

As others have said, this can be done with the head on.

Vyv raises a good point with smoke colour, so you do need to be certain that it is indeed blue. If it is, I'm not sure that advice to leave it is sound. You say it only started after the head was fixed, so it seems likely something was dislodged/disturbed/damaged during that work. If a stem seal completely fails due to reasons such as coming off or splitting, it will allow more oil into a cylinder. You will get a lot of smoke and if you are any distance from a safe harbour you could have a problem with oil loss.

It isn't going to heal up of it's own accord and sooner or later you will need to address the issue. IMO, sooner is better.

Ref glow plugs, if it is blue smoke, it is oil, end of. Glow plugs or injectors will be irrelevant.

 

[PaulRainbow]

Some turbo charged engines suffer from this on start due to turbo not spinning sufficiently to supply air. You do not quote the make.

Lack of air equals an over rich fuel charge, how does this result in blue smoke ?

 

[<152587>]

As others of this parish have quoted, it is very easy to confuse colour of smoke. I note that you do not take issue with that post. Is there an exclusive club here or can anyone provide an opinion?

 

[PaulRainbow]

As others of this parish have quoted, it is very easy to confuse colour of smoke. I note that you do not take issue with that post. Is there an exclusive club here or can anyone provide an opinion?

He said he has blue smoke.

You said

Some turbo charged engines suffer from this on start due to turbo not spinning sufficiently to supply air. You do not quote the make.

Blue smoke is burning oil, nothing to do with fuel.

Rather than cover every possible colour and every possible cause for each colour it might be less confusing for the OP if causes and cures for the problem in hand are dealt with.

 

[GrahamM376]

The key phrase in the original post is: "It didn't do this before the head gasket blew and was repaired."
Before looking for possible new faults, wouldn't it be better to carefully check what was done in that repair?

Whilst it is typical of a valve stem seal problem, I agree with parsifal. Why did the head gasket blow, had the engine been overheated and the head warped, was it skimmed? Does it have an O ring oil feed seal from block to head which was missed or not seated properly allowing some oil to drain past into a cylinder?

 

[<152587>]

It's easy to confuse smoke colours. My BMC 2.2 produces vast quantities of light grey smoke on start-up, no question that it is fuel. But for lesser amounts, maybe a glow plug not working correctly, I suspect your problem might be the same. Unless the oil consumption is excessive I would do nothing at the moment, monitor the usage.

Not relevant as puulrainbow was very adamant, the smoke is BlUE, that indicates oil!

 

[Geordy]

Simple way to tell , are you using any oil . You can check the head gasket , any oil residue in the filler cap area or any bubbles rising up from the coolant ( or is your oil level rising or milky in colour ) Every diesel I have seen smokes to some extent on start-up and clears after a short time .

 

[NormanB]

Always fun to diagnose from remote.:encouragement:

How about the turbo? Could be lubricating oil finding its way past the seals on spool down and then being pushed out into the inlet manifold on subsequent start up.