White vapour only at high revs under load

[Guy J]

I have had a drawn out, puzzling scenario with my BMC 1.5 engine.  It has clocked up 4,000 engine hours and run reliably for the last 30 years. About 18 months ago, I felt puffs of air from the joint between head and block.  I removed the head, had it skimmed and replaced it, with new head gasket, and the valves were ground in at the same time.  The engine ran well for about 200 engine hours  and a substantial period of cruising.

 

Last August it  suddenly started to run really roughly and there was considerable black smoke, whereupon I noticed all the diesel in the tank had turned black and been contaminated.  Thinking that was the cause,  I  disconnected the diesel tank, and for testing have subsequently used only clean diesel from a separate container..  I also flushed out the diesel fuel lines and pumps with clean diesel.   I have fitted a new (reconditioned) injection pump, glow plugs, injectors and lift pump, and I changed the fuel filter on the engine.  I have also rotated the injection pump to the extremes allowed by the pipes, to find optimum timing. with some, but not appreciable difference, in the smoke and rough engine running.

 

This didn’t solve these problems and on closer examination I realised the rockers had been starved of oil and the rockers and shaft were badly worn, giving extremely large tappet clearances.  I diagnosed this as lack of oil supply to the rockers, caused by the head gasket being upside down, blocking the  oil pathway.  This was my fault!

 

I renewed the rockers, rocker shaft and pushrods, and fitted a new head gasket, the correct way up, and lubrication to the rockers was restored.  The engine now started well and ran well and smoothly at all revs, however dense white vapour now billowed out from the exhaust, but only above 1500rpm and under load. It seemed curious that there was none of this white vapour when the engine was in neutral, even at maximum revs.   I captured some of this and let it condense, proving that it is water vapour by tasting and smelling the drops that had appeared after the vapour had condensed. 

 

I fitted another new head gasket, and, as before the engine starts and runs smoothly and sounds good, but as before, white vapour still billows out at higher revs, only under load.  We performed a compression test and found it to be about 400 psi, and within 10% of this in all four cylinders.

 

I have tried to verify that this problem is caused by water leaking into the cylinders or intake ports from the cooling system by looking for bubbles with the radiator cap removed, but the vibrations from the engine make this impossible to determine,

 

I don’t understand why this dramatic exhaust emission only happens under load at high revs, and I am now suspecting a crack in the cylinder head or block.  Is this a possible cause, and can anyone offer any suggestions?

 

 

 

[Tracy D'arth]

Skin tank cooled?

Is it actually losing cooling water?

The only idea I can put forward at this stage with the information supplied is if the water is being sucked in via an inlet valve guide or seat that has become loose in a cracked head. Or a crack in an inlet port.

It may be worth using a radiator sealant ( Rad Weld ) in the hope that it will at least prove where the water is coming from.

[Guy J]

Thanks Tracy, yes it's skin tank cooled.  It doesn't appear to be losing water, and we can't detect any contamination in the water or oil.  Interesting idea, I'll consider trying radweld.

[Tracy D'arth]

20 minutes ago, Guy J said:

Thanks Tracy, yes it's skin tank cooled.  It doesn't appear to be losing water, and we can't detect any contamination in the water or oil.  Interesting idea, I'll consider trying radweld.

If its not loosing water from the cooling system the only other place is from the fuel. Is there a filter or fuel line lying in water somewhere?

[Guy J]

I am using a fuel can with clean fuel, and pipe directly into the lift pump, so there's no water coming from this source.

[Tony Brooks]

If it is not water. and it seems not to be, then all it leaves is a fuelling problem, but it is the high speed bit that makes little sense. All I can think of is very poor atomisation with overruling, but as this happened before the overhauled injector pump, I think we can rule the pump out for now.  That leaves injectors, but they usually cause problems at low speed. It would not hurt to pull the injectors for testing, and at the same time ensuring nothing bad has happened to the top hat heat shields they fit into. Please note that I am far from sure about this, so testing injectors is just a diagnostic step.

 

I also wonder if, for some reason, the injector break pressure is too low, that would cause poor atomisation (but usually at low seed).

 

More very long shot thoughts.

 

I assume that the 0.5 mm hole in the side of the large banjo bolt where the leak off pipe connects to the filter head is clear.

 

I also assume that the leak off pipe back to the fuel tank or your can is clear.

 

There is a large union nut on the return inlet to the fuel filter from the injector pump - the pump connection closest to the engine block. One of those with the inward pointing arrow head. It is a valve so make sure that it is not clogged up with anything - especially if you have been passing buggy fuel

 

If you have not been cleaning the injector pump skew drive gear lubrication strainer and jet regularly, then the skew gears on the drive and camshaft may be badly worn and that can totally upset the pump timing. Did you check the backlash in the pump drive when the pump was off the engine?

Edited June 6 by Tony Brooks

[Tracy D'arth]

51 minutes ago, Tony Brooks said:

If it is not water. and it seems not to be, then all it leaves is a fuelling problem, but it is the high speed bit that makes little sense. All I can think of is very poor atomisation with overruling, but as this happened before the overhauled injector pump, I think we can rule the pump out for now.  That leaves injectors, but they usually cause problems at low speed. It would not hurt to pull the injectors for testing, and at the same time ensuring nothing bad has happened to the top hat heat shields they fit into. Please note that I am far from sure about this, so testing injectors is just a diagnostic step.

 

I also wonder if, for some reason, the injector break pressure is too low, that would cause poor atomisation (but usually at low seed).

 

More very long shot thoughts.

 

I assume that the 0.5 mm hole in the side of the large banjo bolt where the leak off pipe connects to the filter head is clear.

 

I also assume that the leak off pipe back to the fuel tank or your can is clear.

 

There is a large union nut on the return inlet to the fuel filter from the injector pump - the pump connection closest to the engine block. One of those with the inward pointing arrow head. It is a valve so make sure that it is not clogged up with anything - especially if you have been passing buggy fuel

 

If you have not been cleaning the injector pump skew drive gear lubrication strainer and jet regularly, then the skew gears on the drive and camshaft may be badly worn and that can totally upset the pump timing. Did you check the backlash in the pump drive when the pump was off the engine?

It has been established, Tony, that it is water as steam coming from the exhaust. It is getting in somewhere, its just find where!

[Tony Brooks]

10 minutes ago, Tracy D'arth said:

It has been established, Tony, that it is water as steam coming from the exhaust. It is getting in somewhere, its just find where!

 

I must have missed that, but I still can't see where that is stated. He says that he is not losing coolant.

 

I suppose there is a chance that it is tank cooled with wet exhaust, so a lack of exhaust water would create clouds of steam, but that would be a very unusual tank cooled boat.

Edited June 6 by Tony Brooks

[Tracy D'arth]

5 minutes ago, Tony Brooks said:

 

I must have missed that, but I still can't see where that is stated. He says that he is not losing coolant.

 

I suppose there is a chance that it is tank cooled with wet exhaust, so a lack of exhaust water would create clouds of steam, but that would be a very unusual tank cooled boat.

Its here Tony,

""I captured some of this and let it condense, proving that it is water vapour by tasting and smelling the drops that had appeared after the vapour had condensed. ""

[Tony Brooks]

12 minutes ago, Tracy D'arth said:

Its here Tony,

""I captured some of this and let it condense, proving that it is water vapour by tasting and smelling the drops that had appeared after the vapour had condensed. ""

 

Thanks, but I would suggest that that statement and not losing coolant are incompatible, unless by some chance the skin tank is punctured on the outside so it tops itself up from the canal. Also, as any diesel exhaust will contain water vapour or steam from the Oxygen in the air and hydrogen from the fuel, I don't think it is a definitive test. However, it all depends upon volumes and it sounds a lot of white "smoke".

 

More thoughts, I wonder if the exhaust manifold water jacket has cracked/corroded along with a punctured ski tank. if so the exhaust pipe would collect water that would make clouds of steam.

Edited June 6 by Tony Brooks

[Guy J]

Thanks very much for your messages - much appreciated!  Just to clear up a couple of things - I expect that the coolant has been disappearing, but at a rate so small as for me not to detect, as the engine has not been running for long periods of time, and I had to drain some of the coolant when renewing the head gasket last week.  My skin tank is on the inside and not leaking from the outside, and the liquid is most definitely water with not a hint of diesel!

 

I am thinking along the lines of exhaust manifold water jacket or cylinder head, still..... well I think that's what I should be thinking!

 

Guy  

[Tony Brooks]

9 minutes ago, Guy J said:

Thanks very much for your messages - much appreciated!  Just to clear up a couple of things - I expect that the coolant has been disappearing, but at a rate so small as for me not to detect, as the engine has not been running for long periods of time, and I had to drain some of the coolant when renewing the head gasket last week.  My skin tank is on the inside and not leaking from the outside, and the liquid is most definitely water with not a hint of diesel!

 

I am thinking along the lines of exhaust manifold water jacket or cylinder head, still..... well I think that's what I should be thinking!

 

Guy  

 

I think a cooling system pressure test might be illuminating.

[Tracy D'arth]

The exhaust manifold is water cooled but with revs on the engine the internal pressure will be higher than the cooling system pressure so I doubt water would get into the exhaust from the cooling water.

The inlet manifold is not water cooled (unless you have a very odd manifold) and at revs will be at a very low pressure as will the inlet ports so any leakage of water will be drawn in.

[Guy J]

Many thanks!  I will check inlet manifold, do a cooling system pressure test and put some radweld in, not necessarily in that order!  I will let you know.  Guy

[Tony Brooks]

22 minutes ago, Guy J said:

Many thanks!  I will check inlet manifold, do a cooling system pressure test and put some radweld in, not necessarily in that order!  I will let you know.  Guy

 

Personally, I can't see any way water can get into the inlet manifold unless the boat is getting on for sinking, unless a head gasket leak is spraying coolant onto the air cleaner or into the intake.

[Guy J]

I agree, the boat isn't sinking and there is no head gasket leak spraying coolant anywhere externally.

[Paul C]

On 06/06/2024 at 13:53, Guy J said:

I have had a drawn out, puzzling scenario with my BMC 1.5 engine. 

 

.................. for testing have subsequently used only clean diesel from a separate container.................... I have fitted a new (reconditioned) injection pump............... injectors...................  I have also rotated the injection pump to the extremes allowed by the pipes, to find optimum timing. with some, but not appreciable difference, in the smoke and rough engine running.

..........

 

 

 

 

 

 

I've selectively quoted because the OP is quite detailed and I have no comment on the other parts of the post I've deleted out of the quote. Also I'm no expert on BMC diesel specifically, so please excuse my generalised comments. But hopefully they can give you some direction.

 

1) How are you sure it really is clean diesel?

2) Rotating the injection pump isn't a guarantee that you've arrived at the right timing.

3) Its quite possible that something more 'out of the ordinary' is going on, such as the recon injection pump has a miscalibration, fault, or is the wrong one for the engine; or that the injectors are faulty or out of spec too (ie cheap copy ones, not decent).

 

 

[Bod]

@Guy J

An off the wall thought. Are you using any form of diesel treatment?

 

Bod

[agg221]

Another thought - how long have you been running before you tried running at high revs under load, and then how long did you run under load for?

 

I am wondering whether you have water in the form of condensation somewhere downstream of the exhaust ports which is collecting and then when you rev it up is boiling off. If this was the case then running for a long time at light load before revving up would remove it, as would running for a reasonable time at high revs as in both cases the vapour would last for a finite duration and then probably not return whilst running.

 

Alec

[Guy J]

15 hours ago, Paul C said:

 

I've selectively quoted because the OP is quite detailed and I have no comment on the other parts of the post I've deleted out of the quote. Also I'm no expert on BMC diesel specifically, so please excuse my generalised comments. But hopefully they can give you some direction.

 

1) How are you sure it really is clean diesel?

2) Rotating the injection pump isn't a guarantee that you've arrived at the right timing.

3) Its quite possible that something more 'out of the ordinary' is going on, such as the recon injection pump has a miscalibration, fault, or is the wrong one for the engine; or that the injectors are faulty or out of spec too (ie cheap copy ones, not decent).

 

 

 

Thank you Paul!  It is definitely clean diesel from a clean can.  I can't see how injection pump timing could result in water vapour suddenly belching out, but I will  check on this.   I put the old injection pump back on to test, as I'm now not sure that it needed to be changed, and it works but with the same vapour symptoms.  However the drive shaft has substantial wear, so I'm glad to have got the reconditioned one.  Injectors were from a verifiable source, and w again I'm not sure how these could lead to water vapour entering the combustion chamber.  I will discuss these matters with a very knowledgeable friend who has helped me throughout this process.

15 hours ago, Bod said:

@Guy J

An off the wall thought. Are you using any form of diesel treatment?

 

Bod

I use Marine 16 in the main tank, but I haven't been using it in the 5l plastic can which has been my diesel source, however this is a new can and I filled it up from a petrol station a few days ago so I think I can be sure that it's uncontaminated.

15 hours ago, agg221 said:

Another thought - how long have you been running before you tried running at high revs under load, and then how long did you run under load for?

 

I am wondering whether you have water in the form of condensation somewhere downstream of the exhaust ports which is collecting and then when you rev it up is boiling off. If this was the case then running for a long time at light load before revving up would remove it, as would running for a reasonable time at high revs as in both cases the vapour would last for a finite duration and then probably not return whilst running.

 

Alec

Thanks Alec, I've run it at high revs under load for a while, but the amount of vapour is so extreme that people think the boat is on fire! and it is not possible to continue! Anything less than high revs under load produces no vapour at all, so no condensation is being removed.  Guy

[Paul C]

What kind of exhaust does the boat have?

[Guy J]

It's a dry exhaust.

[agg221]

OK, so it looks like this only happens when the engine gets really hot. The pressure in the bore in a diesel usually stops any water leaking in through cracks, and there is even less likely to be any when it is working hard, so that suggests the water is not coming in through the block, the head gasket or the part of the head that opens into the chamber (or injectors or similar).

 

Heat expansion opening a crack somewhere that is not under pressure would be my working hypothesis. If it happens quickly then that means it is somewhere that heats up fast, which suggests nearer to the cylinder. My first though would therefore be a crack in the head down an exhaust valve hole, or on the outside of the head under the exhaust manifold (or, depending on the design, down an exhaust manifold bolt hole). A crack in a water cooled exhaust manifold would be possible but less likely - it would take longer to heat up.

 

Bear in mind that I have no familiarity at all with this engine but am going off basic principles. If it has a suitable fuel pump to allow you to slacken off the fuel supply to one cylinder at a time, that will stop the fuel injecting. Running will be rough, but whichever cylinder does not have fuel will not fire and hence not get hot. That should mean that when you find the right cylinder(s) it should not produce steam. This would give positive diagnosis of a head issue and which cylinder it is on. If all cylinders produce an identical response of an equivalent amount of steam then the issue can reasonably be assumed to be in the inlet side (fuel system) or the exhaust manifold, as it would be an incredible coincidence if all parts of the head failed simultaneously.

 

I could do this test easily on my engine, but I don't know whether it is practical on yours - that would need the expertise of Tony or Tracy to comment.

Alec

Edited June 9 by agg221

[Quattrodave]

23 hours ago, Guy J said:

 the amount of vapour is so extreme that people think the boat is on fire! and it is not possible to continue! Anything less than high revs under load produces no vapour at all

 

Im rather confused with this... steam usually dissipates pretty quickly but i cant thinknof any reason why it would only do it at high revs...

 

Edit: did you have the head pressure tested and skimmed when it was off??

Edited June 9 by Quattrodave

[bizzard]

Steam is invisible. Your all on about water vapour.