BMC engine

[grahoom]

Hello.

 

I was told this weekend that it wasn't a good idea to run the BMC engines in neutral for periods of time (i.e not under load..). Has anyone else heard this and if so can they explain why this is the case?

[gralyn]

Hello.

 

I was told this weekend that it wasn't a good idea to run the BMC engines in neutral for periods of time (i.e not under load..). Has anyone else heard this and if so can they explain why this is the case?

 

It is the perception among some boaters that this will cause bore glaze. I have read papers by qualified mechanical engineers that indicate thet the load of the Alternator is sufficient to prevent it if it really exists. I have just had my BMC 2200cc engine refurbished and although it needed a rebore there was no evidence of bore glaze and I have alwas run the engine out of gear when charging the batteries when moored up.

[grahoom]

It is the perception among some boaters that this will cause bore glaze. I have read papers by qualified mechanical engineers that indicate thet the load of the Alternator is sufficient to prevent it if it really exists. I have just had my BMC 2200cc engine refurbished and although it needed a rebore there was no evidence of bore glaze and I have alwas run the engine out of gear when charging the batteries when moored up.

 

 

Thanks gralyn, - what's bore glaze exactly? sorry for the questions, my knowledge in engines is pretty rubbish (at the moment).

[gralyn]

Thanks gralyn, - what's bore glaze exactly? sorry for the questions, my knowledge in engines is pretty rubbish (at the moment).

 

As far as I Know ,because I have never seen it, it is supposed to be a build up of unburnt oil products on the cylinder walls which causes a less than optimum piston to cylinder fit and all the ills that that results in. (Now prepared to be shot down by more learned opinion.)

[Maverick]

Yes for everyone you find who advocates running the engine in gear you will find one who doesnt. I'm of the latter myself.

[Paul H]

It is the perception among some boaters that this will cause bore glaze. I have read papers by qualified mechanical engineers that indicate thet the load of the Alternator is sufficient to prevent it if it really exists. I have just had my BMC 2200cc engine refurbished and although it needed a rebore there was no evidence of bore glaze and I have alwas run the engine out of gear when charging the batteries when moored up.

This perception was/is quite widespread and led to a great many boaters running their engines in gear when moored up and charging their batteries.

 

BW soon realised just how much bank erosion this causes (leading IIRC to a bank collapse at one particular location) that they outlawed it so it is now forbidden.

 

So if you're still concerned about bore glaze you'll just have to do a bit more cruising!

 

Paul

[WJM]

It is very common to see a narrowboat moored up with the engine running in gear with a jet of water being propelled out behind the boat. It is a bit like the perception that a car that only toodles round town needs to be blasted up the motorway every now and again to 'clear it out'

 

Whatever the myth, I understand that most modern engines will not run cleanly or properly if they are colder than 80 degrees, you get incomplete combustion leading to dirty exhaust and unburned fuel sticking to the internal components- so the argument for running in gear is to keep the engine temperature up. I would have thought you could raise the temperature just as easily by increasing the revs while out of gear.

[onthecut]

Bore glaze, at least by repute, is more common on Perkins than BMC. Broadly it's like a coat of varnish on the cylinder bores which prevents the correct retention of oil on the bores. In turn, this means the piston rings don't seal as well as they should and oil consumption and smoke is increased. A reasonable output alternator controlled by an Adverc, or similar should easily apply enough load on the typical narrowboat BMC to give it something to work at. Good point, though, to ensure the temperature is in the mid to upper eighties (Centigrade !).

 

Mike.

[zenataomm]

I used to have a Lister HA2 which developed glazed bores due to battery charging in neutral, so maybe it's the slower running lumps that like a bit of load on them.

I also had a BMC 1500 in a Dawncraft, and that hated tickover in neutral, but that was due to harmonics I suspect as it used to try and shake the boat apart.

[bristol & argo]

It is very common to see a narrowboat moored up with the engine running in gear with a jet of water being propelled out behind the boat.

 

Yes, i just love finding someone has set up a whirlpool, when poling the boat/boats back to a winding hole or from the water point.

 

Assuming the water is taking me into them i don't mind so much, it's when i have to fight to not hit their neighbours i get p'd off.

 

 

 

Simon.

[Chris-B]

Yes, i just love finding someone has set up a whirlpool, when poling the boat/boats back to a winding hole or from the water point.

 

Assuming the water is taking me into them i don't mind so much, it's when i have to fight to not hit their neighbours i get p'd off.

Simon.

 

Usually for us the "considerate" person with the whirlpool coming out of the back of their boat is normally our next door neighbour !

Just as we are bring our boat back into a tight gap..

[Dave-Shrop]

Barrus Shire-Yanmar recomend Section 4 manual - the engine is run at or near full load for 15 minutes (maxium revs) in gear every 50 hrs to disperse accumulated carbon and condensation enhancing engine life and reducing emissions.

 

David

[Supermalc]

Bore glazing is when the cylinder walls and rings become finely polished, so as to limit the seal between the two. Pistons fitted with chrome rings can be particularly prone to this.

 

I have seen an example where a newly reconditioned petrol engine was fitted. It is usual to let a newly reconditioned engine tick over for a few minutes, before taking it for a gentle drive to run it in. In this instance, the vehicle smoked excessively........and I mean excessively.

 

The reconditioners were called out, and he 'did something' to the engine, then took if for a drive. It returned 20 minutes later with hardly any smoke.

 

A friend who repaired tractors had a similar experience, when he fitted new pistons and liners to a tractor. He told the farmer to work it from the first, but the farmer was too gentle and similar bore glazing took place.

 

I've discovered you can get a substance, a bit like Brasso.......an abraisive liquid that you put into the air cleaner. This has the effect of sandpapering the bores, without taking the engine apart. Far better to prevent bore glazing in the first place though.

 

Many years ago an older friend told me he had to take a car back to Vauxhall for it's first service. I think his father had sold it new. Well while he was waiting he heard a car thrashing round the test track. Being curious he looked over the fence, only to see it was non other than the Vauxhall he had taken. They were doing the 'decoke' by thrashing it.

 

These are factual accounts, not urban myth.

 

Engines with glazed bores smoke and use oil, just as engines with worn pistons and bores do. Gasses from the pressure of compustion are allowed past into the sump, causing excessive crankcase compression. The oil is then blown back up past the rings, only to be burnt on the next firing of that cylinder.

[Yoda]

Jaguar made an engine with chromed bores and piston rings. They never did run in and had excessive oil consumption.

[David Schweizer]

Bore glaze, at least by repute, is more common on Perkins than BMC. Broadly it's like a coat of varnish on the cylinder bores which prevents the correct retention of oil on the bores. In turn, this means the piston rings don't seal as well as they should and oil consumption and smoke is increased. A reasonable output alternator controlled by an Adverc, or similar should easily apply enough load on the typical narrowboat BMC to give it something to work at. Good point, though, to ensure the temperature is in the mid to upper eighties (Centigrade !).

 

Mike.

According to the manuals which I have, the standard thermostat for the BMC 1.5 (and all other BMC Marine diesels) opens at 82 degrees celcius which usually means that the engine temperature is maintained at about 80 degrees. This is presumably the correct working temperature for the BMC 1.5 not mid to upper 80's. The only alternative suggested is one that opens at 74 degrees celcius.

[GUMPY]

Usually for us the "considerate" person with the whirlpool coming out of the back of their boat is normally our next door neighbour !Just as we are bring our boat back into a tight gap..

I find a strategically dropped old wet sweat shirt usually sorts this out

 

 

I've discovered you can get a substance, a bit like Brasso.......an abraisive liquid that you put into the air cleaner. This has the effect of sandpapering the bores, without taking the engine apart. Far better to prevent bore glazing in the first place though.

 

Except the good stuff is nothing like brasso its a fuel additive from morris lubricants

http://www.morrislubricants.com/productinf...?v06c41q7p6=FMH

The way it works is that every bore has honing marks in it, when a bore is glazed these marks are filled with a varnish like substance all that glazebuster does is disolve the substance in the marks, no abrasion at all.

 

J

Edited December 10, 2007 by idleness

[Guest]

I have often wondered whether running a moored boat in gear will increase or decrease the cooling effect to the skin tank?

[bottle]

Depends if it is reverse or forward.

 

 

 

 

 

I'll get my coat, shall I.

[PeterF]

Depends if it is interally or externally heat transfer limited, i.e. is the lowest heat transfer coefficient on the inside of the tank or the canal water side. Also does the skin tank temperature generate enough natural convection when out of gear to remove the heat successfully anyway. The final thought of course is how much heat conducts along the side and bottom of the boat, which acts as a large cooling fin on the skin tank (no I am not expecting a calculated reply to this one).

[magnetman]

I've heard from a knowledgeable chap who's had a BMC 1.5 30+ yrs that the advice of running in gear when charging was introduced by Lister when they started fitting AIR COOLED engines in narrowboats. Apparently they are unlikely to reach their correct working temperature when off load. High speed water cooled engines (like BMC) will generally get up to temperature whatever the load.

[dor]

Don't think anyone has mentioned type of oil. As I understand it, modern additive-rich oils in old type of engines increases the risk of bore-glazing. Using a more basic oil, such as API-CC or -CD is better for low-load running, oils with lots of fancy additives are more suited to higher reving , higher loaded turbos and the like.

[onthecut]

Don't think anyone has mentioned type of oil. As I understand it, modern additive-rich oils in old type of engines increases the risk of bore-glazing. Using a more basic oil, such as API-CC or -CD is better for low-load running, oils with lots of fancy additives are more suited to higher reving , higher loaded turbos and the like.

 

 

Spot on. (and changed from time to time !!)

 

Mike.

[David Schweizer]

Don't think anyone has mentioned type of oil. As I understand it, modern additive-rich oils in old type of engines increases the risk of bore-glazing. Using a more basic oil, such as API-CC or -CD is better for low-load running, oils with lots of fancy additives are more suited to higher reving , higher loaded turbos and the like.

Yes. On the advice of Morris Oils I use their Supreme 30 Oil, which is a straight 30 grade API-CC oil in my BMC 1.5 engine.