BMC 1800

[Hair Bear Bunch]

Hi! New here so be gentle please?!

Ok, BMC 1800 diesel, Bowman marinising gear, 35 yrs old, head last removed about 20 yrs ago.

On turning over from cold, it makes a chuffing noise from the air intake. As soon as it starts the noise dissapears. Now, run for about an hour at half throttle under load and the noise starts again. No misfire or rough running, a steel ruler on the injectors didn't reveal anything. shut back to about quarter throttle for about ten minuites then shut back to tick over no load, remove aircleaner cover and the noise is very clear, then after a few minuites the noise slowly dies away! Open up again to half throttle under load all ok but after a while the noise is back. Beats the hell out of me! I've been told to try a product called 10K, a sort of aerosol decoke, but before that, or a complete strip down (the engine that is!) anyone got any ideas? Thanks.

[John Orentas]

Don't fully understand your post but could be a sticking valve, also they fitted various types of breather mechanisms on BMC's could be something like that, what is this about the steel ruler? Diesel Red-Ex works for sticking valves but lets get a bit clearer on the symptoms.

[Supermalc]

Just a quick thought. Has a cam follower got a hollow, and the tappet has been set leaving the valve clearance too small when the follower turns. Shot in the dark, that's all.

[Hair Bear Bunch]

Hi, Thanks for your help. I would have thought a sticking valve to produce a misfire of some sort? Still, it looks like a head off type job but will certainly give RedX a try first.

Now, the steel ruler. A trick we used to use on tractor a lot, or any diesel engine as long as it's solidly mounted. Hold one end of the ruler to your ear, then rest the other end firmly on each injector in turn. You should be able to distiguish a non firing cylinder as it will have a diferent sound. Don't try it on a diesel car as the engine generally jumps around too much and could cause the ruler to give more than a nasty bruise!

Again, thanks for the info.

[Hairy-Neil]

The old makeshift stethoscope trick, been doing it for years on cars, lorrries, coaches etc but usually using a long screwdriver or even a long length of rod. Also good for detecting the location of worn bearings......

[DHutch]

Yeah, we use that on the steam enigne too, to find or narrow down knocks.

- Infact, it will rev that low, you can place a lengh of wood on the big end, or other moving part, and feel for a knock.

 

 

Daniel

Edited October 2, 2006 by dhutch

[David]

Hi Sounds very like carbon build up in one or more of the exhaust ports, the "chuff" which sounds much like an old time steam train is the gases squeezing their way out and can be heard at the air intake by reason of the inlet ports proximity. The disappearance of the noise is due to the carbon getting blown out a little, sufficent to allow the gas to escape a bit easier, but it very soon builds up again hence more chuffing.

Removal of the Bowman heat exchanger may allow you to see into the port to confirm the carbon build up. After 20 years a de-coke would be a treat for the engine, remember engines of that era petrol and diesel it was common to de-coke on a regular basis.

david

[Sir Nibble]

Logically, this has to be a valve problem with combustion pressures getting past an inlet valve. Not that anything has to be logical of course! Bear in mind that valves usually rotate a degree or two at each opening and that could account for the intermittant nature of the problem. It's head off time! but then you knew that didn't you.

[John Orentas]

Logically, this has to be a valve problem with combustion pressures getting past an inlet valve. Not that anything has to be logical of course! Bear in mind that valves usually rotate a degree or two at each opening and that could account for the intermittant nature of the problem. It's head off time! but then you knew that didn't you.

 

 

That's a bit drastic, I would like to hear a bit more about the symptoms first, as I said earlier those breathers fitted sometimes with one-way valve can sometimes sound very odd. The problem with these engines they have been around for such a long time there are a million little variations. If you take the head off and find bores an valves are ok, what then?

 

Is it using / burning much oil, does it start ok, does it misfire, what type of inlet filter is fitted, does it smoke much, if so under what conditions.

[Yamanx]

Does it matter?

[Sir Nibble]

head last removed about 20 yrs ago.

It's head off time! but then you knew that didn't you.

[tomsk]

QUOTE

head last removed about 20 yrs ago.

 

 

QUOTE

It's head off time! but then you knew that didn't you.

 

VERY CUTE!!!

[David]

Hi

Just so you know the BMC 1800 of that age had no breathers or any fancy emission controls. When Thorneycrofts was the real Thorneycrofts and marinised those engines in their premises by Factory Locks Tipton and a Thorneycroft engine was the beesknees they put a pieces of rubber tube from the steel crankcase breather tube, which was just a piece of steel tube from a cover plate 1 of two on the side of the block, to a spigot on the outer rim of the wire gauze air filter they fitted. The idea being the fumes would be sucked back into the engine along with the small amounts of oil which also escaped via this tube and would just be dumped down on to the road etc when used in the Sherpa van.

I am looking at the Thorneycrofts marine engine 108 parts book (BMC 1800) as I write which shows the whole engine and marinizing parts in exploded detail. If you email me I can maybe let you have more details if thats any help.

david

[John Orentas]

Hi David.

 

What makes you think it is a Thornycroft marinised angine. The original post mentioned Bowman marinising parts but I am not familiar with them, it could just mean a water cooled manifold and a bell housing.

 

Remember there were a lot of back street 'Marinisers' at that time.

[David]

Hi John

Agreed it maynot be a Thorneycroft but I was pointing out they were very simple, by todays standards, in that the base engine before marinizing had no breather valves etc and as in my earlier post they came from a time when de-coking (often annually) was the norm. I myself marinized a 1800 circa 1970'ish in 1983 (Bowman and adaptor plate gearbox etc from Lancing Marine) and visited the Tipton factory having had no idea what to do about the fumes from the breather tube in the enclosed engine space for advice which was readily given along with a gauze filter and tubing and they also gave me the book I refered to as a freebi, don't imagine any engine marinizer would do that today.

David

[Hair Bear Bunch]

Hi, Thanks everyone! What a great response. So to answer some questions...

Cold starting? It's a pig! Even holding the heaters for as long as I dare doesn't help.

Hot starting, on the button every time.

It doesn't burn any oil, but it does loose a little water over a days running. I guess about a pint.

The crankcase breather is a small rubber pipe direct off the side cover to the inlet manifold.

The aircleaner is best described as a "K&N" style two sheets of tin with a wire gauze/mesh arrangement sandwiched between.

It doesn't appear to smoke at all.

The heat exchanger has "Bowman" cast into it, as to any other parts I've no idea.

 

Off to get a gasket set then...

Edited October 5, 2006 by Hair Bear Bunch

[Hairy-Neil]

 

Off to get a gasket set then...

 

Poor cold starting could mean the compressions are down. Before you strip it its worth doing a compression test, it will give you an idea of the general condition of the pistons/rings/bores.

[bottle]

Even holding the heaters for as long as I dare doesn't help

 

How long do you 'hold' them, on some older diesels upto 30 seconds was the norm (need correct and well charged battery)

[Yamanx]

Hi, Thanks everyone! What a great response. So to answer some questions...

Cold starting? It's a pig! Even holding the heaters for as long as I dare doesn't help.

Hot starting, on the button every time.

It doesn't burn any oil, but it does loose a little water over a days running. I guess about a pint.

The crankcase breather is a small rubber pipe direct off the side cover to the inlet manifold.

The aircleaner is best described as a "K&N" style two sheets of tin with a wire gauze/mesh arrangement sandwiched between.

It doesn't appear to smoke at all.

The heat exchanger has "Bowman" cast into it, as to any other parts I've no idea.

 

Off to get a gasket set then...

 

If you get a long series 4mm drill (I think the proper size is 5/32), remove the heater plugs and using a pin chuck or something similar to hold the drill. Turning by hand you can clean out the carbon build up inside the heater plug holes. This will improve your heater plug efficiency and will make starting far easier.

 

If there is a carbon build up, and there will be after a few years of relatively slow running, the heater plugs dont work as they should and heat the carbon instead of the diesel.

 

The opther thing that can cause poor starting is the injection timing. Any smoke at all? What colour?

[Hair Bear Bunch]

Hi All,

I've been using the glow plugs for anything up to a minuite. Now, when it's running there's no perceptible smoke at all. When it first starts from cold I'm sure I've heard fog warnings on the local radio, if I had to give a colour I think white is best description, but it clears within 30 secs. or so.

The 'Carbon' word has appeared again. I think I see a pattern forming here...

[John Orentas]

Hi All,

I've been using the glow plugs for anything up to a minuite. Now, when it's running there's no perceptible smoke at all. When it first starts from cold I'm sure I've heard fog warnings on the local radio, if I had to give a colour I think white is best description, but it clears within 30 secs. or so.

The 'Carbon' word has appeared again. I think I see a pattern forming here...

 

 

What you describe as white smoke is not smoke at all but unburned fuel. This is the only time we get a glimpse of what atomised fuel looks like as it comes out of the injectors.

 

It is possible that one or more of your heater plugs is not working correctly, clean up the injector cavities in the way Yammy suggests. One or two cylinders are not firing up as quickly as the others for the above or some other reason.

Edited October 6, 2006 by John Orentas

[David]

Hi

Agree with John the white smoke is unburnt fuel, if no smoke when running the timing should be OK (if white smoke when running the timing needs advancing).

The bit's and bob's like air cleaner and the tube etc sound pretty standard for that engine (if it is a Thorneycroft they fixed an engine label to the block at one time)

Concerned that you are losing water, if you cannot find a reason like a leak on a hose etc then you may have a crack in the head, that engine was also prone to cracking between the valve seats, which just may be why it is difficult to start. If you have already cleaned the heaterplugs and check they are all working as on that engine one or two could fail but the others still worked, you might have to consider a crack.

If you run the engine with the cap off the Bowman cooler look carefully at the water as is swirls through, if it appears to have bubbles in the water that indicates a crack, hope not as as they are not cheap to replace.

david

[Hair Bear Bunch]

Looks like a winter project so I'll let you know!

Oh how I'm looking forward to this...

[Hair Bear Bunch]

Well there's a thing! Nothing wrong with the injectors, or heater plugs, head gasket ok. the compression was slightly down on no.2, so we had a suspect.

Closer investigation showed a slight mark in the top of no.2 piston, could it be a valve? Surely not. Stripped the head to do the valve seats, and had to drift out valves 1-4! They were in so tight I can only assume they were sticking open allowing the chuff noise, then the tapping noise was the piston closing them again!

Going to rebuild tomorrow so will let you know how it goes!

By the way, can these engines be fitted with a bendix starter rather than the unreliable pre-engaged unit it has at the moment?

Thanks, Rob.

[Alec Gatherer]

Thank you very much for updating this thread. Our collective experience can be enhanced if people who ask for suggestions keep us posted and report eventual conclusions. Most helpful.