Of skin tanks and breathers

[p6rob]

Having recently re-commissioned a BMC 1.5 I've noticed there are a few re-occurring threads (which my boat is also affected with) and was wondering if anyone has tried the following cures, if so did they work?

 

Breathing - currently my boat has a pipe running from the rocker cover breather pipe which leads down to the drip tray in the bilge and produces an oil slick. There is also a vent on one of the tappet chest covers which has no pipework or filter. No air filter at the moment either.

I'm thinking of adding a boy racer style oil catch tank which will take the oily fumes from both engine outlets and have a, hopefully clean, return to the stub on the air filter I'm going to buy.

 

Cooling - As far as I can tell there is no thermostat in the cooling system, well definitely not in the engine thermostat housing anyway. The engine has a bowman heat exchanger and two keel cooling tanks. The tanks are: 26" * 20" * 2" and 28" * 19" * 3" as measured inside the engine 'ole. The bottom of the first tank is fed from the bottom of the water pump and the bottom of the second tank is fed from the top of the first tank. The top of the second tank returns coolant to the bowman. There's a calorifier which heats two cabin radiators fed from what would be the heater connections on a car. Short term I'm thinking of adding a heater matrix in series after the calorifier and either sticking it on the roof with fans blowing through it, or suspending it in the canal somehow. Long term, I'd like to add some extra heat exchangers somewhere in the main circuit.

 

Any other ideas gratefully received.

 

Also, having snapped the bleed screw on the idle governor and replaced it with a std screw, I need to adjust the idle operation, what is the procedure? or is there anywhere that sells the right screw?

 

Thanks in advance

 

Robert

 

[springy]

<snip>

There's a calorifier which heats two cabin radiators fed from what would be the heater connections on a car. Short term I'm thinking of adding a heater matrix in series after the calorifier and either sticking it on the roof with fans blowing through it, or suspending it in the canal somehow. Long term, I'd like to add some extra heat exchangers somewhere in the main circuit.

<snip>

 

the engine "should" only heat the calorifier - if the cabin radiators are being heated by convection then your hot water wont last long. If you add anything to this circuit then you will have to bleed the circuit at any high points, and ideally the highest point should be lower than the top of the header tank - tricky to put a heater matrix on the roof !

 

 

<snip>

 

Also, having snapped the bleed screw on the idle governor and replaced it with a std screw, I need to adjust the idle operation, what is the procedure? or is there anywhere that sells the right screw?

 

<snip>

 

 

Is this the right bleed screw

 

http://www.ssldieselparts.co.uk/fittings-screw-pumps-c-9_123.html

 

 

springy

Edited April 17, 2013 by springy

[alan_fincher]

A missing thermostat is often indicative of someone having thought (usually incorrectly!) that it will deal with some kind of overheating problem that has been encountered.

 

I would suggest it is not good practice to leave it out, as it may stop the engine reaching a sensible operating temperature.

 

I would have thought it also ha the potential to make heating the calorifier a lot less effective than it could be.

Normal values are usually 74 degrees or 82 degrees.

 

Skin tanks as much as 3" thick are not really ideal, as extra water doesn't actually increase the area that is being cooled by the canal, but the amount of expansion that will result in such a large volume of water will often overwhelm a standard Bowman or Polar header tank.

[Iain_S]

(snip)

Breathing - currently my boat has a pipe running from the rocker cover breather pipe which leads down to the drip tray in the bilge and produces an oil slick. There is also a vent on one of the tappet chest covers which has no pipework or filter. No air filter at the moment either.

I'm thinking of adding a boy racer style oil catch tank which will take the oily fumes from both engine outlets and have a, hopefully clean, return to the stub on the air filter I'm going to buy.

 

(snip)

Robert

 

If I recall correctly, the usual set up is a breather pipe from the rocker cover to the air filter. The idea is that oil fumes are burnt in the engine. Snag is that when engne gets a bit worn, there are more fumes, and oil tends to collect in the air filter box, and can get a bit messy, as well as requiring more frequent replacement of air filter (unless it's an oil bath one )

 

Iain

[Tony Brooks]

If I recall correctly, the usual set up is a breather pipe from the rocker cover to the air filter. The idea is that oil fumes are burnt in the engine. Snag is that when engne gets a bit worn, there are more fumes, and oil tends to collect in the air filter box, and can get a bit messy, as well as requiring more frequent replacement of air filter (unless it's an oil bath one )

 

Iain

 

So the OP should stick his hose into a milk bottle or something and empty/change it now and again.

 

SNIP

 

Also, having snapped the bleed screw on the idle governor and replaced it with a std screw, I need to adjust the idle operation, what is the procedure? or is there anywhere that sells the right screw?

 

Thanks in advance

 

Robert

 

 

If it is just the bleed screw itself then as long as it is forming an airtight seal you do not need to change it.

 

The 1.5 DPA pump comes in two types. One with an idle adjusting screw that looks a bit like an old carburettor mixture screw and the later one has a bleed screw let into the idle DAMPER. This is not the idle adjustment. On these pumps that is done by a screw acting as a control lever stop.

 

Inferring from what you wrote I suspect you have the latter pump and, as so many have done before you, you have snapped the idle damper. Any decent fuel injection specialist (usually one at least in all major towns) should be able to supply a new one but then you need to adjust it.

 

Please do NOT bleed from this screw in the future, just stick with the one on the body and 98% of the time it will be fine.

[Iain_S]

(snip)

Cooling - As far as I can tell there is no thermostat in the cooling system, well definitely not in the engine thermostat housing anyway. The engine has a bowman heat exchanger and two keel cooling tanks. The tanks are: 26" * 20" * 2" and 28" * 19" * 3" as measured inside the engine 'ole. The bottom of the first tank is fed from the bottom of the water pump and the bottom of the second tank is fed from the top of the first tank. The top of the second tank returns coolant to the bowman. There's a calorifier which heats two cabin radiators fed from what would be the heater connections on a car. Short term I'm thinking of adding a heater matrix in series after the calorifier and either sticking it on the roof with fans blowing through it, or suspending it in the canal somehow. Long term, I'd like to add some extra heat exchangers somewhere in the main circuit.

(snip)

By my calculations, that gives about 7.3 ft² cooling area, which should be enough. As has been said, the tanks are a bit on the wide side, which may make them less effective, as some of the water may pass through without contact with the sides, IYSWIM! More important, however, is the presence or absence of baffles in the tanks; no baffles makes a very inefficient tank. (On Copperkins, we used to overheat after about 10 minutes of running hard; now that the tank has had baffles fitted, the temp. gauge (once warmed up) hardly moves.

 

Iain

 

P.S. I think you've got the circulation the wrong way round : top of pump to heat exchanger, to top of first tank, bottom of first tank to top of next, bottom of that tank to pump intake.

 

So the OP should stick his hose into a milk bottle or something and empty/change it now and again.

 

SNIP

 

Agreed

Iain

Edited April 17, 2013 by Iain_S

[p6rob]

the engine "should" only heat the calorifier - if the cabin radiators are being heated by convection then your hot water wont last long. If you add anything to this circuit then you will have to bleed the circuit at any high points, and ideally the highest point should be lower than the top of the header tank - tricky to put a heater matrix on the roof !

 

 

<snip>

 

Also, having snapped the bleed screw on the idle governor and replaced it with a std screw, I need to adjust the idle operation, what is the procedure? or is there anywhere that sells the right screw?

 

<snip>

 

 

Is this the right bleed screw

 

http://www.ssldieselparts.co.uk/fittings-screw-pumps-c-9_123.html

 

 

springy

Hi Springy,

I think the calorifier is heated by the engine and the rads are heated by the calorifier. It doesn't seem terribly effective, would adding thermostatic valves between engine and calorifier help keep the heat in the cabin?

 

As for the screws, unfortunately not. I saw a thread about these somewhere else and bought one of each. One is right for the lower bleed screw on the DPA but not the broken idle governor one.

 

So the OP should stick his hose into a milk bottle or something and empty/change it now and again.

 

SNIP

 

Also, having snapped the bleed screw on the idle governor and replaced it with a std screw, I need to adjust the idle operation, what is the procedure? or is there anywhere that sells the right screw?

 

Thanks in advance

 

Robert

 

 

If it is just the bleed screw itself then as long as it is forming an airtight seal you do not need to change it.

 

The 1.5 DPA pump comes in two types. One with an idle adjusting screw that looks a bit like an old carburettor mixture screw and the later one has a bleed screw let into the idle DAMPER. This is not the idle adjustment. On these pumps that is done by a screw acting as a control lever stop.

 

Inferring from what you wrote I suspect you have the latter pump and, as so many have done before you, you have snapped the idle damper. Any decent fuel injection specialist (usually one at least in all major towns) should be able to supply a new one but then you need to adjust it.

 

Please do NOT bleed from this screw in the future, just stick with the one on the body and 98% of the time it will be fine.

You're right Tony, it's the latter. I've learned my lesson and will never use that bleedin screw again. What is the procedure for adjusting it? I found, when warm and in neutral, the idle is raised, in gear it drops to a more normal level. I'm assuming it's something to do with the amount of spring tension on the damper needle. The bolt I've used is a little longer than it should be.

 

By my calculations, that gives about 7.3 ft² cooling area, which should be enough. As has been said, the tanks are a bit on the wide side, which may make them less effective, as some of the water may pass through without contact with the sides, IYSWIM! More important, however, is the presence or absence of baffles in the tanks; no baffles makes a very inefficient tank. (On Copperkins, we used to overheat after about 10 minutes of running hard; now that the tank has had baffles fitted, the temp. gauge (once warmed up) hardly moves.

 

Iain

 

P.S. I think you've got the circulation the wrong way round : top of pump to heat exchanger, to top of first tank, bottom of first tank to top of next, bottom of that tank to pump intake.

 

 

Agreed

Iain

I thought the BMC required more like 11 ftsq of cooling.

I could well have the circuit wrong. My brain struggles working things out while peering over the top of the engine and now I'm nowhere near the boat and haven't any pictures which show it in enough detail.

All I know is there is a pipe from the engine (or bowman), on the left hand side with gearbox oil pipes, that then goes into the bottom of the port skin tank. The top pipe from this goes across the engine bay to the bottom of the starboard skin tank and the top pipe from this goes to the engine, or bowman.

[springy]

Hi Springy,

I think the calorifier is heated by the engine and the rads are heated by the calorifier. It doesn't seem terribly effective, would adding thermostatic valves between engine and calorifier help keep the heat in the cabin?

 

<snip>

 

It just occurred to me to wonder if there is any other heat input into your radiator circuit ? - you dont mention one.

 

Is there forced circulation around the radiator/calorifier circuit ?

 

Yes the calorifier is heated by the engine, but ideally you arrange it so that the water stays hot for a few hours at least (say overnight) rather than passing all that heat on to the ch system, you could achieve something with thermostatically controlled valves (not I think with thermostatic radiator valves) but I get the impression you actually want the heat in the cabin ?

 

springy

Edited April 17, 2013 by springy

[p6rob]

I'm guessing using a milk bottle is equivelant to a catch tank without the expense or installation complexity, or boy racer connotations. Hmmm, remember that for next time

[alan_fincher]

I thought the BMC required more like 11 ftsq of cooling.

From my experience, provided it is baffled and well designed your current 7.3 sq ft will probably be fine, although a bit more would be no bad thing.

 

We had ours rebuilt, and it is now a single tank of about 9.4 square feet, which has so far always proved to be well more than adequate.

[p6rob]

Hi Really struggling trying to work out how to effectively quote passages from this thread. This is in reply to #3:

 

A missing thermostat is often indicative of someone having thought (usually incorrectly!) that it will deal with some kind of overheating problem that has been encountered.

 

I would suggest it is not good practice to leave it out, as it may stop the engine reaching a sensible operating temperature.

 

Agreed, ultimately it will get sorted properly

 

 

I would have thought it also ha the potential to make heating the calorifier a lot less effective than it could be.

 

This is one of the issues that needs looking at. At the moment, if you drive the boat for about an hour, the cabin radiators are getting nicely warm. However, once the engine is stopped, within about 40 minutes the cabin radiators are cold. I think the calorifier is only about 25litres and I think it's not a pumped circuit.

Normal values are usually 74 degrees or 82 degrees.

 

Thank you, that's useful to know. Presumably the hotter one is better once the cooling system is running properly.

 

Skin tanks as much as 3" thick are not really ideal, as extra water doesn't actually increase the area that is being cooled by the canal, but the amount of expansion that will result in such a large volume of water will often overwhelm a standard Bowman or Polar header tank.

 

There are lots of things on this boat that are less than ideal, but, as long as you guys are so helpful, we will get it there

 

Thanks again for all the advice

[RLWP]

 

I'm guessing using a milk bottle is equivelant to a catch tank without the expense or installation complexity, or boy racer connotations. Hmmm, remember that for next time

 

And it gives you an idea of just how much oil is getting where i shouldn't

 

Richard

[Iain_S]

 

I'm guessing using a milk bottle is equivelant to a catch tank without the expense or installation complexity, or boy racer connotations. Hmmm, remember that for next time

It's a marine catch tank. (Doesn't have to be a milk bottle, though)

 

Iain

[Tony Brooks]

You're right Tony, it's the latter. I've learned my lesson and will never use that bleedin screw again. What is the procedure for adjusting it? I found, when warm and in neutral, the idle is raised, in gear it drops to a more normal level. I'm assuming it's something to do with the amount of spring tension on the damper needle. The bolt I've used is a little longer than it should be.

 

I always followed the manual but it would not hurt to gently adjust it a flat at a time as long as you know where to put it back to.

 

I am not convinced this is a damper problem but it will not hurt to experiment.

[Mike Jordan]

Your cooling pipes seem to be the wrong way round from the discription. The hot from the engine should go to the top of the skin tank and the cold return from the bottom to the top of the other tank. putting hot water in at the bottom will simply cause it to rise straight to the top and be drawn back into the engine without much cooling having taken place.

[alan_fincher]

Your cooling pipes seem to be the wrong way round from the discription. The hot from the engine should go to the top of the skin tank and the cold return from the bottom to the top of the other tank. putting hot water in at the bottom will simply cause it to rise straight to the top and be drawn back into the engine without much cooling having taken place.

I took it that the pipes were correctly described as where they should be, but that the flow wasin the other direction to that implied in the post.

[Mike Jordan]

You are right Alan, I must have been sleeping at the wheel when I read the OP.

Mike.

[smileypete]

Breathing - currently my boat has a pipe running from the rocker cover breather pipe which leads down to the drip tray in the bilge and produces an oil slick. There is also a vent on one of the tappet chest covers which has no pipework or filter. No air filter at the moment either.

I'm thinking of adding a boy racer style oil catch tank which will take the oily fumes from both engine outlets and have a, hopefully clean, return to the stub on the air filter I'm going to buy.

The BMC was sometimes fitted with a crankcase breather system that had a crude oil mist separator made of a ball of mesh like a pot scourer or kettle limescale thing. The idea was to catch most of the oil mist and let it run back to crankcase but sometimes the mesh eventually got blocked up causing problems.

 

Try a forum search on 'crankcase breather'. If there's a lot of oil mist then just having an open pipe into a bottle may mean that most of it ends going everywhere.

 

As for the cooling I reckon some older boats had the thermostat removed to stop the calorifer getting too hot and scalding people, but these days a thermostatic shower mixer, or TMV on the calorifier outlet, would be better. If replacing the engine thermostat I'd keep a very close eye on engine temp, it might have been done as a bodge to deal with some problem.

 

cheers, Pete.

~smpt~

Edited April 18, 2013 by smileypete