BMC engine overheating

[Victor Vectis]

2 hours ago, Furness said:

Lighten and simplicate.

[Attributed to Sir Geoffrey De Haviland,of Tiger Moth and Mosquito fame]

I know this as 'Add lightness and simplify' and coming from Edward Turner, the designer of Triumph motorbikes.

(Or more specifically the speed twin engine)

Edited January 22, 2018 by Victor Vectis
Oops, spellin'.

[Dean1977]

50 minutes ago, RLWP said:

Which is fine (well, not really, let's do some more searching)

On the front of the engine is another water pump driven by the vee belt that also drives the alternator. What is that piped up to?

Richard

So are we thinking that the cast alloy thing in picture 2 is a heat exchanger?  As for the engine water pump not sure where that is pumped too. I'm next at the boat on Saturday.

[RLWP]

2 hours ago, Victor Vectis said:

I know this as 'Add lightness and simplify' and coming from Edward Turner, the designer of Triumph motorbikes.

(Or more specifically the speed twin engine)

I recognise 'Add Lightness' as Colin Chapman of Lotus

Truth be told, it's got many attributions if you check

Richard

2 hours ago, Dean1977 said:

So are we thinking that the cast alloy thing in picture 2 is a heat exchanger?  As for the engine water pump not sure where that is pumped too. I'm next at the boat on Saturday.

The horrible greeny thing at the back - yes that looks possible

Richard

[Tony Brooks]

Yes, I think that is a heat exchanger. The two large pipes in the side carry engine coolant that is circulated by the pump that has the alternator belt driving it. This circuit almost certainly goes to the larger diameter cylindrical thing with the little car expansion tank piped to it. I think both are header tanks.

The smaller pipe in the top plus one I can not see in the bottom cover should carry raw water from the brass pump but it could be on the suction or pressure side of that pump.

If you take the end caps off you will see the ends of the tube stack. The caps and the stack are normally sealed by a pair of O rings so if you take the cap off do not pull the O ring out or take the tube stack out because the O rings will probably distorted.

On the engine bed beside the gearbox there is another smaller cylindrical thing with oil pipes connected to the side of the body and raw water pipes connected to either end. This is the gearbox oil cooler and also has a tube stack in it. I suspect its on the suction side of the raw water pump. Thus also has a tube stack in it but no O rings.

BOTH TUBE STACKS ARE SUBJECT TO BLOCKING ON THE INLET SIDE BE DEBRIS IN THE RAW WATER - especially if you have no strainer in the sea inlet or close to it (hence my request for a photo of it. At least reverse flush both tube stacks or better still take the heat exchanger end caps off and make sure they are debris free. The oil cooler is harder a sit has no end caps so at least reverse flush it.

You sea inlet may have a gauze/strainer on the outside of the hull. These can block with mud and things like bread wrappers can get sucked into them so they clog the holes/slots. It can also happen if there is just a hole in the hull. The pipe work/ cap needs removing and a piece of wire coat hanger pushed down to make sure the hole in the hull is not blocked.  Do not try with a mooring stake in case you do have a stainer on the outside of the hull, you need thin strong steel to poke through the holes or slots in any external strainer.

See my post about the gasket on the raw water pump and the need for suction tight hoses & joints on the raw water part of the system.

If the brass pump impeller has shed any wings in the past they may have jammed across an elbow in the raw water system as may any small sticks that have been drawn through the raw water system. These then collect debris and block the pipe. This needs checking.

Once you have reassembled your system and checked the above come back if you can not get plenty of water coming from the exhaust with the engine running.

 

 

[Bee]

I thought that green thing was some sort of water inlet filter from a destroyer or something but now I see it as others have, i.e. its a heat exchanger, I have a heat exchanger on my boat and the water is filtered before it gets to it, there is also a strainer on the outside of the hull. I can guarantee that if I took the end off the thing that there will be a bit of weed and crud in it and a couple of blocked tubes, Therefore I would bet my entire life savings that if there is a tube stack in that green thing it will be blocked. It needs to be taken apart and sorted but be careful, you could sink the boat. (Or is there an inlet on / off valve at the end of that inch dia. copper tube?)

Edited January 23, 2018 by Bee

[Tony Brooks]

Remember that typically the gearbox oil cooler tube stack comes first in the raw water flow so that is often the first one to block but both need cleaning.

I agree that there should be a filter/strainer as part of or close to the sea inlet and the scant description Dean has given us there just might be under the blanking nut on top but on this boat there is no way to be sure without visiting it or getting photos. If there is a stainer in the sea inlet then my bet is its that that's blocked but the oil cooler and heat excharger (raw water sides) still need cleaning/checking.

[Dean1977]

37 minutes ago, Bee said:

I thought that green thing was some sort of water inlet filter from a destroyer or something but now I see it as others have, i.e. its a heat exchanger, I have a heat exchanger on my boat and the water is filtered before it gets to it, there is also a strainer on the outside of the hull. I can guarantee that if I took the end off the thing that there will be a bit of weed and crud in it and a couple of blocked tubes, Therefore I would bet my entire life savings that if there is a tube stack in that green thing it will be blocked. It needs to be taken apart and sorted but be careful, you could sink the boat. (Or is there an inlet on / off valve at the end of that inch dia. copper tube?)

i to thought that it was some sort of medieval inlet filter.

[Dean1977]

31 minutes ago, Tony Brooks said:

Remember that typically the gearbox oil cooler tube stack comes first in the raw water flow so that is often the first one to block but both need cleaning.

I agree that there should be a filter/strainer as part of or close to the sea inlet and the scant description Dean has given us there just might be under the blanking nut on top but on this boat there is no way to be sure without visiting it or getting photos. If there is a stainer in the sea inlet then my bet is its that that's blocked but the oil cooler and heat excharger (raw water sides) still need cleaning/checking.

i am almost certain that the gearbox cooler is after the heat exchanger could this be a problem? could i do away with the header tank assembly, and fit a standard clear modern type, also any recommendation on what type or make filter/strainer to fit? 

[Tony Brooks]

Yes it could because the oil cooler needs the coolest water but at canal speeds and powers I doubt it matters much.

Yes you could fit a Bowman type manifold/heat exchanger but I would advise against the Polar equivalent because they are no longer produced and there are issues with Polar rubber end caps. Not sure what you mean by "clear". If you mean one without a tube stack then no, that is unless you want to also fit keel cooler pipes outside the hull but I would not advise that for canal use.

Consider the big cylindrical thing plus the small car expansion tank as one thing. Yes you could fit any expansion tank in its place but once you get to know your system I can see no reason what you have will not be perfectly satisfactory until the mild steel rusts through. If you are going to change it then the dangers of that mild steel exhaust manifold rusting through, letting water into the cylinders, and doing four figures worth of damage I would suggest that you take your time and seek out a second-hand Bowman manifold/heat exchanger. You would also nee the exhaust mixing elbow & fittings. If you keep your existing heat exchanger you may well find a cast iron manifold from a direct raw water cooled BMC 1.5 even cheaper.

I have yet to be convinced that you do not have a raw water strainer. Your description indicates to me that you might but without seeing it I can not know - hence my request for a photo. As the vast majority of marinisers put the gearbox oil cooler on the suction side of the brass Jabsco pump I am also not convinced your oil cooler is on the pressure side. Again Photos or circuit diagram.

Probably the cheapest and easiest strainer would be an inline type like:- https://www.asap-supplies.com/fittings-valves-strainers/strainers-and-spares/strainers/economic-remote-water-strainer-402199 

But there are many types. Just make sure its cap is lower than the waterline to make it more difficult to suck in air if the cap seal is not good. If I was fitting a boat from new I would use an all brass one with the cap held on with wing nuts. However on your boat its probably not worth the cost.

Edited January 23, 2018 by Tony Brooks

[Alan de Enfield]

We have this type on the Ocean going Catamaran

 

And this type on our 'coastal' cruiser

 

 

Both types allow you to easily see any captured 'rubbish' and easily clean.

[Tony Brooks]

I like the Sherwood one because the biggest problem with top opening ones is that when you lift the gauze out to clean some muck gets dropped into the bowl and from there is drawn through the raw water system, potentially blocking the heat exchanger & oil cooler.

The only thing to watch is getting the pipe connections correct (if they are not marked) so the dirty raw water goes into the strainer cup and not into the bowl.

 

 

[Dean1977]

Can I just replace the blue header tank assembly for a plastic one out of a car. Of so can anyone recommend one for an easy fit.

On 22/01/2018 at 18:57, RLWP said:

Which is fine (well, not really, let's do some more searching)

On the front of the engine is another water pump driven by the vee belt that also drives the alternator. What is that piped up to?

Richard

So are we thinking that the cast alloy thing in picture 2 is a heat exchanger?  As for the engine water pump not sure where that is pumped too. I'm next at the boat on Saturday.

 

Can I just replace the blue header tank assembly for a plastic one out of a car. Of so can anyone recommend one for an easy fit.

[RLWP]

2 minutes ago, Dean1977 said:

Can I just replace the blue header tank assembly for a plastic one out of a car. Of so can anyone recommend one for an easy fit.

I wouldn't do that just yet. Looking (and guessing) at your system, the water is held in the big blue bit, the change in volume due to heat is done by the small blue header tank. That's a bog standard BMC brass one used on MGBs and MG midgets amongst others. If it is only doing volume change due to heat, it's plenty big enough

If that's how the system works...

We need to know how the pump on the front of the engine is piped up. What you have so far identified are parts of the secondary cooling system, not the bits that directly cool the engine

Richard

[Dalslandia]

The heat exchanger in post #28 look like the oilcooler I have on the Scania D11 for the SCG 700 gearbox

[Tony Brooks]

8 minutes ago, Dean1977 said:

Can I just replace the blue header tank assembly for a plastic one out of a car. Of so can anyone recommend one for an easy fit.

So are we thinking that the cast alloy thing in picture 2 is a heat exchanger?  As for the engine water pump not sure where that is pumped too. I'm next at the boat on Saturday.

 

Can I just replace the blue header tank assembly for a plastic one out of a car. Of so can anyone recommend one for an easy fit.

1. You can but as we are not 100% sure how your system is piped you will save money and do far better to sort out your system as it is first, then get the boat home, and only then start spending money re doing it.

2. If its the think with 3 hexagon bolts holding the top (and bottom) on then yes, I am 99% sure that is what it is although when compared with the Bowman tube stack it looks a  bit small to me..

3. See 1 and note I am not the only one advising you to hold fire on replacing parts.

 

4 minutes ago, Dalslandia said:

The heat exchanger in post #28 look like the oilcooler I have on the Scania D11 for the SCG 700 gearbox

May well be but I expect the rubber O ring seals may be a different material for oil and on your engine its subject to a far higher pressure than a cooling heat exchanger.

[Mad Harold]

22 hours ago, Tony Brooks said:

But there are many types. Just make sure its cap is lower than the waterline to make it more difficult to suck in air if the cap seal is not goo

If the cap of the filter is lower than the waterline,is there a danger that if the seal is not good or there is a leak somewhere in the system,that water could syphon in?

I am also rather baffled by the complexity of this cooling system,[me not coming from a boating background] but having many years of fettling all types of engines [motorbike,car,dumper,aircraft,and lately,outboards.]

Surely Dean would be better off scrapping this system and installing a simple raw water cooling system.[Water in,around the engine,and out]

You can call me a nitwit if you like Mr.Brooks,because I have overlooked this,this,and this,but the engine on my boat [BMC 1500] is cooled in this way,and in the time I have owned it ,has been quite satisfactory. 

[David Mack]

1 minute ago, Furness said:

If the cap of the filter is lower than the waterline,is there a danger that if the seal is not good or there is a leak somewhere in the system,that water could syphon in?

I am also rather baffled by the complexity of this cooling system,[me not coming from a boating background] but having many years of fettling all types of engines [motorbike,car,dumper,aircraft,and lately,outboards.]

Surely Dean would be better off scrapping this system and installing a simple raw water cooling system.[Water in,around the engine,and out]

You can call me a nitwit if you like Mr.Brooks,because I have overlooked this,this,and this,but the engine on my boat [BMC 1500] is cooled in this way,and in the time I have owned it ,has been quite satisfactory. 

If you circulate raw water around a BMC engine you are likely to get more corrosion than if it is a closed circuit with corrosion inhibitor and antifreeze. 

I once had a raw water cooled BMC 1.5 and a core plug rusted through. The resulting jet of water hit the dipstick and ran down into the sump, turning the oil into grey sludgy emulsion.

[MtB]

2 minutes ago, David Mack said:

If you circulate raw water around a BMC engine you are likely to get more corrosion than if it is a closed circuit with corrosion inhibitor and antifreeze. 

I once had a raw water cooled BMC 1.5 and a core plug rusted through. The resulting jet of water hit the dipstick and ran down into the sump, turning the oil into grey sludgy emulsion.

Quite.

The BMC is not designed for raw water cooling. The constant flow of freshly-oxygenated water corrodes steel, and the thin steel core plugs will rust through. 

[Mad Harold]

22 minutes ago, Mike the Boilerman said:

Quite.

The BMC is not designed for raw water cooling. The constant flow of freshly-oxygenated water corrodes steel, and the thin steel core plugs will rust through. 

Thank you for the reply,but as far as I am aware,my boat has had raw water cooling from new. [1978].

Core plugs are £3-56 from ASAP supplies,and a thermostat without shutoff is£5.

There are drawbacks to raw water cooling,but in my humble opinion,these are outweighed by the simplicity of it.

[MtB]

Just now, Furness said:

Thank you for the reply,but as far as I am aware,my boat has had raw water cooling from new. [1978].

Core plugs are £3-56 from ASAP supplies,and a thermostat without shutoff is£5.

There are drawbacks to raw water cooling,but in my humble opinion,these are outweighed by the simplicity of it.

 

I get what you're saying, but a rusted though core plug is capable of sinking the boat and this is one reason SOME people prefer indirect cooling on a BMC. You may be a dab hand at replacing them but a lot of boaters these days would not know how or be the slightest it interested in learning. AND want to rest easy there is no risk of sinking from one rusting through. 

 

Is your raw water cooling thermostatically controlled?

[Tony Brooks]

58 minutes ago, Furness said:

If the cap of the filter is lower than the waterline,is there a danger that if the seal is not good or there is a leak somewhere in the system,that water could syphon in?

I am also rather baffled by the complexity of this cooling system,[me not coming from a boating background] but having many years of fettling all types of engines [motorbike,car,dumper,aircraft,and lately,outboards.]

Surely Dean would be better off scrapping this system and installing a simple raw water cooling system.[Water in,around the engine,and out]

You can call me a nitwit if you like Mr.Brooks,because I have overlooked this,this,and this,but the engine on my boat [BMC 1500] is cooled in this way,and in the time I have owned it ,has been quite satisfactory. 

1. If the cap is higher than the waterline, especially with modern plastic strainers, there is a very good chance that it will allow the raw water pump to suck air rather than prime. With the most common types of strainer it is also a recipe for getting crud that ha dropped out of the strainer basket trapped in the heat exchanger. I have dealt with both these faults many times. 

The sea inlet should have a cock on it that good practice dictates is turned off when the boat is left unattended  so a leak on the strainer should either be seen when it is cleaned each morning or, with the cock turned off, can not sink the boat. The best way is arguable but all I know is that we had more air leak and blocked heat exchanger problems on the fleet than we did leaks from the strainer cap and no strainer cap leak came anywhere near to sinking the boat.

2. I do not THINK the system is complicated, its a straight forward heat exchanger system put together by an idiot and obviously modified over the years. The fabricated parts plus  a lack of information/relevant images given to the forum just makes it seem complicated.

3. As others have said direct raw water cooling is far from an ideal cooling solution for marinised industrial or automotive engines although back in the day that was the only option available. Proper marine engines are different and designed to run at far (sub 60C ) temperatures. Quite apart from the corrosion issues other have mentioned unless a low temperature thermostat is fitted the inside of the head will fur up leading to head and combustion chamber insert cracking. We found the BMC 1.5 particularly bad for this.

Another problem for this particular boat is the fabricated mild steel water cooled exhaust manifold. (I bet yours is cast iron but we had one of those corrode through on a BMC 2.2). Raw water without inhibitor will in time corrode through the mild steel. That will be fine as long as its the case that fails. If its an actual exhaust tube then it could easily wreck the engine. I have experienced this on Ex Broads marinisations.

As long as your engine is working well and is a decent marinisation there is no need to worry about it and it will be fine for years. However the OP's system is a very different matter so I agree that once the overheating is solved and he gets it home there is work that would best be done but definitely not change it to direct raw water cooling.

27 minutes ago, Mike the Boilerman said:

 

I get what you're saying, but a rusted though core plug is capable of sinking the boat and this is one reason SOME people prefer indirect cooling on a BMC. You may be a dab hand at replacing them but a lot of boaters these days would not know how or be the slightest it interested in learning. AND want to rest easy there is no risk of sinking from one rusting through. 

 

Is your raw water cooling thermostatically controlled?

I'd love to see a "dab hand" do the one(s) behind the engine backplate without major work!

[Mad Harold]

58 minutes ago, Tony Brooks said:

I'd love to see a "dab hand" do the one(s) behind the engine backplate without major work!

 

59 minutes ago, Tony Brooks said:

Is your raw water cooling thermostatically controlled?

You've got me worried now. I'm beginning to wish I hadn't posted!  How many core plugs are there ? I've looked at the manual online,and although it's not very clear It appears to show three at either side.I can't see any behind the backplate.

Yes, the raw water cooling is thermostatically controlled,with an 82degree non shutoff thermostat.

Many thanks for your replies.

[MtB]

Scale deposition is greatly accelerated above 60C. On the other hand your engine will be running quite cleanly at 82C, unlike if the temp was uncontrolled. 

I reckon there will be four core plugs. Three in the side and one in the back. Just a guess though!

[Tony Brooks]

1 hour ago, Furness said:

 

You've got me worried now. I'm beginning to wish I hadn't posted!  How many core plugs are there ? I've looked at the manual online,and although it's not very clear It appears to show three at either side.I can't see any behind the backplate.

Yes, the raw water cooling is thermostatically controlled,with an 82degree non shutoff thermostat.

Many thanks for your replies.

I have no idea what you mean by "a non-shut off thermostat". If you mean one with a bleed hole in the valve disk (with or without a jiggle pin) then its just a standard thermostat as opposed to a bypass thermostat that I doubt would fit into a 1.5.

I think but can not be sure, that there is one core plug behind the backplate but that may depend upon how old the engine is, who's marinisation it is and which gearbox is fitted. The lien diagram here http://www.ioffer.com/i/bmc-1-5l-diesel-engine-bmc-5-1-sea-lord-marine-engine-service-manual-508711607

on the right of the photo shows a sort of clear rectangle in the back of the block - that's a core plug.

An 82 degree thermostat is way too hot for a direct raw water cooled BMC 1.5, you need nothing much above 70 degrees. I would try for 62 degrees.  82 is the standard marine stat for a heat exchanger engine so are you sure its not a heat exchanger engine? By all means post a photo.

Don't worry but just be aware that all may not be a straight forward in the longer term as you think it is. There were loads of direct raw water cooled 1.5s (both petrol & diesel) in the 1970s. Once you are sure it really is direct raw water cooled then please fit a cooler thermostat to avoid a  furred up and cracked cylinder head

 

PS if you do want to post a photo so we can confirm it is/is not direct raw water cooled I would suggets that you start a new topic in the BMC section so it does not confuse the OP.

Edited January 24, 2018 by Tony Brooks

[Alan de Enfield]

1 hour ago, Mike the Boilerman said:

I reckon there will be four core plugs. Three in the side and one in the back. Just a guess though!

He has already posted that he has located six