Sensible place to plumb in oil coolers

[p6rob]

Hi,

 

I'm still struggling with the engine in my 40ft boat, it's a 1.5BMC with bowman header, skin tanks and dry exhaust, smaller diameter water pump impeller which looks to be in good condition. 82 thermostat fitted which tests ok in a pan.

 

After welding up a couple more suspect areas on the starboard skin tank I took the boat out for a spin around Birmingham on Saturday. The trip was a bit of a challenge.

The water leaks have all been fixed and the system was bled fully, each skin tank has a bleed screw on the top

 

From our mooring in Sherborne Wharf we got as far as the bridge before the engine cut out, a whole 100yards maybe. It would run ok in neutral but stall as soon as drive was engaged. After pulling up outside Banatynes, getting a late lunch and letting off a bit of steam, we discovered the prop was fouled. So, with that cleared we carried on, the idea being to complete the Lozells Loop as a test run.

However as we got around the corner it was apparent there was still an issue with the cooling system, the gauge steadily climbed up and up to the red zone so I shut the engine down.

 

We pulled up, had a check of the system and discovered the port skin tank was stone cold whereas the starboard was warm. The pipe between the two was cold.

 

Last night I drained the tanks, took off all the pipes and gave each tank a thorough flushing for 20 minutes. As I'd been through a similar exercise recently, I hadn't expected to see much rust and sure enough, the water ran crystal clear throughout.

One thing that occurred to me is that the gearbox and engine oil coolers are probably not in the best part of the system. They sit, in series, between the port skin tank and water pump with various reducers and adapters in the way. I'm sort of hoping that between the bore differences and the restricted flow through core of the heat exchangers, the pump struggles to lift the water up and around the system and is probably just cavitating. The starboard tank (I assume) heats up through thermo syphoning. If this is the case, a bit of re-engineering will hopefully suffice.

 

Assuming the cooling system is running properly, is there any need for an engine oil cooler?

Is there a better place in the circuit to run the coolers? I noticed a picture here recently where the cooler was plumbed through the end caps of the header tank.

 

Any advice or pictures of successful cooling systems will be gratefully recieved.

 

Thanks in advance

 

Robert

 

 

 

 

 

[bigste]

I can only say what I've seen on here and other forums. It seems your type of engine is a pig to bleed and many have almost given up and slit their wrists. Your problem does sound like and air in system problem.

[MtB]

 

Assuming the cooling system is running properly, is there any need for an engine oil cooler?

 

I'd say 'no'. Hydraulic gearboxes usually need one but not a BMC 1.5.

 

From your description of the fault I'd say there is no circulation through the skin tanks. You have demonstrated they are not obstructed so the fault liles in the hose pipe connections or the engine.

 

It could be an absence of any circulating force - air locked water pump, not enough water in the system, missing or knackered impeller in the pump, very loose fan belt etc. Have you tried running the skin tank hose into a bucket to see if the pump is shifting water?

 

OR, it could be absence of a circuit to circulate through. A pipework error. Did it ever work properly?

 

 

MtB

[Tony Brooks]

I do not like the sound of "various reducers and adaptors". My guess is that you have a gearbox oil cooler designed for cooling by raw water not skin tank/keel cooling. If the oil gearbox cooler is one of the very old "all copper bodied" ones them my advice would be to test my theory by TEMPORARY removing it from the circuit and joining the two large diameter cooling pipes by a large bore pipe. If it is one of the modern "rubber end cap" ones I think ASAP Supplies will be able to supply you with two new end caps that will accept the large bore cooling pipes with no reducers. As long as the engine sump holds around a gallon of oil I can see no reason it was ever fitted with an engine oil cooler as MB says.

 

Raw water oil coolers used to only use a 1/2" connection but I would want a good 1" or more for tank cooling.

 

The cooler should be in the coldest part of the circuit. That is between skin tank outlet and water pump.

 

Have you tries to "rod through" any interconnecting pipes welded to the hull?

[p6rob]

Hi Mike,

 

Thanks for taking time to reply.

 

It could be an absence of any circulating force - air locked water pump, not enough water in the system, missing or knackered impeller in the pump, very loose fan belt etc. Have you tried running the skin tank hose into a bucket to see if the pump is shifting water?

 

I can say for certain that the impeller looks good and is attached to the spindle and the fan belt is tight. I know there are two different size water pumps, this is the smaller one, whether that is correct or not, I don't know for certain yet. Are they interchangeable?

 

OR, it could be absence of a circuit to circulate through. A pipework error. Did it ever work properly?

I bought it as a non runner, it's 30 years old, so in theory, it's either worked in the past or been a static home.

 

 

MtB

 

The light was fading before I finished last night but. All the hoses and pipes between the engine and both skin tanks are clear. I ran out of light before checking the waterways in the oil coolers were clear, that's tonight's little job.

[p6rob]

Hi Tony,

Thanks for taking time to reply.

I'll try and attach a link to the pictures of one of the reducers. This particular one connects the two oil coolers in series. I'm thinking replacing this with a straight 2" section of hose will help with flow.

Ultimately though I think I'll get rid of the engine oil cooler. I was planning to replace the filter with a spin on adapter so it would be going soon anyway.

I'll get some pictures of the oil coolers tonight. They are fitted between the skin tank and water pump, which I guess is a good sign, I'm no engineer but it seems odd to cool the water right down, then heat it back up, before sending it to cool the engine.

 

 

I do not like the sound of "various reducers and adaptors". My guess is that you have a gearbox oil cooler designed for cooling by raw water not skin tank/keel cooling. If the oil gearbox cooler is one of the very old "all copper bodied" ones them my advice would be to test my theory by TEMPORARY removing it from the circuit and joining the two large diameter cooling pipes by a large bore pipe. If it is one of the modern "rubber end cap" ones I think ASAP Supplies will be able to supply you with two new end caps that will accept the large bore cooling pipes with no reducers. As long as the engine sump holds around a gallon of oil I can see no reason it was ever fitted with an engine oil cooler as MB says.

 

Raw water oil coolers used to only use a 1/2" connection but I would want a good 1" or more for tank cooling.

 

The cooler should be in the coldest part of the circuit. That is between skin tank outlet and water pump.

 

Have you tries to "rod through" any interconnecting pipes welded to the hull?

 

http://www.shipmatesahoy.co.uk/gallery2/main.php?g2_itemId=10714&g2_imageViewsIndex=1

http://www.shipmatesahoy.co.uk/gallery2/main.php?g2_itemId=10706

[smileypete]

A load of photos and a diagram would help.

 

If the tanks are in parallel they may need a way of balancing flow between them. If flow is too restrictive it may be less likely to shift any trapped air. A cheap IR thermometer off Ebay can help tell how hot things are getting.

 

Maybe google and dig out some manuals for different marinised engines, they sometimes include a layout.

 

cheers, Pete.

~smpt~

Edited July 15, 2013 by smileypete

[p6rob]

Hi Pete,

 

I'll try and get a photo of the layout this evening but it's a bit awkward especially now all the interconnecting pipes have been removed.

 

The tanks are in series. I have an IR thermometer, it was useful for checking the state of things when we bought the boat down from Willington to Brum. At the time the engine would run for about 45 minutes and reach about 90 - 95 degrees when we would shut the engine of and let it cool for 1/2 hour. At the time the skin tanks would both read around 70deg.

Since then, I've had some leaks on the starboard tank repaired, flushed the whole system and had some repairs done to the cylinder head.

 

I'll look at as many pics and manuals as I can find and if anyone here has a similar, but efficient setup, I'd be grateful for images of those too.

 

Cheers

 

Rob

[Tony Brooks]

Certainly look like raw water end caps to me.

 

As I said simply bypass the pair for a short while and see if the problem goes away. If so get a pair of end caps for the gearbox oil cooler that will accept much larger diameter pipes. What you have must restrict the flow otherwise cars would have 1/2 bore cooling pipes and they do not.

 

It will be perfectly safe to carry out the test without the gearbox cooler in use but just keep and eye (hand actually) on the box to ensure it does not get burning hot. If it does stop at once.

 

Leave the engine cooler out of circuit but connected until you do the oil filter mod. It should be fine. You do not need any end caps on it if no water is flowing through it.

[smileypete]

If they're in series and one is warm, the other cold, while the engine is overheating, it definitely sounds like a flow problem, probably too much restriction. Having that coupler in circuit is certainly not going to help things if it's an inch bore or less in the narrower part, with raw water a smaller diameter is less of a problem.

 

If that works and then both tanks are hot but the engine's still overheating, then flow is OK but there's not enough heat transfer; could be the tanks are too small, lacking baffles or even too thick. An IR thermometer can help trace the flow path around the tank in that case.

 

As Mike said it's unusual for a BMC 1.5 to need an engine oil cooler, it may have been fitted in the past as a misguided attempt to cure a cooling problem.

 

cheers, Pete.

~smpt~

Edited July 15, 2013 by smileypete

[p6rob]

Thanks Tony,

 

I think they are closer to 19, or 22mm but you're right, it does look too restricted, there are two more endcaps and another reducer before the pump, I don't what effect that'll have on pump suction, but assumed it wouldn't be good.

 

I've had a look on the Asap website and found some more appropriate sized adaptors. I have to buy some pipe to bypass the coolers, so I'll work out whats needed tonight and check the gearbox oil cooler holes are clear, reassemble the rest of the pipework and dry out the bilge ready for the next phase.

 

Rob

[David Mack]

I would expect a BMC to run OK with those oil cooler connections at the modest power levels of canal boating. Might be different punching the current on a river.

 

Have you checked that the pump impeller is in good condition and that it is actually rotating? It wouldn't be the first time I've come across slipping between the shaft and the impeller (or the pulley for that matter).

[p6rob]

The bits have arrived from asap supplies and auto performance on ebay, so I can get rid of the small bore reducers and replace them with some couplers that match the size of the rest of the coolant pipework.

If you see a smiley person with a slightly smoky narrowboat pootling around the Lozells loop in the next few days, that's me and it worked.

If you see a stressed looking person with a dead boat, that might also be me.

 

Either way a drink will be in order.

[RLWP]

Do take a lot of care over bleeding, especially the skin tanks and connecting pipe

 

Richard

[p6rob]

There are bleed screw on the top of both tanks and I've added one into the pipe runs. It's still overheating. I'm convinced the water just isn't being pumped around. I can feel water in the pipes, they are mostly rubber with solid connecting elbows.

The pump tolerances are good, the impeller looks good, there is a bit of corrosion in the housing but nothing drastic.

 

Latest theory is that the pump head is to high/long and therefore the pump is just cavitating. Not sure what else to try except add an electric pump, which will have to wait another week or two.

[David Mack]

The pump tolerances are good, the impeller looks good, there is a bit of corrosion in the housing but nothing drastic.

 

 

Have you checked that the impeller is actually rotating? If it was slipping on the shaft....

[p6rob]

It looked to be well attached and I couldn't turn the impeller while holding the pulley. There weren't any signs of wear to suggest it was loose either.

 

I've taken some pictures and will try and upload them later.

 

Rob

[smileypete]

Just a thought maybe try testing the thermostat in a pan of water to check it opens fully OK, or even try a run without the thermostat to rule it out.

 

cheers, Pete.

~smpt~

[Tony Brooks]

I have just noticed "small impeller". Just to be clear - you are talking about the cast iron or aluminium ENGINE water pump, not a brass one.

[Arthur Brown]

How big is the expansion vessel? Is there air space in it? Is there always water in it

 

If the expansion vessel is too small then as the coolant expands some must be lost, then as the system cools the lost coolant is replaced by air, the bigger the skin tank the bigger the issue.

 

What has changed since the system last worked correctly? Work done? Parts swapped?

[p6rob]

I have just noticed "small impeller". Just to be clear - you are talking about the cast iron or aluminium ENGINE water pump, not a brass one.

Hi Tony, Yes I'm talking about the 60mm engine water pump, it has an alloy housing. I've checked the orifice in the engine and it couldn't take the larger pump.

 

I've taken several pictures but am struggling to get them online at the moment. Will upload tomorrow when I'm in the office.

[p6rob]

How big is the expansion vessel? Is there air space in it? Is there always water in it

 

If the expansion vessel is too small then as the coolant expands some must be lost, then as the system cools the lost coolant is replaced by air, the bigger the skin tank the bigger the issue.

 

What has changed since the system last worked correctly? Work done? Parts swapped?

Hi Arthur, there's not an expansion tank, unless you count the pop bottle, I've poked the vent tube into.

 

The skin tanks are too broad, they are at least 3inches thick. However, I think the problem is more to do with getting the water from the skin tank up into the water pump. The port side tank, the one that feeds the waterpump is stone cold, whereas the starboard tank and engine are hot. You can feel the point at which the cold and hot coolant interface on a vertical section of hose which is supposed to take the coolant from the bottom of the starboard tank to the top of the port side tank. As the main pipework is rubber, it is easy to feel that water is filling all the pipe runs and I've added various bleed points to help remove any trapped air.

 

I don't know when the system last worked correctly. I bought the boat in February as a non runner that had had 2k spent on the engine but hadn't been completed. The owners had emigrated to Australia and from what I can make out, they had lived aboard in a marina but not moved the boat in at least two years. The receipts for the work date to around Feb - April 2012. I bought the boat through the previous owners relatives.

 

 

The engine had had a crank grind, hone and new rings, recon injector pump, recon head and new injectors bought by the previous owner.

I finished putting the engine back together and got it running, albeit smokily and overheating and coaxed it back from Willington to Brum.

Since then I have fitted new glow plugs, had the head repaired where a core plug on the mating face was missing and replaced a pre combustion chamber, had the timing adjusted, flushed the skin tanks, had some holes in them welded, flushed the engine, fitted a thermostat, redid some of the coolant pipework to remove some reducers and taken the oil cooler heat exchanger out of the circuit, replaced the lift pump and one of the injector pipes and repaired the starter motor.

 

Despite totally even compression readings, I think there is too much crankcase pressure and am saving to get oversize pistons, while hoping it's smoking because the rings aren't bedded in. When I removed the head, the bores looked to be in a good state and there are no noises to indicate broken rings.

 

Cheers

 

Rob

[smileypete]

Another thought, if you added antifreeze was it premixed with the water before filling the cooling system up? Neat antifreeze can stratify with water and resist circulation where there's not much pump pressure to push it around.

 

Also is the pop bottle serving as an expansion tank well enough. Usually an expansion tank has 2 level markings and is filled to the lower, that way when the engine heats up it fills with water and the level rise towards the second marking, then as it cools the water is sucked back in without any air as well.

 

ETA: I wonder if the skin tanks have some totally half *rsed internal design that's trapping air? If they're 3" thick that's doesn't point to a good design, does seem strange the hose between them is heating only half way. Is there a calorifier circuit that could be allowing flow to be diverted away from the skin tanks?

 

cheers, Pete.

~smpt~

Edited July 21, 2013 by smileypete

[bizzard]

I think I'd experiment by connecting to one skin tank only, and see if that improves the circulation, then connect to the other one only as well to see how they performs individually . If one or the other is faulty internally or has a Thrombosis (blockage) it should reveal itself. Ok the engine will probably try to overheat working on only one tank, but don't let it do that. ''Elimination purposes only''.

[Arthur Brown]

Sorry but I'm going back to the expansion vessel. As the coolant expands as it warms up it must go somewhere. If there is an air space in an expansion vessel that will take up the expanded coolant and allow it to return to the engine as needed. If there is no (or just too small) expansion tank coolant will be lost on heating and NOT returned to the circulation. This will leave an air lock in the engine or pipes. Big skin tanks need big expansion vessels. The expansion vessel is in the pressurised coolant circuit,

 

Have you (or can you get) a reliable drawing of how your engine should be laid out? NOW is the time to get the engine correctly built to it's proper marinised state. Are you 100% CERTAIN that the gaskets used by the previous rebuilder are correct?