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wet exhaust system for B m c 1.5


montezuma

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Hi, I have a a 1.5 which has fresh water cooling by way of a heat exchanger. I haven't been able to find any information or photos of the particular configuration I have although it looks like a factory marinisation job. From the raw water pump the water goes into the bottom of the cylindrical heat exchanger which is cast aluminium with aprprox 5" dia and 10" long this is bolted under the rectangular cast iron header tank which in turn is bolted to the thermostat housing the raw water exits the heat exchanger an goes into the exhaust manifold which is also cast aluminium, from the end of the manifold a pipe emerges and enters the exhaust elbow.Am I right in thinking that the aluminium casting I can see is a water jacket around the actual manifold ? I have noticed there is a small a mount of rust on the rocker shaft if my manifold is cracked or rusted through could water get in to the rocker cover to cause the rust? Last time out it over heated and their seems to be a lack of oil around the rocker gear how can I check that the oil pump is working where can i connect an oil pressure gauge [it dosen't have one] if the engine has been assembled with the head gasket the wrong way around thereby blocking the oil supply to the rockers can i just drill through the head gasket with out removing the head? If any one recognise the set up I have described I would greatly appreciate any information regarding the manufacturer. Thanks.

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6 minutes ago, montezuma said:

Hi, I have a a 1.5 which has fresh water cooling by way of a heat exchanger. I haven't been able to find any information or photos of the particular configuration I have although it looks like a factory marinisation job.

 

From the raw water pump the water goes into the bottom of the cylindrical heat exchanger which is cast aluminium with aprprox 5" dia and 10" long this is bolted under the rectangular cast iron header tank which in turn is bolted to the thermostat housing

 

the raw water exits the heat exchanger an goes into the exhaust manifold which is also cast aluminium, from the end of the manifold a pipe emerges and enters the exhaust elbow.

 

Am I right in thinking that the aluminium casting I can see is a water jacket around the actual manifold ?

 

I have noticed there is a small a mount of rust on the rocker shaft if my manifold is cracked or rusted through could water get in to the rocker cover to cause the rust? Last time out it over heated and their seems to be a lack of oil around the rocker gear

 

how can I check that the oil pump is working where can i connect an oil pressure gauge [it dosen't have one] if the engine has been assembled with the head gasket the wrong way around thereby blocking the oil supply to the rockers can i just drill through the head gasket with out removing the head?

 

If any one recognise the set up I have described I would greatly appreciate any information regarding the manufacturer. Thanks.

It seems like a pretty standard heat exchange system, except there are lots of different versions of them made by different people

 

Really, we need some photos

 

No, you can't drill the head gasket with the head in place. Are the rockers bone dry - they will be if the head gasket is the wrong way round? If not, there is probably oil getting there.

 

Richard

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If the system is the same as the one on Theodora the cylinder is the gearbox oil cooler.  The raw water from the canal passes through a set of small bore tubes with the oil surrounding them.  This was the source of a problem that we had which I tracked down to a small snail shell blocking each of the holes.

 

After doing its thing in the oil cooler the raw water passes through the moving vane pump which is driven by a belt frome the crank shaft.  This could be a problem if one or me of the vanes breaks off.  Not only will this make the pump less efficient but the vane coould pass on up the pipes to the heat interchanger in the cast aluminium box that you told us about.

 

The raw water then passes through a set of thin brass tubes immersed in the engine coolant in the rectangular box so cooling it.  After that it joins the exhaust gasses through an aluminium Y piece at the after end of the exhaust manifold.

 

So there are three points where there can be problems.  1) the oil cooler, 2) the pump and 3) the main coolant heat interchanger.

 

Is there a spash of water emerging from the exhaust pipe every ten seconds or so?  When you put your hand in the flow of water is it hot or just a bit warm? If the water is just a bit warm you will need to investigate something other than the raw water.

 

Nick

Edited by Theo
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Apart from the rectangular header tank being BOLTED to the circular heat exchanger this sounds like an early cast iron heat exchanger 1.5 with the heat exchanger cum header tank transversely across the front of the engine. Hard to tell without photos. These used a much slimmer cast iron exhaust manifold when compared with the Bowman ones normally seen. However I think I have seen home brew lash-up using a stainless steel header tank that might fit your description.

 

The cast iron manifolds can crack during frost if not properly winterised but the water would tend to  get into the exhaust ports and as they are lower than the manifold water jacket would tend to fill a cylinder. From that you can get emulsified engine oil, bent con rods/damaged pistons, difficulty starting or starting on less than four cylinders and if only a minor leak then condensation inside the engine when it cools down.

 

The normal oil pressure switch that you remove is (I think, I am always getting it mixed up with other engines) is on the starboard side of the engine block just in front of the bell housing in a gap between bell housing & injector pump. About half way down the block and into a longitudinal bump that is the main oil gallery.

 

Run the engine with the rocker cover off, you will soon see if any oil is getting to the rockers, you can even safely rev it at the expense of oil splatters.

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3 minutes ago, Theo said:

I knew that TB would soon be here...

 

The one that I described is a Bowman system.

 

N

So is the one I tried to describe but not the Bowman aluminium manifold we are more used to seeing. That is why we really need a photo.

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