Possible loss of water in Bowman heat exchager on BMC Commander diesel

[NealB]

As mentioned, the bowman heat exchanger has fresh cooling water entering one end and leaving the other so i cant see its possible for cooling water to ever get into the cylinders from the heat exchanger

Thanks for bringing us back on course!

 

[Rappey]

Mine had a leak which made the side of the engine constanly damp.. Was like it for years... Decided to finally remove it as i suspected the exhaust /heat exchanger gasket.
I finally decided to remove it and then discovered the exhausts dont have any water near them and no cooling water flows directly from the engine block into the heat exchanger, it only enters and exits via rubber pipes on each end.
Turned out my leak was the car heater or now califier and car heater outlet on the back of the block weeping and giving the appearance of the heat exchanger leaking - DOH..
At least the new exhaust manifold was less than £5. If it were yanmar it would have at least another zero on the end !

 

[rogerthebodger]

As mentioned, the bowman heat exchanger has fresh cooling water entering one end and leaving the other so i cant see its possible for cooling water to ever get into the cylinders from the heat exchanger

All I want to do is help any one who as a problem of needs advice.

in simple terns the fresh water in the heat exchanger does go in one end and out the other, The out end is connected to the input of the engine block/head and is pumped round until it comes out the other and into the input end of the heat exchanger. Thi is the same as on a car radiator

on the raw water from the raw water pump passes through the outer part of the heat exchanger

The fresh water in a car radiator is cooled by the air flowing through the radiator where in a boat engine heat exchanger is cooled by the sea water pumper through and often passes through the exhaust

This is a typical indirect cooled marine engine

Some times there is a separate raw water cooled exhaust manifold some times the raw water cooled exhaust manifold is combined with the heat exchanger

 

[Rappey]

some times the raw water cooled exhaust manifold is combined with the heat exchanger

Thats what i though a bowman on a bmc/leyland was going to be... but i was wrong..
I connected a car heater to the engine, just as it would have been when it was in a van.. It blows warm air very soon after starting and nice hot air not long after and still has enough heat to also heat up the calorifier.
A further modification is copper coils in the sump so the cold seawater acts as an oil cooler before it goes to the heat exchanger.

 

[Boater Sam]

Quote "on the raw water from the raw water pump passes through the outer part of the heat exchanger" End Quote.

I think that this is not the usual way, to prevent corrosion of the aluminium exhaust cum heat exchanger/header the raw water is through the non ferrous heat exchanger matrix, the engine water containing antifreeze or/and corrosion inhibitor flows in the outer chamber.

 

[NealB]

Quote "on the raw water from the raw water pump passes through the outer part of the heat exchanger" End Quote.

I think that this is not the usual way, to prevent corrosion of the aluminium exhaust cum heat exchanger/header the raw water is through the non ferrous heat exchanger matrix, the engine water containing antifreeze or/and corrosion inhibitor flows in the outer chamber.

That is certainly the way it flows on my heat exchangers (ie fresh water/ coolant/ inhibitor on the outside: raw water on the inside).

 

[rogerthebodger]

Quote "on the raw water from the raw water pump passes through the outer part of the heat exchanger" End Quote.

I think that this is not the usual way, to prevent corrosion of the aluminium exhaust cum heat exchanger/header the raw water is through the non ferrous heat exchanger matrix, the engine water containing antifreeze or/and corrosion inhibitor flows in the outer chamber.

Yes you are correct their the raw water passes through the matrix.

My leyland engine has a front mounted heat exchange with a seperate raw water cooled exhaust manifold.

The perkins on my old boat had a combined manifold and heat exchanger.

The advantage is there is only one unit. The disadvantage is that the fresh water cools the exhaust of the heat exchanger must be bigger to transfer the extra heat from the exhaust to the sea water. The alternative is to do it as I said but that means that cast aluminium should not be used. My raw water cooled exhaust manifold i fabricated from stainless steel so I I need to watch for is any crevice corrosion in the stainless steel.

There are some pics of my leyland aluminium heat exchanger where the seal (o ring) between the matrix and the aluminium failed and corroded the aluminium and my repairs by welding the aluminium and hand filing the seal profile.

 

[rogerthebodger]

Thats what i though a bowman on a bmc/leyland was going to be... but i was wrong..
I connected a car heater to the engine, just as it would have been when it was in a van.. It blows warm air very soon after starting and nice hot air not long after and still has enough heat to also heat up the calorifier.
A further modification is copper coils in the sump so the cold seawater acts as an oil cooler before it goes to the heat exchanger.

An Engine I marised in the UK some years ago had a conlined heat exchanger and water cooled manifold from Bowman. I also built a calorifier from a galvanized tank with copper tubes inside. The engine oil cooler was again like you a copper coil in the sump. The boat was used only in fresh water so less corrosion issues

 

[NealB]

You'll recall that I topped up the fresh water side of the heat exchanger in the port engine on Monday.

I managed to spend a short while there again this afternoon.

The coolant in the port engine's heat exchanger is still visible, though the level has definitely dropped since Monday. There was, maybe, half a cupful of water in the bilges (which were dry on Monday), and a pretty little tell-tale stream of droplets that lead back to the bottom of the coolant circulation pump on the front of the block.

So the plan for tomorrow is:

- just a quick look at the pump to see whether there's anything obvious that can be greased or tightened. If there is: do it. If there isn't: ignore the drips (just for now)

- hook up a hose and bucket water supply, and see, in turn, if both engines will run.

- if they do: try to cure the leak on the port pump, and attend to other much needed maintenance jobs.

- if they don't: sit down and cry for a while, then start rebleeding.

Phew .... I'm exhausted already.

 

[RichardS]

The coolant is probably dripping out of a small hole in your water pump casing somewhere behind the pulley. It's a tell-tale hole and is there to tell you that the water pump seal has gone. The usual solution is to replace the water pump. In some cases it is possible to dismantle the pump and replace the seal, however you will usually need a workshop press.

The pump might continue to drip steadily for several more months .... or it might fail catastrophically at any time and start spraying coolant out with gay abandon. resulting in an engine overheat in double quick time. This could be at a crucial time although with two engines you do have options.

If you only had one engine, I would say get it changed asap as it will only get worse and will be a constant worry.

Richard

 

[Boater Sam]

Change it, once they start to leak it destroys the bearing, you risk a total mechanical fail and lose the belt and all cooling. They don't get better, only rapidly worse,

 

[NealB]

Huge thanks to RichardS and Boater Sam for their rapid diagnoses.

This boat is ashore at the moment, so, in some ways, a rapid total failure shouldn't be too catastrophic in safety terms.

However, I am also, of course, keen to avoid too much avoidable damage to my bank account, so I'll add searching out a replacement pump to tomorrow's 'to do'list.

Thanks again.

 

[rogerthebodger]

If you look at vintage tractor spares suppliers you may find one a lot cheaper than a marine/boat engine spares supplier.

Google vintage tractor spares will find several suppliers in the UK