Cooling Water Problems - Any Ideas?

[shaula]

I have a fresh water cooled VP2030 and when fully warmed -up and under load I am getting discharge from the pressure cap overflow. It would appear that sea water is finding its way into the fresh water system. Water is flowing OK through the exhaust. Any ideas before I start stripping things off, is it the heat exchanger?

 

[VicS]

Probably that one of the rubber end caps is not sealing properly on the on the heat excahnger tube bundle

Check the smaller of the two clips at each end. #4 in the diagram below

Ccheck for restriction of the water flow into the exhaust causing excess pressure in the seawater system

also check the pressure cap

A tube leak is a very remote possibility

 

[DJE]

My 2040 did that last year. There must be a restriction to the sea water flow in, or downstream of, the heat exchanger. This produces back pressure which forces the sea water past the clips on the rubber boots, into the fresh water system, and out of the pressure cap. In our case it was the injection port into the exhaust elbow which was nearly blocked. I took off the rubber boots off both ends of the heat exchanger and checked that the tube stack was clear then I found that the injection port was 90% obstructed with limescale. Cleaned it all out re-assembled and everthing was fine. Re-fitting the end cap at the exhaust end was a struggle though, then I had to flush the fresh water side of the system a few times to get rid of the sea water.

It took a bit of working out - we were on the delivery trip with a boat we had just bought when I lifted a floor board and found all the green coolant in bilges. But the engine was still running quite happily! I had to phone a friendly mechanic to work out what was going on. The exhaust elbow itself might be clogged which will be more difficult to fix. I checked mine by fitting a bit of hose to the injection port and blowing down it!

 

[vyv_cox]

Several owners have reported this problem over the years. In theory it is impossible for seawater to enter the coolant, as its pressure is nominally atmospheric with an open ended system, whereas the coolant is pressurised at 4 - 12 psi, dependent upon the cap fitted. However, it seems that when the manifold becomes clogged with carbonates it can generate back-pressure in the seawater that is sufficient to breach the seals in the heat exchanger. So the first thing to check is the manifold, which does seem to clog easily with this engine.

 

[Allergy]

Agree with the exhaust elbow being very restricted. I renewed the elbow & clean it annually. No more sea water coming out the pressure cap.

 

[duncan99210]

Just a thought. Last summer I found coolant being dumped out of the engine. I tasted it and it as fresh not salt. I eventually traced the problem to the calorifier coil, which had developed a small leak and the domestic water system was slowly pushing water into the cooking system. Worth doing a quick taste check just to make sure it's really salt water.....

 

[vyv_cox]

Just a thought. Last summer I found coolant being dumped out of the engine. I tasted it and it as fresh not salt. I eventually traced the problem to the calorifier coil, which had developed a small leak and the domestic water system was slowly pushing water into the cooking system. Worth doing a quick taste check just to make sure it's really salt water.....

I wrote an article for PBO on this topic, after the same problem with Carmel2's coolant. Easily checked by removing a calorifier hose and leaving the domestic water pump on.

 

[shaula]

Many thanks for your reply's. The water does taste of salt and the calorifer hoses were isolated anyway. I will start by inspecting the heat exchanger connections and exhaust bend this weekend.

 

[Birdseye]

I have a fresh water cooled VP2030 and when fully warmed -up and under load I am getting discharge from the pressure cap overflow. It would appear that sea water is finding its way into the fresh water system. Water is flowing OK through the exhaust. Any ideas before I start stripping things off, is it the heat exchanger?

When your engine is hot the pressure cap on the heat exchanger means that the pressure in the fresh water circuit is much higher than in the salt water so no way can salt water get in whilst running

Overflow from the pressure cap when running under load is a classic sign of head gasket failure between combustion chamber and water jacket. In this case when the engine cools down again you will find a shortage of water in the cooling system. Have you checked the oil? Is there any milkyness?

Before you start assuming the worst and most expensive, check the simple and cheap. Radiator cap - has it failed? Fresh water pump - has it failed causing local overheating? Indee is the engine overheating anyway ie blocked heat exchanger tubes?

 

[DJE]

When your engine is hot the pressure cap on the heat exchanger means that the pressure in the fresh water circuit is much higher than in the salt water so no way can salt water get in whilst running

Oh yes it can! You are assuming that the sea water outlet is clear. If it is obstructed the sea water pump can develop plenty of pressure.

 

[vyv_cox]

When your engine is hot the pressure cap on the heat exchanger means that the pressure in the fresh water circuit is much higher than in the salt water so no way can salt water get in whilst running

Overflow from the pressure cap when running under load is a classic sign of head gasket failure between combustion chamber and water jacket. In this case when the engine cools down again you will find a shortage of water in the cooling system. Have you checked the oil? Is there any milkyness?

Before you start assuming the worst and most expensive, check the simple and cheap. Radiator cap - has it failed? Fresh water pump - has it failed causing local overheating? Indee is the engine overheating anyway ie blocked heat exchanger tubes?

See my post #4. This has come up quite a few times over the years and was solved in most of them by cleaning up the manifold. My experience is that when head gaskets fail the first sign is that the heater/calorifier stops working because gases cause airlocks in the small hoses.

 

[Venus1]

Just a thought. Last summer I found coolant being dumped out of the engine. I tasted it and it as fresh not salt. I eventually traced the problem to the calorifier coil, which had developed a small leak and the domestic water system was slowly pushing water into the cooking system. Worth doing a quick taste check just to make sure it's really salt water.....

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