Intermittent cooling water flow - how to seal water strainer?

[Kyle2]

I have a problem with my raw-water cooled Volvo MD1B, which seems similar to problems described in other posts. The cooling water does not always flow when starting the engine at first, and also can stop sometimes when running the engine. The sea water strainer lid seems inadequately sealed at the moment, by a rather soft home-made disc of rubber, so I would like to eliminate this from the possible causes by sealing it properly to stop air leaking into the system. The water strainer is brass, approx. 3cm diameter, and incorporated with the sea-cock. Should the screw-on brass lid have a sealing ring or disc, and if so where could I get one to fit? Also, should sealant be applied to the screw threads? Thanks for any help that can be given on this.

 

[MoodySabre]

The strainer on my VP2003 is about that size but the swivel top is just held tight by a wing nut - no O-ring or seal. I wouldn't have thought that it could leak enough air to stop the flow when the engine is running. I'd be looking at the inlet or further up the system for a broken off impeller blade in the pipework or some other leak in the hose.

 

[Stemar]

From memory, there should be a rubber disk in the lid of these strainers. Personnally, I wouldn't use a sealant on the thread as you may need to undo it in the future without wasting time; waterproof grease would be better. There should be a strainer cylinder inside that you can withdraw to clean. Mine was quite difficult to clean - be careful, the gauze is fragile.

 

[Poignard]

Does it say STUART on the side of it? If so it's like one I removed from my boat. That had a disc of rubber inside the cap. I once made a new one from a scrap piece of sheet rubber. You could make one from an old wellie or cork sheet.

 

[pappaecho]

A strainer is not expensive, and a new one will solve the problem, without posing a greater strain on the engine which if it overheats will blow the head gasket which then really will cost megabucks because it has the word Volvo on it.
You might also look at the raw water impellor, as intermittent flow could be caused by a broken blade

 

[ADLS]

Smear grease or petroleum gelly on the seal and around the hold down threads, this will also make it easier to undo. Do check the impeller and sea cock as well some seaweed or other might flap across the opening.

 

[thalassa]

Had a strainer like this on my old boat, and it was much better than the plastic strainer type with the central butterfly nut. There should be a flat rubber ring inside the cap. Mine took a standard flat ring from the plumber's - I think it is used in toilet flushes. Petroleum jelly will break down most rubbers quite fast; instead, use a silicon based oil.
More often than not, you will find that this problem on non-starting can be traced back to the pump. Even with a new impeller, it will not create sufficient vacuum to pump up the sea water if the cover plate and/or the inner side is worn, even by as little as 0,3 mm .

 

[VicS]

Try anything to make a decent seal, heavy grease, ptfe tape, a joining compound that wont set hard, as a temporary measure to prove if this is your problem or not.

If the top of the strainer body is below the water line then it is unlikely that air is being drawn in unless the inlet is restricted or the seacock (or is it a gate valve?) partly closed.

Have you checked the condition of the hoses from the inlet to the pump (via the gearbox cooler ?) If one is getting weak it could flatten or kink and stop the flow. Even a reinforced double skinned hose could have the inner layer collapsing.

I would not worry about there being a short delay between starting the engine and water being ejected from the exhaust as the water lying in the exhaust sytem, and trap if fitted, can leak away slowly. It takes 1/4 to 1/2 minute perhaps to refill it. The important thing is that after a little delay you do get a good flow.

BTW Stemar refers to the strainer basket itself being fragile. In my experience that is because it is likely to be brass and to have dezincified. Hopefully the valve and strainer body are bronze or at the very least "dezicification resistant" brass.

 

[Richard10002]

[ QUOTE ]
I would not worry about there being a short delay between starting the engine and water being ejected from the exhaust as the water lying in the exhaust sytem, and trap if fitted, can leak away slowly. It takes 1/4 to 1/2 minute perhaps to refill it. The important thing is that after a little delay you do get a good flow.

[/ QUOTE ]

When I did the Inland waterways helmsmans Course with SWMBO, the instructor suggested a couple of high revs after starting, (I'm guessing this is to get the water and stuff flowing).

Does getting a good flow apply to all engines? I find that I dont get a flow, whatever the revs or load. It comes in spurts, either frequent, or not so frequent, and either big, or not so big, (ooh err mother <g>).

 

[VicS]

[ QUOTE ]
the instructor suggested a couple of high revs after starting,

[/ QUOTE ] It is not generally recommended that any engine should be revved highly immediately after starting or while still cold for that matter as the oil will not be circulating to all the bearing surfaces and in particular to the cylinder walls. Quite what you instuctor had in mind I don't know but it can hardly have been the engine's well-being.

The water flow from the exhaust quite often does come as a series of spurts, some however do seem to produce a more even flow. It depends on the design of the exhaust system and the overall flow. The important thing is that on average you get a decent total volume of water through. It is probably a good idea to ty to memorise what it looks like when the sytem is in good order with a new pump impeller and to act when the flow is obviously less.

 

[Kyle2]

I don't think that the water strainer has any writing on the side - I can't identify it. I also can't easily replace it, as it is part of the through-hull seacock fitting. I will try making a new rubber seal as suggested. Many thanks for all the responses.