cooling system problems

[Anita]

I have problem with the cooling system on my Yanmar 2M 20 engine. The overheating alarm went off last week and when we checked there was no water coming through the water filter. Then checked water inlet below sea cock and only a trickle there. Attacked the inlet pipe with trusty coathanger, retrieved some wadding, and had full water pressure again. Engine started no problem today, but after 30 mins, alarm went off again (am now an expect at sailing onto my mooring). Water still gushing through inlet, so checked impeller. Looked fine, but replaced impeller and gasket just in case. Started engine - no water coming through the filter. Anyone have any ideas what the problem might be? /forums/images/graemlins/confused.gif

 

[Pye_End]

Is water filter sealed? Maybe two separate problems, but if filter above waterline then it is possible to draw air in through the lid, stopping the water suction.

Prseume filter fine enough to catch whatever you found? Is it possible some got through and has fouled one of the pipes from the impellor or even after?

If you take off pater inlet pipe on the impellor you may be able to tell if this pipe is clear (depending how high up the filter is). Water pressure from the sea is often a good way to flush through pipe work.

 

[Anita]

Thanks for your advice. The water filter is a 4 in diameter strainer at least 2 ft above water level. No wadding found in the strainer, so I doubt it's blocked further down. We poured water back down from filter to seacock level and it appears unobstructed, so it looks like water suction could be the problem. Will try replacing the o ring in the filter. Do you think it would be worth renewing jubilee clips on the pipe work, too?

 

[Pye_End]

Wouldn't have thought jubilee clips would cause it. If there joints look a bit iffy (ie leak) then a bit of silicone sealant sorts them out.

Presume raw water cooled. Really a matter of working it through the system. If filter so high you may not be able to check water flow through to the impellor, although taking the pipe off after it will certainly tell you if you run the engine for a few seconds. Just one thought - you replaced the impellor - presume the metal piece restricing the diamater (I am sure it has a real name!) that squashes the impellor was still there?

It is no doubt possible to have a blockage further on, but your problems are more likely to be earlier on.

 

[Anita]

The impeller sits in a cast metal housing, there was not separate metal piece around the impeller when we took it out.

 

[Pye_End]

It may look cast, but the shape should not be completely round. The 'non-roundness' is a grub screwed separate piece (from memory) - not very obvious.

So long as some of the impellor is getting squashed more than the rest it will be fine. Never known it as a problem, but you never know...

 

[PaulR]

hi - we used to have occasional problems with water strainer on our freedom with volvo installation- cure for us was to open top of strainer and pour in water (with engine off) and seacock closed so that the pipe between the seacock and strainer was full of water and the pipe from the strainer to engine likewise, then with it topped up as much as we could, top back on strainer , open seacock and start - seemed to get rid of annoying air lock which otherwise sometimes didn't get sucked through engine and stopped water flow- could be worth trying - good luck

 

[Anita]

Thanks - hadn't thought about air lock. Will try this next weekend.

 

[Anita]

Thanks Paul - tried your suggestion and it worked! Water pressure back to normal and everything now working well. Thanks so much - we were about to pay out for an engineer, so this has saved us £££.