Overheating Volvo 2030

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ozzyb

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I changed the impeller whilst servicing the engine about a month ago (Volvo MD 2030C). Since then the engine overheat warning has come on a couple of times when under load at high revs. Are these engines sensitive to type of impeller, air lock etc. I've checked water flow, topped up/flushed strainer, checked position of impeller. Any suggestions?
 
Were there any blades missing from the old impellor, if so remove the seawater hose from the rubber end cap on the heat exchanger and check for debris in the cap which can restrict flow through the exchanger. Do you have a sail drive? if so I have experienced a blockage in the intake on these many times, the favourite place is right before the stop cock in the top of the sail drive, usually a mussel which gets sucked in when small and grows until it restricts the flow. You can try back flushing by closing the cock fitting a hosepipe to it and then opening and backflushing. If this doesn't work then really you need to take the boat up and then unscrew the stop cock and look down the hole with a torch, have found shells in here frequently, also check the long vertical water passage which goes up the front of the drive leg, in the worst case you will have to split the drive to clean it out.
 
ozzyb,

What revs does your engine reach when you are motoring flat out? The reason I ask is that our MD2030 will eventually sound its overheat alarm at 3000 rpm plus. This is simply because it is slightly overpropped. I guess I should get it repitched but the up side is relaxed motoring at cruising speeds.
 
Assuming you've done all correctly, which I'm sure you have, it might just pay you to measure the width of the new impeller. I replace these things every year and the last one gave a derisory output. I took it out and after much fiddling, couldn't find anything wrong so measured it. The new one was 0.5mm less in width than any of the older ones (which I've kept). This won't be efficient given the way these things work, so, back went in one of the old ones ... I complained, but was told they're all like that and they're not made to a tolerance or they (Barrus) didn't know what the tolerance should be or that they expand once out of water (complete bolx) ... engine's a yanmar 3gm but would assume your volvo has similar setup. As far as I know, the rubber impellers are all made by the same company ..
 
Another thing to check, if all the obvious things fail is that the impellor actually turns! It's not unheard of for the metal sleeve to come unglued from the rubber bit, but unless you specifically check, you won't see anything wrong - except overheating!
 
Exactly the same thing happened to me first time out this year.

The strainer was alive with marine organisms and shells, and allowed enough water at low revs, but not enough at high revs.

Is it worth a second check?

Alternatively has the thermostat stuck closed (they should fail safe but who knows). There will be a bypass which will alow some cooling - enoughfor low rpm perhaps.

Alternatively a system blockage - old bits of impellor or calcium build up or impellor fault. I always keep my old one as a spare if it is servicable on removal. Try swapping back. Check the hub is bonded in the new impellor, and the thickness is correct - as noted elswhere.
 
Just my 2 bobs worth! I had this on a Volvo penta. I kept overheating and tried everything thermostat,clearing pipes etc etc. I then noticed my impellers were all getting slightly damage on the blades! I got though about 5 I think! It turned out the impellor housing in the end had slightly worn causing the blades to get damaged!!! Unfortunatly then needed to replace said housing.

Cheers

Karl
 
Had same prob on my 2030, mine turned out to be marine growth in the saildrive leg. ok at low revs but overheating at higher. after checking strainer,pump etc and all found ok removed pipe of water inlet to find only a dribble coming in. So with valve in open position pushed straightened out wire coathanger down hole wiggled it about and urika water came in at the rush, along with the remains of several mussels. Had a friend who even had a crab in his.
 
Thank for replies, the only other time it over heated was after 11 hrs motoring x channel to Cherbourg, total flat calm until just off entrance ie. x tide. I felt at the time that was weed intake. Recently its only been after change of impeller and at high revs when against tide in or out of Langstone Hbr. Just seen search on heat exchanger will check that and switch back to old impeller. This had no damage, it was just changed as precaution, I'll also check into other sugestions. I'm not sure its that overproped, can't adjust it easily cos its folding type, but it does rev to 3K

Thanks
 
If the old impellor was Ok and still had all its blades I would be tempted to put it back in again and see if the problem recurrs...
If not then it is the new impellor .
I have mentally debated whether to change in the impellor on my 4108, and have a spare but every year it carries on chucking water out the back, and yesterday the water coming out the heat exchanger was just over blood heat... Nah dont fix wot aint broke
 
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