Volvo penta Md2030 coolant loss

[eagle160]

Hi, yet another engine issue topic.

My Md2030b has been running fine at 2000rpm for last several hundred hours (approx 2000 total), very occasionally seemed to have a bit of coolant boiled over, and on replacing coolant it's usually quite brown & dirty (after a year guess that's usual?)

Recently we decided to rev the engine a bit higher 2600 rpm and max out for a few minutes (as I read running at too low revs will result in excess carbon build up). Few issues since then :

- max rev 3100 below spec
- occasional loss of coolant (small amounts 100-200ml)
- occasional addition of something to coolant (fumes or water unsure but it's brownish) which results in overflow.

No consistent pattern has emerged, some days no loss, some days A bit of overflow, some days a bit of loss.

No evidence of water in oil, no smoke, and runs smoothly as usual.

Hence I suspect a potential leak in salt /fresh water system and /or blocked exhaust elbow which causes excess suction at higher revs.

Tomorrow will dismantle heat exchanger, check all hoses & jubilee, and plan to clean /replace exhaust elbow (this one has done at least 500hrs, perhaps a lot more).

Am I on the right track in terms of diagnosis and potential fix? Or looking in wrong area? Any tips?

 

[blaggard]

Ive had this problem a few times, almost certainly the exhaust elbow blocked up, try dismantling and cleaning with a wire rod and muritic acid. doesnt hurt to clean the heat exchanger as well, I use wooden kebab sticks to poke through the holes to avoid damaging the tubes.

 

[VicS]

Hi, yet another engine issue topic.

My Md2030b
Tomorrow will dismantle heat exchanger, check all hoses & jubilee, and plan to clean /replace exhaust elbow (this one has done at least 500hrs, perhaps a lot more).

Am I on the right track in terms of diagnosis and potential fix? Or looking in wrong area? Any tips?

Yes you are probably on the right track .

Ensure that the clips on the heat exchanger end caps are tight when rebuilding as coolant can be lost to the seawater side or seawater enter the coolant if they are not.

The apparent state of your coolant is a little worrying . It should not be brown after a year if it has been filled with the correct concentration of antifreeze. It seems very likely than seawater has been getting in and causing corrosion of the engine coolant circuit. Due probably to a combination of a restricted exhaust injection point and one of the end caps not sealing properly on the tube bundle.


If you remove the tube bundle for cleaning ensure that its is replaced correctly with the various holes correctly aligned.

Worshop manual on Bluemoment might be useful http://www.bluemoment.com/manuals/Volvo_Penta_MD2010-20-30-40.pdf

 

[eagle160]

Thanks all, will start tomorrow and report back.

 

[eagle160]

So I've spent most of the day (and 350 euros!), preliminary conclusions are half blocked but quite corroded exhaust elbow, leaking heat exchanger end muff (most likely cause of salt water ingress hence corrosion inside heat exchanger as evidenced by brown water), and heat exchanger insert having been placed upside down by previous owner. Not sure what the effect of the incorrectly placed insert was, engine been running ok for a year...

 

[john_morris_uk]

Heat exchanger stack fitted the wrong way up would lead to a slight loss of efficiency in the cooling system. The hole is to allow air out and therefore allow the heat exchange stack to fully flood itself with coolant round the pipes. I expect the pumped coolant sorted itself out for the most part and the cooling system is so over rated that it didn't make any difference.

Have you thought of flushing the engine through with some suitable cleaner to remove any 'brown sludge' left?

 

[Cantata]

A spate of these problems occurred recently over on the Moody Owners forum with the heat exchanger in the MD2020 which is presumably a similar design to the 2030.
Perhaps triggered by partly blocked exhaust elbow, the rubber boot on the upstream end of the heat exchanger leaks sea water into the fresh water circuit. The coolant gets discoloured, coolant is dumped thro the overflow but confusingly the level often stays at normal in the heat exchanger.
There are two hose clips on the forward rubber boot, the inner and smaller one is the culprit having slipped forward and off the end of the tube stack. Certainly on the 2020 the tube stack is only just long enough to be clamped by the boot at each end and needs to be carefully centred (as well as the right way up) before tightening the clips.

 

[Allergy]

A spate of these problems occurred recently over on the Moody Owners forum with the heat exchanger in the MD2020 which is presumably a similar design to the 2030.
Perhaps triggered by partly blocked exhaust elbow, the rubber boot on the upstream end of the heat exchanger leaks sea water into the fresh water circuit. The coolant gets discoloured, coolant is dumped thro the overflow but confusingly the level often stays at normal in the heat exchanger.
There are two hose clips on the forward rubber boot, the inner and smaller one is the culprit having slipped forward and off the end of the tube stack. Certainly on the 2020 the tube stack is only just long enough to be clamped by the boot at each end and needs to be carefully centred (as well as the right way up) before tightening the clips.

+1 to the above & can be a right sod to get the tube stack centred

 

[eagle160]

Thanks for help, managed to get it centred I think, no more coolant loss and running fine.

 

[wiggy]

Thanks for help, managed to get it centred I think, no more coolant loss and running fine.

I would recommend checking your thermostat, my 2020 was doing the same as the OPs and eventually the thermostat failed shut due to corrosion, from salt water entering the fresh system, causing overheat and seizing.