Volvo MD2020 overheating

[Plevier]

Plevier
Did you ever get a reason / solution ? I have similar problem on my own boat now.

Not really but I have heard of some other incidents suggesting the cooling system may be a bit marginal in capacity. It was certainly working hard at the time of the problem.
Immediately after that I fitted a temperature gauge. Never had another problem before I sold boat!

 

[TSB240]

We had a very similar problem and found the aluminum spigot on the fw drain from the heat exchanger block was virtually blocked by crud an corrosion. No sign of any kind of sludge in heat exchanger tubes! Check all fw hoses and connections for blockages kinks and crud.

 

[Neeves]

I had a Volvo service engineer on our cat, for reasons other than engines, and he looked at our engine and made the comment that taking the heat exchanger off completely and having it professionally cleaned and painted would be advantageous. I took it to a local car radiator service company, they sand plated the whole thing and painted it. it look as good as new and cost about Stg35. Which I thought was good value, especially in Sydney. The engine has 2,000hrs and is about 18 years old.

Jonathan

 

[john_morris_uk]

A restricted exhaust (build up of carbon etc) in the water injection elbow can also give problems with overheating and loss of power. It's a common problem and worth checking. (Take the exhaust elbow off and have a look...)

 

[Ric]

My 2020D was plagued with baffling overheating problems for years. Diagnosis was very difficult because the overheating seemed to occur at random - sometimes it would work for hours and hours, then suddenly it would overheat within minutes of starting. I had to completely rebuild the engine before the problem cleared up - and I still don't know exactly what the problem was.

If I were faced with the same problems again, I would start with the cheap and easy things to check, working to more difficult later.
1) Check raw water circuit is giving a plentiful flow and exhaust outlet water is not hot. On my boat, it is about 10C warmer than the seawater at full revs.
2) Give the closed water circuit a good clean with Wynns radiator flush - there are some small cooling channels in the cylinder head and these can easily get blocked by corrosion crud.
3) Check the exhaust elbow. If blocked or partially blocked don't buy another Volvo elbow - fit a stainless steel replacement for about £240.
4) Replace thermostat - it is a cheap part but not so easy to get at.
5) Replace closed circuit water pump - expensive and difficult to get at
6) Take off cylinder head, check gasket for signs of blow past, check the small channels for crud.

I think my problems were a combination of reasons which is why it was so hard to diagnose.

 

[Neeves]

If you want detail on how to change your exhaust elbow search the forum for instructions and photos posted here by MM5AHO (aka Geoff) some time ago, maybe 1-3 years.

 

[ItchenSailor]

Our Sun Odessey 37 came with a 2030 matched to a Kiwi prop. It wouldn't allow any revs above 2700, although it would go to 3600 without a load. WOT would just give black smoke as expected and steam from the exhaust so we had to throttle back.
After a trip down the western Solent into the wind but with a weak tide doing just over a knot we decided to replace the prop with a Featherstream that self adjusts/ balances.
We now achieve 3400 and in calm waters we get 7+ knots and we run it for around 15mins wide open, although we start to see traces of steam from the exhaust it appears to be performing ok.
In the meantime we replaced all hoses,flushed the system, it was very gooey within the pipes of the heat exchanger although the pipes themselves were clean, exhaust elbow replaced, impellor replaced.

 

[Jokani]

Not really but I have heard of some other incidents suggesting the cooling system may be a bit marginal in capacity. It was certainly working hard at the time of the problem.
Immediately after that I fitted a temperature gauge. Never had another problem before I sold boat!

I believe early model 2020's had Jabsco raw water pumps, later models had a much larger capacity Johnson pump, the impeller size is significantly larger.

The two pumps are interchangeable, I have swapped for the larger.

I have taken a quick photo for comparison here:

http://www.westerly-centaur.co.uk/impeller-sizes

 

[electra]

I posted a few weeks ago that I had an overheating problem on an MD2020C. Symptoms were the heat alarm going off and a discharge of hot coolant from the tube below the cap on top of the heat exchanger. It would happen after running the engine at 2500 rpm for about 10 minutes or so. Running the engine had lower revs allowed it to run longer but eventually same problem.
The usual suspects on the sea water side were checked and appeared to be functioning correctly. The saltwater pipes through the heat exchanger appeared to be blocked and were rodded through - ran engine but same problem.
Despite removing the heat exchanger core which appeared to be thoroughly clogged and cleaning it in an ultrasonic bath the problem persisted. We then removed the heat exchanger completely to check the thermostat and this proved to be the the source of the problem. It had stopped working properly and now longer opened sufficiently. It was replaced, and everything else put back together, and no more heating problem. The end?

 

[Leighb]

When you said the thermostat no longer opened "sufficiently " I assume you mean that it opened a bit but not fully?
I have an overheat problem and the thermostats are next in line to check I had thought that they would either work or not at all.
Only partial opening could be the cause of my problem.

 

[electra]

The guys in the local engine workshop did the work. They showed the old thermostat to me but didn't say nor did I ask what precisely was wrong with it. Before the heat exchanger was removed we had discussed next steps which included looking at the thermostat and also at the fresh water pump. However when the HE was removed they immediately saw there was a problem with the thermostat and went no further. There appeared to be very minor discolouration / corrosion (?) on the engine block surrounding the thermostat. They suspected there may have been small ingress of salt water at some stage but of course we cannot prove this. They suggested that this may have been the result of hoses and jubilee clips not being correctly positioned (my words and not theirs) - implied it was a design issue which could potentially allow this type of problem to occur.
We had used a heat probe to determine the variation in temperature in the engine block and at the front and the back of the heat exchanger as the engine started and then heated up. Before the problem was diagnosed it seemed as if the thermostat was working as it should but patently it wasn't working properly. Now it has been replaced the engine is running normally. The above doesn't directly answer the question asked but describes what happened from my own inexperienced and not very technical perspective. On my return from holiday I will ask the engineer about the old thermostat but it won't be for a couple of weeks.