Volvo MD2020 overheating

[Plevier]

I have a 2003 Volvo MD2020D in a 31 ft boat, total engine hours from new 445 so quite young. Fitted with a Kiwi Prop pitched for 3400rpm at WOT under way. Normally I use 2200-2500 cruising rpm, occasionally more for a cleanout. Never had overheating.
On Saturday afternoon we were trying to go from Beaulieu to Lymington into 30kts wind and 3kts tide. (You can tell we don't know the Solent well.) I was using more revs than normal, about 3000. After a while the engine high temp alarm went off and on investigation about 1.5L of coolant was in the tray under the engine.
Cautiously refilled with hot water, no boiling off when doing that so the engine wasn't terribly hot. All seemed OK. Carried on (slowly!) at 2500rpm then after a while increased to 2700 then 2900. A bit later it happened again, alarm went and there was bubbly water/steam mixture coming from the header tank overflow pipe.
Refilled and carried on a bit slower and finally got there.
Next morning I took out the heat exchanger to clean, it was fine. All the seawater side is good, lots of flow and the exhaust elbow, pipe and water trap are cold. Feeling the calorifier hoses when running at 2500rpm they are pretty hot to touch but not boiling hot and you can just about keep your hand on the engine header tank, so I think the 'stat (operating range 75-87 deg C) is OK.
So I can find nothing wrong. Have done several hours since then at lower power with no problems.
I thought an engine like this would be configured so it would run indefinitely at high power without overheating, particularly in a cool climate. Am I wrong?
Has anyone had similar experience or any ideas of potential problems please?

The engine has always had a/freeze with inhibitors in it, there's no reason to expect sludge in the cylinder block. I changed the a/f 2 years ago and tried to drain and flush the engine but couldn't undo the dreadful square headed cast iron drain plug on the block so couldn't flush. Anyone got any tips on getting the little so and so out? You can't get a spanner near it and a hex socket just rounds the corners; is it possible to get a square socket to fit it?

 

[scottie]

May be worth checking the fresh water pump drive belt

Try a crow foot socket on the plug and change it to the earlier model engines set up which had drain cock
Get your VP supplier to check for you.

 

[Plevier]

Thanks, the belt is fine, forgot to mention it as checked.

 

[puddock]

Temporary blockage on seawater cooling inlet? (Polybag etc?).
How long were you at 3000 rpm?
I know the max revs quoted are @3500 rpm but I don't think this takes into account prop pitch etc (how hard the engine is working to get there- I could be totally wrong there though).

 

[Mrnotming]

End rubber caps on heat exchanger, larger clips and smaller clips really tight?
But as you say you disassembled so were the clips tight?
Also ruled out bits of previous impeller rubber lodged anywhere?If you have been able to see through the heat exchanger tubes as you suggest, not the reason!
OP's suggestion of temp plastic bag sucked over inlet may be the answer?
Coolant level was short of the collar of the filler pressure cap by about an inch?They do no like to be filled up. Mine exits to a Plastic lemonade bottle 1.5 l but never much in there.
Only time we had your scenario was when we sucked up mud.Then the alarm went off pronto(we were in Italy!) smelly rubber aroma and impellor in bits.Coolant all over the place too despite the overflow bottle.
Don't know why I'm writing this as I do not have a good answer!
I suppose a sail drive inlet could be wrapped both sides by a plastic bag, but the prop would likely be vibrating muchly!Did you notice any vibration or imbalance?
Going back to car mechanics, for a moment, if there is bubbling to your overflow tank, could be a blown head gasket?
Check oil for whiteness, and any mystery increase in oil level on the dipstick indicating water in the sump under the oil.

 

[vyv_cox]

The two phrases you have used,'bubbly water/steam' and 'not boiling hot' suggest the cause may be a gasket failure or crack. When engines boil they are clearly very hot, smell of oil and the whole engine compartment suggests very strongly that something is wrong. Yours doesn't sound like that from your description. When gaskets fail the high temperature is local, hence the alarm sounding without all the coolant coming to the boil.

A good mechanic can carry out a pressure test of the coolant system to establish whether this is the cause. For petrol engines they can also examine the coolant for traces of hydrocarbons but I'm not sure this can be done for diesels.

 

[Plevier]

End rubber caps on heat exchanger, larger clips and smaller clips really tight?
yes

But as you say you disassembled so were the clips tight?
Also ruled out bits of previous impeller rubber lodged anywhere?If you have been able to see through the heat exchanger tubes as you suggest, not the reason!
yes

OP's suggestion of temp plastic bag sucked over inlet may be the answer?
The inlet is one of the teardrop shaped ones on the bottom of the hull. If a bag was held by suction it would soon drop off when engine stopped - but it happened again. No I don't think so.

Coolant level was short of the collar of the filler pressure cap by about an inch?They do no like to be filled up. Mine exits to a Plastic lemonade bottle 1.5 l but never much in there.
I've also fitteda n overflow bottle. That's where it was gushing out of.

Only time we had your scenario was when we sucked up mud.Then the alarm went off pronto(we were in Italy!) smelly rubber aroma and impellor in bits.Coolant all over the place too despite the overflow bottle.
Don't know why I'm writing this as I do not have a good answer!
I suppose a sail drive inlet could be wrapped both sides by a plastic bag, but the prop would likely be vibrating muchly!Did you notice any vibration or imbalance?
No

Going back to car mechanics, for a moment, if there is bubbling to your overflow tank, could be a blown head gasket?
Gentle bubbling yes, but this was ejection of a very bubbly mixture after stopping the engine.

Check oil for whiteness, and any mystery increase in oil level on the dipstick indicating water in the sump under the oil.
Neither.

Thank you for your time thinking, but I don't think any of those fits, but yes I'm scared about the gasket.

PS Not a bag on the inlet - as soon as the alarm went I looked over the side there was plenty of water flowing.

 

[Plevier]

Temporary blockage on seawater cooling inlet? (Polybag etc?).
Don't think so - see other reply.

How long were you at 3000 rpm?
30 mins maybe.

I know the max revs quoted are @3500 rpm but I don't think this takes into account prop pitch etc (how hard the engine is working to get there- I could be totally wrong there though).
I was thinking this way too. In the same way that WOT static revs are lower than under way, with the resistance of a strong headwind it will take more power for the same revs.
But the engine is only 18HP and has a huge heat exchanger, I would have thought it would take it.

.

 

[Plevier]

The two phrases you have used,'bubbly water/steam' and 'not boiling hot' suggest the cause may be a gasket failure or crack. When engines boil they are clearly very hot, smell of oil and the whole engine compartment suggests very strongly that something is wrong. Yours doesn't sound like that from your description. When gaskets fail the high temperature is local, hence the alarm sounding without all the coolant coming to the boil.

A good mechanic can carry out a pressure test of the coolant system to establish whether this is the cause. For petrol engines they can also examine the coolant for traces of hydrocarbons but I'm not sure this can be done for diesels.

Yes this is my biggest fear, but it should not be likely on a young engine normally gently treated, and as I said aren't these things built for prolonged running at high (relative!) power? It's a Perkins industrial engine isn't it?
The bubbly mixture was VERY frothy, and giving off plenty of steam, only time I've seen a case of gasket leak it was fine froth. Also it was continuing to eject for some while after stopping the engine. It was like depressurisation boiling as it got past the 12psi radiator cap. It was showering up through the neck of the overflow bottle (no cap, it's just an Oasis bottle with a pipe into it) like race winner's champagne. It was completely clean, no trace of soot or oil scum.
I've only overheated once before when I forgot to turn the seacock on. That time the alarm sounded but the engine didn't boil over, no fluid loss at all, just a bit more expansion loss into the bottle. This sucks back in as the engine cools. It did smell hot.
When running again at 2700rpm for over an hour on Saturday, there was no trace of anything coming from the overflow apart from the initial small expansion loss. I have an overflow bottle and would have seen any gas bubbling or the level rising.
I'm very perplexed.

Edit - to me it seems like localised boiling in part of the block but an engine this age with inhibitor in should not have any sludge blockages. I want to get the wretched drain plug out and poke around with a wire.

 

[united]

Did you find out what the problem was - I have the same problem! Thanks.

 

[Plevier]

Did you find out what the problem was - I have the same problem! Thanks.

Not with any certainty.
I finally got the drain plug out - tip, the female end of a 3/8" sq drive socket set extension fits it and use a wrench on the male end of it! - but there was no trace of sludge in there.
I've checked the rocker clearances all OK.
Yesterday it was OK for 30 mins at about 2600.
Puzzlingly I found that at wot it wouldn't reach 3000 so something has happened to either the engine or more likely (I hope) the kiwiprop.
I did a run up in neutral and it reached 3900 which is correct.
So indications are that I simply ran it too hard but it's mysterious.
What are the circumstances of your problem?

 

[Retired in Crete]

The OP should try changing the filler cap. (You could use the one from your car, they are usually interchangeable)

John

 

[Plevier]

The OP should try changing the filler cap. (You could use the one from your car, they are usually interchangeable)

John

The filler cap is fine and holds pressure thanks.
It's not designed to run with pressure normally - the high temp alarm is 95 degrees.

 

[rivonia]

We have twin MD 2020's Have never run them above 3200 RPM's Mine are year 2000. Never had any heating probs. I just think that the MD2020's are not meant to go over 3200, whatever anyone says.

Hope you get your problem sorted soon. Must be worrying

 

[Plevier]

VP's spec for the engine is max power is at 3600 and it should be propped for wot to give 3200-3600.
Hence my tweaking of the prop to fall in that range. Kiwi's recommended pitch gave well under 3000.
Normally I use up to 2500 with an occasional high power run to desoot.
Do you mean you run at 3200 for significant periods?

 

[Merlin38]

Sounds like the head gasket leaking under heavy load and will get worse over time. If the coolant is frothy then it is almost certain to be the head gasket. Sorry, but I had the same problem on my Volvo md 17c and ignored it and hoped it would go away until I got a hydraulic lock in one cylinder. Oops, but luckily no bent con rod. I changed all 3 head gaskets and re-torqued after 50 hrs.

 

[Plevier]

Sounds like the head gasket leaking under heavy load and will get worse over time.

Thoughts appreciated, but to save repeating it all, please see post 9 for why I don't think so.
I'm still getting nothing down the overflow pipe at all, no coolant loss and no trace of water in the oil. The coolant has never been frothy other than during the "boiling" incident.
My experience is that once a head gasket has started to leak it won't do it only at high power but all the time. Is your experience different?

 

[rivonia]

VP's spec for the engine is max power is at 3600 and it should be propped for wot to give 3200-3600.
Hence my tweaking of the prop to fall in that range. Kiwi's recommended pitch gave well under 3000.
Normally I use up to 2500 with an occasional high power run to desoot.
Do you mean you run at 3200 for significant periods?

Yes that's what I mean- works for us.

 

[Plevier]

Yes that's what I mean- works for us.

What rpm do you get at wot then?
You appear to be running at a much higher power level than me if you cruise at 3200. Not 2300?

 

[Daydream believer]

I run at 2000 to 2300 on a 31 ft yacht with saildrive. This gives 6 knts plus & fuel economy is good. Any more revs & fuel economy plummets ie 1.66 litres per hour down to 2.5 litres per hour
Check the inlet has not been antifoulled & not cleaned out between coatings. You can soon restrict flow
Check you have the inlet cock open fully & the handle has not worn & slipped on the spindle
You still get water through but not enough so the engine gets hot
Check the switch panel. I had to have a new one at £300-00 could be incorrect setting making it go off at too low a temperature
To reduce temperature a bit in an emergency ie entering harbour, try running the hot water off slowly so the water heater draws some heat off the system
If you are running correctly there is quite a strong flow of water though the exhaust