Volvo MD2020 overheating

[Plevier]

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

I normally use about 2300 I was only up near 3000 because of exceptional conditions. I get more like 5kts though (Sun Odyssey 32).
I had cleared grille the week before.
Lots of water coming through.
Alarm going off too low wouldn't explain the steam and eruption from the overflow bottle!

 

[jerram]

Had the same problem 2 years ago mine was a part blockage on the fresh water side of the heat exchanger it is the hose/joint that is under the heat exchanger a right bugger to get at but cheap to fix, I would think it was 75% blocked with crud and ran fine until you push the revs up.

 

[rivonia]

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?

NOOOO Sorry. We cruise at between 1500 and 2300 rpm's and that is economical and gives between 4-6 Kts.

However we do not push her above 3200 RPM's at all.

 

[penfold]

Things to check; is the FW coolant pump impellor worn to any extent(also the housing which it runs in) and is it securely attached to its shaft? Is the thermostat working?

 

[Plevier]

Had the same problem 2 years ago mine was a part blockage on the fresh water side of the heat exchanger it is the hose/joint that is under the heat exchanger a right bugger to get at but cheap to fix, I would think it was 75% blocked with crud and ran fine until you push the revs up.

Hadn't thought of that will check. Thanks.

 

[Plevier]

Things to check; is the FW coolant pump impellor worn to any extent(also the housing which it runs in) and is it securely attached to its shaft? Is the thermostat working?

FW pump is iron centrifugal like a car one isn't it? Shouldn't be worn at 450 hours. No seal leaks. Good circulation through calorifier.
Stat definitely opens at sensible temperature - you feel header tank warm up suddenly after a few minutes. Can't guarantee it opens fully of course. Swine to remove to test!

 

[penfold]

FW pump is iron centrifugal like a car one isn't it? Shouldn't be worn at 450 hours.

No it shouldn't, but if the impellor is spinning on its shaft or has lost blades then it will not work well enough to keep the engine cool at high power settings.

 

[All The Gear No Idea]

No it shouldn't, but if the impellor is spinning on its shaft or has lost blades then it will not work well enough to keep the engine cool at high power settings.

The sea water impeller is indeed rubber, but this the previous entry is about the fresh water pump.

Did anyone mention the exhaust elbow? These can coke up and rust up leaving a very narrow opening, thus restricting output gases. I believe this would cause an overheating situation.

My engine only revs to 3k rpm - I guess that's down to the way the linkages are set up/a throttle end stop or the like.

My Saildrive leg has the water inlets on each side, but also a 1" diameter hole on the bottom of the leg. When I replaced my lower drive seals, I took a piece of cane to clear out the void in the leg, using the hole in the base. It's a big void and was pretty clear on mine. However I have heard of a case where mussels had taken up residence in this void. I was going to say food for thought, but that'd be crass!

Good luck and please let us know the fix!

 

[Neeves]

Our MD2020, or one of 2, overheated once - we had a jelly fish 'impaled' over the saildrive - so it did not affect the prop but basically sealed the water intakes.

You can check the blocking of the water intakes of the saildrive easily, just take the hose pipe of the inlet valve at the top of the saildrive - you can also blow down the hosepipe. We ream the saildrive out with a wire coathanger every time we haul out or beach and back flush with a hosepipe (fitted to the valve on the top of the saildrive). Here many of the dealers bypass the saildrive inlets and simply introduce a new hull fitting for the salt water feed (the holes on the saildrives are a bit small and easily blocked) If it was coking/calcium blockage of the exhaust elbow - it'd expect a dirty discharge.

Jonathan

 

[penfold]

The sea water impeller is indeed rubber, but this the previous entry is about the fresh water pump.

Yes, it was me who posted about it. I have encountered cast metal coolant pump impellors with lost blades due to casting flaws, and others that have become loose on their shafts. The ones with plastic impellors are less prone to blade loss, but seem more prone to being loose on the shaft.

 

[Plevier]

No it shouldn't, but if the impellor is spinning on its shaft or has lost blades then it will not work well enough to keep the engine cool at high power settings.

Yes, anything can fail, agreed, but it does seem rather unlikely!
However, when you've exhausted the possible.....
Another thing I may have to check.
Still no definite answer.

 

[Plevier]

NOOOO Sorry. We cruise at between 1500 and 2300 rpm's and that is economical and gives between 4-6 Kts.

However we do not push her above 3200 RPM's at all.

Yes I thought we had a misunderstanding!

 

[Ruffles]

You can establish if the cause is insufficient raw water cooling by placing your hand (cautiously) over the exit of the wet exhaust. The water shouldn't be more than warm.

If the raw water is flow restricted by the exhaust then the rubber seal on the input side of the calorifier will balloon when you rev the engine. It doesn't take much corrosion to restrict the wet exhaust manifold and cause overheating. You can try blowing into the inlet but without a new manifold to compare with it's hard to tell.

I've replace our MD2030 manifold twice in 12 years. Each time we had overflowing fresh water coolant and warm water in the bilge.

 

[Plevier]

You can establish if the cause is insufficient raw water cooling by placing your hand (cautiously) over the exit of the wet exhaust. The water shouldn't be more than warm.

If the raw water is flow restricted by the exhaust then the rubber seal on the input side of the calorifier will balloon when you rev the engine. It doesn't take much corrosion to restrict the wet exhaust manifold and cause overheating. You can try blowing into the inlet but without a new manifold to compare with it's hard to tell.

I've replace our MD2030 manifold twice in 12 years. Each time we had overflowing fresh water coolant and warm water in the bilge.

I really don't think this was it. As soon as the alarm went I looked over the side and there was lots of water flowing as usual.
The exhaust elbow stays cold to the touch.
The rubber seals on the heat exchanger do not feel pressurised.
When you say you have replaced the manifold, I suspect you mean the elbow? The manifold is part of the heat exchanger housing casting and is 1100 euros! http://www.marinepartseurope.com/en/volvo-penta-explodedview-7740690-25-4152.aspx

 

[Ruffles]

I really don't think this was it. As soon as the alarm went I looked over the side and there was lots of water flowing as usual.
The exhaust elbow stays cold to the touch.
The rubber seals on the heat exchanger do not feel pressurised.
When you say you have replaced the manifold, I suspect you mean the elbow? The manifold is part of the heat exchanger housing casting and is 1100 euros! http://www.marinepartseurope.com/en/volvo-penta-explodedview-7740690-25-4152.aspx

Agreed. My suggestion only works if you end up with MORE water in the fresh side.

Try the cheap things first! Buy a new thermostat. Take the old one out and pop both together in a saucepan. Heat and see if they open at the same time and the same amount. You will need a new fresh water pump gasket - I think. Ours failed yonks ago. Shortly after forgetting to open the sea cock before starting the engine

 

[Plevier]

Try the cheap things first! Buy a new thermostat. (

Unfortunately on the 2020 (unlike the 2030) that means removing the header tank/exhaust manifold the 'stat is in there! Quite a job.
http://www.marinepartseurope.com/en/volvo-penta-explodedview-7740690-26-4159.aspx

As stated before, it's certainly opening promptly at a sensible temperature, of course just possible it is not opening fully.

 

[JohnGC]

Sorry to come late to this thread but we had an overheating incident with our 2020 + saildrive last week. The circumstances are not quite the same but the cause hasn't been mentioned so far and could lead to different symptoms depending on the circumstances.

Raw water from the exhaust had always seemed on the low side to me (this is our 2nd season of ownership on a boat 10 years old) but picked up as soon as the revs increased.

Having entered Salcombe, the engine was idling while we tidied the mooring when the overheat alarm sounded.

The impeller, raw water strainer and anti-syphon where all OK so I used the dinghy pump to blow air back down into the intake (saildrive) in order to check for blockages. I could hear air escaping from the raw water filter / hose joint. Tightening the hose clip didn't help so I removed the hose and discovered that the plastic spigot to which the hose attaches had collapsed and cracked. It is significant to note that air was being drawn into the raw water system - raw water was not being ejected.

A short length of copper pipe and some silicon sealant where enough to fix the leak and the flow of water from the exhaust at idle is much increased.

If you have found no other fault it may be worth testing for a leak that will allow air to be drawn into the raw water system. I know you said your water flow was OK but did you reduce the revs before checking over the side? I've described my symptoms but these could vary depending on the size of leak, engine speed, water temperature and engine load.

Finally two notes of appreciation;
- to someone on these forums who suggested using the dinghy pump to check (and attempt to clear) blockages.
- Brian at www.sailingmarine.co.uk who cheerfully gave his time for free, suggested the solution (without selling me a new strainer) and who supplied me with an inch of copper pipe.

 

[fontmell]

I had the same problem, found it difficult to isolate and kept re curring whatever I did (i convinced myself for with no logical reason it was the head gasket) - A passing coment of if wrong anti freeze used will cause crud convinced me to clean whole system using rad flush (did it twice and was very murky) and changed thermostat (I am still convinced old one was ok) Filled with VP anti freeze and now all is spot on. so my bet is crud.,

 

[john_morris_uk]

A couple of points:

On our 2040 there is a plate on the side of the header tank/manifold that gives you access to the thermostat.

Secondly, we have had overheating on our 2040. The symptoms were the coolant pouring out of the header tank overflow pipe and the engine bilge filling up. After lots of head scratching and testing all sorts of things (including setting up a test bed to pressure test the heat exchanger stack) it was discovered that the exhaust elbow had clogged up. Brick cleaner ( as others have said) sorted it out and all problems solved.

 

[electra]

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