Volvo Penta MD2020D Overheating.....Again!!!

steveej

steveej

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So I have had an intermittent overheating issue on a new to me boat since the start of this season.

I believe there were a number of causes all contributing to the issue most of which should now have been resolved.

Before the delivery to my home port, I stripped the heat exchanger pipe stack, had it cleaned, the fresh water system flushed, acid bathed, flushed many more times. Struggled to get above 2k revs on delivery and by the time I got back I stripped it all again to find standing water in the spigot coming out the exhaust elbow.

Struggled to get the elbow off as the previous owner had managed to completely round off the most difficult to access nut holding the elbow to the studs.

Got the local volvo dealer involved, removed the entire header tank in order to get the elbow off, replaced elbow and at the same time replaced the thermostat. Was fine when I picked it up in October and not overheating at 2,500 revs..

Took it for a spin around the bay on Saturday to warm the oil up for an oil change and guess what, after no more than 5 mins at 2,200 revs, the alarm goes off and there is about 800ml of coolant in the engine bay.

Plenty of raw water out of the exhaust so the I am absolutely convinced it is to do with the fresh water side.

I am now wondering whether the belt could be slipping. Are they prone to slip at higher revs when they are worn? It appears tight enough. I plan to replace this on the weekend and try again as I am at my wits end as to what it could be given the overheating is so intermittent.

Could it be that the cap on the header tank is not holding pressure and allowing the coolant to boil?

Only other thing I can think of is the fresh water circulation pump is not working properly but it appears to be spinning around and nothing is leaking out of it.

Any other suggestions?
 
I had a similar problem with our smaller 2010. I went through all the seawater side and had good flow but still had an overheat issue. Slipping belt is a possibility especially if your battery has run down a bit.Usually accompanied by lots of black dust in the engine bay.

Before you either buy a very expensive water pump:
Check belt tension
If this still doesnt solve your problem then consider looking for a blockage or restriction in the flow to and from the manifold to the water pump.
I had a really blocked outlet spigot caused by lack of inhibitor or antifreeze .

Check the rubber pipes have not gone soft and are collapsing a combination of slight restriction and the pump working fine might suck a pipe flat down intermittently?
Check finally if the thermostat correctly fitted and opening.

I was led to believe the water pump is pretty well bomb proof so keep looking elsewhere first.

On my 2010d the thermostat is seated between block and manifold so I found it easier to remove flexible tube off exhaust elbow and remove entire manifold with elbow attached. The 2020 may be mounted differently.
 
I would look to establish whether the coolant pump is circulating coolant.
Does the coolant get to an even temperature around the relevant part of the circuit before the thermostat opens?
I'm not that familiar with that model of engine to know whether there is any good place to check the water temp in the block.

Is there a calorifier? is it plumbed in correctly? is it getting hot? Could there be excess air in that circuit?
An IR thermometer can be useful to see if the block is not heating or you can strap temperature sensors to hoses to get a clue if water is circulating as it should.

Thermostats mostly seem to fail open but you can test it.
As well as failing hoses, it's possible for things to be blocked by rust, gasket goo, bits of old gasket etc.

But sometimes, it's head gasket allowing air into the circuit creating an airlock.

As an experiment you could run it with no thermostat, but that is an experiment not a fix.
 
Are you sure the rubber end caps are not leaking from the salt water circuit to header tank and expelling the coolant,quite common on this Perkins based engine.
 
steveej said:
Plenty of raw water out of the exhaust so the I am absolutely convinced it is to do with the fresh water side.

I am now wondering whether the belt could be slipping. Are they prone to slip at higher revs when they are worn? It appears tight enough. I plan to replace this on the weekend and try again as I am at my wits end as to what it could be given the overheating is so intermittent.

Only other thing I can think of is the fresh water circulation pump is not working properly but it appears to be spinning around and nothing is leaking out of it.

Any other suggestions?
Click to expand...

I'm assuming that both your references above are to the coolant circulation pump. Provided that the belt is reasonably tight, say 1.5cm deflection each way on the longest run, then the pump pulley will not be slipping unless the pump bearings were seized, which they obviously are not. The alternator is more likely to start slipping before the circulation pump.

Check to see exactly where the coolant is coming out from as this will enable you to decide whether a raised engine temperature is causing the coolant to be expelled or whether a coolant leak is causing the engine to overheat.

Richard
 
The thermostat was replaced when at the volvo dealer. It is a pain to get to as you need to remove the entire heat exchanger housing (but I had to do that anyway to get the exhaust off).

There is a calorifier the hot water tap does produce VERY hot water!

End caps are also new and are sealing properly. If they were not sealing, the raw water pump would be forcing sea water into the fresh side , pressureising it and it then venting into the bilge. I have had this problem when I cleaned the pipestack before the delivery and did not replace the hose clips properly. It is however quite easy to spot as when you take the cap off, the heat exchanger appears still full of coolant even though there are litres of coolant in the bilge. This requires a full flush of the fresh water side to get rid of the salt.
 
I would imagine it's possible for the coolant to be at higher pressure than the seawater, so the exchange might go the other way?
If the calorifier is getting hot, that suggests coolant is circulating from the head through the calorifier. Probably means the circulation pump is working.
So, either the heat exchanger is not being put in circuit by the thermostat, or it's not working. Seawater only flowing through a few tubes or something?
Does the header tank get hot as soon as the thermostat should be open?
 
From memory, the heat exchanger tube has 2 holes in it that must be aligned with their respective holes in the housing, if they are not and say the tube has been rotated by 90 degrees, then as I understand it the coolant cannot flow - I couldn't imagine a Volvo dealer getting that wrong, but worth checking, simple fix if it is that.
 
If you have a calorifier, just check that there isn't an airlock in it. If there is air trapped in it, this will cause the engine to overheat
 
I went through this a couple of months ago

http://www.ybw.com/forums/showthrea...ant-auto-removes&highlight=MD2020+overheating

The thread is worth a read as it incorporates all the possible reasons for over heating - and, importantly, remedies.

The replies and advise are professional and valid.

My problem was caused by the belt slipping caused by the alternator 'slipping' on its bracket. This might be impossible - but it happened.

Our heat exchanger tube had no top or bottom (nor left and right) but it did fit better end to end differently. It fitted better one way round than the other.

Having solved the problem we did have an airlock - which did not cause any issues - but did mean that the coolant side was not totally full - initially - and needed to be topped up.

Do have lots of spare coolant. It is likely you will be removing and re-attaching the rubber gasket things at each end of the heat exchanger tube - and loss of coolant is inevitable. Do attach a bottle at the end of the coolant overflow and if the issue continues you can at least re-use the coolant expelled. Coolant is not expensive but you don't want to to be forced to stop working on the issue as a result of something as simple as - not enough coolant.

Don't be intimidated by an absence of technical terms - most of us are similarly handicapped - and we will understand and, provided you are descriptive, know what you are talking about.

To test for belt tension - can you turn the coolant pump by hand - as is. If so - the belt is too loose. I had no black dust from the belt slipping - but I could turn the pump by hand. Sadly I did not try this first up (as I never thought the alternator could slip). To tension the belt you need 3 hands - 2 to hold the bolt and nut on the 'tensioner' and one to lever the alternator 'out' to tighten the belt. And you need a hefty rod to lever the alternator. I used a bit of re-bar (reinforced concrete rod) but you might have a socket brace or a hefty screwdriver.

As you have had a Volvo service engineer on site I would have thought he would have looked at the coolant pump (and belt) and ensure the alternator was well secured.

Jonathan
 
I have plenty of spare coolant. The more I think about it, the more It hink it could be the belt slipping. I could turn the coolant pump in one direction but not the other, but the tension seems ok.

However, there is heavy corrosion on the sliding plate that the alternator tightens onto in order to tension the belt. I am wondering if it slipping over time. The belt also appears worn as the teeth have turned diagonal shape where they have been worn by the pulleys over time.

I think cleaning up the corrosion and a new belt may sort it.

Does anyone know if a loose header tank cap would allow the coolant to boil?
 
steveej said:
I have plenty of spare coolant. The more I think about it, the more It hink it could be the belt slipping. I could turn the coolant pump in one direction but not the other, but the tension seems ok.

However, there is heavy corrosion on the sliding plate that the alternator tightens onto in order to tension the belt. I am wondering if it slipping over time. The belt also appears worn as the teeth have turned diagonal shape where they have been worn by the pulleys over time.

I think cleaning up the corrosion and a new belt may sort it.

Does anyone know if a loose header tank cap would allow the coolant to boil?
Click to expand...

A loose header tank cap or one where the rubber seal has gone will make boiling much more likely and will definitely allow the coolant to be ejected from the overflow and overheating to occur.

Richard
 
steveej said:
Does anyone know if a loose header tank cap would allow the coolant to boil?
Click to expand...

If the coolant reaches 100C (or whatever the boiling point of the mix is a ~1 bar) then it will boil if the system is unpressurised. If it's pressurised then the boiling point will be higher. But surely it shouldn't be reaching 100C anyway - if it is then a leaky cap will exacerbate the problem.
 
I think that black dust from the alternator belt could arise from a misalignment perhaps due to a bearing slackness on e.g. the circulation pump pulley. If so, perhaps the pump seals are leaking?
 
steveej said:
I have plenty of spare coolant. The more I think about it, the more It hink it could be the belt slipping. I could turn the coolant pump in one direction but not the other, but the tension seems ok.

However, there is heavy corrosion on the sliding plate that the alternator tightens onto in order to tension the belt. I am wondering if it slipping over time. The belt also appears worn as the teeth have turned diagonal shape where they have been worn by the pulleys over time.

I think cleaning up the corrosion and a new belt may sort it.

Does anyone know if a loose header tank cap would allow the coolant to boil?
Click to expand...

I should remember this as I spent a lot of time playing with the alternator position and the sliding bar (with the slot up the middle). Ours was also corroded, or the paint was bubbling and flaking, but no such that I thought it needed to be replaced. However it is very simple and, now that I think about it, should be easy to replace - but I don't recall exactly how it is configured.

The biggest problem is - you need to lever the alternator so as to tension the belt - you then need to tighten the nut on the bolt that secures the alternator in the desired position but to tighten the nut you need to restrain the bolt - and the hand needed to restrain the bolt is operating the lever. You need a third hand (wife (if available) - or think how to retain the bolt by jamming a spanner so that the bolt cannot move.

I could turn our coolant pump in either direction.

We had no sign of belt wear. Once the belt was tightened the problem disappeared - and the belt seems fine (we do carry a spare belt - which we have had, unused, since the engines were commissioned)

I don't know if rad caps are standard - if so any scrap yard would have lots. This was not an issue for me - we have 2 engines and could swap caps and eliminate the caps as the source of woe. You could take your cap to a scrap dealer - and see if they have one that matches.

Jonathan
 
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A friend bought one with the correct pressure rating from a local car spares shop for under £5.
This was after trying various scrapyards with no luck as he didnt want to pay marine prices.
 
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I had mystifying overheating on a Volvo 2003. Checked everything, everything seemed fine but it still got hot.

Eventually bought an IR thermometer which was invaluable in locating the problem - in the coolant circulation pump.

This had been refurbished by a a Volvo agent a few months before but the new impeller was an imperfect fit on its shaft. At the low temperatures at which I could check it the impeller was a tight fit on the shaft and seemed OK. When heated up it rotated on the shaft and so all circulation stopped.

Worth a look?

The effect was as you describe - overheating at anything above tickover.
 
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