Volvo MD11C Cooling

CPD

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I have nopticed the temp gauge creeping up more often recently and think I should be looking at descaling the direct cooling bits of the engine. Does anyone have a step by step idiots guide as to how to do this, chemicals, what, how, what to look out for etc ?. Thanks again.
 

CPD

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PS. The impeller is fine and inlet filter is clean. Engine is original 31 years old and has been getting a lot of use recently.
 

pyrojames

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If is it the same as the MD2B check the thermostate housing. There is a small bypass bleed hole which can sometimes get blocked by debris. If is it blocked the thermostat fails to get a uniform supply of engine water and tends to cycle violently.
 

VicS

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Assuming you have considered all the obvious like inlet, strainer, pipework, gearbox cooler, thermostat, exhaust injection point that the pump is in good condition. ie body and cover plate not worn, AND you have a GOOD flow of water from the exhaust. The first thing to look at are the small water passages in the exhaust manifold that carry the incoming water from the inlet connection on the underside to the two cylinder heads. They are quite small and could well now be nearly blocked. Take the manifold off and clear them with a stout wire. It may be all that is necessary.

While the manifold is off you will get a chance to peek inside the water galleries in the heads and assess the amount of scaling present.

Once the manifold is clean if you still have a problem then the engine cooling itself is probably well and truly clagged up.

Do you get a decent flow of water from both cylinder block drain cocks. If not that probably indicates that the water jackets are bunged up but check that it is not just the cocks that are blocked especially the one on an elbow behind the alternator.

A steady rising and falling of the temperature reading also indicates a clagged up cooling system.

There are two possible routes. One is to dismantle the whole thing, heads and blocks off (OK if you are OK with that sort of work) and clean it all mechanically. Ideally that means removing the liners as well. According to the w/s manual they can easily be removed by hand .... but after 30 years they'll almost certainly need apress The alternative is to try to improve things to a satisfactory state by chemical cleaning.

Hydrochloric acid, obtainable as brick cleaner, is the quick drastic method, but I would be afraid of doing more harm than good. I would opt for an acid based central heating boiler descaler such as Fernox DS1 or DS3. DS1 is based on organic acids and will probably be better on iron oxide deposits while DS3 is based on sulphamic acid and may be better on limescale.

It will be a slow process with either of these two which will need to be circulated fairly warm.

What you need to do is rig up a decent sized bucket that the inlet suction can be fed from and another to catch the water coming out of the exaust. You then need a means of transfering the water from the second back to the first. Ideally that will be a small electric pump but it could be done manually with another bucket.

Before you start remove the thermostat so that the solution has a chace of going round the engine and not just through the bypass. In fact even block off the bypass in the thermostat cover if you can

Fill the system wth fresh water and run the engine for a bit before introducing the descaler. Use it more concentrated than suggested for boilers (double say) Run the engine to circulate the solution and warm it up. When it is getting hot stop the engine for a bit and let it soak then run it again and repeat for as long as you can.

The problem is that the cylinder blocks are only convection cooled so periodically drain a litre or thereabouts from the drain cocks and return it to the bucket so that you do definitely get the cleaning solution down into the blocks.

When it's all done drain it all down and flush it through to waste with fresh water. Flush out the blocks via the drain cocks.

Do not forget to replace the thermostat and un block the bypass.

Your suction bucket is most convenient in the cockpit so that you do not spill stuff in the cabin but be careful to stop the flow when the engine is stopped or you will syphon the whole lot into the exhaust system and possibly the cylinders themselves.

Pyrojames may be right about the the bypass into the thermostat housing but at some stage that was changed. If yours is an early engine what he says may apply but not if is a later one.

Good luck and lets us know how you got on.
 
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I used Fernox DS3 (based on sulphamic acid) a coupld of time in the past - though in the end I got rid of the engine.

Basically I made up a solution as per instructions into a large bucket, removed the raw water intake hose from the skin fitting / sail drive leg and placed it in the bucket.

I then hung a bucket under the exhaust on the transom and used a little 12volt bilge pump to lift this back upto main reservoir with the raw water intake in it.

In this way you can run the engine circulating the water with the acid in it. The idea is to get the temperature of the engine high enough so that the thermostat opens and so that the chemical is at its working temperature. I found this a bit tricky in winter to be honest - might be easier in summer.

Having run it all through for a while once upto temperature, I flushed the whole thing through with fresh water.

It certainly reduced my overheating problems for the rest of that season (c. 2 years ago) - but I had to do it again the following year. It didn't seem to cause me any problems with seals / gaskets etc - but some seem to worry about this ...

Good luck
 

CPD

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Vics, thank you so much for your comprehnsive comments. I have a few questions regarding your initial checks. By gearbox cooler i take it you mean just check that there is a healthy through flow, that by "pump in good condition" again you mean that the water pump is ok, but what do you mean by checking the exhaust injection point ?. Thank you again for your help.
 

VicS

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[ QUOTE ]
I have a few questions regarding your initial checks

[/ QUOTE ] Yes to the gearbox cooler. Yes to the water pump, remembering that the inside of the pump can wear especially the cam plate, the end cover and the opposite end inside the body. Re the water injection point I meant make sure that is not restricted.

The general point was that it would be silly to start tearing into the engine without being absolutely certain that the problem was not external. If you have got a good flow coming out of the exhaust then it confirms that all the other things are OK.

A nice refinement of the whole procedure would be to return the solution leaving the engine from the top of the thermostat cover to the bucket in the cockpit and to rig up a separate supply of water to the exhaust injection. That would do away with the need to use a pump or an extra bucket but you would have to be VERY careful not to over do the exhaust cooling and to turn it off before stopping the engine.

Once you have rigged up all the temporary pipework it will be easy to repeat the clean in subseqeunt years.

Dont overlook those waterways in the exhaust manifold. The one to the rear cylinder is longer tha the one to the front one and is the one more likely to be the choked. It is also the more difficult to unblock.

Check the availablity of spares before you do any serious dismantling ( see a comment on the thread about the MD7)
 
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