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BARGES: All about barges and barging - building, buying, maintaining, equipment, handling on the water, etc. (Public)
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TOPIC: Engine coolant system - clean and replenish

Engine coolant system - clean and replenish 25 Nov 2021 17:31 #126911

  • Paul Hayes
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Hi Andy

From what you say, it sounds like there is one circuit, serving both engines.

This would be keel tank of some sorts, from which coolant is drawn by the engine water pumps, and circulated around the blocks,
exhaust cooler (if fitted) and presumably the oil coolers, and then returned to the keel tank for the absorbed heat to be dissipated by conduction to the river water, on the outside of the keel tank.

I've seen John Deere engines that use a one circuit cooling system, as described above, the engine cast iron water pump circulating keel cooled coolant through the block and coolers, return to the keel coolers.

I've seen a few Mitsubishi engined generators, which have definitely been two circuit systems, primary - engine water pump circulating coolant around block and one side of a heat exchanger.
Secondary - a rubber impeller type pump driven by the engine circulating either keel tank coolant or river water through the other side of the heat exchanger. The heat exchanger working like a car radiator.

Could it be that you have a single circuit (direct cooling) main engine, and a two circuit (indirect cooling) generator?

To answer your question, the only way to find out if it will work is to try it. Make sure that you have a good hose supply to make up the losses, and run the engines in short bursts. The effects will soon soon become apparent.

Some photos of the generator, and main engine pipe layout may help in predicting what may or not happen.

Where is your barge?

Paul Hayes

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Engine coolant system - clean and replenish 25 Nov 2021 15:55 #126908

  • Andy Parker
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Thanks Paul however as I mentioned there are no lower drain plugs and certainly nothing that will drain the contents of the keel cooling block. If I drain the system I'll have to undo several hose connections and find a way of sucking out the cooling block (assuming I want to be that thorough).
Alternatively (as mentioned in my original post), is it possible simply to drain and top up with water at the same time, as the engines run, until I'm happy all the old coolant has washed through. Then drain sufficient water from the system to allow for the addition of antifreeze concentrate.

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Engine coolant system - clean and replenish 25 Nov 2021 14:45 #126907

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I fully agree with Balliol's post.

There's nearly always a hose at a lower point than the engine block drain, especially if keel cooled.

Loosen the clips, and wiggle the hose partly off the spigot to allow coolant to drain into a bucket or similar. Remember to take off the pressure cap to stop a vacuum forming.

Paul Hayes

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Engine coolant system - clean and replenish 25 Nov 2021 10:59 #126904

  • Andy Parker
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Thanks Balliol
Given what you've said I think my use of the word flush is incorrect. Everything on the engine looks really sound, no sign of deterioration of hoses, clips etc.
So I need to remove the existing coolant and replace it. With that in mind can you envisage any issues with my proposed approach, bearing in mind that I cannot find any drain plugs/taps lower on the engine.
Many thanks

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Engine coolant system - clean and replenish 25 Nov 2021 10:47 #126903

  • Balliol Fowden
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I don’t have specific experience of the Scania engine but the cylinder block drain tap is likely to be small bore and easily blocked by any solid debris. Removing the tap from the block normally opens a larger hole, which will allow the block to drain more effectively.

But, presuming a keel cooled closed circuit system, the block drain will almost certainly not be the lowest point in the system and solid debris (corrosion scale etc.) will obviously tend to collect at the lowest point. You need to establish where the lowest point is and try and break into the system there.

It is usually better to back flush the system. This is more likely to remove debris trapped or lodged in “corners” of the system, behind cylinder liners or in cooler stack tubes etc. With the engine running there is usually a generally upward trend in the cooling system flow so a static back flush is likely to be more effective.

You are likely to need to remove any thermostat fitted to allow back flushing, which is best achieved using a water hose connected in to the system positively at the highest point.

Personally if I felt it desirable to flush the engine then I would be taking the opportunity to remove all hoses to check them or replace routinely, replace any suspect clips, directly flush oil coolers, coolant heat exchangers etc. Even a power back flush will not remove everything.

Do you have symptoms? Overheating? At the risk of appearing lazy I think I can say that in over 50 years owning numerous engines in boats (private and commercial), plant, cars, generators etc. I have never specifically set out to routinely flush a system. I might do it in a racing engine of course!

But it would be a good idea to check all plumbing, and take the opportunity to flush every area you open up.

If the engine is or has been direct raw water cooled, or if it has been left for extended periods without inhibitor in the cooling system, then it is a different matter and there is every reason to give it a good flush, but I don’t think that your proposal will achieve a lot beyond replacing the fluid content.

Balliol.
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Engine coolant system - clean and replenish 25 Nov 2021 10:08 #126902

  • Andy Parker
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Hi Paul
From what I can tell, it is one interconnected cooling system for both main engine and generator with one pressurised top up tank with radiator style cap.
My thinking is that if I use just the drain on the main engine and run both engine and genny I will flush both through as they're on the same circuit.

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Engine coolant system - clean and replenish 25 Nov 2021 09:55 #126901

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Hi Andy

I'm guessing a few of us are in a similar position.

I've just found this advice from an Antifreeze manufacturer.
Here

I found the "when should I change" bit interesting. Specifically on the appearance and consistency remarks.

I use a hydrometer type "antifreeze checker", which not being as totally accurate as a refractometer, gives a good indication of coolant protection level.

You do not say if you have keel cooling? Whether you have "Primary" and "Secondary" circuits?

Does the expansion / headed tank supply the "Primary" engine contained circuits only?

Most engines have an integral coolant header / expansion tank for the sealed (engine only) circuit. Check each for a car type "radiator cap".

Or does it supply a keel system?

Does the keel circuit cool the engines via heat exchangers? A good indication that you have two types of circuit.

Is the "Secondary" circuit river water?

I would expect to find a drain point on the generator engine as well.

Sorry if this is not the direct answer you were looking for. But it's important to identify exactly what you are trying to achieve.

Paul Hayes

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Engine coolant system - clean and replenish 24 Nov 2021 16:59 #126898

  • Andy Parker
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I want to flush through our engine coolant system. We have a Scania Vabis DN11 and a Mitsubishi SL4 generator. Both are hooked into the same cooling system. As I don't know when it was last flushed and the inhibitor replaced and we have now had the boat for 2 years, I would like to nail it.
I have found a drain tap half way up the main engine casing. The coolant top up tank (in the wheel house) is connect with a 22m copper pipe. My question is:

Can I run both engine and generator, open up the drain tap to a collecting vessel, keep a flow of water in to the top up tank and assuming I don't let it run low and allow air in, flush the system through?

Once clean, I was hoping I could then drain sufficient water from the drain tap to make space for the appropriate quantity of inhibitor.

Any thoughts very welcome

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