Little Dorrit
Well-known member
I have spent some time researching how to do this on a Bukh DV24 but am none the wiser. How should I approach this task?
Idiots guide to flushing a raw water engine
- Thread starter Little Dorrit
- Start date
vyv_cox
Well-known member
Are talking flushing through with fresh water or acid to remove deposits?
Little Dorrit
Well-known member
I was planning on using an acid solution to remove any deposits. My temperature alarm occasionally goes off when the engine has been running for about 15 minutes but just for a few minutes and then the alarm stops. The engine block does not seem too hot (warm to the touch) and the outlet water hose attached to the exhaust is warm so I am assuming water is going through the block. I have checked the thermostat and it's working ok. So I thought it would be a good idea to do a flush of the raw water cooling system using Redlyme (or diluted brick cleaner/radiator descaler) to eliminate that as a possible cause of the alarm occasionally going off.
vyv_cox
Well-known member
Flushing it hot is complicated and based on my toilet experience with HCl, totally unnecessary. I would drain the block first, then remove the thermostat and pour in Rydlyme slowly. You may get quite a bit of effervescence so take it steady.
Dellquay13
Well-known member
This is method I used on my Yanmar 1gm10, but the principle is the same.
Remove the engine block internal anode and seal the hole with the plate (I reversed it)
Clamp the thermostat bypass hose (with a small g clamp)
Remove the thermostat and refit the cover.
Take the hose from the water pump output and connect it to an old bilge pump.
Put 1litre Rydlyme and 1 litre freshwater in a bucket with the bilge pump (and the thermostat)
Take the water hose off the exhaust mixing elbow and put in the bucket
Pump the Rydlyme mix around the engine, in bursts and rests for a couple of hours.
Flush it with freshwater for 10mins using the same setup
Put the engine back together
Remove the engine block internal anode and seal the hole with the plate (I reversed it)
Clamp the thermostat bypass hose (with a small g clamp)
Remove the thermostat and refit the cover.
Take the hose from the water pump output and connect it to an old bilge pump.
Put 1litre Rydlyme and 1 litre freshwater in a bucket with the bilge pump (and the thermostat)
Take the water hose off the exhaust mixing elbow and put in the bucket
Pump the Rydlyme mix around the engine, in bursts and rests for a couple of hours.
Flush it with freshwater for 10mins using the same setup
Put the engine back together
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Little Dorrit
Well-known member
I am not sure that would work on the Bukh engines, it's not easy to dismantle the thermostat housing.
Gixer
Well-known member
Dellquay, that’s a great system.
Sorry if this is a daft question but why do you reverse the anode?
Sorry if this is a daft question but why do you reverse the anode?
Little Dorrit
Well-known member
I think it probably would dissolve in the acid although Rydlyme only contains 10% HCl so probably not necessary.
Dellquay13
Well-known member
I read it somewhere, possibly on the Rydlyme instructions, it is to protect the anode. It may also lessen the effects of the Rydlyme, if it is reacting with the zinc as well as the salts
Dellquay13
Well-known member
It wasn’t that easy on the Yanmar either, there was a rigid steel oil tube in the way that made it hard to get the ‘stat cover off.
James_Calvert
Well-known member
If the engine isn't overheating, as you describe it, then maybe all is fine except for an oversensitive temperature sensor. Had that with a Bukh 20.
seumask
Well-known member
I used this method on my Bukh DV 24 4 years ago and can recommend it. Rydlyme is the right stuff to use and is very unlikely to do damage that more concentrated acids could do. I can confirm that there was a fair amount of foaming up at the begining and that it is really important to take out the thermostat which is not difficult on the Bukh's.
I used a caravan water pump, the type that goes in the water tank avaliable for under £20 eg.
12V Submersible Water Pump Camper For Caravan Motorhome High Flow Whale Pump | eBay
morgandlm
Active member
I used Proflush on my old DV10. I set up a circuit around the engine with a connection to the raw water inlet pipe to the engine that is normally fed by the water pump. I connected the pipe from the thermostat cover back into the bucket containing the Proflush and had an old central heating pump to pump the whole lot round. I had removed the thermostat itself and the pencil anode which I feared would disappear anyway. It worked really well. You get a colour change in the Proflush fluid as the salt and lime dissolves. It also fizzes well at first! A bit of a faff but the cooling water quantity increased noticeably after the process.
David
David
Little Dorrit
Well-known member
I have managed to remove the thermostat and it's totally gunged up so I am sure that's the problem.
Little Dorrit
Well-known member
I have managed to remove the thermostat so will try your method or simply pour the mixture in and leave it for a few hours before pumping it out.
seumask
Well-known member
I Suggest you arrange a pump around the system as I understand from previous threads the Bukh often builds up scale on the injection pipe going into the engine block, just behind the flywheel IIRC. Secondly you have no way of knowing where the poured in fluid will reach unless you pump it around.
If you cant get a pump rigged up then rig up an in and an out so you can flush a few litre's repeatedly though the engine. High level funnel into the pipe as it exits the water pump and drain from the pipe to the exhaust elbow into a bucket?
PS remember to leave the thermostat in the bucket to clean it as well.
davidmh
Active member
Since you say the thermostat is all caked up I suggest you clean the thermostat with a kettle descaler, I would also scrape out any muck in in the thermostat housing. That may solve the problem.
David MH
David MH
Dellquay13
Well-known member
If the thermostat needs descaling, shouldn’t the rest of the cooling system should be done as well?
I have been told by marine engineers that the bukh engines are happiest when freshwater cooled as they are prone to scale problems when raw water cooled as they have some narrow waterways.
Little Dorrit
Well-known member
Yes, a good idea to descale the cooling system too as the same time which I have now done.
davidmh
Active member
Little Dorritt , did you flush it out with the circulation method or just filling it up and letting it sit for an hour. I figure on the Bukh if you fill it from the thermostat housing it will reach all the parts by gravity.
David MH
David MH
