Select to expand quoteTrek said..UncleBob said..Trek said..
The conclusion .... Grich you were right to be suspicious about the lack of coolant in the water, and your magnet idea Sam, I should have tried that, the black stuff is cast iron fragments.
Sandy went out to the boat today with a magnet and thats what he found. Motor is fine, just needs flushing and put in coolant! Recommendations for what kind of coolant would be welcome.
I think I would want to know where the iron fragments came from! Fresh water pump perhaps?
Cheers Bob.
Agreed Bob.
I believe they have come from the walls of the cooling system in its entirety. ie. The cooling system consists of holes bored through a cast iron block and the walls of those holes have oxidized. Previously I put a filter in line with the water and each time I flushed the cooling system with fresh water less was captured by the filter.
After we've flushed the motor a few times and put the right additives in we'll see if it comes back. Grich if you are around what additives do you suggest?
volvo coolant is the best for this eng ,it will have glycol and a inhibitor.glycol is for the anti freeze,anti boil and the inhibitor is for the corrosion control,it is very important that the inhibitor is kept at its correct level ,you normally buy test strips to keep an eye on it and top it up. fleetgaurd also make a good product available as a premix at most truck places.castrol sell glycol in concentrate which you can mix 50/50 with water then add a inhibitor.dont use car coolants as they are for alloy engs, most eng makes sell a cleaning agent to clean out the block,great to hear the eng is ok .
greg
Is there a sacrificial anode in the fresh water circuit? There are special types for fresh water, so if not, I guess the design would then rely on the additives for corrosion inhibition.
The result.... after concluding the black stuff was some kind of oxidation of the cast iron block by checking with a magnet (and it was magnetic) I got some radiator cleaner (for cast iron blocks) and as grich suggested some of the proper coolant containing rust inhibitor. Over four trips to boat since its on a mooring I ran the motor for 10 min on trip 1, with the radiator cleaner then drained it. Then refilled the cooling water system three times and drained it each time. One drain time number four I mixed in the right amount of coolant. Each time I carried out to boat 10L of distilled water and 10L of dirty water back to the shore. Got string arms now. Now the coolant is transparent and green and I think the motor is actually smiling 
Select to expand quoteTrek said..
The result.... after concluding the black stuff was some kind of oxidation of the cast iron block by checking with a magnet (and it was magnetic) I got some radiator cleaner (for cast iron blocks) and as grich suggested some of the proper coolant containing rust inhibitor. Over four trips to boat since its on a mooring I ran the motor for 10 min on trip 1, with the radiator cleaner then drained it. Then refilled the cooling water system three times and drained it each time. One drain time number four I mixed in the right amount of coolant. Each time I carried out to boat 10L of distilled water and 10L of dirty water back to the shore. Got string arms now. Now the coolant is transparent and green and I think the motor is actually smiling
great to hear its good,dont forget to test the injector leakage,it is a problem if the injectors have been removed at all
cheers greg
Select to expand quotegrich62 said..Trek said..
The result.... after concluding the black stuff was some kind of oxidation of the cast iron block by checking with a magnet (and it was magnetic) I got some radiator cleaner (for cast iron blocks) and as grich suggested some of the proper coolant containing rust inhibitor. Over four trips to boat since its on a mooring I ran the motor for 10 min on trip 1, with the radiator cleaner then drained it. Then refilled the cooling water system three times and drained it each time. One drain time number four I mixed in the right amount of coolant. Each time I carried out to boat 10L of distilled water and 10L of dirty water back to the shore. Got string arms now. Now the coolant is transparent and green and I think the motor is actually smiling
great to hear its good,dont forget to test the injector leakage,it is a problem if the injectors have been removed at all
cheers greg
OK I will. One think I forgot to mention in the cleaning process. I taped a super strong magnetic outside and under the cooling water reservoir during the process and it sucked up tons of the black stuff that I could then rinse out. Since it worked so well I left it there.
