Strange blockage in cooling system

[galeus]

I am servicing the cooling system on my BMC 1.5 Thornycroft diesel engine. When i came to the short water pipe from the thermostat housing to the Bowman heat exchanger, the exit pipe was blocked with blue a/freeze sludge and gel. The boat was running fine last November when we came out of the water. Am I looking at problems further back in the system i.e the water pump, or is it an over winter thing from me winterising the cooling system?

 

[Ammonite]

Have you changed the type of antifreeze you are using as mixing inorganic and organic types can do this?

 

[galeus]

Have you changed the type of antifreeze you are using as mixing inorganic and organic types can do this?

Interesting thought, I can't remember when I last changed the a/freeze or what sort it was, but for about the last three years I have been on Morris antifreeze from ASAP. I think I'll get the 5 litre container out and do a bit of research of what I have in now. Thanks for the info.

 

[LittleSister]

Interesting thought, I can't remember when I last changed the a/freeze or what sort it was, but for about the last three years I have been on Morris antifreeze from ASAP. I think I'll get the 5 litre container out and do a bit of research of what I have in now. Thanks for the info.

I don't think you need to worry about what you have in now. It sounds like your first job needs to be removing all the current coolant, along with the congealed sludge, then flushing through thoroughly with fresh water, then filling with a suitable water/anti-freeze mix.

I've read of enough people finding engine coolant outlets etc. being blocked by sludge, and having to poke them through or siphon coolant out to change it, that I don't think sludge in coolant only comes from incompatible anti-freeze mixtures.