Tony-B
Posted: Mon Sep 06, 2010 8:52am
Post Subject:
changing anti freeze
First of all I am going to assume this is a typical tank cooled system with the tank on the hull side and not keel cooler tubes or a horizontal tank. The tubes would probably be OK to just ignore but a horizontal skin tank would need a pump and small pipe rigging up to drain the horizontal tank. Remember antifreeze is classed as hazardous waste and must be disposed of in a responsible manner. Your local tip may have facilities. The easiest way is to drain into the bilge and engine drip tray so first of all throughly clean the drip tray of oil and fuel. Buy 2 x 5 litres of antifreeze unless you already know the capacity of the system. On a skin tank system any capacity quoted in the manual is probably incorrect. You can use two or five year life antifreeze but it is important that you do not refill with red/orange/purple antifreeze if the old stuff is blue/green. If you do get the "wrong" type do not panic, just go through the changing procedure three times with ordinary water, running the engine to warm each time to flush all the old stuff out of the system. If your coolant is horribly brown you may want to use a cooling system cleaner before putting the new stuff in. The instructions are normally on the package. Somewhere on the engine there should be an engine block drain plug or tap so locate it. At the same time check to see if the engine has an internal anode. If it has obtain a new one so you can replace it when the system is drained. Remove the filler cap. Remove the lowest hose on the skin tank - it may be easier to remove it from the engine end and push it down into the bilge. This will drain most of the coolant. Remove the block plug or turn on the tap. Pump the coolant from the bilge and drip try into drums for disposal. Replace the plug/turn off the tap. Check all hoses for hardness, crunching when squeezed, softness caused by fuel/oil contamination and perishing/splitting. Change any affected hoses. Replace the lower cooling hose. Now, using a suitable pot like a pint glass or jug, refill pint of water, pint of antifreeze until the system is full. Remove the skin tank bleed plug or turn on the skin tank bleed tap until coolant comes out, continue the refilling. Now run the engine on fast idle with the filler off, manipulating any hoses with bows in the to ensure air trapped in the bends rises up to the filler. If you suddenly get a lot of air out top up as required. when the engine is hot re-bleed the tank, fill the system right up to the filler neck and refit the filler cap. When the system cools note the coolant level, this is the "full" level that you will normally top up to. Note how many pints you have put into the system so you know how much antifreeze to buy next time. Normally the calorifier will not need bleeding but if it now refuses to heat the water locate the return hose (usually going into the engine close to the hose running to the engine water pump). Get someone with a can of antifreeze mixture to help you. Remove the filler cap, run the engine at fast idle, remove the return hose quickly placing your thumb over the engine side of the break. Friend keeps the system topped up and you replace the hose after the air bubbles have come out. Tony Brooks
