CRV Sport Mystery

gday guys, well here goes...son bought a 2003 CRV sports with 215000kms, started and drove without a hitch, he noticed that it would "use" about 20mm of water out of the radiator every day or so

took to mechanic who pressure tested cooling system, held pressure but noticed that the overflow was 3/4 full (that's where water was going) sooo new radiator cap and keep eye on levels. noticed after week that it started to send water to overflow tank and not sucking back, checked radiator cap, covered with copper stuff (crack sealing stuff), cleaned that off and all was good for another week then same again...repeated above all good..

son took car to city and had temp get to 3/4's pulled over and put approx 1 - 2 liters water/coolant in radiator didn't check overflow, bled system of air and then drove to accommodation for night, got to accommodation and noticed a hissing noise and steam from under bonnet, temp on 3/4...popped bonnet and steam/water coming from overflow bottle it was full of coolant..

next morning topped up drained overflow and drove home 200kms, got home no loss of fluid, took back to mechanic who got it to running temp and pressure tested system with no drop in pressure, left pressurized for 24 hours and popped out spark plugs, no water in cylinders...

last couple of days back to coolant going into overflow and not sucking back, no oil in water and no water in oil, starts and runs like a dream, have noticed the main fan is not working, we are doing our heads in so have come to ask the collective some help to see what else we should check out...many thanks and appreciate the help, he feels like shite as his first car he has bought

So just to make sure we get off on the right foot. No water in oil and vice versa. Car doesnt leak fluid anywhere and doesnt drop pressure overnight. While car runs for longer periods, it overheats (sorta) and sends water to overflow (classic job of rad cap when the temps go up). Then noticed the fan isn't working. Ok well replace the fan but that doesn't fix the water being sucked back into the motor from the overflow which is what we want. You replaced the radiator cap and cleaned it (cooling system is full of gunk) but what you didnt mention you did or checked is the hose going to the overflow. It sounds like the pressure is pushing whatever shit is in it out so the water can flow to the overflow BUT it appears that MAYBE the gunk is preventing the water from going BACK into the cooling system so maybe take off the hose, clean it, pull out the overflow and clean that too then we can rule out that its a hose/overflow bottle issue. Get back to us when you've sorted that out :)