sloshing sound after coolant change

Not sure about the Megane, but quite a lot of Renaults have a bleed-screw fitted in one of the coolant hoses that needs to be opened during refilling the system. This caught me out on a Renault 5 many years ago - after fitting a new radiator it only took about half the expected amount of water to refill the cooling system because there was the mother of all airlocks in the feed to the heater/autochoke.

Air trapped in the cooling system is generally a bad idea, especially on french cars- they tend to overheat given any excuse!

I would locate the heater pipes at the bulkhead or nearby and prepare one by loosening the clip and breaking the pipes hold on the stub, loosen the expansion cap and run the engine upto temperature. Jam the throttle at a fast idle, then wearing gloves carefully pull back the pipe and let some squirt out[1]- with luck you'll get some air out.

You may need to do the same else where on the system at a point near where you can hear the sloshing sounds.

Tim..

Hi,

There is a bleed screw at the thermostat. I followed the instructions in the Haynes manual which told me to fill the system until coolant containing no bubbles emerged from the hole. I found that I quite quickly got a steady stream of coolant coming out of the hole so I plugged it up.

The engine doesn't appear to be over heating.

I'm a little confused about your technique for getting rid of a air lock: Wouldn't opening pipes up cause more air to get into the system? I had a bit of difficulty getting pipes on and off before (but that was the first time I've ever done it) so I'm a little wary of doing that with the engine running.

Rob

It won't if its just got an air lock in, its just that the bit where the air is will overheat....

Is the top of the expansion tank higher than the rest of the cooling system? I know on the 405 you have to make a header bottle, from a coke bottle or something, to put in and then fill, making sure that the level is higher than the rest of the system.

The time honoured method on Renault 5/9/11/19/Clio etc is to fill the expansion bottle to near the top, open the bleed screws on the top hose and waterpump to carb base hose, then stick your mouth round the top of the expansion bottle and blow. When you spray water everywhere with no bubbles, shut the bleeds and stop blowing. Then run the engine for a couple of minutes, switch off and repeat.

Rich.

After having driven it a couple of times and topped up the coolant, the sloshing noise appears to have gone away. I'm taking this to mean that there are no more air pockets. I suppose I could open the bleed screw to check but I see no reason why this should be needed at this point.

Rob