Hi, I have a Peugeot 307 and a while back whilst driving the display said stop. I had someone look over it and they said the water was fine and then undone a little valve cap and said water should be flowing through this but it wasn't. They got it flowing and i regularly checked it although each time it was not flowing. Today i noticed when the water tank cap was on tightly no water flowed through this valve pipe when the cap was removed however if i undone the water cap so it was only on loose then the water flowed fine. Today whilst driving on the motorway my car told me to stop and when i checked there was no water in the water tank at all. I topped it up and drove about a mile and the cars temp shot up again and told me to stop. The water had all gone again. I managed to get home but cannot understand where the water is going as there is no leaks that can be seen however although water can flow through the pipes it is getting blocked somewhere. I have had the thermostat changed but it has made no difference. I really need my car but am very scared to drive it now. Any help will be really appreciated.

nike1601, June 2012

Check your coolant temperature sensor, it's located at top right side of block. This is the heart of your cooling system.

Brett, February 2017

doens't seem to get water going around the motor get hot

barney, June 2014

ps is the oil level overfull and milky looking if it is water is getting into oil

bob, June 2012

if bleed it at both places then start it up fill water bottle 1/2 to 3/4 full leave room for some air and water expansion.start it up with bottle cap tight ,after about 10 secs rev it up.do this 4 times if you loosen top and there is pressure there then most likely the head gasket has gone.once its run for 5 mins it will build up pressure as normal due to water getting hot and expanding.if there is air in the top of the engine this quickly makes steam and builds up pressure so it must be bled first.if you have no pressure after you have first started it but still have a problem it then take out the termostat and try it without as these are often faulty.hope this helps

bob, June 2012

Thank you. I will try starting the engine tomorrow (it's already dark here) and wait to see if the water goes down. I shall then top up to the correct point and see if it helps. Someone mentioned water getting into the engine to me - Is this something that could be happening? If so is it easy for me to check if this is happening? Sorry for the questions and lack of knowledge! Many Thanks

nike1601, June 2012

if they get empty you need to bleed them at termostat housing as well.some have a small brass allen key on the top to let it out ,if theres air in the water can not get in to keep the head cool.on the termostat housing there 17mm nut you can take this out to let air out.when water comes out just screw it back in and nip it tight.if you have any air in it will soon get warm and damage head gasket.do not foget to antifreeze it if is right as with being alloy they soon do damage, and if they freeze up the water pump they strip the cambelt and do valves

bob, June 2012

Water in the cooling system, is under pressure, Its temperature will be able to go above boiling point, without boiling. (Boyles Law) So undoing a valve, should release the excess pressure, That is basically what radiator caps did. As no water flowed out of valve, until you opened the cap, NO pressure in the system, So probably not enough water in the system. Opening the cap, allowed air to go in, so water came out, releasing the vacuum, rather than from a pressure build up. You might have topped the tank up, But what about the rest of the cooling system. When you start engine, at a certain point water will be pumped around. At that point, extra water will need to be added, to top up again, the rest went into the block, You will need to do that a few times until the block is full, and the top tank is upto mark. Then when opening the valve, without opening the cap, water will flow. BUT do not forget to close all valves etc, and have the water up to mark. YOU will also need to do something about antifreeze/summer coolant. AS none will be in your system.

SD, June 2012