Technical Coolant level question.

[Stavros2]

I don't want to hijack an earlier thread about cooling system so i will start my own.
I have a 2009 1.1 active eco. I have had an airlock in the system for some time, heater on and off, sometimes its hot other times cool, i set about fixing this and bled the system using the screw near the heater hose, this has fixed it, heater hot now, the coolant system holds pressure for days when cold (car not used) if i unscrew the header tank cap i can hear the pressure hiss out (no leaks) question is this, i fill the tank to max, then go for a run, when i shine a torch to check level, it is below minimum, if i undo the cap, the water level rises to where it was when i filled it, is this how it should work? ie, is this ok.

 

[jimboy]

Yes.

 

[varesecrazy]

Its a pressurised system.. so it looks like the cap is doing its job

IF the reservoir was easier to see..

You would see the level drop away as the cooling fan cuts in..

Charlie

 

[koalar]

You still have air or gas in the system. As it compresses the level goes down. As it expands when the cap is removed the level goes up. Needs sorting ASAP

 

[koalar]

There's two bleed screws the other is at the top of the radiator left hand side if you are facing the car. This should be done first. Undo when cold then top up until some liquid starts to exit the hole.

 

[koalar]

When pressurized the level shouldn't go to minimum. When hot the level should rise slightly

 

[Stavros2]

You still have air or gas in the system. As it compresses the level goes down. As it expands when the cap is removed the level goes up. Needs sorting ASAP

I don't quite understand why you think i have a problem, i seem to have conflicting replies, i would have thought that when the car gets hot, pressure should build up, every car i have owned, if you loosen the rad cap pressure hisses out, my panda does not overheat, does not lose water etc. where should the water level be when the car is hot and cap still in place?

 

[DaveMcT]

Coolant level cold should be above the minimum. I set mine between max and min lines. Level goes up when hot as coolant expands.

Paraoxically the hot level is different if you run engine until hot with radiator cap removed. This is because the hoses expand slightly with normal running pressure. However, the fluid expansion causes a much bigger volume difference.
Set level between the lines when cold. Job done.
If the coolant tank is too dirty, use a wood dowel as a dip stick to check fluid level.

 

[koalar]

is below minimum, if i undo the cap, the water level rises

shouldn't do this unless there is air/gas in the system

 

[Stavros2]

OK, i have just been to the car, i have filled the rad tank to the max mark, then run the engine till the temperature midway, i checked both bleed screws, the one near the heater matrix still had air in it, so i bled it, stopped the engine, water level was just above min, so i topped it up to max, ran the car again, heater mad hot now! far better than it has been, temperature reading normal, no overheat, stopped the engine, shone torch on reservoir, level at max, it seems ok, will not know until i go for a decent run next week, but i am confident i have got all the air out, presumably all this started off when i had cam belt and waterpump done last year.
Thanks for all the help and advice

 

[koalar]

just keep an close eye on it over the next few weeks.

 

[Stavros2]

just keep an close eye on it over the next few weeks.

Will do, thanks

 

[DaveMcT]

OK, i have just been to the car, i have filled the rad tank to the max mark, then run the engine till the temperature midway, i checked both bleed screws, the one near the heater matrix still had air in it, so i bled it, stopped the engine, water level was just above min, so i topped it up to max, ran the car again, heater mad hot now! far better than it has been, temperature reading normal, no overheat, stopped the engine, shone torch on reservoir, level at max, it seems ok, will not know until i go for a decent run next week, but i am confident i have got all the air out, presumably all this started off when i had cam belt and waterpump done last year.
Thanks for all the help and advice

Filling it to max when hot means the system will most likely throw out some excess coolant. A lower level after the first drive would be normal as the coolant has found its correct level. It should then remain constant.