Coolant level question

[colnet]

I have a B4204t2, when i check the coolant level 1st thing when cold the level is bang on the max mark, when i drive her till hot the level drops to just on the min mark, i leave her for several hrs and the level returns to bang on the max mark, is this a turbo thing? I ask this as my B4204s the level stays the same hot or cold, cheers for any advice.

colnet

[pierremcalpine]

Mine does the same thing (not sure if it goes all the way down to min but the level definitely goes down). It might just be that the pipes start to flex a bit as the engine heats up (and as the car gets older). I do not believe that it is turbo related. You will note that if you let the car sit for a bit (say 45min) and then CAREFULLY take the coolant cap off using a big rag for extra protection that the fluid will very likely bounce back to the high mark. You will also hear some pressure being released. It's just some minor pressure build up is all.

[colnet]

Hello Pierre, cheers for that, i only thought it turbo related as my S stays the same level which obviously is not a turbo, and as you described, my level after 30 mins, taking off expansion lid returns to the correct level with a hiss, once again cheers.

[loely]

As the temp goos up you have more pressure on your water. Water under pressure boils at higher temperature so the coolant water does not boil around 100° C but at a much higher t° so it will not boil out the tank (radiator)and the cold level regains normal as you would not lose any water.

[colnet]

Cheers loely, I learn something new everyday, just have never noticed this before, once again thanks.

[IainG]

Hi
I would imagine there is a small air pocket somewhere in the coolant system. As the engine warms up the coolant will expand, and as there is some air in the system the water will expand into that air pocket and the level in the reservoir will fall. If there are no air pockets in the coolant system the coolant will then only be able to expand into the coolant reservoir(expansion vessel) and the level will rise.

Iain

[clarkey1984]

Mine always sits around an inch or so above the max when's up to temp, thats why on cars that have a cold level and a hot one, the hot level is always higher than the cold, I think that might be why they call it an expansion bottle because it literally does expand with heat, I would wholeheartedly agree with the sentiment of there being air in the system somewhere.

[druid]

Mine's like it to - Gdi

[colnet]

Seems to me some do this, some do not, normal in other words. There might be a small air lock somewhere but it can stay where it is (not doing any harm) and I know what a world of pain that can be finding that. As long as the level returns to normal im happy.

cheers

[loely]

Can someone tell me where that air is hidden? It moves along with the water so it must be on the highest point which is the expantion tank.
Most French cars have little plastic screws on the rubber pipes to let the air escape .If you exeed the boiling point under pressure 120° + the pressure will open the expantion container filling cap and let go some water to reduce the max pressure. When motor is cold the water level will be to low.
When you heat up water in your kitchen you can see little bubbles comming up ,where are they hidden?