Expansion bottle - correct levels

[cockybundoo]

Hi

I wonder if someone can clarrify something for me. At what level should the water be in the expansion bottle?

The FULL marker is very low down on the tank, almost at the bottom and my levels always seem to be visible in a tube at the bottom and never in the tank.
However I have read several times that the expansion bottle should be about 1/2 full !!

This would mean that the water level in my bottle would be WELL over the Max Full mark.

Any help would be gratefully appreciated.

Regards
Mike

[kitesurf_phil]

The level in the expansion bottle should be to the min mark when cold and the max mark when hot. Try taking your rad cap off when the engine is cold to see if you have enough coolant. The other thing to check is that the pipe from the exapansion bottle is not perished, so it is sucking air in instead of the water from the bottle.

[cockybundoo]

Cheers Phil

One of the things that I find confusing, is that I cannot see a MIN level, only the FULL or MAX level which is where the bottle starts to narrow/funnel down to a pipe at the bottom, which is about an 1".

I take it that if I take the Rad cap off, the indication that there is enough coolant is by the presence of coolent?

Do I need to top up the coolent in the bottle, upto the bottom of the tube that goes from the rad cap into the expansion bottle, in order that it can be sucked back into the rad?

[Gamedawn]

I take it that if I take the Rad cap off, the indication that there is enough coolant is by the presence of coolent?

Yes

Do I need to top up the coolent in the bottle, upto the bottom of the tube that goes from the rad cap into the expansion bottle, in order that it can be sucked back into the rad?

Fill the bottle to around the max mark when cold. Don't worry about putting too much in - any extra will get blown out the overflow when the engine is hot

[NiftyNev]

Here is a pic of expansion tank with the hose removed to show the correct length and the Full and Low marks. Coolant should be at the Full mark when cold. These marks can not be seen when it is in installed position so use the widest section as a guide. Level can be seen easily by looking down between side of radiator and the tank.



Nev

[TonyN]

As long as there is coolant in it between the levels its generally OK.

More important is the level at the cap on the engine.

The expansion tank is only a reservour for when the hot water expands to a greater volume than the system can hold, then it squeezes past the cap and into the bottle. As the coolant in the engine cools, it contracts leaving a vacuum, so the coolant in the bottle is sucked back into the engine.

So if you fill the bottle up, it will overflow when the coolant from the engine trys to go into it. If its empty, its a sign the motor is losing water, and its replacing it with what was in the expansion tank.