Guys,

My over flow bottle is nearly full and I have noticed it bubble slightly, one or two a second. Is this normal?

 

Pour the excess coolant back to the header tank, squeeze any air out of the system and then take it for a blast with lots of boost.
If the expansion tank is full again then chances are its a head gasket failure.

 

Is the temp gauge running hot?
I'm not sure but if your giving the car loads of stick and the temps are high you would see a rise in the expansion tank and when the car returns to cold it should go down, But I'm probably wrong

 

ive had small bubbles in my over flow since i got the car 2 years ago. never overheats, never overflows. try changing the rad cap. it might not be sucking the water back into the header tank properly. when it overheats is when you need to worry.

 

If the tank is emptied first down to the min level then it may rise an inch or two over the max level when driven but WILL drop back to min when allowed to cool overnight.

A major HG failure adding gas to the system will cause the expansion level to rise rapidly and spill out.
HGs on their way out will cause the level to rise well above normal and perhaps top the expansion tank and will not allow the level to return to min. when allowed to cool down.

The key points are to empty the expansion tank contents back to the system, bleed the system and have the expansion tank level at min. when cool.
This can then be a reference point to spot what is going on.

The OP may just have an airlock in his system.

 

If the tank is emptied first down to the min level then it may rise an inch or two over the max level when driven but WILL drop back to min when allowed to cool overnight.

A major HG failure adding gas to the system will cause the expansion level to rise rapidly and spill out.
HGs on their way out will cause the level to rise well above normal and perhaps top the expansion tank and will not allow the level to return to min. when allowed to cool down.

The key points are to empty the expansion tank contents back to the system, bleed the system and have the expansion tank level at min. when cool.
This can then be a reference point to spot what is going on.

The OP may just have an airlock in his system.

 

good advice there butty. that is what i did. i set mine to min level when cold as a reference.

 

what year car is it I had something very similar but found it was the plastic header tank,the joint had gone where the metal goes round the middle allowing air into the system.