What is an expansion tank on a BMW?
A BMW expansion tank ensures that your radiator is always full, even when cold, and provides a way for hot fluid to expand without releasing fluid on the road below you. Factory BMW tanks are made of plastic, and will eventually crack, leak and fail. Check out our BMW cooling system tech page by clicking here.
What causes BMW expansion tank crack?
Expansion tanks cracking are caused either by the viscous fan coupling failing or the head gaskets are leaking but check the fan coupling first, If it just free wheels without pushing air when the engine is hot and the car is stationary.
Why is my expansion tank empty?
If you take a look at your coolant reservoir and notice that it’s nearly empty, this is typically a sign that you have a leak somewhere in your cooling system. If you don’t do this, it’s going to lead to even more coolant leaking out and, before long, you’ll have a coolant reservoir empty.
How does coolant expansion tank work?
Instead of sending the expanding coolant to the tank once it reaches a certain pressure, the coolant is always cycled through the radiator and out to the expansion tank. Here the pressure released from the hot coolant fills the top half of the tank and acts as a force to push the coolant back into the system.
Do you need a coolant expansion tank?
When the radiator is high enough to act as a fill point and pressure relief an expansion tank is not necessarily required. In those applications a recovery style tank may be used instead. Liquid cooled systems are pressurized in order to raise the boiling point of the coolant.
Can you drive with a cracked expansion tank?
Yeah you’re not gonna be able to make it, that’s too far to go. Hell make it if its just a hairline crack and there’s still coolant circulating. If there’s no coolant at all you can drive it maybe 2 miles at a time on a COMPLETELY cold engine. I wouldn’t risk it unless there’s actually coolant in the engine.
What causes coolant expansion tank to crack?
Failure can be caused by damage to the radiator cap or radiator hoses when the radiator is not sealed properly. It could also happen if the radiator tank itself has sustained damage and has cracks. The radiator expansion tank performance also decays naturally over time.
Should the expansion tank be empty?
You are correct. The expansion tank is usually about half full of water and half full of air–by volume. One tank full of air at atmospheric pressure will be about half its volume when pressurized. When in doubt, drain it.