Coolant expansion tank cap no longer tight.

[Rich196]

Hi,

Have an 08 135i, I have a problem where the expansion tank cap is no longer tight to do up, and im loosing a little coolant.

I believe the coolant is being lost as the cap is not tight and the system isnt holding pressure.

So the coolant cap. I remember from when it was okay, that it started to get stiff to do up, and then finally clicked into place.

However now, the force needed to tighten doesnt seem to change whilest doing it up. When I click it tight, you can rock the cap round slight with just a finger.

When the coolant is hot, and you try to undo the cap ( dangerous in normal circumstance) there is no pressure behind the cap at all.

I have tried a new cap, and the situation is no better, its almost like the expansion tank itself has failed, perhaps round the thread. Unless I am missing a seal somewhere.

Anyone had anything similar, or got any good ideas?

[Rich196]

Just me then, or is this in the wrong section?

[livnpaintball2]

Wrong time of day

[livnpaintball2]

Buy a new cap!

[MightyMouseTech]

Originally Posted by livnpaintball2

Buy a new cap!

Originally Posted by Rich196

I have tried a new cap, and the situation is no better, its almost like the expansion tank itself has failed, perhaps round the thread. Unless I am missing a seal somewhere.

It is either the cap or the tank. Only two parts involved. Cap did not fix it, so you need a new tank.

[Rich196]

Originally Posted by MightyMouseTech

It is either the cap or the tank. Only two parts involved. Cap did not fix it, so you need a new tank.

Fair enough just seems a random thing to go. wondered if anyone else had suffered it