coolant loss from tank...

[warge]

Hi there....anyone got any ideas on this one ? My van (2.1 petrol) is losing coolant from the top of the expansion tank...it's coming out from where the coolant level sensor goes into. I've replaced the level sensor and O-ring (and used p.t.f.e. tape on the threads) but no joy. What appears to be happening is that coolant is being pulled from the top up tank behind the number plate into the expansion tank and leaking through the top, effectively over filling ....I know this because this problem occurs when I fill up the top up tank only to find it empty after a couple of journeys later.The level in the expansion tank does not drop and the van does not overheat when it runs or idles. Is this due to a faulty dalek cap or something more sinister and evil....many thanks in advance..warge

[R0B]

If it was me i would replace the tank(And cap) If its not a new one.You should only be able to blow through the dalek not suck.The threads on the tank can become worn over time.Brickwerks can supply both.

[Ian Hulley]

If the sensor has been overtightened the threaded section can crack (common fault) also look for thin white lines down from the filler neck of the header tank down to the sensor ... they often develope hairline cracks which only show up when hot and the coolant collects in the well around the sensor leading you to the conclusion it's come up the threads.

Ian