Citroen Xsara Picasso water blowing from expansion tank

Ecessive pressure in cooling system,would ensure it,s correctly bled,fan,s working,water pump impeller has not come off,thermostat working ok,block test for emission gasses.

Thanks for your advice but the car is still in the garage and no one can fathom out why the water is boiling out of the expansion tank, the temp.gauge reads normal. He the mechanic has done the compression test which is fine fan cutting in and out at the right temp.no leaks on any hoses changed the thermostat for a new one no airlocks and water pump fine. God I wish he could find something wrong and get my car back to me.Please any help more than wecome.

Can the heater matrix cause water to blow out of the expansion tank by having a partial blockage in it? I'v replaced the engine,radiator,2 expansion bottle caps,3 thermostats,temp sensor, water pump taken out and checked fan cutting in at right temp. Bled the system more times than i'v had cooked dinners and used more diesel than anyone would like to pay for.
When the coolant is topped up to the correct level, after the engine comes to correct temp.it blows it out and there is about an inch left after cooling down which is well below the min. mark on the bottle.
Then the coolant warning light comes on constantly which is worrying.
The engine temp.never goes above normal temp.even after boiling over from the coolant bottle.The car is now in the 3rd garage and am thinking of scrapping it,I'v spent approx. £1400 in all,if you can solve this problem will make it worth your while (nice bonus)

there comes a time to stop spending !!!!!!!!!

Can the heater matrix cause water to blow out of the expansion tank by having a partial blockage in it? I'v replaced the engine,radiator,2 expansion bottle caps,3 thermostats,temp sensor, water pump taken out and checked fan cutting in at right temp. Bled the system more times than i'v had cooked dinners and used more diesel than anyone would like to pay for.
When the coolant is topped up to the correct level, after the engine comes to correct temp.it blows it out and there is about an inch left after cooling down which is well below the min. mark on the bottle.
Then the coolant warning light comes on constantly which is worrying.
The engine temp.never goes above normal temp.even after boiling over from the coolant bottle.The car is now in the 3rd garage and am thinking of scrapping it,I'v spent approx. £1400 in all,if you can solve this problem will make it worth your while (nice bonus)

there comes a time to stop spending !!!!!!!!!

Had the same problem with mine, just disconnect the water sensor from the header tank, so you will not get the Low water warning. Water level falls just below the minimum level, but thats where it stays, engine does not overheat, you can always keep an eye on the water temperature from inside the car, mine never goes over 2 bars on the digital temperature gauge. You just have to accept that the car is different from the normal car, once you do that, you will save yourself an awful lot of money. Which I have. I suppose you could try putting some K-Seal in the water. I did this, but it had no effect, water level always stayed just below the minimum level. So with adding the K-seal, this should have fixed and water loss if there was a leak somewhere.

Just accept that the water level is below the minimum level.