Hi, My seicento abarth is losing coolant when driven. Ive had it checked over and the garage said basically they dont know what it is and they would have to strip the engine and find out whats happening and they still might not find the fault. Is there anything trivial it could be? I found this site out of desperation and any help is much appreciated

Get another garage!

But, it'll either be the head gasket (compression test or coolant pressurisation test done by someone competent) or a simple water leak.

Most common places for a leak are the water pump itself, the water pump to water rail O ring, or the water rail running along the front of the engine just above the oil filter. Often you'll only be able to spot leaks from these by crawling under the car with the engine running and up to temperature. Or a coolant pressurisation tester will probably help find.

More rarely, rotten water rail, rotten core plug, heater matrix (damp passenger side carpet in this case!) cracked radiator or simply a slightly loose coolant hose.

All, except the heater matrix, head gasket and core plug are easy DIY jobs.

Crucial thing to remember is that the cooling system is pressurised: often you won't see a leak until it's hot and up to pressure.

Thanks for your advice, ive been told its not the head gasket as its been compression tested. I was wondering if it could be the coolant tank cap? I wouldnt know how to check for the other faults u listed.

The caps are cheap -- may as well change it to rule in/out.

The coolant only seems to leak when the heaters are on?

Could be that the matrix has gone. They generally leak into the passenger footwell.

New garage diagnosed faulty water pump. Had it done drove it for a few miles and it proceeded to bubble and drain all coolant thru to the floor! Filled it up and drove a few miles seems fine but the heaters only ever get lukewarm. Totally confused?!

Needs bleeding probably. On Sei, must be done with heater turned to full. 2 bleed screws -- one on a tube near the windscreen washer filler, the other on the bulkhead where the heater lives (more or less centre back of engine compartment. Do one at a time.