good one Martin1981 but can i just add that i have done pressure tests before and just sometimes it doesnt show on the guage even though i know somethings wrong
i was recommended a few years ago to get a substance to put in the water to help but being tight i never bothered
a co test helps though by checking if the hydrocarbons are high
The coolant is obviously disappearing somewhere. If it's the head gasket, coolant will be lost either water to oil, whereby coolant becomes contaminated with the oil- check for creamy deposits on the oil filler cap and oil in the coolant. A failing head gasket can also result in coolant being forced out of the expansion tank filler cap due to pressure in the cooling system caused by combustion gases entering the system from the cylinders. This is where a CO2 'sniffer' test can be useful in determining HGF.
Fill the ehader tank when cold, replace cap run/drive for 10mins and check how firm the hoses are, now carefully release the pressure. I said carefully. now replace the cap hold the engine at 3000 ish for 30 secs and recheck pressure, if the hoses have re-pressurized it point to a head gasket. Remove plugs and see if one is amazingly clean, if so then thats the proble. Your local garage can also sniff the header take for combustion fumes. Regards Peter
The OP said
'had a few problems with the engine ticking over and not switching off via the imobiliser thats all sorted, no longer have an imobiliser.
Which is a bit strange so he needs to clarify this point.