Land Rover Repair: water boiling, head gasket, header tank

Question
I have 95 v8 dicovery with lpg conversion.My problem is after about 10 miles or less if heater or air con is on the water starts to come out of the header tank cap under pressure the temp gauge stays at normal ( i have had this tested and it is working ) I have had a new thermostate and the rad seems ok warm all over no cool spots.Also when hot very hard to start. whenrunning after about 10miles or so somtimes it will not tick over at a steady rev , if not careful will cut out.Not sure what to do. I have had the head gasket tested and that is ok.hope you can help, how do I flush the system? thank you for your time. Regards

Answer
You could have a clogged radiator, or a bad hed gasket, or something else.  SOunds like you need to find a shop with the skill to solve your problem.

Look in the recent Rover News for two articles I wrote on this topic.  You can find back issues in PDF form at www.roversnorth.com or the robisonservice web site