radiator?A/C?Engine?--S.O.S

Hi Guys,
I'm just recovering my 2000 XJ from the 5th broken radiator in the last 2 years. Official service could not give any solution beside saying they don't have time o deal with such an old Jeep..¿¿?? (they already replaced one on guaranty). Now I decided to put a real Metal radiator, but I'm 100% sure the problem will come again. At this stage, my 2 only possible problems are... a) Engine is sending compression to the refrigeration system and b) A/C is causing the problem.
a) from my ponit of view very improbably....coolant always clear and the problem seems to start from one momento to the other and not from the moment radiator is replaced. b) sometime has make strange noises but then gone. Electric fun NEVER starts as a direct consequence of turning A/C on (just related to Coolant temp)
¿How can I test A/C making elec fan starting? ...I mean independant from Coolant temp?
Tks

My 2000 electric cooling fan only runs when the temperature rises above 215 degrees on the temp gauge. It never runs just because I turn on the Air Conditioning.

The failed radiators may be from engine compression and combustion gases entering the cooling system from a leaky head gasket or a cracked head. You can have the cooling system tested. They will be looking for exhaust gases mixed into the coolant.

The a/c system is totaly seperate from the engine and cooling sytem.There is no way that engine compression can enter the a/c system nor can the a/c be the cause for blown rads.I know this may be grasping for straws,but the rads you have replaced,were they good quality parts?I know there are alot of companies out there that sell cheap junk rads made in china,that you won't get 6 months out of.

when you say they are "broken" -- how have they failed? Do you still have any of them to inspect for cause?

Thanks for your interest in solving my problem. Answer is super easy. It is over pressure. It starts, from one moment to the other, to expel coolant with pressure through the cup or through rubber hoses unions. When you change the cup or tighten the "embrasing clamps" on the end of rubber hose where it leaks, then, after 1, 2 or 3 days pressure goes out throug radiator. Where?...mostly through the plastic/metal union (typical), but last time (in the 4 month old radiator) throug a tube in the middle.
Meter-needle never has shown an overheating...in fact no symptoms of overheated coolant. I Think is not coming from compression of engine as that should happen always, so hoses or cups should immediately show excess of pressure. I keep A/C functioning almost all the time and i thing it is more feasible that A/C has an intermitent failure.
I do not go offroading for already 4 years and since then engine never is never forced... Because of fuel price i drive like an old Grandma.

You have an open cooling system. Any excess pressure should be relieved through the radiator cap, which is only 15-16lbs/in, if I remember correctly, and into the overflow.

Like Frank36 said, your A/C has nothing to do with your radiator pressure - the only thing it is doing is making your engine work harder, creating more heat, which will create more pressure.

malfunctioning cap? If it failed to release pressure you could damage the weakest point.