Are you saying that your radiators fail.. i.e that they actually split or burst
If you had a stack of pressure in the system it's far more likely that a rubber hose would burst or leak.. or the (plastic) expansion tank would split/explode, even if the expansion tank's cap (which has a 1.2-ish bar pressure release ) didn't release the pressure first. The radiator should be able to take far
more pressure than any other component in the cooling system.
First of all, are you fitting a brand new radiator each time? Are they the same brand (too cheap?) or have you used different brands? Go to About Us | NRG v3
and buy one of theirs.
When you fit it, make sure you bleed the radiator. This is veeeeeery simple. The rad' should have a bleed screw at one end or the other. As you fill the system, leave the screw slightly undone (enough to let air out) and fill the system slowly until fluid seeps out of the screw. Tighten it and Robert is your mother's brother.
Next drive the car about a bit for a few miles.. just enough to get it warmed up but not hot. Leave the heater turned to maximum so that the heater circuit is open. This will allow the coolant to flow through there and drive the air out.
Let the beast cool down and bleed the radiator again.. just undo that screw until the air hisses out and then when fluid emerges, tighten it again.
That should be it.. the system can purge air out in normal circumstances so all you need to do is keep an eye on the expansion tank level and top it up every now and then.
If you have a head gasket problem then the engine might be pressurising the system. This "gas" collects in the radiator and either forces coolant out of the header tank cap, or it sucks it into the combustion chamber and burns it (steam out the back).
It shouldn't burst the rad'... but let's keep an open mind. Check the rad' after a week (cold). Simply undo the bleed screw and see what comes out. If it's coolant then you have no problems in the radiator. If it's "gas"... then the Head Gasket is mortally wounded.
Is the radiator mounted properly? My thought is that the beast is getting fractured, rather than bursting. It should sit with its lugs in a rubber bush and each rubber bush should be mounted in a hole in the support bracket. The rad' should just sit there and be held in place by a couple of screws. It should not have to be forced into position or held under any sort of tension.