Re: Radiator Problems!
Brass/Alloy header plates fail from stress corrosion or electrolysis corrosion, stress corrosion cracks in the o'ring gutter on the header plate is caused by work hardening and dezincification, a chemical attack on the zinc component, if you have a close look at a header plate crack it will be blackish and pitted, causes are low quality coolant, irregular coolant changes and one of the main causes is cleaning under bonnet with ammonia based cleaning chemicals.
Electrolysis corrosion is caused by stray current, badly earthed accessories, 1 out of 3 older vehicles that come into our Radiator shop have stray current, some manufacturers are starting to use dedicated earth return systems which is preventing premature radiator failures, but crash repairers and mechanics seem to leave off earth wires or attach them to dirty/painted surfaces.
A good indication you have stray current is a brownish, soft build up in the hose outlets (alluminium hydroxide), the coolant becomes acidic, can do a PH test on the coolant, should be neutral.
Two tests you can do,
1. with the engine off and all accessories off set probe between coolant and earth with a multi meter, it should be zero.
2. with engine running and all accessories on probe between coolant and earth straps, engine and body.
I have worked with Radiators for 15 years, hope this helps understand them a bit more.