'96 1.8L Ae102 Rad Cap Fail

Hey guys!

Had the OEM rad cap fail in Feb, six months ago. Replaced it with an aftermarket one, CPC brand.

This appears now to have failed also.

No oil in water, no water in oil, when engine oveheats is *definitely* venting via overflow pipe, and surging, in bursts - like pressure builds, releases, builds, releases...

So pretty certain it's cap, not air bubble, thermostat or head gasket.

Had a closer look at the radiator, and the eges of the orifice against which the cap is supposed to seal are *very* rough - a degree of corrosion on the rim of the orifice.

My *guess* is that this corrosion is not helping the seal, and may be allowing the rad to break seal when under pressure, hence blowing off a cupful or two every short trip, until eventually, enough has blown by the seal that there isn't enough left to keep the motor cool, at which point it overheats.

So far I have caught it before the temp gauge went off the dial, usually around the three-quarters mark (normal is bang on halfway up the dial).

So rather than replace the radiator - costly expense for an old and near end of life vehicle - I'm contemplating adding a dab of silicon gasket goo to the rim of the rad orifice, and cutting out a 'washer' of silcon rubber from a rubber glove (not latex), and fitting that to the cap and then re-sealing.

If this works and engine stops overheating, I confirm it's the corrosion on the rad orifice that's the problem.

Is this a crazy idea?

Anyone got a better one?

Anything else I should be checking (hoses appear OK, can't spot any obvious leaks, drips or steam jets, other than the overflow pipe....)

Next would be pressure test to confirm head gasket is not sucking the water out and 'burning' it, as there's no sign of it in the engine oil.

If it's that, then it's a dead car. Not worth fixing.