Water pump replaced on my Lexus RX 400h ...and a few days later radiator died

They are related in the sense that there in the same system, they are both parts help keep the car from over heating. If you are asking if the pump caused the radiator to go, then the answer would be no. I think it was on its way out, that's why you were having the 90k service done. I think it should have been replace then...

Lmost same thing happened to my lexus 400H. After they changed the timing belt and water pump, I discovered a hairline crack on the upper side of the radiator. Whenever I filled the radiator it leaked out.Finally I decided not to fill it anymore. So I kept it the way it is, but kept a gallon of anti freeze in the car. It has been 5 years. It has not over heated even in the hottest summer with a/c on and plenty of heat in the winter. But I think it had a tow package which means bigger radiator? At 151K it is still running like a champ. What I am wondering when the Hybreed battery dies, will it run on its own gasoline engine? Common sense says it should. Does anybody has any idea?

What usually happens is that the radiator will need to be replaced after any work is done to the other parts of the system . When the hoses attached to the radiator are moved the newer cheaper radiators develop hairline fractures. Most mechanics do not treat this stuff as if it were your family delicate s, hence the damage. Almost no repair shop will own up to this, so expect to have to pay for a new radiator also.