water pump replacement failure?

I am not sure what they put in the vehicle for a water pump. The radiator is possibly weak and the hose as well. If you can say the age of them you will be a rare person. I venture to say that the new pump is working well and pushing the coolant at a much faster rate. It could be due to age that these things are giving out OR it could be that they have installed a higher performance pump. You need to find out if the pump was an OEM replacement.

is it better to change the radiator or overhaul it? cuz they're asking a huge amount for the overhaul the radiator.

and what if it's a OEM?

Don't let them overhaul the radiator. You can find a radiator at a parts store for about $120, however, I have purchased them from ebay for about $85 with free shipping in some cases or off froogle.com. One brand is Toyo I believe.

You should be fine with an OEM radiator. I expressed concern about the water pump but if it is OEM you will be fine. I would replace both hoses on the radiator. If you do it yourself, which is a pretty easy job, make sure that you bleed the air out of the system, ALL of the air.

is there a specific radiator for my car? cuz im not in the state and this car is imported from japan.

You provided this information to me

1991 honda civic vtec 4dr.

You need to know the type of engine 4 or 6 cylinder

The model of the car LX DX, etc

The size of the engine 1.5 1.6 2.0 2.2 etc.

They make a universal one as well that should work well on your car. In fact, if you look closely at radiator from your car, you will see the manufacturer name stamped or printed on it.