If you suspect that you have a leak from your radiator (but not from one of the hoses) but you cant find it heres how:

Step 1: Chop !

Get an old bicycle tyre inner tube and inflate it quite hard and check that it doesnt have a leak. Cut it in half, so you have one long length with the valve somewhere near the middle.

 Step 2: Pump & Wait !

Attach one end to the top hose neck and the other to the bottom hose neck. Make sure the radiator cap is in place and firmly closed. Pump up the tyre this will pressurise the radiator. Pump the tyre until it is quite hard. If you wait a while and the tyre goes soft then you either have a leak or you didnt tie the tyre tightly enough at the radiators necks. The best method for attaching the inner tube is to use tightly wound string as this bites down into the rubber for a good seal. Put a little liquid soap around the join then if you have a leak you see air bubbles (see figure 1).

 Step 3: Find it !

If its a big leak youll probably be able to hear the air escaping and feel it on your hand. If its small, the best way is to spray the radiator with a soapy water mix. The escaping air will make bubbles.

You can do this test with the radiator in the car but once youve removed the hoses youre most of the way to getting the radiator out anyway

Inner Tube Attached and Inflated