I have coolant leaking underneath the engine not by radiator cant see where its comeing from what could it be

coolant level only changes because coolant leaks out. It does not burn or otherwise evaporate. you have a leak somewhere. Start car slide a sheet of cardboard underneath engine area and see drips. You must let engine heat adequately to create pressure.

Can be several things. Bad Radiator, Bad hoses on radiator, or nearby water pump is leaking.

They make a Radiator pressure tester which will put pressure in the system so you can see where the leak is coming from.

There is absolutely no way possible that the air con unit is going to cause an engine coolant "leak". The air conditioner can cause the engine to overheat if the fans are not working properly, but you will see coolant coming out of the radiator cap if it is overheating.

To find a coolant leak you just have to look for it while it is leaking. If you can see it dripping out on the ground, then you should be able to follow it up to see where it is coming from. Cracks in the plastic radiator tanks are common in all Honda vehicles. These cracks can have the characteristic of only leaking after reaching a certain temperature. You will probably have to remove the plastic shrouding from under the vehicle to see many of the leaks that can be coming from the front radiator area.

Water pumps can also leak at only certain temperatures. Sometimes they can fool you also because there are channels on the back of the pump that will direct coolant away from the water pump/ timing belt area in the event of a leak. It can look like it is leaking from the side of the engine that is away from the water pump. Again, you have to LOOK to see where it is originating from.

There are several areas where the coolant can leak from.
Cylinder heads, intake manifold, frost plugs in the cylinder block, heater or radiator hoses, block heater if so equiped.
The leak may be on top of the engine leaking down and appearing on the bottom of the engine.

You leak is the heater core . This requires dash removal,

If you cant see where it is leaking from at the top of engine compartment it could be a bad bottom hose from the radiator to the engine.. Best way to find where the leak is - get engine warmed up real good.. Check for leak top and underneath wall it is running.. if you dont see it - shut off (the pressure will build some) and check again and you should see where leak is coming from.. Your description dose not indicate where its coming from..

Good luck ;)

Be sure to check your engine coolant as well, the trans is cooled via the radiator, so you may be losing ATF there. Where does the fluid appear to be coming from? You can use a can of brake cleaner to wash down the trans underneath, and blow dry with compressed air. Maybe once its cleaned off, you will be able to determine where the leak is coming from.

this most likely means that you have a leak in a hose somewhere between your engine and the radiator, when you open up the rad cap it lets the leak breath causing it to gush out, go to napa and buy a replacement radiator hose it shouldn't cost but a few dollars and that should fix your problem. 

You have answered your own question almost. You will need to jack the car up and inspect everything being that its 91 camara, there is defintely enough room to inspect everything. You either have a hose leak, a radiator or water pump leak. Only inspection will find that out. Thank you,
Lee