My 1997 honda civic is leaking coolant under right back side of the engine.(right side of engine if sitting in car). I have checked both upper and lower hoses and they are fine and have also checked reserve tank and there are no cracks. However my car loses a considerable amount of coolant in a very short time. Any suggestions?

A few things could have happen,
1 you overheated and blew the head gasket and now the oil in mixing with the anti-freeze,
OR due to high Mileage the head gasket has just failed and is leaking into the anti-freeze journals inside the engine.,

Did you check the oil to make sure it's not a white'ish sludge on the inside of the cap, you might be mixing both back and forth..

well simple answer is it is only losing coolant when under presure so i would tighten all coolant hoses to be sure they are air tight then start the engine leave untill the fan comes on then check for a leak as will be under presure if you find the leak dont work on the cooling system untill compleatly cooled down then remove coolant cap then fix the leak fillwith coolant to just under max level replace coolant cap and start engine leave running untill fan kicks in and then see if leak has sealed dont forget check around cylinder head when checking for leaks

I Have a 94 Rodeo,3.2l v6 I had the same problem...Yes it is a drain hole..You might have a coolant pipe running under your lower intake if so it's the "O" ring on that pipe..It runs from the upper radiator hose to rear of block...50 cent part. If you are doing it yourself check the other heater hose metal pipe O ring also. towards the front under the thermostat housing. I just fixed mine.I had antifreeze coming out the inspection plates on the trans took off the upper plenium and lower intake and the rubber O ring was shot.Clean out flange use a wire V shaped wheel. make sure the Ring fits Snug on the coolant pipe,dry fit in the flange.( Got assorted sizes at NAPA) put a good coat of Black RTV silicon on O ring,And some in the hole itself press pipe in hole and install the bolts.Allow to set for 3hrs. Again this is on a 94 Isuzu Rodeo 3.2 L V6 5spd. Hope that helps you

There is air in the cooling system. All you need to do is get it purged out. Air causes both of these problems. When it passes thru the heater core, no heat. when it passes by the cooling sensors it is a lot hotter than the coolant and makes the gauge shoot up and down fast.

If your not over miles then it should be covered under warranty, take it to the dealer for inspection. they have standard 3 year 36,000 mile bumper to bumper warranty... 3 years 50,000 miles on power train...

check your radiator cap

Sounds like a blown coolant hose, or a faulty coolant water pump.

heater core ..smells sweet?....you coolant is leaking inside cabin..check top off radiator coolant ..replace heater core

COULD BE COOLANT SENSOR,HEAD GASKET,CHECK THE TIMING,THE PROPER MIXTURE OF COOLANT,WATER PUMP.DID YOU HAVE IT CHECKED OUT?ANY LEAKS?HEAT WORK WITH FAN?

try the thermostat or flush your engine water system though