Rep Power: 0

Just recently bought a 2007 Honda civic, I keep losing coolant in both the reservoir and the radiator. No white smoke, plugs look okay, no overheating, car is running like normal, I'm not sure what i could be.
The system seems to be holding pressure as the hoses are kinda hard when I run it. When i top it up and drive for a few KM and i check it, it's takes a lot of coolant to full up again, I am not seeing any visible leaks. Not sure what's going on.

 
Rep Power: 0

Pressure test on cooling system to help locate leaks.

 
Rep Power: 211

To start with fill up both radiator and reservoir. Place a large piece of cardboard under car and run engine for 20 minutes. Pull cardboard out and check for leaks on cardboard. Also place cardboard under car for a period of operating temp to cold engine (overnight) and then check cardboard for leaks.

As CJ1 suggested do a coolant system pressure test when engine is cold. If no externals leaks are seen then your looking at an internal leak/blown head gasket or crack in cylinder head or block. The typical sign of a breeched head gasket in Honda engines is coolant loss in radiator with coolant gain in reservoir. Do a Block Test on it ..block tester is a free rental tool at Autozone or O'Reilly's..test fluid is $10. Youtube block test.

 
Rep Power: 518

Suspect cracked block.
Check if your oil level is mysteriously rising and the oil looks like chocolate milkshake.

Here's where to look for the evidence, usually only one cracklocation is found.

Image links:
http://photobucket.com/gallery/user/Jaralaccs/media/bWVkaWFJZDo3MjU2NTY4Mw==?ref=
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http://photobucket.com/gallery/user/Jaralaccs/media/bWVkaWFJZDo3MzAwNjI1NQ==?ref=

http://photobucket.com/gallery/user/...NTMzMQ==/?ref=



If it's been overheated, suspect warped cylinder head.

 
Rep Power: 0

Well to update you guys, it was a leak, Didn't pressure test anything. It was the Gooseneck/connector going to to the heater core next to the airbox. it noticed what looked like rust on the rim of the hose, turned out it was dry coolant, when i removed the hose, the neck was filled with built up corrosion, i scraped it off, there was no pitting, so i used 600 sandpaper to sand it smooth and i used a hose clamp to secure it, running like a champ now. So if anyone has this issue always take a look.

It seems the coolant was spraying out and drying on the block/ transmission so i never saw it falling. this car is new to me btw. it has never overheated.

 
Rep Power: 211

Good find. Best to bleed air from coolant system again if you haven't done so already since finding /fixing the leak.