93 Z34 Leaking Water/Coolant from Radiator Outlet Tank

Car runs normal with plenty of power. Temperature gauge remains within normal temperature range when running but at prolonged stop such as DMV for emission, car heats up. Does not go all the way to RED since fan kicks in between last white line and 1st red line in temperature gauge. When I turn the engine off, water leaks out from underneath and also saw water/coolant comes out of the radiator outlet tank (some call it expansion tank). Does this mean I have a cracked expansion outlet tank? can I replace just that or I need the whole radiator replaced? is this something I can do or a job for the shop? Please help....

expantion or outlet tank?are you talking about the plastic bottle over flow tank
the leak is in this tank??if so you may be able to repair/replace yourself
sounds like system maybe low do to leak & running hot.need more info on
leak underneath,try a pressure tester to see if you find the leak under pressure

Car runs normal with plenty of power. Temperature gauge remains within normal temperature range when running but at prolonged stop such as DMV for emission, car heats up. Does not go all the way to RED since fan kicks in between last white line and 1st red line in temperature gauge. When I turn the engine off, water leaks out from underneath and also saw water/coolant comes out of the radiator outlet tank (some call it expansion tank). Does this mean I have a cracked expansion outlet tank? can I replace just that or I need the whole radiator replaced? is this something I can do or a job for the shop? Please help....
When its cold unbolt the overflow tank and look if you observe a crack purchase a good used one from a junk yard.

Thanks to both of you. Sorry for the confusion. It's from the outlet tank (the one on the right side if you're facing the car). Making this car a project so don't want to spend much right away. All hoses looked old and can tell that because it was so easy to rip from the radiator with the clamps from hell. I thought it's a good idea to do this and see. But to make it convenient, I had to take the fans out and still battling to take one more clamp from the lower hose. I can almost take the whole radiator out. Is there a way to take out the outlet tank and test it? Any suggestions regarding this topic is really appreciated and many thanks to each of you.....

Thanks to both of you. Sorry for the confusion. It's from the outlet tank (the one on the right side if you're facing the car). Making this car a project so don't want to spend much right away. All hoses looked old and can tell that because it was so easy to rip from the radiator with the clamps from hell. I thought it's a good idea to do this and see. But to make it convenient, I had to take the fans out and still battling to take one more clamp from the lower hose. I can almost take the whole radiator out. Is there a way to take out the outlet tank and test it? Any suggestions regarding this topic is really appreciated and many thanks to each of you.....
Radiator shops use rubber plugs or caps and put around 10psi inside the radiator and hold it under water. If it bubbles its leaking. You can install a hose on one end put a wooden plug in it borrow a pressure tester from Advance or Auto Zone. Pump it up to around 10 psi. Use a large sponge and use soap and water. You should be able to find a leak.

Thank you. I will do that. Off the subject, this car came with one of those K&N filter that is cone shaped and the stock air box was taken out. It sounded really good and loud and the two cannon-like exhaust look a little too much for me (in the future i'm getting rid of them). Anyway, I took it to the emissions yesterday and it failed the carbon monoxide test by 0.12. Do you think this modification he did affected the results? What are the pros and cons of having this kind of stuff in this car? I'm more of keeping everything stock rather than adding things that does not belong.