Hey guys I have an 05 r52 with 113k miles. Daily driver, NOT stock, rarely in traffic

I'm experiencing a coolant leak ONLY when the a/c is running. Any other time, it's dry. Yes coolant, not refrigerant. ( I know, I think people see girls and think we're idiots) Drip runs the skid plate underneath the radiator. I've pressure tested the system multiple times, it's steady, not even the slightest drop in pressure. A/c blows cold. With car age and prepping for mods most of my cooling system has been systematically replaced within the past 4 years (both fluid & air flow). The car has never overheated nor shows any signs that it might. I just have a mystery leak. It does sound stressed when the a/c is running.

Water pump has less than 5k on it, cleaned up supercharger ect, replaced the falange and all gaskets in process. I have a new heater core, CSF rad (less than 6mo/ 2k on it), Canton steel overflow tank w/ 30 psi cap (no signs of weeping), new hoses, clamps and junctions, new thermostat with housing and gasket, new engine oil cooler and all gaskets

* Water pump did NOT fail, it was replaced precautionary b/c of age
* This is the 2nd CSF rad, the 1st one cracked

On the non fluid side, auxiliary fan and both relays have been replaced. I have the Forge top mount intercooler, new boots, new gaskets throughout everything including the supercharger, manifold, throttle body, everything, M7 cold air intake and have dropped 1 heat cycle on the spark plugs.

Soooooo any ideas of where else to look? Or how else to test since it holds pressure? I've had this car since 40k mi. I'm the one who does the work, no corners have been cut on parts or work. I torque everything properly, flush/ clean, replace every gasket ect that gets touched. This is my lil baby. Only engine stressor I have is a 15% pulley..... I'm baffled and have a delish cat back waiting in my dining room for me to fix this

 

Are u sure it’s not the condensation from the ac drain? The ac evaporator will drip water when running

 

No evap is in a diff place, fluid color, consistency and smell is coolant, also level decreases in the overflow tank. It stays at a steady level unless I run the a/c. I live in Florida and with the convertible I keep the top down most of the time so don't run it. Topped it off yesterday, ran a/c today while I went downtown tank is low now. But I can run for weeks without a change

 

Radiators expand quite a bit when they get hot. So maybe it leaks only when hot. Could be from the crimped gasket. Maybe use some paper towels under suspect areas to see if you can find the drip path.

 

Running AC in your neck of woods will result in much higher coolant temperature, and hence more expansion of the coolant. You know the OE plastic tank has the fill mark inside the tank that is about 1/3 from the bottom of the tank? I have found driving on tracks the coolant will overflow if I fill it above the "island" inside the tank. One thing about all these metal tanks is there is no max level fill indication. I suspect you are overfilling the tank, and the leak is just normal that the expanded liquid has no where to go but expelled at the tank.

Doesn't Canton tank have a spill hose nipple by the pressure regulation cap?

It may be deceiving how large the OE plastic tank compared to some aftermarket tanks, so something to keep in mind.

 

So for anyone else who runs into this prob... It was a rad leak (the top right). Took an additional 3 months for it to get bad enough I could find anything. Even with the location, I still had to take the bumper off to find TINY bubbles b/c it was still maintaining pressure. I have a friend who is a motorcycle guy who suggested maybe the a/c was just just too much given a standard race car doesn't have one. However, he's a motorcycle mechanic not car and I've never heard anything similar from any other mechanics. So take that for what it's worth. ECS has been wonderful with the warranty process!! Highly recommend the company. Looking now to swap the CSF out to something else. For anyone entertaining different radiator options, this was my 2nd CSF rad leak. I live in central Florida. I'm def not stock but haven't been on the track.