Peculiar coolant spot under my car

Not sure how different the radiator/engine configuration is from the 308/328, but if it's similar you have two long hoses running fore and aft between the radiator and engine. I had a minor leak in a similar location two weeks ago and it was a loose hose clamp at the rear connection. I would lift the car at the rear right corner and have a look for moisture around those clamps.

Another other thing to check, because it's vulnerable to heat - at least the way it runs in the 328 - is the rubber hose running between the expansion tank to the engine. Although if that one goes you'd have more of a geyser than a drip...

Again, the 328 is probably different so I'd defer to any GT4 owners who post here.

 

One thing to check off your list is the condition of the radiator cap. These cars are notorious for spitting out of the overflow and it usually is caused by and aged cap.

 

Correct... Start with the cheap stuff first! A Stant cap (P/N 10229) is a direct replacement for the GT4's overflow tank. At $6 or whatever, it's almost silly NOT to replace it on principle!

 

What could be the culprit here is the main supply hose for the heater system, as it exits the rear bank cylinder head, then goes over and in front of the driver's side gas tank, down the driver's side door sill and up into the front compartment (where the heater cores are). Your leak may be close to the cylinder head (based on your observed "pee" mark). This is a typical problem and is usually caused by old hose finally giving up the ghost...

It is a big job to replace (some people have done it without removing the gas tank, but it makes the job so much easier to do so), but is do-able by a DIY'er. Do not be tempted to splice in a section of new hose to repair the leak, as the remaining old hose in the inaccessible areas of the car will still be prone to failure. Replace the whole length. Replace the brake booster hose while there as it too will be old and prone to leak and/or collapse:
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A lot of people splice-in a piece of heater hose instead of replacing the whole length. Hoses generally fail where they attach to the hot metal on the engine. You can reach-in and feel the heater hose from the top on a 328. If it is bulging, you can replace a foot or so and keep driving for another year. Barring trauma, heater hoses generally fail where they attach to the block.

Mark

 

before you freak out there is a metal pipe and hoses that go from the center of the engine down the drivers side to the pipe going from the front radiator, there are at least 2 hose clamps here that could be loose probably the one at the bottom near the fuel pump check that one and tighten it.

Rob