Radiator is an almost brand new unit though that i swapped in

Until you do some investigating, who knows what the real problems is? Check for corrosion and sludge before you start swapping parts.

If corrosion is not the problem, check for flow. FSM may have a procedure.

I'd also double-check fan speed. I doubt that they are the problem but one may not be getting up to speed.

Will do, thank you sir! :)

I started turning wrenches 5 years ago at one manufacturer(lexus) so I can only base my experience from that. I came from oil changes, diagnosis to engine overhauls. Generic diagnosis might be similar but part design, type of noises, common issues, procedures, etc could be way different so sometimes trying to fix one car based on another doesn't always work. Fortunately switched to Porsche two months ago so no longer with boring lexus :driving:

Anyhow lets try to help OP to fix his car. Since the car is only overheating on idle with ac on I cant really think of anything except insufficient air flow through the radiator. If there was an air pocket it would still overheat with AC off, the heat in the cabin would fall off from hot to warm during idle. Strange..

It has been very strange for me as well, I've been going through the most common points of failure in the system starting with the thermostat and working through the most common procedures to address the issue. The only thing that i havent changed in the system is the water pump which is partly what leads me to believe it may be the culprit by process of elimination. I appreciate the help in this situation and look forward to any more input anyone has on the issue :)

Yeah, it sounds like a fan issue while the OP is at an idle, even though the OP has said the fans are working.

its not just the fans are working though, I can feel with my hand a pretty good amount of air being blown through the engine compartment when they are on and also feel a good bit of air being sucked through the front air dam when I put my hand in front of it. also, as someone suggested I went and rented a radiator pressure tester. pumped it up to 16 psi and it holds pressure steady with no indication of any leaks, let it sit there for a good 5 minutes too with no drop in psi at all.

The two basic problems that I've run into with air/liquid heat exchangers both have to do with flow - either the air or the liquid is moving too slow (too fast is also a possibility, but not very common and certainly not your problem).

You seem to have good air flow (although your testing methods are not very reliable). Low flow is usually caused by a bad pump or blockage (stuck 'stat, something in a passage, heat exchanger pluggage, etc).

You've checked all the easy stuff. Go ahead and pull the pump for inspection. Use your borescope on the block while you have things apart.

Before you drive yourself crazy and start taking the car apart, I suggest you get a proper coolant funnel kit (link below). What Im about to suggest is not possible without one because coolant would spill everywhere. So fill the coolant to 1/3 full of the funnel, start the car and turn on the heater all the way to max temp and max fan speed. Also make sure to adjust vents to face mode only and make sure AC is off! Run the car and give it several good revs to like 4-5k and hold for 5-10sec. Back off and repeat. This way you build extra pressure to push coolant around and possibly eliminate any air pockets that still might've been trapped in the system. Make sure you keep watching funnel through your windshield to make sure coolant is not excessively raising. If it does, back off for little and try again. Keep doing until fan kicks on and off couple of times. From experience some cars will bleed just fine from idling, others need that extra push especially when cooling system was completely opened. Hope it helps

https://www.amazon.com/Lisle-24610-S...ice+kit+funnel

I realize my hand is not a very reliable way of testing, but it's what I have access to lol. I don't have access to the tool to set the crankshaft in place to loosen the crankshaft pulley so looks like I will be saving up for a little bit before I can have the shop inspect the water pump for me. gonna drain the system this weekend in the interim and take a look around with my borescope and try to get pictures for those interested.

I'd like to see some pics.

that's the first thing I bought when I started trying to diagnose the issue lol...works very well for getting air out of the system, but sadly the last time I tried it which was about 2 weeks ago, I got no air bubbles escaping from the system. Thanks for the suggestion though :)

Come on your at Porsche now, time to throw that funnel in the trash where it belongs. Get yourself an airlift kit or similar (I use mityvac mv4525, most complete cooking system tester I've ever used). Truly the only way to get all air out of today's engine with all their crossover passages etc etc. Japanese still seem to design systems that are easier to bleed conventionaly though.

One thought is there are two designs of the z cooling system. One uses a conventional expansion tank system and the later (I think 2012) use the tank as part of the pressurized system. If you have the later there is usually a upper return hose (I'm not at my car or looking at it currently so I'll have to verify this later and hopefully not look stupid) the return hose should have a pretty steady stream of coolant back to the reservoir. This was always a good indicator for when the plastic impeller would break on 1.8t vw engines.

Oh and ps just kidding about throwing the funnel away, keep it as the taper hole is much easier to secure the block checker in than some radiator openings, but that's really all I used it for after having a vacuum fill. Also on subject of block checkers there are different designs and the ones with two chambers are much more sensitive to very small gasket leaks (second chamber will change color)

I have the old system with the expansion tank. Also where can i get one of these two chamber block checkers that you mentioned? Would i be able to rent one from somewhere?

I doubt you can rent one. I got mine from my Matco guy but I don't think it's your headgasket.