About two months ago, I noticed coolant leaking from the front of the engine and also from the back onto the transmission case. I took it to an independent shop, and they said the water pump, thermostat, and a coolant line were bad. They replaced those, but when I got it back leak was still in the same spots. So I went back to the shop, they said the front crossover pipe was cracked and needed to remove the supercharger to fix it. They agreed to cover labor since they just worked on it and only have me pay for the parts. so I told them to go ahead. After that repair, the front leak stopped, but the back is still leaking, and the coolant tank drops about half an inch each week. When I went back the shop said it’s probably leftover coolant or pressure being releasedbut said they would check it out now they are saying the heater core is bad. But I’m not sure because the heat works fine, there’s no coolant smell inside, and they haven’t fixed the leak after two tries. I’ve attached a photo of the leak at the back any ideas where it might be coming from would be appreciated.

 

Odds on it's the rear heater pipe which is notorious on the AJ126 for springing a leak.
Either in the plastic seam or more commonly where the plastic pipe plugs into the engine block and the o-rings have gone hard and flat.
You can now get this pipe in aluminium, see here for example: https://euro-amp.com/collections/jag...arged-v6-aj126
Some people who have bought this pipe have commented that the supplied o-rings are not the greatest and a pair of factory o-rings do a much better job.

Edit - having a closer look at the pics I can now see a coolant leak in pic #2, just below the word "sound".
On the end of the left side of the heater pipe, right where the two halves join.

 

When installed the rear crossover pipe,the sensor maybe leaking, could be many things when they did the install, watch this video how to find the leak and it's not the heater core