Hi All,

new to audi, new to diesel, Classic vw background. Been trying to solve problems using logic and transferable skills, but logic often fails with cars.
I've seen plenty of similar symptoms discussed, but none that match. I've been fiddling with the tandem fuel pump for ages and finally swapped for a used one which has been great. I'm now seeing a coolant leak trickling down the side of the block.

Its only surfaced since the fuel pressure has increased due to stopping the fuel leak at the pump. Might be coincidence, or I may have broke something during the weeks of playing in that area.

It it appears to be coming from the corner of the head gasket on driver's side at the rear. I have run my finger above the area and it doesn't seem to be originating any higher. The flow eases when I remove the expansion tank cap, and increases when replaced.
Ive thrown a bottle of steel seal through it and no improvement.

Its an AWX with 170k on it. Any. Chance it's not the head gasket and simply a cracked temp sensor?
Ever the optomist