Towards circular bonnet insulation citout closer to grill. looks like it is closest to coolant cap and belt. sludgy oily buildup.

anyone familiar with this?

 

Assuming you have a V12.....

Sounds like the a/c compressor shaft seal is leaking. Oil ooozes out and gets slung onto the underside of the hood.

This is a pretty normal operating condition for the old A6 compressors. The esxception was one that *didn't* leak a bit. If you look in the old GM service manuals from the 60s-70s you'll read where 'some leakage' is considered normal.

If it gets too messy the shaft seal can be replaced. Thinking back to the 70s-80s I recall the technicians used some special tools for this job so don't order a shaft seal without doing some research first. The tools might not be absolutely essential but I just can't remember for sure.

You could Google "A6 compressor front seal replacement" and see what comes up.

Cheers
DD

 

Doug you're the man. Would also explain why the AC hasnt worked of late!!

Luckily autumn is here, and today was a top down heat on low type of day.