Use the pelican parts site to look up what the part looks like and they usually have the part number.

However if any sort of liquid gets down inside of the threads it is typical to see some mild bubbling. It in normally is not leaks. No one has proven one way or another but I think there is a shock from the fuel injection that causes vibration that creates the bubbles.

Getting Brake Cleaner, Carburetor cleaner down in there to dilute and float out the lighter stuff and the mentioned items evaporate will eventually leave the level too low to bubble out.

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84 300D, 82 Volvo 244Gl Diesel