matticus

I have a small leak (a drop or two per night) that seems to be coming from between the catalytic converters (2.8 quattro B5), but I don't have a service manual with me or access to jack stands because I'm on a road trip. What could this leak be, and is it a potentially major problem?

I think it's engine oil--it's not antifreeze and it's not transmission fluid. Could it be brake fluid?

rickw

rear main crankshaft seal (engine oil) or transmission input shaft seal (gear oil) would be the likely culprits. The clutch slave cylinder on a manual trans car is on top of the transmission housing and could, conceivably, be leaking brake fluid into that area.

S4_Cinci (I S'edTFA)

rear of engine area that seems like a RMS, but most likely culprit are these common leaky seals. Normally, you will smell buring oil before you will see oil on the ground. If you have never had work done on the cam cover areas and you have more than 70k miles, then yours are almost guaranteed to be leaking some oil! It's that common.

matticus

I'm not convinced it's engine oil yet (it seems to have a slight sulfur smell to it, making me suspect gear oil, but I won't be able to tell for sure until I get to a place where I can get under the car and take a look. It's a very, very slow leak so I don't think I'm in any immediate danger.