99 Jetta Coolant Leak Mystery

[Quercitin]

1999 Jetta GLS 2.0L AEG engine. Automatic transmission. 62,000 miles.

I’ve had a slow coolant leak from bottom of engine for several months. The leak accumulates to a visible droplet at the lowest point where the engine attaches to the transaxle, but the source appears to be from somewhere above this spot.

The leak rate has been the same whether engine was running or not. And the same rate whether the engine is hot or cold. And it had gotten no worse over these last months.

Two weeks ago, the vehicle began overheating, so I figured the leak was due to a failing water pump although that seemed unlikely given where the leak was coming from. I replaced the thermostat and water pump (and timing belt), which solved the over-heating, but the leak persisted exactly as before.

I jerry-rigged a coolant-system pressure tester (O’Reillys rental kit was for systems with radiator caps only) and have been able to get a few psi on the system. I continue to be unable to see where the leak originates. Of note, the rate of the leak appears less after the pressure test – perhaps I forced some debris into the source of the leak?

Thanks in advance for any feedback you all have.