Cylinder leak down tester. If you are experiencing a loss of compression in your engine this tool will help you pinpoint its location. This leak down tester uses a pressurized air source for pinpointing leaks in your VW engine. Tester kit includes 1/4"FPT fitting for connecting to airline; 14mm, 14mm long, and 18mm spark plug adapters. The diesel engine adapter is not included (#19122).
Diesels are compression fired engines, so really testing your engine compression along with the leak down tester is the first step in diagnosing engine woes. The compression tester tool below will help you out. And the adapter shown below is required for testing your cylinder leak down and compression on diesel engines.