Not sure if the gizmo works on diesels or not, but there is a device that can sniff out hydrocarbons in coolant. Simply open the radiator cap and run the engine, if there is a head gasket leak chance are good you're getting exhaust into the coolant and the device will sniff it out.

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Mike Tangas
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72

'02 CLK320 Cabriolet - wifey's mid-life crisis

2012 VW Jetta Sportwagon TDI...at least its a diesel

Non illegitemae carborundum.