Leak Detection Methods

The right method for each type of leak.

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What you will learn

Match method to leak type
Use pressure and smoke tests
Confirm the repair

Leaks are found with the right method for the medium. Coolant and oil leaks respond to pressure tests and UV dye; intake leaks are found with smoke; exhaust leaks with back-pressure or smoke; refrigerant leaks with electronic detectors or UV dye; and EVAP leaks with smoke or a leak-detection machine.

The professional sequence is: confirm there is a leak, choose the method for that medium, find the exact point, and then confirm the repair under the same conditions. Guessing at the symptom leads to comebacks.

Leak type	Best method
Coolant / oil	Pressure test, UV dye
Intake / vacuum	Smoke test
Exhaust	Back-pressure, smoke
Refrigerant	Electronic detector, UV dye
EVAP	Smoke / leak machine

Key points

Match the method to the medium.
Pressure and smoke expose hidden leaks.
Confirm the repair under the original conditions.

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Key points

Different leaks need different tests
Pressure and smoke reveal the hidden
UV dye and electronics find slow leaks

All values shown are training examples. Real thresholds depend on the manufacturer, engine, temperature and system — always confirm with the vehicle service documentation.