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Causes, Symptoms and Tests for a Blown Head Gasket

Model: (Various brands) Various
Part: Checks and maintenance

Video tutorial

This video presents the causes, symptoms, and tests for a blown head gasket. The main causes include engine overheating; low coolant, a stuck thermostat, and a non-functioning fan. Turbocharging can also be a reason.

In PSA vehicles and some diesels, the issue may also be the fragility of the metals: the cylinder head or block can easily deform. Lack of maintenance is another cause (old antifreeze, dirty oil). Typical symptoms include white/blue smoke; yellowish foam emulsion of oil and water; brown sludge in the reservoir or radiator, coolant loss, power loss, bubbles in the radiator, oil-soaked spark plugs, and excessive pressure in the cooling circuit.

To determine if it is truly blown, verification tests are needed: connect a pressure gauge to the radiator, and if the pressure drops without external leaks, the gasket or head is cracked. Another test is to run the engine cold with a funnel full of water on the radiator.

If you see continuous bubbles rising, it indicates exhaust gases are entering the coolant, meaning the gasket is blown. You can also measure the compression of each cylinder; if there is a significant difference between two adjacent cylinders, the gasket between them is blown.


Posted on 7 June 2026 by ScegliAuto


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