Q: Mechanic issue

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Hello,i recently took my car in for a full major engine service and left it overnight ( coolant,oil,fuel filter,oil filter,air filter,ac re-charge,spark plugs,brake fluid,power steering fluid) i went out today and there was a thin layer of white sludge on the oil cap which was NOT there before i took it in for the service. However,when i went to collect the car i opened the bonnet and the mechanic allowed me to check the oil before i left and before i paid for the service and i lifted the oil cap an the sludge was on the cap. Is this a headgasket leak or something worse? The coolant/antifreeze is clean and all fluids have been changed with top quality fluid

Hi There, It sounds like you may have some traces of oil getting into the coolant, which may be caused by a head gasket leaking problem as you know. A blown head gasket may cause a number of different symptoms. A head gasket that fails between cylinders will generally cause a misfire and potentially compression leaks from one cylinder into another. Low compression will eventually result in a rough idling engine. When the head gasket fails between a cylinder and the coolant port, coolant may leak into the cylinder causing it to be burnt with the fuel charge in the combustion chamber. This often results in misfires on startup, especially after the engine is run, turned off and restarted. This type of failure may not always show with a compression test. I would recommend having an expert from YourMechanic come to your location to properly diagnose the symptoms you describe.

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