What does a knock sensor do?

Asked by Jan 03, 2017 at 09:12 PM about the 2002 Chrysler PT Cruiser Limited Wagon FWD

Question type: Maintenance & Repair

My car was running hot ,I had a new radiator and
radiator fan installed... still ran hot so took it to
someone else and was told I may have a cracked
or blown head gasket but no one will touch it! How
do you know if your head gasket is blown?

2 Answers

81,505

The knock sensor is like a microphone. It listens for spark/knock. If your engine starts knocking or pinging it sends a signal to the computer. The computer then retards ignition timing until the knocking or pinging stops. To test for a head gasket blown into the cooling system, pull the oil dipstick. If there's white milky "goop" on the dipstick that's a pretty good indicator of a blown head gasket. White billowing clouds of water condensation from the tailpipe is another good indicator. You can, with the engine cold, pressurize the cooling system with a cooling system pressure tester. Then start the engine. If the needle on the pressure tester's gauge bounces, the head gasket is blown. HTH. -Jim

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68,005

A compression test might show that the head gasket is bad. Also you will not always have coolant in the oil as sometimes the coolant goes straight out of the tailpipe.

1 people found this helpful.

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