Need help with cross threaded plugs

JEREMYTHRUSTON

MEMBER
1989 MAZDA 626
174,000 MILES

What can be done to get cross threaded spark plugs out of the engine without breaking them or ruining the engine? I have a non-turbo 1989 mazda 626 that has 3 of 4 spark plugs cross threaded and stuck in the engine. Im afraid if I try any harder, I will break them and render the car useless.

1 Reply

CARADIODOC

MECHANIC
33,737 POSTS

They aren't really cross-threaded, but the spark plugs are stuck to the aluminum in the head. First try to remove the plugs right after stopping the engine when it's still real warm. You might try dribbling a LITTLE water on the plugs while trying to avoid the hot cylinder head.

Next, I don't know how this will work on aluminum, but for cast iron, diesel fuel works real well to free up stuck parts. Pour a little by each plug and let it sit overnight. Chrysler also has a REAL effective "Rust Penetrant". It comes out of the spray can black and it bubbles and sizzles. Spray some of that on for a few minutes to see if it helps.

When you get the plugs out, coat the new ones with anti-seize compound on the threads. If you force the old ones, you'll be peeling the threads out of the head. Repair kits are made for that but it's a lot easier to avoid that if possible.