Dear Tom and Ray:

I own a 2005 Ford F-150 truck with 31,000 miles that I purchased new in May 2005. A backyard mechanic told me that I should replace the spark plugs now, because if I don't, I could damage the motor, and that would cost more than $2,400. The service manual states that the spark plugs should be replaced at 100,000 miles. I stopped by the Ford dealership and talked to the service manager, and he stated that I should replace the spark plugs now to avoid possible engine damage if the spark plugs break off. He said the cost of replacing the spark plugs if they have no problems would be $302. I can't believe that replacing eight plugs costs more than $300 and that I need to do it 70,000 miles early. What's the real story here? Thank you. -- Ralph

RAY: It's not a happy story, Ralph. Between 2004 and 2007, Ford made several 3-valve engines that had the unfortunate habit of refusing to give up their spark plugs. And you've got one of them.

TOM: For those who have Ford trucks from this era, the offending engines are the 3-valve 5.4-liter from 2004 to 2007, the 3-valve 4.6-liter from 2005 to 2007, and the 3-valve 6.8-liter from 2005 to 2007.

RAY: Here's the problem. Apparently the head is designed in such a way that the heat or carbon from combustion fuses the plug into the head. When you try to remove the plug, it can break off. If it breaks, it takes a special tool and about $300 to get the remaining piece out of there. And if you have to drill out all eight of them, that's $2,400. Not pretty.

TOM: Ford claims that it has released detailed instructions for using a special cleaner and penetrating oil to loosen up the plugs before taking them out. But as many owners can attest, it doesn't always work.

RAY: So even though you're not due to install new plugs for another 69,000 miles, if it were my truck, I'd change them now rather than take a chance. The longer they stay in there, presumably, the more likely they are to snap off when you take them out.

TOM: To rub a little salt in the wound, these plugs are expensive -- they're about $25 each. That's why the dealer wants $300 to replace them, including labor. But if even one of them gets stuck and breaks, that's $300 right there. And since at your current rate of driving you won't get to 100,000 miles until around 2058, I think it's worth swapping out the plugs now.

RAY: And have it done by the dealer or a mechanic who is very familiar with the procedure, to increase your chances of success.

TOM: Is it something Ford really should pay for? In my opinion, yes. It sold you a car that promised 100,000 miles between spark-plug changes. And if you have to change them sooner as a precaution, or drill them out of the head later, that's a defect, in my opinion. But as far as I know, Ford dealers are charging these expenses to the owners. So bring your wallet, and your anger-management tapes, Ralph.