I have a 2002 f150 and have changed the plugs 3 times since new. I never replaced the boots as it did not show as a maintainence item. Big mistake. I replaced the waterpump last week and decided to power wash the engine. I have done this at least 8 times since new and never had an issue with water leaking past the COPs. This time I ruined number 1 and 5 COP. When I blew the water out of the plug holes proir to replacing 1 and 5 to see if I could get it to stop missing, I noticed the boots were cracked on the tips and kind of brittle. The miss is gone now, but as a precaution I will be replacing the plugs and the remaining boots this weekend. I have researched the right way to install the plugs and boots but get mixed techniques. I have always put alot of dieletric grease inside the boot. Some say this is wrong. I found a ford tech book page on the internet that stated to use dieletric inside and silicon brake caliper grease on the outside of the boot? Does anyone work as a tech with knowledge of how ford states to do this job?

 

Use dielectric on the inside of the boots - not a whole lot, avoid getting it on the springs and contacts.

At this point, you may want to replace all the cops themselves - you can get a set of Visteon DG508's on Ebay for about $180.

Oh - never power wash a COP engine.