As luck would have it my pickup (1998 F-150 4.6L V8) decided to sputter violently as I brought my daughters to soccer the other night. When we sputtered home, a quick check of the engine code confirmed my fear: Cylinder 4 was mad at me! The reason I was worried, is that for an f-150 of this age the problem was likely that the air intake gasket has been eroded by the radiator fluid. The erosion causes holes to form and presto you get radiator fluid leaking into your cylinder 4 sparkplug. As it turns out, nobody at ford was too interested in corrosion when they started making aluminum cylinder blocks. Yay Ford!
|Figure 1. Corrsion damage to old gasket and air intake plenum. Note the grey RTV sealant from last time I fixed this. It seems to last about 5 years. White deposits are the corrosion, dark spots on the aluminum are pitting.|
Well, after a few weekends (I get a lot of help from my kids so this takes longer than it might elsewhere) I managed to get things down to the block (see the image) confirming the problem. The corrosion deposits between the rigid plastic and soft elastic part of the gasket slowly grow and push the two parts apart. Concurrently with this process, the aluminum is being pitted by the corrosion. Yuck! A new gasket is not enough, the holes in the block must be fixed.
|Figure 2. New gasket sitting on the block. RTV to fix the pitting. Hurrah! fixed truck.|
If I had a nice milling machine, I could (in principle) mill down the top of the block until the pitting was once again smooth. Even if I were good enough to do this, it would be much more work to get the block out. As fall was approaching at this point, I needed a quicker fix. Never fear, polymers to the rescue (see figure 2). With some high temperature RTV sealant you can fill the holes, plop on the new gasket bolt everything together and allow the RTV to cure. Presto, fixed engine! Is there nothing a good polymer can’t fix?