I've had a broken valve cover bolt for a long time. It's a shoulder bolt, and snapped below the shoulder when I tried to remove it. Very little pressure and just snapped.
So I drilled it out, and promptly snapped off the EZ out in the broken bolt. Grrrr.
Can't drill out the EZ out because it's down in there about an inch, and the broken EZ out is raised. No way to get a drill bit on it, and even if I could, the EZ out is too hard.
I can remove the valve cover and seal it up, but it will start leaking again in a few hours. That drips on the heads and smokes and I'm concerned about a fire. So I only mow about half an hour at a time.
Last week it started smoking really bad, and I pulled in the driveway and it was dripping pretty bad from the bottom of the pan. That much is not coming out of the valve cover, so I have a pretty bad oil leak coming from somewhere else.
So first things first, clean the entire engine and engine compartment and tackle the known leak first.
I found a youtube video of someone with the same problem, and they used a diamond bit hole saw from Harbor Freight. It's not meant for metal, but it works. About $9.
So I bought a few bits of different sizes and settled on the 3/16" bit. Dip it in water, drill for 5 seconds. Dip. Drill. Dip. Drill. Repeat.
About 15 minutes and it was out. Worked pretty well. Went right down around the broken EZ out and ate the softer bolt and part of the EZ out bit as well.
I lost the threads on the hole, of course. So I cleaned it all out, packed it full of JB Weld and the next day I drilled and tapped the hole. To make sure the hole was mostly centered, I drilled a 1/8" hole through the broken shoulder bolt head and used that for a jig. Got the starter hole pretty well centered, and enlarged it with a 5mm drill bit for a 6mm tap.
Cleaned up the valve cover and head surface, put on a fresh bead of gasket material and put it all back together. Waited the appropriate amount of time, snugged it all up, and gave it a try.
Seems to have worked. Mowed for half an hour with no oil leaks from the valve cover. Now I have to figure out where the big leak is coming from.
(click to enlarge)
