Rounded-Off bolt head


I was planning to drain and refill my transmission fluid today. When I got under the car, I successfully broke loose 4 of the tranny pan bolts about 1/4 turn, but the 5th bolt I rounded the corners of the hex head. This particular bolt is unfortunately between the exhaust and the pan, so I can’t get a locking pliers onto it.

Does anyone have any good tricks for removing such a problem bolt? I’m not real fond of easy-outs (ever had to easy-out an easy out?). No welder available to weld a nut onto it.

Maybe I’m better off to take it to a shop and let them figure it out?

Vehicle is a 1995 Cougar w/ 4.6 V8. 165k miles. I purchased at 40,000 and have had the fluid replaced at 85k and ~130k. Interestingly on the ~130k fluid change, I moved immediately after the change and then noticed I was leaking fluid. I took the car to a new shop where they lifted it up and found 3 of the pan nuts were not tight. They nicely only charged $25 to ‘diagnose’ and retighten. I’m suspicious that the bolt was actually rounded at that time, as I had a pretty good bite on the head. Regardless, it’s my problem now.

I suppose before I have a mechanic fight this for a while I should track down the coolant leak that seems to be originating from the engine somewhere above the water pump.

If I just retightened the first 4 pan bolts and drove, what are the chances of the tranny lasting another 50k? This is my work car and gets 8-10k/year now.


Couple of ideas…if you used a 12 point socket, try a 6 point on the rounded bolt head. If no go, sometimes you get lucky and find the next size smaller socket (metric, if the pan bolt is US thread) can be forced --tapped lightly onto the bolt-- and will let you loosen it.


There are special sockets available to grip rounded hexes. They are different brands called various names such as bolt out, twist sockets, and similar names. Sears carries them too.


The six-point worked great, thanks for the tip. Luckily I didn’t try to keep working at it with the 12 point or I would have had more trouble.



A Snap-On socket may also work. Their design is called Flank Drive and is configured to get a better bite on bolts with rounded corners.

What size bolt heads are on there? Just figuring something.


Also “JB Weld” or any cold-weld epoxy a bolt head onto it. This naturally will work only in low-torque scenarios such as tranny oil pan bolts, etc. You may also try heating the bolt up first with a propane torch, and theyll usually turn like butter.


YOu don’t need any more suggestions for the bolt. I just want to add that you have a torque converter drain in this car so you can do more effective fluid changes. Do use Mercon V.