Cheap 12 pt socket vs monkey tight drain plug

JHZR2

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This was supposed to be easy… and I don’t think I’ve ever done this before on an oil drain plug.

The drain plug on my new to me 1991 350sd was really tight. I didn’t realize just how tight it was, and initially tried a 13mm cheap 12pt husky socket from the set that I have at my remote garage, and it rounded off. I managed to get a 13 mm six point socket, but it just kept on rounding over. I then hammered on a 1/2 inch socket which went on tight but it too kept rounding the plugs. It also was a six point socket but it just kept on rounding over. I think the issue is is an aluminum pan with a copper gasket, so you have a good galvanic series there to corrode against each other.. At my remote garage I don’t have very good tools, the cheap set of vice grips that I got from someplace for free couldn’t grab the drain plug size enough.

I need to get this drain plug off, I’m assuming a spiral extractor is the best way? I’m a little bit worried because these pans are pretty fragile, I had issues with the pan on my other 1991, 350 SD, and how do use a time sert insert. I really don’t want to do that again.

Any recommendations?

I have rocket socket extractors, but I’m a little bit worried that the one that and we’ll grab since they wouldn’t have been socket will slide on the head now.

Thanks!
 
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12 points are always a no for me. If you have a pair of dull vice grips I'd get some new ones at wallys and really tighten it which I've done to a bolt but though it wasn't a drain bolt but it worked. If you have a grinder and a careful hand you can make two flat vertical cuts without touching the pan and get a spanner on it. I've done that once to a rusted nut but had much more space.
 
A 6 pt socket and an electric 250ft lb impact gun back and forth is what I've done on stubborn drain plugs like that. Just let it bang away until it moves, then back in and out a few times until it spins out freely.
For now, I assume welding a nut on is not an option? Grinding a couple flats for an open end wrench with an angle grinder would get the bolt heated a bit. Then a few moderate whacks with a solid punch and hammer straight on, to let it know your serious and try turning the wrench. When you do your flat grinding, size it so you need to hammer on the open end wrench. Also if you use vice grips, get some large adjustable pliers to close them...
I'd get a decent quality cheap 1/2" drive impact socket set and leave it at your shop, once I got that, I find I don't strip anything anymore on a car. Those and a 3' ratcheting breaker bar seem to persuade everything I work on that its time to come apart.
 
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My metrinch will grab that.

Small pipe wrench, a vise grip, channel lock pliers... are all options.

If you don't have a good tool, you'll need to buy one!

 
My metrinch will grab that.

Small pipe wrench, a vise grip, channel lock pliers... are all options.

If you don't have a good tool, you'll need to buy one!

I have good tools. I didn’t have them with me. I was at my 10-bay garage which is a bit of a drive and I don’t keep my nice tools there, because usually if I’m going to do a big job I’ll do it at home. I had a set of cheap husky ratchets there that I got from some garage sale. Never thought the 12pt would be so bad that it would round it over. Or that the plug would be so tight. Not sure if I have a pipe wrench that fits.

I have a quality set of extractors, US made, very sharp.
 
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12 points are always a no for me. If you have a pair of dull vice grips I'd get some new ones at wallys and really tighten it which I've done to a bolt but though it wasn't a drain bolt but it worked. If you have a grinder and a careful hand you can make two flat vertical cuts without touching the pan and get a spanner on it. I've done that once to a rusted nut but had much more space.
Oh I have Malco Eagle Grips. It’s just that I didn’t have them there. What I keep there are old used tools that the prior owner left behind or I’ve found Uber cheap at garage sales.
 
Weld a socket onto it, maybe even that cheap 13mm 12 pt.

I have the same situation with my plow truck, siphoned oil out the diptstick using aquarium plastic tubing. Took a week, cold.
 
A 6 pt socket and an electric 250ft lb impact gun back and forth is what I've done on stubborn drain plugs like that. Just let it bang away until it moves, then back in and out a few times until it spins out freely.
For now, I assume welding a nut on is not an option? Grinding a couple flats for an open end wrench with an angle grinder would get the bolt heated a bit. Then a few moderate whacks with a solid punch and hammer straight on, to let it know your serious and try turning the wrench. When you do your flat grinding, size it so you need to hammer on the open end wrench. Also if you use vice grips, get some large adjustable pliers to close them...
I'd get a decent quality cheap 1/2" drive impact socket set and leave it at your shop, once I got that, I find I don't strip anything anymore on a car. Those and a 3' ratcheting breaker bar seem to persuade everything I work on that its time to come apart.
These old Mercedes Aluminum drain pans scare me.

My other 1991 350sd had a stripped plug with some other expansion plug when I got it. So impacting, tightening, hitting, all worry me a bit.

When I was installing a time sert on my other 1991 350sd it didn’t take much to rip out some of the structure around the plug female threads.

 
Weld a socket onto it, maybe even that cheap 13mm 12 pt.

I have the same situation with my plow truck, siphoned oil out the diptstick using aquarium plastic tubing. Took a week, cold.
I don’t weld. At least currently.
 
Welding a nut on is the easiest, fastest. Clean all the flammable oil from around the pan bolt ( make sure there is no diesel fuel anywhere around it) clean the bolt with carb cleaner and let it dry and weld on an appropriate nut.

If you don't weld, I'd try the rocket socket. It that does not work, I'd drill it , heat it with a torch ,and use a fluted extractor. Not spiral.
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These old Mercedes Aluminum drain pans scare me.

My other 1991 350sd had a stripped plug with some other expansion plug when I got it. So impacting, tightening, hitting, all worry me a bit.

When I was installing a time sert on my other 1991 350sd it didn’t take much to rip out some of the structure around the plug female threads.

Yeah, I guess you don't really know how strong they are. When we had our 06 CRV the transmission drain plug was overtightened for quite a few (10?)years before I got it. I just happened to use my impact socket and a regular length 1/2" ratchet and it wouldn't budge, I don't think I had my breaker bar then, so I grabbed the impact gun and let it hammer for a bit. To me there's less chance of rounding or snapping the head off with an impact gun than with a breaker bar, as all the force is rotational, and the impact seems to help sheer corrosion in the threads? Also that's the theory behind whacking the bolt head straight on with a hammer, just to break the corrosion.
I guess those pans are probably cast aluminum, I tried to smash some structural aluminum holding the one end of a motor mount out of my parts car and it was incredibly tough! Thinking now, it was probably forged, but it was pretty soft and just took multiple hits with a large ballpeen hammer with no significant damage... It was faster to swiss cheese it with a drill and then break it up with the hammer....
 
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Your first goof was using a 13mm tool on an sae 1/2 bolt. 13 mm is slightly larger and will slip. Now just put a pair of vice grips on it and kick them to get it loose.
It’s not. Every single MB I own (7 currently I think) or have owned uses a 13mm head drain bolt. They changed from M12 to M14 shaft at some point but the correct heads are 13mm. It’s by far the most common fastener on these cars.
 
Get out your flat chisel and ball peen and get busy. It looks like you have plenty of room on that nice, plump shoulder to get a perfect bite.
 
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