I wasn't getting any help on another MB forum, so I thought I'd try this one. I would appreciate any help.

So since my control arms are shot I decided to replace them. The driver's side came out fairly easily, while the passenger's side is sticking. I have taken the nut off of the bolt that attaches the UCA to the body, but the bolt simply rotates in its position and is not coming out. Is my only option to cut this control arm off? I need some help, because I need to get this thing off or else my car will never get back on the road.

By the way, it's a 1982 300D (w123) with 360k on the clock

The bolt sometimes will stick inside the control arm. If you've disconnected the upper ball joint and the bushings for the stabilizer bar, wiggling the arm will usually unload the bolt.

If not, you'll need to get a drift and a hammer in there and drive it out. Of course, the available room for this endeavor isn't the best.

Be thankful that it's not the driver's side............

Hopefully BC's suggestions will work, but if yours is as bad as mine was, you may need more drastic measures. Mine was so thoroughly corroded to the old UCA bushings (the metal sleeves inside them) that it wasn't going to move for love nor money. I very carefully and with much difficultly wedged a sawzall up there and severed the bolt on either side of the UCA. After getting the UCA out, I still had a "nub" of a sleeve holding the bolt head onto the chassi, and had the hack the living heck out of it to free that last bit up. Needless to say, I replaced the bolt with a shiny new one.
http://www.peachparts.com/shopforum/showthread.php?t=249774
Hopefully you won't have that bad a situation. Take out the air cleaner housing and battery if you haven't already, and chances are you can drive that sucker outta there.

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1987 300D, arctic white/palomino--314,000 miles
1978 240D 4-speed, Euro Delivery, light ivory/bamboo--370,000 miles
2005 Jeep Liberty CRD Limited, light khaki/slate--140,000 miles
2018 Chevy Cruze diesel, 6-speed manual, satin steel metallic/kalahari--19,000 miles
1982 Peugeot 505 diesel, 4-speed manual, blue/blue, 130,000 miles
1995 S320, black/parchment--34,000 miles (Dad's car)

Place emphasis on "carefully." Another forum participant recently reported that he had sawed into his torsion bar while attempting a similar feat.

yeah- dont cut anything else. the sway bar is a PITA to replace, and $$$

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1984 123.193 372,xxx miles, room for Seven.

1999 Dodge Durango Cummins 4BTAA 47RE 5k lb 4x4 getting 25+mpgs, room for Seven.

haha, funny thing is that I'm replacing that too so it wouldn't really matter. The passenger's side end of the torsion bar ripped off probably due to the worn out UCA (bushing is completely gone).

Yikes ... my UCA bushings were absolutely toast as well but I saw no damage on the torsion bar in my case. I guess the good news is it will be easier for you to get at the bolt if you do need to cut it. It's definitely a last measure, but if you do, like I and others have said, be very careful. I just went really slowly and made sure that blade was on the bolt and stayed on the bolt. I had one big advantage: I'm small ... so I could fit my arms and part of my torso up under the wheel well to get at it, safety goggles on, of course.

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1987 300D, arctic white/palomino--314,000 miles
1978 240D 4-speed, Euro Delivery, light ivory/bamboo--370,000 miles
2005 Jeep Liberty CRD Limited, light khaki/slate--140,000 miles
2018 Chevy Cruze diesel, 6-speed manual, satin steel metallic/kalahari--19,000 miles
1982 Peugeot 505 diesel, 4-speed manual, blue/blue, 130,000 miles
1995 S320, black/parchment--34,000 miles (Dad's car)

I'm not looking foreward to this......

It's not that bad a job if your bolt isn't petrified in there. Getting the UCA back into the frame was a little tough, but if you stick a screwdriver in the frame hole and into the UCA hole, you can pry it into position ... easier than pushing it from below. So just cross your fingers that that bolt comes out ...

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1987 300D, arctic white/palomino--314,000 miles
1978 240D 4-speed, Euro Delivery, light ivory/bamboo--370,000 miles
2005 Jeep Liberty CRD Limited, light khaki/slate--140,000 miles
2018 Chevy Cruze diesel, 6-speed manual, satin steel metallic/kalahari--19,000 miles
1982 Peugeot 505 diesel, 4-speed manual, blue/blue, 130,000 miles
1995 S320, black/parchment--34,000 miles (Dad's car)

Does anybody know if I can rent a reciprocating saw from somewhere? I am away from all my tools this summer and don't want to buy a new one. Is there any way that a dremel with a tough bit would work? Cuz I do have one of those.

look under tool rental in the phone book.
There are places here that will rent just about anything, and you would have to buy a blade.
Hit it with some PB blaster, and see if that will free the sleeve and bolt before hammering on it.

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83 300SD Dark Silver Dark brown inside

snapon tool rentals. they have just about everything, try that or RAC rent a center.

as for other forums, im a member of benz world. and have visited some others. this is by far my favorite. everyone on here is really nice. im staying here for a long time.

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Current
2006 E320 CDI, 57K bought at 67K "Liesl"
1986 190E 2.3-16, 198K bought at 56K "Brigitta"
1987 300TD (Chuggin Along), 292K "Friedrich"
1995 E320 Wagon, 200K "Louisa"

Past
1987 300SDL, (sold) 125K, bought for 1$ "Kurt"

This is one way to repair the Swaybar if the tip is rusted off.
http://www.peachparts.com/shopforum/showthread.php?t=144023

Another way is to use a repair kit that the Parts company thay sponsers this Forum sells.
However they need to be welded on.

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84 300D, 82 Volvo 244Gl Diesel

Ya, I already got the new sway bar in. I'll post pictures of the old tip just so people can see what kind of damage can occur when nothing has been replaced in 2 1/2 decades.

I love this forum too. People actually respond!

I'll check out those rental centers. Does anyone know where I can get a replacement bolt for the UCA to body connection?

So I got the bolt out by cutting it on the left side (towards the bolt head). I used a reciprocating saw that I borrowed from a friend. The only bit that did consistent damage was a carbide blade (looks like it has gravel glued to the edge for those unaware). Don't waste your money buying 3 or 4 metal saws because that bolt will just eat them up.

Nobody answered about the replacement bolt, so I ended up going to Lowe's and finding something similar. I recommend getting something small rather than larger if you want it to fit.

Good luck to anyone who has this similar problem and just remember that it can be done.