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  #1  
Old 02-25-2015, 09:51 PM
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Location: Irvine, CA
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Blew my B2 piston

Hi,

No warning, I pulled away from a friend's place in the SD and I lost all forward gears. Reverse worked. I got towed home and read up on the B2 piston.

Though I worried that I broke the B2 band which is not an easy repair, I took the cover off and discovered my B2 piston was all in pieces and cracked like all the images online. Textbook b2 piston failure. The band had spring back when I pushed on it with my finger.

I had the silver cylinder bushing. I thought it was scored so I set out to replace it. And I'm having a tough time. I wish I'd just put the new piston in and buttoned it up. I've mangled the oil seal. I cannot even remove that.

As I fabricated the washer bolt puller folks use to do this I pulled it through and folded it up on what I thought was the inside edge of the bushing. Then I realized darn, I was looking at the inside of the aluminum transmission case. The scoring I thought I saw was just the case. I thought I was looking at a big step worn into the steel bushing. Ima idiot. I looked at the bushing and it had a nice polished surface. My piston was lightly scuffed but not gouged.

Anyway I haven't given up. I'll try to get it all out tomorrow and install the plastic bushing. I'll make another washer tool. Now I'm committed to doing the whole enchilada. I've scratched up my steel bushing and torn my oil seal. It's gotta come out.

Wish me luck. I'm having that sinking feeling but I am counting my blessings that I didn't break my B2 band. I will get that ring out. Not sure what my options are aside from just giving up and buying a Civic. No way...time to rest up and hit it again tomorrow.

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79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles
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  #2  
Old 02-25-2015, 09:56 PM
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Good luck. Keep us posted. Take pics.
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  #3  
Old 02-26-2015, 01:34 PM
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Owwwwh Gawd I got it out!!!

Hey this was really hard. As promised, images.

broken parts that fell out:


textbook broken B2 piston:


Other piece of B2:
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79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles
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  #4  
Old 02-26-2015, 01:40 PM
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And there's more

Clever tool cribbed from google images from another benz forum
I used a tire iron as a puller. I had an old one that I didn't need. I thought it would be strong enough...




Here is the business end of the sleeve puller. 1.5" fender washer with 1/4" hole. I shaved down the washer to 1.47" using an electric drill with a bolt through the middle of the washer and a file (hillbilly lathe). Note the backup washer behind the nut. This is important...I folded up my first fender washer. Also note peened 1/4-20 rod end...you don't want the nut falling off into the tranny.



Final result. It's out. Tire iron was strong enough...just barely.



What did I learn? Well, I'm pretty dumb. I should have just left the steel bushing in and used a new B2 piston. The little shoulder I saw in the sleeve was indeed part of the sleeve and not the tranny wall. It has an unmachined step in it. Intentionally. The polished part looked just fine. I thought I was looking at gouging but I was looking at an unmachined groove. You can see the two inner surfaces on the sleeve.

I didn't drop the pan though I did drain the fluid. Perfectly clean mobil 1 synthetic ATF $$$ down the drain. I was pleasantly surprised to find it at O'reilly for $10/qt. I haven't put it all back together but I think I'll try to hold the dogbone in place on the band using grease and then inserting the piston over it.

I didn't remove the pipe. I think the W126 has this advantage. There was room, not much, but enough after I dropped the center support on the tranny. I usually fool myself into taking these shortcuts...removing everything may have made things easier. I'm naturally lazy.

Heck, I know, it may have broken again, but it lasted 200k so there. I won't own this car that long. I've learned a long time ago these cars last longer than we want to look at them. The tragedy of my life is I'll never get to experience a new car after getting one of these diesels. Kind of like marrying the perfect wife out of high school.
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79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles
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  #5  
Old 02-26-2015, 03:09 PM
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That we could all be so fortunate.
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  #6  
Old 02-26-2015, 10:48 PM
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B2 Bushing Tool
Removing the B2 Piston Seal and Bushing Benzworld. B2 Piston Bushing Puller Benzworld.
I go by 300Dman over Benzworld. In post #8 I drew a sketch and gave some instructions on how to make a cheap Tool that will pull the B2 Bushing and Seal all at one time the same as I did on My own.
B2 Piston destroyed in 722.315 tranny - Mercedes-Benz Forum

When I did mine I picked a thicker washer to begin with and then I also added another smaller Washer but I epoxied it to the larger Washer. Both washers had an ovel hole in the center so you could tilt it on the shaft.
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  #7  
Old 02-27-2015, 06:39 PM
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Works!

Ok, got it all buttoned up. Just took it for a shakedown run. It shifts a bit more smoothly. The 1-2 jerk that seemed to come on as the car warmed up is much better. I need to really drive it though to check that.

Some tips:

I poured my drained ATF Into a milk jug for disposal and only drained off 3.5 Quarts. I didn't drain the torque converter because I just changed fluid. So that's what I replaced. Dipstick smear mess looks about the same.

I never dropped the pan. I'm not saying to do it this way. I'm just lazy. I used a glob of Vaseline to hold the dog one in. Once the piston was in I could push it in and out and feel the B2 band pushing back. You push on the outer rim of the piston so you don't feel the piston's integrated spring. I could actually feel the band pushing back slightly and it was repeatable.

The cover went on nicely. On mine there was a molded feature that forces you to put the circlip on in a specific position. the cut has to slip past a shoulder. No biggie just had to install the clip twice.

I didn't remove my down pipe. There wasn't much room. I pounded in the seal with a long 1/2" drive extension and socket. The outer edge got a little grungy but the sealing lip was intact. Had I dropped the down pipe I could have properly driven the seal.

After my 50 mile tow ($220), $220 of peachparts and synth ATF ($45) I'm looking at close to $500 for this whole ordeal. Wish it hadn't happened but $500 isn't bad. If I'd been smart and done it during my filter change and K1 spring job I'd have saved some money.

And that's it. All is good!

I'm at 200k. Wonder when I'll need to take the trans in for a full rebuild.
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79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles
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  #8  
Old 02-27-2015, 06:41 PM
ykobayashi's Avatar
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Location: Irvine, CA
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Thanks for this!

Quote:
Originally Posted by Diesel911 View Post
B2 Bushing Tool
Removing the B2 Piston Seal and Bushing Benzworld. B2 Piston Bushing Puller Benzworld.
I go by 300Dman over Benzworld. In post #8 I drew a sketch and gave some instructions on how to make a cheap Tool that will pull the B2 Bushing and Seal all at one time the same as I did on My own.
B2 Piston destroyed in 722.315 tranny - Mercedes-Benz Forum

When I did mine I picked a thicker washer to begin with and then I also added another smaller Washer but I epoxied it to the larger Washer. Both washers had an ovel hole in the center so you could tilt it on the shaft.
Yep, I actually used your sketch. Thanks once again (I've used a lot of your posts).
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79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles
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  #9  
Old 02-27-2015, 06:54 PM
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Join Date: Jun 2005
Location: Irvine, CA
Posts: 1,261
Almost forgot.

DIY folks 1. Transmission rebuilders 0. Yeaahhhhh!

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79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles
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