Put in new b2 piston and won't go foward! - PeachParts Mercedes-Benz Forum

dazsa · #1 11-04-2007, 12:54 PM

I put in a new b2 piston in my 81-300SD yesterday, filled the tranny today and the car will go in reverse but will NOT go forward!!!

What did I do wrong??

Have I screwed up something?

PLEASE help with some advice.

Thanks, Don

dazsa · #2 11-04-2007, 06:02 PM

Well, I assumed that would be a next step...but what I am looking for? I did not know what to look for the first. It at least went into first gear before I replaced the B2 piston, even if it did kind of slam into it. Now, the car kind of creeps along and when you push the accelerator the RPMs just go up with no engagement.

Do I have to drain the transmission by the pan again to get the B2 out, and if so, do I have to replace the gasket again?

Thanks for tolerating the "clueless" questions.

Don

Adenauer · #3 11-04-2007, 06:11 PM

I'm just going to throw this out there for what it's worth. I read an article by Stu Ritter about the B2. It has been my understanding that when replacing the B2, a sleeve will need to be installed in the bore as the valve body is aluminum and the sleeve is steel I believe. Additionally, I believe that I had read that the replacement B2 pistons are slightly undersized to account for the I.D. of the sleeve. It seemed that the B2 would wear on the aluminum bore over time and that subsequent valve bodies from the factory had a steel sleeve inserted.

Any truth to this?

If so, I would think an undersized, replacement B2 would not be able to perform inside the original valve body bore - the fluid would blow past the seals.

Can anyone jump on that one way or another?

DeliveryValve · #4 11-04-2007, 07:21 PM

Yes as Adenauer pointed out, you have to replace the B2 piston Sleeve and seal. The sleeve is originally made of aluminum, but the updated sleeve is plastic. The aluminum sleeve would cause the steel rod on the B2 pistion to bind. So I am guessing that you did not replace the sleeve and the new piston is still binding. If you didn't, the fix is around 10 bucks for a new sleeve and seal.

lietuviai · #5 11-04-2007, 09:25 PM

I've got the exact same problem with my 84 300D. When I put my tranny in at the time I installed my "new" engine I blew the B2 piston seal. I pulled the tranny not really knowing its possible to change it without removing it.
I had it all together this weekend and it wouldn't go forward. Yes I still had reverse. I did notice my B2 piston was a newer type because of the date stamp.
I didn't see any sleeve so if that's my only problem then finding this thread is a big relief. I thought the tranny was toast and I'd have to R&R it again.

Adenauer · #6 11-04-2007, 09:49 PM

Stu Ritter gets the credit. Or, at least the engineers in Stuttgart. Let's just see if that yields a result worth writin' home about first.

lietuviai · #7 11-04-2007, 10:30 PM

Does anyone know where we can find Stu Ritter's article on the subject?

Adenauer · #8 11-04-2007, 10:37 PM

It was actually a good write-up in the "124 owner's bible," which, he wrote.

lietuviai · #9 11-04-2007, 10:40 PM

I actually found his email address on the Bentley publishers forum and sent him an email. I'll see if I get an answer.

Adenauer · #10 11-04-2007, 10:49 PM

I believe he's especially helpful if you mention MBCA.

dazsa · #11 11-05-2007, 07:52 AM

The old b2 piston had the white plastic sleeve but the black seal ring had a few dings on it. I did not have a replacement for that black seal ring, so I reused it. I had a new white plastic bushing and used it, but reused the black seal ring.

Could it be that I need a new one of the black seal rings if I had replaced the white plastic bushing?

Also, do I have to replace the tranny pan gasket if I drain it from there?

Thanks...I need the car by Friday, so I am a little stressed about it.

Don (obviously clueless!)

MaydayMike · #12 11-05-2007, 07:58 AM

Did you make sure the pushrod was in place between the b-2 and the cup on the end of the band? With the pan off, you can look up and see if the very end of it, where it goes into the band.

dazsa · #13 11-05-2007, 12:03 PM

I did not visually check the pushrod from the pan-side, so I guess the pushrod could be out.

I guess I will take it all apart again to see.

Thanks

lietuviai · #14 11-05-2007, 09:17 PM

I made sure my push rod was installed. My tranny actually worked fine when the wheels were off the ground. It shifted smoothly through all the gears. When it was on the ground it would barely even budge.

lietuviai · #15 11-05-2007, 09:21 PM

Dazsa, you don't need to remove your tranny to check. In fact dieselgiant has a step by step page how to do the B2 R&R at: http://dieselgiant.com/Mercedesb2pistonsealreplacementl.htm