I have a 87 sdl that I have had for about 6 months. Since having it it has twice shown symptoms of a b2 piston failure. Both times i pulled up a a stop sign and when I went to accelerate it seemed to be stuck out of gear. Also, a couple of times it had trouble up shifting from first. Yesterday it had trouble up shifting and so I looked under the hood and found the b2 piston cover seal blown out through the side of the cover. I took the piston out and discovered that the trans has the newer b2 piston and bushing. I ordered a new seal thinking that the only thing wrong was a bad cover seal. I installed drained the tranny fluid, put piston and dog bone back in and new cover the new cover seal. I put 4 quarts of merc/dex in started car, put it in drive and nothing. I looked under the car and the seal has blown out again. Anyone know what would be causing this and have a solution? I've searched the forum and found a couple others have had same problem but they never posted a solution. Thanks

Has the casting on the transmission got damage or corrosion where the piston seal fits?

Have you made any (hydraulic) pressure tests?

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

I don't have the tools to pressure check. I cleaned every surface very well and found no damage. I ordered another seal and I'm going to try to soak it in a transmission stop leak fluid before installing.

I don't know if it is true but I have been told the Stop Leak makes the Seals swell.
If that is the case the O-ring is going to swell and make it hard to get the O-ring and Cover Plate Installed.

Your Transmission has a Pump Working Pressure and a Modulated Pressure that can be checked.

The obvious thought would be that something it causeing too much pressure inside of the Trans. Meaning some passage could be blocked or some Valve Stuck.

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84 300D, 82 Volvo 244Gl Diesel

I was thinking id soak the seal for 30min and intall everything and let it sit over night and hope the seal swells enough to seal. I don't think I can presure check anything because the b2 piston is out.

did JUST the o-ring blow out, or did the entire cover pop off?

if the entire cover came out, did you put the wire circlip back in to hold in the cover?

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

I just took it for a drive! When I went to put the seal in for the second time i noticed that I could see the blown seal all the way around the bore and realized the cover was not up against the clip. I took it apart and put a new seal in and then put the cover on sure enough the piston doesn't quite push the cover back to the clip. I took some pliers and crabbed a web on the cover and pulled it 1/8 up to the clip and it's now working!

So it's not fixed, after about 100 miles it blew back out. I think that the cover is moving into the bore when the piston moves exposing the seal and when the piston move outward the pressure is pushing out the seal. In other words, the piston is moving to far into the bore which leads me to think my connecting rod from b2 piston to b2 band is to short. Does this sound right? I guess I'll measure the play and see if it calls for a longer rod.

is the LARGE spring still in place under the cover? is it intact?

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

There is a large spring on the cover side of the piston, it attached to piston. The spring feels very stiff with stuff inside spring moving easily.

The car shifted well since the repair, only problem is seal.