Mrmerlin

here is how to replace the leaking switch on your 87 or newer transmission
here is a link to see other pictures on a MB transmission
http://www.benzworld.org/forums/r129...on-leak-3.html


these are the parts you need to order
140 277 01 51 Spacer Ring To Reaction Valve Band B-2 $0.92
016 997 34 48 Transmission O-Ring To Rear Case Plug $0.81
005 997 80 48 Transmission O-Ring For Reaction Valve At Band B-1 $0.35
016 997 35 48 Transmission O-Ring For Overload Protection Switch (4.5 X 9.5 X 2.5 mm) $1.72
002 545 45 14 Switch on Automatic Transmission (Overload Protector) NOTE: Also Use: (1) 016 997 35 48 O-Ring $56.52


Special tools you will need .
36MM short socket
a few Q tips with wooden handles they are longer
Brake cleaner
Inspection mirror
Dow Corning 111
Thick grease

I got the parts from Importec in Dallas,
they sell MB parts

Jack up the car so its level support on 4 stands.
Remove the bolts for the left heat shield slide to the side.
Remove the brass collar with a set of channel locks.
Pull the plastic connector off the switch.
Remove the switch with the big socket.
Have a drain pan to catch some fluid less than an OZ.
Unscrew the switch the inner barrel will also come out with it.
There is a slot in the trans and a tab on the barrel that lines things up,
remove the switch from the barrel they pull apart.
Remove the 2 O rings from the barrel and clean the barrel.
Remove the plastic collar thats holding the metal rod to the tip of the barrel.
Clean this well.
Put some thick grease on the tip of the rod where it seats into the barrel the bevel end goes into the trans band.
Put the new plastic collar onto the barrel.
NOTE I used a small socket to press it on after leaving the plastic to sit in the sun for 5 mins as it seems flimsy you might want to order 2 of these collars.

Use DC111 on the new O rings for the barrel, pay attention they are different sizes.
Install the new O ring to the new switch with DC111.

Go under the car take a drop light and mirror and inspect the hole for debris,
wipe out the loose fluid with a shop rag then get the Q tips,
final wipe the grooves out in the bore.

Fit the barrel to the transmission this may take a few tries, it will easily slide in.
NOTE get a Q tip and wrap it with a small piece of towel then fit it into the hole in the barrel, this is so you can hold it and move it, once its into the bore.

NOTE HOWEVER what will be the difficult part will be the beveled rod to find its home, so this may take a few tries ,
I got this one in by tilting the pin to the up position the grease should hold it, and quickly sliding it into the bore in rapid succession till the pin goes into the band,
you will know it went into the band because the little tab that fits into the slot in the bore will be fully into the cutout,

WARNING if you try to seat the Barrel with the switch by screwing it home your going to damage the transmission band.

Once the barrel is seated then install the switch it will screw into the bore easily then tighten it with the 36MM socket.
Install the wire harness, NOTE clean the wires and the rubber cover with brake cleaner first.

Install the heatshield .
Run the engine and check the fluid for the correct level.
If its all good then lower the car.
Go for a ride

Charley B

Thanks Stan. This is going in my archive.

WallyP

Good post, Stan!

Mrmerlin

your welcome,
I just swapped out the switch on my 88 it has been making a small mark for a long time and then it finally started getting worse.
Plus there was another thread asking how to go about fixing this part.

NOTE the switch part I got looked just like the one that was removed,
the prices for this switch part go from 56.00 to 247.00 for the same switch,
so a little careful shopping will put these parts to your door for under 70.00 including shipping.

Make sure to get the spacer ring as mine was cracked so its a needed part my old one was black the new ring is white.
be generous with the grease you want the rod to be a sticky fit in its seat, this will aid installation into the band

fonetico

I've been posting (incorrectly) on a previous "modulator valve" thread.

I ordered the part from Porsche but, when I came to changing it, it turns out that it's in fact this protection switch that's leaking. So I'm now waiting for the new part to arrive.

However, the PET diagram does not show the barrel section. Nor does it show the O rings. From the above info I assume these may be critical and need replacing. The link to benzworld seems to confirm this.

Do I need to order them from Mercedes?

Incidentally, Porsche quotes just over £100 UK for the switch. Bit unreasonable!?

MainePorsche

Thanks Stan. Great find.

Randy V

What is the function of this overload protection switch?

MainePorsche

'Transmission protection switch

The overload protection switch or transmission protection switch has a two wire connector on the drivers side of the transmission just left of the vacuum modulator. The plug is a female connector which attaches to the 2pin counterpart which is screwed into the transmission with a but copper colored round-shaped nut.
The connector connects a wire to a three pin two wire connector inside the car in the spare tire well right front corner. It is supposed to see open in P and N , closed in drive . It feeds 12 volts from the EZK ecu to the switch which is then connected to ground by the switch. The pressure-switch closes when shifting 1-2 nd opens from 2 -3 and also closes when shifting down from 2 - 1st ....it momentarily retards ignition timing. The Ezk has an input that is used for this transmission protect feature. The Ezk retards briefly by 16 degrees to reduce the torque and allow the brake bands / friction disks to get a firm grip again when changing gears.

The signal path is this: Ezk pin 26 to CEB V12, from there to U22 of the CEB, then to T32 (in the spare tire room) and to the switch, from the switch to T32 and to GP IV which is chassis ground.'

From 928 Tech Tips at jenniskens - a transmission tech Forum - good one too.

http://jenniskens.livedsl.nl/Technic...3/MyTip362.htm

Mrmerlin

time for a bump, my yellow car isnt the only one with leaking wires.
looks like my White 88 one might have a weeps as well

Bill Ball

Wow. I was going to say I've seen everything else on these trannies leak but this, and you have 2 protection switch leakers. Thanks for writing this up, Stan.

khalloudy

Bump his one...

Stan,

thanks for the write up.

We have been chasing a leak on my 87 and I thought it was coming initially from the secondary pump. Got all the parts for a refresh. Took it to my trusted mech that works on Range Rovers, Porches, Bentleys etc. and he pulled the car up cleaned the tranny well. Ran the car on the lift a little then left it overnight. Called me in the morning and he said that my assessment was wrong and the fluid is seeking slowly from between the switch and tranny housing. I was skeptical, so he cleaned the tranny again and ran it while I was there and sure about, pink quickly developed there! Now time to call Benz and see what parts are available locally!

Rexxus

ok so I followed the instructions like 96% and everything was perfect. Now I need HEEEEEEELLLLLLLLPPPPPPPPPP.

oh man. I seated the barrel easily from what I could tell. There’s a little metal tab on it that fit nicely at the very back of the threads. I go to screw in the switch and could only make like 1 turn by hand. Grab the torque wrench and do a few quarter turns. Switch is crooked. Backed it out and did it again like 6 times. Crooked every time. Decided to screw it in anyway and broke the nib on the switch into to barrel. I removed the switch and managed to get the o-ring out. There’s a little scoring / damage to the transmission threads but doesn’t seem like much. How do I know if this is a problem? The switch will leak I’m guessing? Or no switch will screw in??

how do I get the barrel out? I tried putting the q tips in and pulling but no joy. The nib is too far in the barrel now as well. I could probably buy a thin magnet to pull the nib out but how do I get the barrel out? It doesn’t seem damaged, the metal tab is straight not bent.

can I drive the car as it to a mechanic with the switch disconnected or will it leak ATF everywhere?

omg omg omg omg…

Mrmerlin

Please post pictures of what parts are damaged
don’t run the engine
it sounds like the pin was never seated properly and the switch part was used to drive the barrel in
as previously warned the barrel and pin assembly may take a few tries to properly seat if you didn’t use enough sticky grease to hold the pin it may be falling out of the correct position

Rexxus

interesting. The barrel felt like it was seating. It went into the hole and the metal tab was all the way in past the threads? But maybe it was too easy and that should have been the warning?



The tiny metal tip with the tiny o-ring on it is what broke clean off the switch. The metal tip is inside the barrel and the barrel is inserted into the hole. I’m not sure the best way to get the broken tip out of the barrel while the barrel is in the hole and I’m not sure how to remove the barrel. Also, does anyone know where I can buy another barrel if this one is broken? Any good sources for the switch? Please let me know if you need more pictures. I can take one of the barrel

GregBBRD

I'm going to guess that the difficult part will be getting the existing threads straightened out.
And them being the "ever common" 27 x 1.5mm threads means some hunting to find a shop with that tap.
Maybe you can grind a notch in the broken switch and use it a thread chaser?

You should be able to grab the "barrel" with a pair of "broad nose" pliers...that's how I get them out.
And then you need a switch.