Mercedes R129 SL-Class - Chapter 4 - Replacing the Rear Lock and Tonneau Cover Lift Cylinders

Klaus of Top Hydraulics, Inc. walks you step-by-step through the process of replacing the two Rear Lock Cylinders cylinders with rebuilt and upgraded units.
Mercedes P/N: 129 800 2172 (Rear Lock Cylinders)
P/N: 129 800 2072 (Tonneau Cover Lift Cylinders)
Order parts and find more helpful info on our website at www.tophydraul...

[@irontoolgoddess]

I am part way through the 4 rear-most (in the trunk) cylinders, and I can honestly say your videos, AND commentary, are absolutely SUPERB ! They have been a huge help. Thank you.

[@TopHydraulics]

Thank you for your kind words!

[@ryanmontgomery4302]

Absolute genius at conveyance of process.......well played! Thank you

[@davidn4562]

Great tip at time 13:15 to extend the cylinder shaft! Thanks.

[@TopHydraulics]

Glad you noticed and thanks for pointing it out - this is essential for model years '95+. I have been writing about it in the forums for almost ten years. We also put warning stickers on the packages with rear lock cylinders in them to perform this procedure.

[@misguidedsaint3693]

this is very helpful, i have a 99 sl500 im trying to fix up, and ive been stuck on figuring out the lift cylinders for a bit. this definitely helps, thank you

[@bsclifton]

Serious screwdriver skills at 1:00! I got the E clips off the tonneau lift cylinder without losing them... but putting them on is another story. Had it fly off about 10 times - ended up losing 2 before giving up. Burned off some calories chasing the clip down after it flew off though 😂 Will have a go at it fresh tomorrow 🙂

[@bsclifton]

Ok - found the problem I think! Tonneau cover e-clip is 5mm and the included e-clips for bow cylinder are 4mm. I then put the clip on and snapped into place with needle nose pliers

[@ernestogarcia3715]

Thank you for making these videos I'm going to try to fix my top and I was going in blind but after what you have shown I feel like I'm going to be fine

[@martinloke1455]

Great video. Thanks for sharing.😊

[@jasroopathwal7971]

I’m having issues with my 1993 SL500. The soft top goes up and down fine however when I put the hard top on, the rear left side doesn’t catch. The other 3 corners all catch and lock but not the rear left. Do you think this is just because it’s not aligned or could it be another issue. Would be good to hear any views?

[@TopHydraulics]

Sounds like either the left side rear lock is not in the original position or the weatherstripping on the hard top got so stiff that the rear lock is too tight now. The hard top is always tighter than the soft top. Check the left rear lock where the three hex nuts are holding it in place. I'll bet you that you can find some marks on the lock from where the lock used to be mounted and those marks are currently a bit higher than the nuts. This would be resolved by sliding the culprit up 1/4" or so.

[@modellbobby]

My softop doesn’t open automatic because I always need to lift the softop a bit at the rear latch and then it continues. Do I need to adjust the microswitcjes in the rear latch? If yes how ?

[@TopHydraulics]

Which model year is your R129 and has anyone tried DIY repairs on the cylinders?

[@hugojorge4572]

Hello! .After replacing my rear locks, when I close the soft top, the warning is on with that annoying buzzer, when the top is down no warning. What could that be? Thank you.

[@TopHydraulics]

The cause is one of the front locks giving the signal that it is unlocked, even though it is closed. The front locks develop a little play with time and the steel lever that pushes on the micro switch needs a tiny adjustment. We are talking less than a millimeter. Here is the in-depth description: kzbin.info/www/bejne/qqaUZ5usgMxgl5Y Maybe you installed the rear locks a little lower than they used to be and that created more tension on the canvas, which in turn pulled up harder on the front locks. In either case, you want to find out which one of the front locks is giving the erroneous signal and bend the lever on that lock's micro switch up between 0.5 mm and 1 mm. A little is s lot - take before and after pics so that you can reverse any over-adjustments. To find out which one needs adjustment, put the soft top tool in the lock and turn as if to close it some more. If this makes the red light go out, then you found the culprit.

[@joe5087]

Hi. I just bought a sl320 1995 last year. The previous owner told me he replaced most of the cylinders already. I’m having a problem that I can’t find the solution to. Whenever I drive the top stops working. If my top is closed then when I get to my destination the pump will only work if I try to close it even more(even though it’s closed all the way). The switch blinks when I try to open the softtop and no power goes to the pump. The opposite happens when I drive with the top open. It will pump if I try to open it more but it won’t have power when I try to close it. I’m sorry. I’m not even sure if this is a cylinder problem but I don’t know where else to turn. If I disconnect the battery a few times it will start working again but then once I drive it somewhere it will revert back to thinking it’s closed when it’s open and vice versa

[@TopHydraulics]

Will the top work if you turn off the ignition and turn it back on? In that case, you may have a dirty speed sensor in the left front wheel.

[@joe5087]

@@TopHydraulics no. I have to disconnect the battery but I do have my ets and abs light illuminated

[@TopHydraulics]

@@joe5087 Sounds like a speed sensor issue - the computer reads that the car is still in motion.

[@joe5087]

@@TopHydraulics oh. Ok. Can you send me in the right direction to figure out how to fix the doors sensor issue?

[@joe5087]

@@TopHydraulics oh. You already said the left front wheel. I suppose I’ll lift it up and see if cleaning it will do the trick?

[@adoniscastillo]

Hi Klaus, do you know what size are the wave washers for the tonneau cover lift cylinders?

[@TopHydraulics]

The pin diameter is 6mm and you would want to go for washers as thin as they come.

[@adoniscastillo]

@@TopHydraulics thank you and the c clip also 6mm?

[@TopHydraulics]

The e-clip groove in the pin is about 4 mm. That means e-clips size M4, M4.5 or 3/16” will work.

[@ozziesutcliffe3791]

Do you need to add locktite Red to the threads on the pistons?

[@TopHydraulics]

Only in theory. There is a little bit of thread locker left on the nuts, which is of course not nearly as effective as freshly applied, but chances of a reasonably tightened shaft unthreading itself are very remote.

[@adoniscastillo]

I dropped a bayonet clip 😢. Any chance you know where they are sold?

[@TopHydraulics]

Use an M4 or 3/16” e-clip instead

[@adoniscastillo]

@@TopHydraulics thank so much for all your help

[@stevealvord4825]

I can’t raise tonneau cover if I can’t get top down. ?

[@TopHydraulics]

It sounds like you are asking how to raise the tonneau cover manually when the top is up. Is that correct? If so, which model year is your SL?

[@stevealvord4825]

1995 SL 500

[@TopHydraulics]

@@stevealvord4825 Model year 95 can have the newer style rear locks, which have only an about inch long aluminum release lever in the rear. Or it can have the older style with about three inch long steel release lever with red paint at the end. Which ones do you have?

[@matthewschwimmer2455]

@@TopHydraulics I have a 1992 SL500, I believe I have this three inch long steel release lever with red paint at the end as I don't see this small notch that you can just attack a wrench to, to release the rear latches for my hard top. I've been searching everywhere but there's no information on what to do with these red-tipped levers I have, do I pull down or up, or must I use a tool to release my latches. What do I do D:

[@TopHydraulics]

@@matthewschwimmer2455 The owner's manual would clarify for you that you need to insert the soft top tool into the rear lock release levers and move the up in order to open the rear locks.

[@stevealvord4825]

My rear release levers have RED at the ends.

[@TopHydraulics]

Excellent, that makes it easy to release the rear bow and open the tonneau cover if you have the soft top tool with an open 10-mm wrench on one end.