This topic comes up alot on the SL forum>>>
 

people asking why the auto top hydraulics become slow or inoperative. I am hoping someone here can shed some light on the top hydraulics for the 129 model. If anyone has a working experience with this, please post your input. Thanks, Eli.

Internal hydraulic leakage in the front bow lock elements are very common!!
MB part number is 129-800-16-72 (2 required).

Is this a DYI job or is it a trip to the dealer??:)

OF that can be subjective! Ihave replaced at least 100 of these & takes 20 minutes each when the hard top is off. NOT difficult to remove the trim on the windshield frame & look at the way that they mount. The top system is self bleeding so it is a BOLT-ON job.

Thanks!:D :D

M.B. Doc advice sought...
 

My 1990 SL soft top has no trouble unlatching, but never latches. Is this symptomatic of the front lock elements part 129-800-16-72 going bad?

Also, regarding the hydraulics, do find many problems with the left or right valve blocks? Or is the trouble usually with the various actuators such as the locks?

Thanks.

The front lock elements(above part number) is the cause of most hyrdaulic R129 soft top problems!

Replacing front lock cylinders fixed everything
 

My soft top would never lock at the windshield when raising the top. And in hot weather, the compartment cover would not raise under its own power. I replaced both the left and right front lock cylinders (easy job) and all of these problems disappeared. Evidently the old cylinders were leaking, and not only did this prevent the front locks from locking (though they could unlock), but it was causing a significant loss in system hydraulic pressure that was affecting the other cylinders as well.

We tend to have alot of problems with having the soft top operate in the spring, when the hardtop is removed for the season. The soft top will be very sluggish. Very often one of the rear bow latches will be down, when they are supposed to both be up. The rear bow latch is then unlocked manually and held in the "up" position with a small prybar (tonneau cover unlatched and raised manually), then the soft top will begin working (need one person to hold the latch up with a prybar, and another to operate the switch). Per MB the trick is to get the soft top up and latched, then allow the car to sit overnight, this will enable the hydraulic system to bleed out air after a long winters rest.
Of all the components we have replaced, the top bow latches are definitely the most common, at least for hydraulic components.
To verify which one is needed, remove the trim cover on top of the windshield header panel and operate the top until the front latches fail to lock, operate the pump for maybe 15-30 seconds longer while the latches attempt to lock. Then put the top down. The latch (hydraulic cylinder) that is failing will feel hot.
Gilly

Is that for every year of the 129?
 

?

Yes, there were some changes made to the electrical operation of the 129 soft top system, and also a change made to the pump, but otherwise the hydraulic system was unchanged.

Gilly

Leaking RH Front Top Lock
 

I see this thread has been around for years, but I hope it is still being monitored.

My 1992 MBZ 300SL VIN WDBFA61E3NF057803, just this past week started having a leak on the right side top latch at the top of the windshield, dealer here in LV provided part number of 129 800 08 74 at a cost of $578.14, just in parts alone.

Are we talking about the same part, or has he chosen a major assembly instead of a component that can be changed out? I feel comfortable doing the work, but need to confirm the part and find out if I'm being screwed on the pricing or not. We only have one MBZ dealer in a town of nearly 1.8 million, so I know they don't face much pressure to price aggressively.

Chuck Parker
Las Vegas

Contact Phil at FastLane...
 

They have the parts you need and they sponsor THIS website as well. I'm most positive they can help you out.

In regards to the replacing of the actuators, do you just remove the little black cover surrounding the latch?

Yes remove those black covers & then pull back on the w/s top trim & tou will see the actuators mounted to the latches!

hyd cylinders
 

The cylinders are $127.00 US. ea at fast lane .I'd just order one last week thursday and received it monday no freight charge,when the cylinders leak hyd fluid will drip on the seats the fluid comes out of the channel thru the visor attachment cover.They are two, if you have to change one you better change the other one because it is soon to follow,be carefull when removing the top channel cover there is a proximity sensor underneath with wires that can be damage.The cover slides towards the back of the car after the hardware is remove,there is 2 hidden screws under the rubber at the corners .Easy job.