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03 SL Kleemann, 97 SL320, 95 E320 cab, Tesla X, Ferrari 360, etc
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Front locks noisy when latching

Hi folks, it's nice to see this old thread popping up again after five years, and thanks for all the kind comments!

Hi all, great post! May I jump in with a quick question? When operating the soft top on my r129 1997, the front latches seem to unlock fine but when the hooks get detached the make a very loud and scary bang. Both of them make that noise and somtimes half a second appart. Thus, since one detatches first the top headbord of the top seems to bend. I have tried to align the locks with the latches by unscrewing the two t30 torks on them and placing the hook in the latch and them fastem them. They improved slightly by doing that but still that noise frightens me.
Roy, as LWB250 and e-420 are correctly pointing out, the popping noise from the front latches is normal. Half a second delay between the two popping noises sounds about right, all pun intended...

Here is what's going on:
Both front lock cylinders A 129 800 16 72 inside the left and right front locks A 129 800 07 74 and A 129 800 08 74 get pressurized at the same time. However, the hydraulic fluid will take the path of least resistance. Both locks/latches will pretty much start moving together while it is easy to move them. Once they come closer to the point where the front of the soft top or the hard top gets pulled down the furthest against the weatherstripping, one of them is inevitably easier to move than the other. The fluid will keep moving the cylinder on the lock that is easier to latch, until it is over the tightest spot. Then, the same cylinder's movement will accelerate until the cylinder's piston has reached the end of travel. The popping noise is from the piston's rounded end hitting the bottom of the cylinder housing. It's designed that way - no need to worry. Once the first lock has finished it's movement, the second one can take up all the pump's power and move over the tightest spot, again ending in a popping noise.

The popping will be louder if there is any air in the system, because the air first gets compressed close to 100 atmospheres before the lock gets over the tightest spot (on average, that is, depending on how tightly the top seats on the weather stripping), and the compressed air can then expand and help accelerate the piston's movement towards the end. If the front lock cylinders 1298001672 (A 129 800 16 72) have been removed from the locks, then they have been re-installed with air in them. There is more volume in the cylinders than in the hydraulic lines, so all air will eventually get vented into the pump's reservoir. That process is pretty fast on the rear locks and on the tonneau cover locks, but it takes a number of cycles on the front locks. (It becomes more complicated for some other models, where the front lock hoses hold more volume than the front locks...)

Hope this makes sense. I am including below an updated location diagram, plus a list of part numbers.

Klaus
Top Hydraulics, Inc.



Part numbers for components in the Mercedes R129 roadster convertible top hydraulic system:
A 124 800 02 72 (1248000272) right bow extension cylinder (model year '92+)
A 129 800 00 72 (1298000072) tonneau cover lock cylinder
A 129 800 02 72 (1298000272) main lift (top drive) cylinder
A 129 800 16 72 (1298001672) front lock cylinder
A 129 800 17 72 (1298001772) left bow extension cylinder
A 129 800 18 72 (1298001872) right bow extension cylinder (model years '89-'91)
A 129 800 20 72 (1298002072) tonneau cover lift cylinder
A 129 800 21 72 (1298002172) rear lock cylinder

A 129 800 03 72 (1298000372) early version tonneau cover lift cylinder

A 129 800 00 22 distributor windshield frame (all models)
A 129 800 05 22 distributor near left main lift cylinder bottom, on frame stiffener (up to '96)
A 129 800 06 22 distributor near right main lift cylinder bottom, on frame stiffener (up to '96)
A 129 800 07 22 distributor near left valve block, on compartment partition

Valve blocks behind the carpeted panels, varying with model years (yes, we are rebuilding all of them...):
A 129 800 01 78 (1298000178)
A 129 800 02 78 (1298000278)
A 129 800 03 78 (1298000378)
A 129 800 07 78 (1298000778)
A 129 800 08 78 (1298000878)
A 129 800 15 78 (1298001578)
A 129 800 16 78 (1298001678)
A 129 800 17 78 (1298001778)
A 129 800 19 78 (1298001978)
A 129 800 20 78 (1298002078)
A 129 800 23 78 (1298002378)
A 129 800 24 78 (1298002478)
A 129 800 25 78 (1298002578)
A 129 800 26 78 (1298002678)

Pumps, varying with model year (yes, we rebuild them all...):
A 129 800 00 48 aka 1298000048
A 129 800 05 48 aka 1298000548
A 129 800 07 48 aka 1298000748
A 129 800 14 48 aka 1298001448
A 124 800 23 48 aka 1248002348

Locks/latches:
A 129 800 01 74 (1298000174) and A 129 800 02 74 (1298000274)earliest version front locks ('89)
A 129 800 03 74 (1298000374) and A 129 800 04 74 (1298000474) tonneau cover locks '89-'94
A 129 800 05 74 (1298000574) and A 129 800 06 74 (1298000674) rear locks (mostly '89-'91)
A 129 800 07 74 (1298000774) and A 129 800 08 74 (1298000874) front locks
A 129 800 11 74 (1298001174) and A 129 800 12 74 (1298001274) rear locks intermediate to late model years
A 129 800 17 74 (1298001774) right rear lock '95-'02
 

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98 SL500 Black & Tan, 86 944 Turbo- Sold
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44 Posts
Thanks for the post! Top Hydraulics step by step instructions made my top lock cylinder removal a breeze. Cylinder removed and bled and ready to ship off to Klaus.

A word to the wise: Order the FEBI hydraulic fluid online vs. buying genuine MB HF from the stealership @ $25/quart!!!! I wish they sold KY there after that prison rape!
 

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98 SL500 Black & Tan, 86 944 Turbo- Sold
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A huge shout out to Klaus and Top Hydraulics! Same day turnaround on my cylinder and back in the car within a week. It is very refreshing to experience great customer service and respectable pricing. I will refer anyone I know that has a drop top to Top Hydraulics.
 

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Sticky Roof

Hi

I'm hoping you might be able to point me in the right direction, have just taken the hardtop of my mums SL having not been moved for years. I had a real struggle to get the soft top up took about 4 attempts would go so far through the cycle and stick would then have to stop the engine and restart and it would go a little further until eventually after 4 or 5 attempts it would finally be up. Same issue trying to take it back down. The car is 20 years old and has done nothing for the last 6 years.
Could you offer any advice as to what the issue might be and how to diagnose it further.

Thanks in advance
binary
 

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Departed 1998 SL500 (and the Pano is in Bogota)
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11,020 Posts
First of all check fluid level in the tank, if it is not between Max and Min then you have a leak.
As you were able to complete the cycle after a few try, so system seems to be operational, hopefully things are just sticky after non-use for all those years. So may be just run it up and down a few more cycles to see if it improves. Do it with the engine running so not to run down your battery.
 

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Thanks for the quick reply, have checked the reservoir and the fluid level is at max, will keep trying during the week to see if it gets looser.
 

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03 SL Kleemann, 97 SL320, 95 E320 cab, Tesla X, Ferrari 360, etc
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949 Posts
Hello Binary, welcome to the forum!
Where are you located, and which model year is your (mum's) SL? Ideally, please add that info to your profile. It helps us in figuring out what might be going on here.

I'm hoping you might be able to point me in the right direction, have just taken the hardtop of my mums SL having not been moved for years. I had a real struggle to get the soft top up took about 4 attempts would go so far through the cycle and stick would then have to stop the engine and restart and it would go a little further until eventually after 4 or 5 attempts it would finally be up. Same issue trying to take it back down. The car is 20 years old and has done nothing for the last 6 years.
Is there any repair history on the top?
If you have an early model year, then I will ask you to take the return line off that goes into the reservoir, make the pump run without moving the top, and see if there is fluid coming out of the return line. If there is fluid coming out of the return line with the pump running, but without the top moving, then you have an internal bypass in the system that is robbing power from the pump.

Klaus
 

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Departed 1998 SL500 (and the Pano is in Bogota)
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11,020 Posts
For early model cars, there are 3 line to the tank and the return line is the one attached top the cap.
For newer models with only 2 lines, the return line is the one closest to you
 

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1991 500SL
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I always read but never post. What a weekend! I spent a Saturday removing all 12 hydraulic cylinders on my 91 500SL. Sent them to Klaus at Top Hydraulics to repair and got them back timely! Bent all the large clips thinking I'd get new ones. BAD IDEA! Could not find them. Contacted Klaus who advised I bend them back into shape. Worked perfectly! I replaced all this weekend and top works flawlessly. Took about 6 or 8 cycles to get the air out and work properly! No leaks.

KLAUS IS DA MAN! Responded quickly to emails and very patient! Guys, I wouldn't bother using anyone else. This was my most rewarding project.

I call my 500SL Hellyun and I'll post pics soon.

D.
 

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1998 SL500
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Devolus: for those of use who have not done this yet, and from what I understand we all will, how long did it take you to remove all of the cylinders? Also, do you consider yourself to be mechanically inclined, average mechanical ability, etc.

Thanks.
 

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97 SL500, 98 E320 Wagon, 2002 ML500 - former W108/W112/W114/W123/W124/W126/W140/W220
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6,252 Posts
Just an FYI:

There are a number of threads on this job that go into detail.

I replaced all 11 cylinders and the distribution block on my 1997 R129 last year. I am a former mechanic and probably what one would qualify as an advanced DIY'er. I have never done top hydraulics on any car previous to this.

It took me about six hours to remove everything working at a leisurely pace and bagging/cataloging all the parts.

It took about eight hours to put everything back on the car, again, taking my time and not rushing.

Dan
 

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1998 SL500
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Dan, believe me I know there are multiple threads on this topic, I have read them all with great interest-before i got my vehicle. I continue to look for and read these threads when on the forum.

I was asking the author of the most recent post as i am interested in knowing how long it takes for people to accomplish this and how they rate their abilities. It helps others who have not done this yet to get an idea of what they are up against.

Thanks for posting about your experience and all of the other info you help people with.
 

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1991 500SL
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ILSL500,

I consider myself average to slightly above average. The process is doable with basic hand tools (small screw drivers, needle nose pliers, an Allen wrench, and a star wrench). It took me 8 hours to take off and about the same to install. The only difficult ones were the Main Lift and Bow extension cylinders. These were the last to remove and it took 4 hours to remove these 4. The first 8 were very easy! I started at 8 AM and finished at 4 PM.

The hydraulic lines are numbered and the corresponding numbers are on the cylinders. Do not destroy the large clips...they simply slide off when you lift the center. Klaus is very helpful and supportive.

Take your time and enjoy time with your car! Hellyun and I bonded:)

Devolus
 

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1997 SL600 Brilliant Silver Sport with grey/dark metal interior, 234K miles
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1,977 Posts
2x Devolus' assessment of what is easy and what is more challenging is correct.

Removing the 2 storage compartments before trying to remove/displace the side panels makes the 4 difficult cylinders replacement much easier. The compartment removal is very easy (4 screws, 2 vacuum clip slides) and quick to perform. Removal of the compartments allows you to easily remove/replace the side panels without destroying their sometimes fragile attachment points.
 

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2000 SL500 (R129)
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16 Posts
Hello and please help. I have at least one dreaded leaking hydraulic cylinder. I want to fix them all over the winter but for right now I just want to fix the one or two that are leaking. I am getting a puddle of hydraulic fluid in front of one rear tire. Which cylinder is it and which diagram should I look at to remove it for repair?
 

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Departed 1998 SL500 (and the Pano is in Bogota)
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Leak from any of the rear cylinders on that side will end up in front of that rear wheel.
 

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Departed 1998 SL500 (and the Pano is in Bogota)
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Older cars has 12 cylinders total and newer cars like your 2000 may have only 11.
Minus the 2 in the front and you have either 9 or 10 in the rear.
So depending on which side, you should have either 4 or 5 cylinders to look at for leak.

See Post #21
 
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