Mercedes-Benz Convertible top hydraulic seals.

R129 (300SL, 500SL, 600SL, SL320, SL500 and SL600 and A124 (W124 Cabriolet) models affected (300CE, E320).
Most likely some newer models too.

If the soft top of your beloved SL roadster or W124 Cabriolet is not working any more or is very slow, chances are that the hydraulic cylinders that operate the top are leaking. This is the main cause of failure of the soft top of these cars. The hydraulic seals inside the cylinders are made of material that is not very durable and degrade over the years in the mineral fluid independently whether you use the soft top a lot or do not use it at all. Some info says the seals are made of caprolactane (name of this material varies as flavors are patented under different names). The hydraulic seals usually simply disintegrate. No stop leak is able to fix the problem as sometimes sections of the seal crack away.

One solution is to replace all the cylinders with the new supplied by the dealer. The replacement cylinders probably use the same seals as the old ones. They are also pricey. All 12 replacement cylinders cost more than $3500 depending on your local dealer greed.

Another solution is to replace the seals. Seals made of polyurethane should be a much better option and should be much more durable and last much longer. A little problem however is that the seals are not a standard SAE or metric size. This is typical for Mercedes. Moreover, some seals have their cross-section smaller than the limit of modern machinery. Making molds is not an option as the molds are very costly, tens of thousands of dollars each. For a limited number of seals to be made it does not have any economical sense.

The seals on the picture are made on a very precise equipment used for military applications as well. Because the seal sizes mentioned above, machines are run beyond the limit which does not guarantee that the seals are made perfect on the first attempt. It took many tries to find the correct machine settings for some of the seals. It is still not easy, but we are here. The first seals were made in 2008. No failures were reported. The seals are available if you want to try and rebuild the hydraulic cylinders in your car by yourself.


Seals for all 12 hydraulic cylinders

Rebuilding the cylinders is not that difficult. Some take only few minutes, like the cylinders above the windshield of the SL model, see the picture tutorial below. Some take a little longer and require some common garage tools and at least a vise with thick rubber or leather overgrips. In any case, getting the cylinder out usually takes 90% of the time.

Cylinder 1298001672 rebuilding
Above the windshield cylinders rebuilding.

Main cylinder rebuilding

Here is a writeup about the A124 main cylinder rebuilding. SL model is similar.

Here is a discussion about materials choice for the soft top hydraulic seals.

A124 cylinders removal instructions thanks to Timroperco. Rear bow can be directly applied to R129 as well.

Front locks removal and resealing video Video showing how to remove and reseal front lock cylinders of R129 model. Thanks to Craig Wilson who used my seals and created this video.

Availability and cost

The seals are made in small quantities, but we always try to keep at least few of each size on hand. The seals very often shipped the same day your payment is received. However, we are not professional vendors and just trying to help the community. Please, understand if there is a slight delay. The price is $23.97 per seal kit for one cylinder. Minimum order is two kits. You can order the kits for any two cylinders. They do not have to be the same. Each kit contains a seal and a nitrile rubber (N70) o-ring. The o-ring rarely goes bad and it is totally up to you if you want to replace it or not. The o-ring is nothing special and we simply include it in to our kit. if you want to rebuild all 12 cylinders at the same time (not necessary, you can rebuild them one by one, two by two or in any other odd or even combinations you like) the cost of the whole set is $275.00. There is also $4.95 shipping and handling per each order. If you are ready, simply send you payment by paypal to mbcylinders@gmail.com. Please, do not forget to mention your name, shipping address and seals for which cylinders you are interested in. The sizes are different!

Preferred payment methods:

Send a check to: KBelov, 10767 Woodbine St. #118, Los Angeles, CA 90034.

Square cash: send an email to: mbcylinders@gmail.com with cc: cash@square.com and subject: $52.90 (or other amount appropriate). In the body put your shipping address and which seals you need. The first time you use square cash they will send you a link to enter your debit card number. After that, it is as easy as sending an email, instant and free as they use ACH to send payments between the debit cards without revealing the bank information. And you can receive payments too!

In any case, please, do not forget to include your correct shipping address and tell me which seals you are up to. Also your car model year and VIN is very helpful. Please, read FAQ about the information about determining the size of the seals for the main and rear (center) locks of your car. They are different. If you prefer, you can pay by paypal (see below).

Good news! Euro is falling and we predict it will continue to fall. As of February 2012 We cut prices 20% to pass the savings on to our Benz owners.

Available Seal Kits
Which seals you want? Put your VIN (optional)

For questions or to arrange different forms of payment please email us.

Please, read FAQ.