Soft top hydraulic problem

[cigarracer]

I recently purchased a 98 500 SL. I used the soft top about a dozen times and then put the hard top on for a few weeks. After having difficulty in removing the hard top the soft top will no long work properly. I had the dealer look at it and they said "it is most likely the hydraulic pump - about a $2,500 job). I have checked the fluid which is full. The back of the top will go up but the bonnet will not release. With help I can get the bonnet to go up and then with considerable help get the soft top up and in position. It will then manually lock in the front and with assistance lock the back. Similar scenario for putting it down. I must manually unlock the front right after the left auto unlocks and can help the top down. Any way to "test" the hydraulic pump or look for some other problem? Is there a shop that will rebuild the pump? I was able to find a new pump online for about $800 if needed. Help in Toledo the weather is getting nice.

[bobterry99]

I wouldn't buy a replacement pump until the problem has been properly diagnosed. There are procedures for testing the hydraulic system which require a pressure gauge and fittings to attach to the system. I believe these are pretty expensive and you may as well pay your dealer or a well-equiped independent to perform them.

[cigarracer]

I found a local hydraulic shop that can test the pump and if necessary rebuild it. Does anyone know what the propert operating pressures are for the bosch pump?

[bobterry99]

I believe the correct pressure is 180-200 bar.

[dkveuro]

Originally Posted by cigarracer

I recently purchased a 98 500 SL. ................................... I used the soft top about a dozen times and then put the hard top on for a few weeks. ....................... After having difficulty in removing the hard top the soft top will no long work properly....................... I had the dealer look at it and they said "it is most likely the hydraulic pump - about a $2,500 job). .................. new pump online for about $800 ........ Help in Toledo the weather is getting nice.

The top has several micro switches that the body computer uses to do the job. Any one of these will cause your problem as would hydraulic pressure.

These tops and roll bars have been a continuing problem for some time and the few I have worked on have all had different problems.
Some could be reset...others needed new components or switch adjustment....correction....switch replacement. Two had switches that would sometimes not go from open to closed and visa versa.

Most have given problems after a battery failure or change out....one was fried due to the customer installing the battery polarity in reverse...

One method you might try is : Get radio code. Remove battery teminals. Touch terminals together for about 1 minute....this should discharge the volotile memory and reset the top.......(Not always a winner. )

You local MB dealer should be able to positively locate the failed component(s).
You could insist they give you a diagnosis that itemises the problem and assurance that this will fix the problem.

Be prepared to pay heavy for work of this kind though your OEM dealer.

[SoCalSun]

FYI
I had the same problem with my '00 SL500 while it was still under warranty (luckily). I don't know what the cost was to fix the problem, but they first started with replacing the fabric bow latch/switch after finding an electrical fault in the bow switch. That didn't fix the problem so they checked and found an intermittent electrical fault in the hydraulic pump. They did a pump test and "found 145 bars of pressure from pump at times." So, they replaced the pump altogether and that seemed to fix the problem.
We had a 300D for over 10 years back in the 80's and that thing was built solid like a tank and we never had any problems with it. But these new models are definitely not built to last...

[cigarracer]

After being told by the dealer that I had a bad pump (hydraulic roof pump) and being told the bill will be about $2,500, I took my car to a hydraulic shop in Toledo, Ohio. I appreciate getting info from another member that the correct operating pressure is 180 - 200 BPI. The shop found that a set screw on the pump (inside the oil tank) which adjusts the pump for the correct pressure simply backed off which reduced the hydraulic pressure thus causing the top not to work. They reset and adjusted the pump, changed the fluid, used a sealer to make sure the set screw does not come out again and I was on my way. Total bill - $254. I will now be looking toward the dealer to reimburse me my $100 bucks for the misdiagnosis.

Weather is getting nicer and the top is down.