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Discussion Starter · #1 ·
Am a new member, having recently purchased 1998 SLK230 in really good condition, only done 37k. Delighted with car, apart from roof. Previous owner told me it occasionally plays up but yesterday boot opened and roof would not close. Had to do it manually although it did then engage front roof catches and close windows. Today the boot opens and the roof opens to approx midway and then stops. The motor is running ok but it seems something mechanical is stopping it opening any more. Can close roof ok but each time I try to open it, it stops in same place. Any ideas?
 

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Perhaps the simplest potential issues first . . .


1) Does it have enough hydraulic fluid in the reservoir?
2) Is there any noticeable leaks in the system? (Which would also show up in a low level.)


Switch problems usually stop the sequence at the next step where as the motions would stop where ever it runs out of fluid to pump.


Fluid level is always the first thing to check.
 

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Discussion Starter · #4 ·
Hi, fluid level is fine, no sign of leaks. When roof stops it feels like the mechanism is hitting something solid - you can hear the pump start to work harder to try to keep roof opening.
 

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Hmmm. But if you do it manually, do you feel like it's hitting or catching anything at that same point?

If you can cycle the roof manually, the hydraulics should be able to do the same. The roof joints are all pretty simple, there are only 2 cylinders for the trunk, 2 for the roof, and 1 for the latch. They all work individually, and they only have to move full stroke each before the next step in the sequence. (i.e. 2 motions are not happening at the same time.)

If I understand what you're describing, the trunk/boot always opens and closes automatically, and then the latch always works automatically. It's only the roof/roof cylinders that are starting, but failing, to complete their automatic cycle?

Is it only/always on the open or close cycles? Or both? If both, does it stop in the same place going up and down?

The only specific issue I could think of that might cause this would be where one or both of the cylinder piston seals is failing, and those cylinders can no longer generate the force needed at some (the same) high load point in the stroke. Which is why I ask if you can raise/lower the roof manually without issue. If you can, then the cylinders should also be able to. Most of the times when we talk about the cylinders leaking, we are talking about the rod seal leaking; but there is a piston ring/seal too. If this seems to be the case, those cylinders will need to be refurbished or replaced.

Unfortunately, not an uncommon issue with our cars. (And you might as well decide to deal with the whole set if that's the case.)

Obviously if you aren't able to do it manually, and it does seem to be hitting something, tracking down what it's hitting is the next task. I think there are some threads with pictures (some of mine perhaps) but these cylinders are not easy to get to in any case. They are positioned behind the driver's and passenger's outside shoulders, the upper most, outer most confines of the trunk. If something is sticking or hitting, taking these two areas apart will probably be your only recourse.

Either way, the work will be about the same, and a pretty fair challenge.
 

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Premium Member 2010 SLK300 2LOOK
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Welcome from central Florida!
 

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Premium Member 2005 SLK55 AMG; 2005 SLK350
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It's probably switch S69/9 "boot lid up" which is in the right-rear corner. Next time it fails like that, lift up slightly on the boot lid (like you're trying to raise it even higher) and see if 1) you hear the switch clicking, and 2) if the roof then continues normally.

If it will fail solid, try grounding MFCU Pin 62 (Blue/Yellow) and see if it then continues normally -- only do that after the boot lid is fully up -- that would confirm it's S69/9.
 

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It's probably switch S69/9 "boot lid up" which is in the right-rear corner. Next time it fails like that, lift up slightly on the boot lid (like you're trying to raise it even higher) and see if 1) you hear the switch clicking, and 2) if the roof then continues normally.

If it will fail solid, try grounding MFCU Pin 62 (Blue/Yellow) and see if it then continues normally -- only do that after the boot lid is fully up -- that would confirm it's S69/9.

I haven't worked as much with the switches as I have with the mechanics, so I'm asking as much as anything. Would you have an intermittent switch issue that would stop the system mid stroke? He indicates that the roof is stopping mid-stroke (at times) which to me means that the system had to have seen the trunk lid up switch. I don't know if the system is continually monitoring all the switches all the time, or (my guess) it's just looking for a specific switch at a specific time in the sequence in order to proceed.


It would certainly be easier to replace the switch/check the wiring if it is an intermittent make or break than dealing with the cylinders.
 

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Welcome From the Sacramento Valley SLK Enthusiasts!
 

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Discussion Starter · #12 ·
The problem only occurs on opening. Boot lid opens and roof opens approx halfway and then always stops in same place. If you try to force it open, it feels as if something solid is stopping it. It is not possible to make the roof open further, either manually or powered. Will look for switch S69/9 and carry on looking for obstructions!
 

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Premium Member 2005 SLK55 AMG; 2005 SLK350
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Sorry I didn't read carefully enough... That's true.

Once you open the emergency relief the roof should move manually. Be careful opening it only when the roof is open.

I had this happen one time after *lowering* the roof manually - I manually *raised* it and all was well thereafter. I am not sure why but it did. Try the manual raise procedure?

I totally don't understand the hydraulics of the thing though, I've not seen a diagram that includes the pump, solenoids, relays, emergency open valve, and the extra relief valve next to it.
 

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The problem only occurs on opening. Boot lid opens and roof opens approx halfway and then always stops in same place. If you try to force it open, it feels as if something solid is stopping it. It is not possible to make the roof open further, either manually or powered. Will look for switch S69/9 and carry on looking for obstructions!

So, if I understand what you just said above, you are currently driving (or not) with the roof down? (But it went down automatically, and it hasn't been up since? (Either by the pump or by hand?))

So the latch cylinder seems to work and the trunk lid cylinders seems to work. If I understand efair's last comment correctly, it doesn't sound like a switch issue, but you can try it to eliminate it as a possibility just in case.

I've attached a few pictures of the roof cylinder to give you an idea of how it should look. To get a good look at it, it would have been easier to pull some of the trunk panels by reverse opening the trunk then, then lean in and look up; but you got to deal with it as it is.

It's all very cramped, but with the roof down, I think I'd try to pull the seatbelt entry covers off. Then you should be able to look down onto the cylinder.

Hope that helps.
 

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Sorry I didn't read carefully enough... That's true.

Once you open the emergency relief the roof should move manually. Be careful opening it only when the roof is open.

I had this happen one time after *lowering* the roof manually - I manually *raised* it and all was well thereafter. I am not sure why but it did. Try the manual raise procedure?

I totally don't understand the hydraulics of the thing though, I've not seen a diagram that includes the pump, solenoids, relays, emergency open valve, and the extra relief valve next to it.

Generally, if the system has enough "clean" fluid, and doesn't leak, the system should work. (As long as nobody has moved the hoses around on the valve body.) If all that is true, the system should either work or the pump unit is bad. I do a fair amount of mechanical and hydraulic work in my day job, but I was really reluctant to dig too deeply into this packaged pump/control/valve unit. I have a post where I clean out the system, but that was as far as I went.

None of these issues should stop the roof half way though. So his next step should be to verify that nothing is impeding the roof cylinder.
 

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Hello & Welcome.... Sorry to hear about your roof problem. Hope it is some thing simple and working soon again.

jnc1948 Charlotte NC USA
 

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Premium Member 2005 SLK55 AMG; 2005 SLK350
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Assuming the roof is currently open:
In the trunk, open the emergency valve and pull the latch release cables.
Lift up on the leading edge of the trunk.
Can you lift it? If no, stop and find out why. If yes, lift it to the maximum height and continue.
Now, with a helper, lift the roof out of the trunk towards the windshield.
Does it move all the way to the windshield? If no, you have a mechanical issue - find out why.
If yes, you have electrical or hydraulic issue.

I have no idea if the MFCU checks the switches continually or not, but I'd c it just to be sure.

S69/12 (trunk closed lid/rotary tumbler/trunk lamp switch) might be a good one to check too since the wiring for this switch flexes as the roof moves.

Attach a test lamp to battery + and probe the following MFCU pins to sanity test their function (if test light illuminates, then "function" is asserted):

S69/1 "roof closed" switch (in top of right A pillar): pin 32 GNBK;
S69/2 & S69/3 "roof locked" (right & left rotary tumbler are in series) pin 30 GNGY;
S69/7 & S69/8 "lid down" (Left & right) are in series: pin 37 BUYE;
S69/9 "lid open" (right rear crner): pin 52 BUYE;
S69/10 "luggage cover extended": pin 54 GYVT;
S69/11 roof open (starboard near quarter window): pin 33 GYPK;
S69/12 trunk closed lid/rotary tumbler/trunk lamp switch (insures nobody is putting groceries in the trunk) pin 69 BUGY;
S84 roof switch w/integral lamp: pin 28 WHVT & 29 GNVT

For example if pin 32 lights the test lamp the MFCU thinks "yes the roof is closed"
 

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Discussion Starter · #19 ·
Thanks for all the welcomes and the advice on roof problems. To clarify situation, roof is in closed position and will only open halfway. Rather annoying when UK is actually enjoying some sunshine and I cannot get top down!
 

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Premium Member 2005 SLK55 AMG
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Hi and welcome from the UK Midlands... good luck with solving the roof issue, it looks like you're getting great input to try to help you! :)
 
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