Mercedes SLK World banner

Status
Not open for further replies.
1 - 20 of 20 Posts

·
Registered
Joined
·
101 Posts
Discussion Starter #1
Hi all. Just wanted to know if it is normal for the hydraulic cylinders. To be hard to push in and out, and seem to be choppy and not smooth. When I compress or expand the cylinder it seems to jump then go smooth. This happens when expanding and contracting the cylinder.
I'm talking about the 2 trunk/boot lift cylinders that seem to work, but it's very slow and after the trunk/boot lifts nothing else happen. The first thing that happens is the roof unlocks, then the trunk/boot opens then nothing.
 

·
Premium Member 2005 SLK55 AMG; 2005 SLK350
Joined
·
4,965 Posts
It could be air in the system. If you go up and down a few times it should self bleed, does it smooth out then?

I had the same situation recently, the two roof latch switches were sticking closed even though the roof was clearly unlatched. You should clearly see these switches moving as the rotary mechanism turns. If you poke at these switches with a small screwdriver and it pops out, you may be in the same boat.

If you want to take a more rigorous approach:

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"
 

·
Registered
Joined
·
101 Posts
Discussion Starter #3
Thanks. It seems like air in the cylinder. Is the air supposed to bleed out? Should I try to run it a couple of times?
I have to "rearm" the system take the rear cylinders off so that the front trunk/boot switch engages.
There is an adjustment on the cable that goes to the cylinder but I don't want to start playing with everything. I'm figuring it worked before with the setting it is at.
 

·
Premium Member 2005 SLK55 AMG; 2005 SLK350
Joined
·
4,965 Posts
Yes the system is self bleeding. And it is a little chunky when you operate it by hand. Is it relatively smooth when operating by the pump?

I don't understand what you mean by "rearm".

I agree with you on not adjusting until youre sure you need to.

Did you check the switches as above by probing the mfcu pins?

Normally, If your roof is closed, and you try to open it with the red switch, the first thing that happens hydraulically is the two boot pistons and the overhead piston are simultaneously pressurized by the pump (to lift the boot lid and unlatch the roof). The pump just keeps running until it sees the boot lid is raised and the roof is unlatched. Once it sees these two things, it reroutes the pressure to the roof pistons to stow the roof.

So the questions are 1) are you seeing the boot lid raise 2) are you seeing the overhead latches unlatch 3) are you seeing any motion (even a fraction of an inch) in the roof? Next steps depend on which question you answer" no"...
 

·
Registered
Joined
·
101 Posts
Discussion Starter #5
Yes the system is self bleeding. And it is a little chunky when you operate it by hand. Is it relatively smooth when operating by the pump?

I don't understand what you mean by "rearm".

I agree with you on not adjusting until youre sure you need to.

Did you check the switches as above by probing the mfcu pins?

Normally, If your roof is closed, and you try to open it with the red switch, the first thing that happens hydraulically is the two boot pistons and the overhead piston are simultaneously pressurized by the pump (to lift the boot lid and unlatch the roof). The pump just keeps running until it sees the boot lid is raised and the roof is unlatched. Once it sees these two things, it reroutes the pressure to the roof pistons to stow the roof.

So the questions are 1) are you seeing the boot lid raise 2) are you seeing the overhead latches unlatch 3) are you seeing any motion (even a fraction of an inch) in the roof? Next steps depend on which question you answer" no"...
All that is happening. Then nothing the top seems to move a tiny bit when the roof latches are released. The trunk/boot lid tilts back all the way then nothing. I believe the 2 cylinders that operate the top are leaking, because when I put the top down manually and leave it for a couple of days there is a small puddle on hydraulic fluid on the back window. I'm going to wrap the front cylinder with a paper towel and see if it is possibly coming from it ( I did rebuild it) I have the headliner off and the panels removed (I'm using a rubber band on the microswitch to simulate the slide it the trunk) till I get it figured out.
Next job I can see is take the 2 roof cylinders out and rebuild them. I bought the kit. Haven't tried the electrical approach yet.
 

·
Premium Member 2005 SLK55 AMG; 2005 SLK350
Joined
·
4,965 Posts
Good you have the covers off so you can see the roof cylinders. Wrap those with rags too.

The roof cylinders are the hardest working cylinders, and from my limited experience when they leak under pressure you know it without doubt due to the noise and sight of it. It's like old faithful - loud and clear.

I'm thinking you do have a leak (because of the puddle) but that the roof cylinders aren't pressurizing (because the leak's not fully apparent to you yet).

Do you have one of these?
 

Attachments

·
Registered
Joined
·
101 Posts
Discussion Starter #7
Good you have the covers off so you can see the roof cylinders. Wrap those with rags too.

The roof cylinders are the hardest working cylinders, and from my limited experience when they leak under pressure you know it without doubt due to the noise and sight of it. It's like old faithful - loud and clear.

I'm thinking you do have a leak (because of the puddle) but that the roof cylinders aren't pressurizing (because the leak's not fully apparent to you yet).

Do you have one of these?
Yes I have one somewhere, haven't used it in a while.
The next thing I'm going to do is put paper towels on all 5 cylinders. Put the top down manually. And see if I push any fluid out. The fluid on the rear window almost has to be either a roof cylinder or the lines leading to it. The locking cylinder doesn't seem to leak at all (I have had the headliner off since I bought the car. I did realign the latches because the pins did not line up with the holes in the windshield frame. They might be sticking now. The mechanical things I can and will figure out. The electrical is more of a challenge, but I will get it eventually.
 

·
Premium Member 2005 SLK55 AMG; 2005 SLK350
Joined
·
4,965 Posts
Here's a picture and a detailed pinout of the MFCU.

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"
 

Attachments

·
Registered
Joined
·
101 Posts
Discussion Starter #9
Here's a picture and a detailed pinout of the MFCU.

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"
Where is the control unit located?
 

·
Premium Member 2005 SLK55 AMG; 2005 SLK350
Joined
·
4,965 Posts
Under the hood in the "apparatus case" next to the battery. There are four phillips screws that hold the lid on, just loosen them fully and the top can be removed.

There are four units in there, the MFCU is the unit closest to the battery. Don't disconnect anything - just back-probe the pins mentioned above. You may have to use your fingertips to push aside some of the other wires so you can see and reach the right ones. Also, if necessary, cut the wire-tie on the MFCU to make access easier (replace it with a new one when you're done).

Print out the mfcu pinout.jpg above, it'll help.
 

·
Registered
Joined
·
101 Posts
Discussion Starter #11
Under the hood in the "apparatus case" next to the battery. There are four phillips screws that hold the lid on, just loosen them fully and the top can be removed.

There are four units in there, the MFCU is the unit closest to the battery. Don't disconnect anything - just back-probe the pins mentioned above. You may have to use your fingertips to push aside some of the other wires so you can see and reach the right ones. Also, if necessary, cut the wire-tie on the MFCU to make access easier (replace it with a new one when you're done).

Print out the mfcu pinout.jpg above, it'll help.
Thanks. I wasn't sure if that was the one. I'll get on it in the next week. I take it all the microswitches are connecting to ground if the switch is not open.
 

·
Premium Member 2005 SLK55 AMG; 2005 SLK350
Joined
·
4,965 Posts
That's correct -- if you connect the clamp end of your test light to +12V, and touch one of the pins above, and the switch is closed, the test light will glow.

I believe you said A) starting from fully closed and latched, then B) start opening by pulling the red switch back, C) the latches unlatched and the boot lid raised, but D) roof motion never started. So your failure is at point D. Start by checking S69/1 (should be open), S69/2 & S69/3 (should be open), and S69/9 (should be closed).
 

·
Premium Member 2005 SLK55 AMG; 2005 SLK350
Joined
·
4,965 Posts
I noticed in your other post - you think just one side of your latching cylinder is leaking? There is only one seal for the cylinder, but perhaps one of the two connectors to the cylinder is leaking.
 

·
Registered
Joined
·
101 Posts
Discussion Starter #14
I noticed in your other post - you think just one side of your latching cylinder is leaking? There is only one seal for the cylinder, but perhaps one of the two connectors to the cylinder is leaking.
I get fluid in the center of the window when I put the top down manually. When I bought the car they gave me a front cylinder and the 2 rear cylinders. They told me they had replaced the 2 rears. The front cylinder was apart but lines were not disconnected. I just cleaned up the shaft, put an o ring on it and put it back together. My plan is to rebuild the spare I have and put it in lines and all.
I'm still "boggled" over the locks/microswitches for the front of the trunk/boot lid. I can compress the rear cylinders completely. Put the cable ball in the slot. Put the pins in. And it's fine. Till I lift the front of the trunk/boot. The only way I can get them to lock is by removing the cylinders and reinstalling them (manually). I think I can get it to function properly by either shimming the locking mechanism, or adjusting the unlocking cables that go to the cylinders.
Next week I'm going to be using the SLK so I just left the cylinders off and laying in the trunk.
BTW with the top up and locked all the microswitches are showing properly.
 

·
Premium Member 2005 SLK55 AMG; 2005 SLK350
Joined
·
4,965 Posts
I'm speculating wildly here... because I've only briefly looked at the bottom of the two boot lid cylinders. It looks like there is a sliding mechanism at the bottom where the cable ties in. I suspect this sliding mechanism is counteracted by a spring although i dont know where it's located. The idea, again speculation, is that when the cylinder first starts to expand its first centimeter, the cable is drawn tight - before the boot lid is acted on. This is what disengages those two latches. I also suspect the cables stay drawn tight until the cylinder contracts.

If the cables are seizing, or the springs are not counteracting, it might account for your symptoms.
 

·
Registered
Joined
·
101 Posts
Discussion Starter #16
I'm speculating wildly here... because I've only briefly looked at the bottom of the two boot lid cylinders. It looks like there is a sliding mechanism at the bottom where the cable ties in. I suspect this sliding mechanism is counteracted by a spring although i dont know where it's located. The idea, again speculation, is that when the cylinder first starts to expand its first centimeter, the cable is drawn tight - before the boot lid is acted on. This is what disengages those two latches. I also suspect the cables stay drawn tight until the cylinder contracts.

If the cables are seizing, or the springs are not counteracting, it might account for your symptoms.
You are correct about the slot ( I tried to lube it up, but no change). I didn't see any spring. But that would make a lot of sense. The other possibility is that when the cylinder is functioning properly it closes itself at the end of the sequence. If I close the cylinder almost all the way manually I can put it back on and the locks will function. The cables themselves are free and working properly. I might be able to adjust the cables. But I don't think that is the right way to go about it. The lid goes down the right amount, so pushing on it won't make any difference. It's that the locking mechanism doesn't lock the cable stops it from locking, much the same as pulling the hand pull cables.
 

·
Premium Member 2005 SLK55 AMG; 2005 SLK350
Joined
·
4,965 Posts
I'm not understanding exactly what you're doing manually that's different from what the hydraulics are doing... Do you think, once you've done your manual steps, the rod is seated further into the cylinder than "normal"?
 

·
Registered
Joined
·
101 Posts
Discussion Starter #18
I'm not understanding exactly what you're doing manually that's different from what the hydraulics are doing... Do you think, once you've done your manual steps, the rod is seated further into the cylinder than "normal"?
It seems like the rod is not retracted enough in the cylinder.
When it energizes it sends the rod out and it pushes down on the cable ball to unlock the trunk/boot front locks.
That is why I asked about how much pressure you needed to move the rod in the cylinder. I see there are 2 lines on each cylinder so one expands it and the other retracts it.
 

·
Premium Member 2005 SLK55 AMG; 2005 SLK350
Joined
·
4,965 Posts
Hard to guess much further. With accuracy at least.

It doesn't seem likely the cylinder is obstructed since it retracts when you remove and reinstall it.

Guessing anyway:

- wrong cylinders installed. Do you have p/n handy?
- sliding mechanism at foot worn/ binding / broken.
- cables too tight
- latches broken
- MFCU shutting off pressure too soon
- pump not pressurizing it fully
 

·
Premium Member 2005 SLK55 AMG; 2005 SLK350
Joined
·
4,965 Posts
Did you resolve your roof issues?

I've learned a little more this week working on my 98. The sliding mechanism at the foot of each lid cylinder is not counteracted by any spring, and the cables are counteracted by springs in the latches.
 
1 - 20 of 20 Posts
Status
Not open for further replies.
Top