Hello everybody, I am having some issues with the power trunk on my 03 S600. When I bought the car, the trunk worked perfectly fine as it should. Sometime later, the power hydraulic assist failed and the gas struts were also shot, meaning the trunk would always slam shut if not supported with my hands and I would have to always hold it up when using it (it also weighs like 5000 pounds).

I started off by changing out the gas struts, and now the trunk holds itself like normal. Then, I moved onto the pump. I checked the fluid reservoir and, alas, it was empty. So I went and bought some Pentosin CHF 11s and filled the reservoir accordingly to a useful thread I saw. Here is where I started having some trouble.

Once I filled the reservoir with fluid, I shut the trunk manually and went inside to do a trunk reset (holding the button for 3 seconds). After everything was theoretically good to go, I tried opening the trunk. Nothing happened. The pump didn't lift the trunk.

So I was disappointed at first, but when I tried pressing the button to close the trunk, it actually worked! It also lowered that pesky right hinge on the trunk that always sticks out on every single W220! So at that point, I was trying to figure out why it would only work whenever its closed and not opened.

After troubleshooting a bit and closing it a few times with the power assist, I start to notice a seeping sound from the area where the pump lays. I open it up, and I notice that the brand new fluid I just put in is leaking out! I take apart the side trunk panel, and find that the leak is coming from one of the hydraulic lines and not the pump itself, luckily saving me the cost of a new pump (I think). I just disconnected the pump from its electrical plug for now until I can figure things out.

So here is where I come in asking for help. My pump works fine, and sounds completely healthy when it was running. I don't want to pay a ridiculous price for a new pump when all I need are some new hydraulic lines. Is there any place I can take the pump assembly to just so they can repair only the hydraulic lines? Also, what caused my trunk to close with the power assist but not open with it? My vacuum trunk latch seems to be working fine, so I assume it has nothing to do with that. Any help here is appreciated guys, thank you.

 

How much did you fill the pump reservoir?
With the trunk lid open, the fluid level should be in the center (bulls eye) of the plastic reservoir. As this is a "run-around" system, the level will go up on lid closing. If you overfilled it, it has to come out somewhere.

You an check my nick on the proper filling on both forums.
Good luck!

 

www.tophydraulicsinc.com

Klaus is a great guy and they have a cylinder rebuild service only. My CL needs it. You can also send in the whole unit and get it built better than new for way less than what MB wants for a replacement.

I don't understand why you can't order just the ram separately, they are usually all that leaks.

 

I filled the fluid at the proper level, right at the center while the trunk was open. One of the hydraulic lines connecting the pump to the hydraulic cylinder was ruptured, so the fluid leaked out. Can I replace the line somehow? The ends that connect to the pump is tied on with a hex nut, so that side is removable. However, the end that connects to the hydraulic cylinder seem to be fixed with the lines. Will certain hardware stores repair it if I bring just the lines and the cylinder without the pump?

 

Any good forklift repair /hydraulic repair shop can do it

Or buy a used one on eBay

 

I'm going to get the lines repaired soon, but I'm still unsure as to why the trunk doesn't open with the hydraulic assist, it only works when you go to close it. The trunk latch pops the trunk immediately when it the open button is pressed, but the hydraulic pump does not lift the trunk. Any idea for why it's doing this?

 

I'm guessing a wire has broken contact , mine does the opposite , it will lift hydraulically but will not close

The hydraulic pump isn't receiving the electrical signal to run the opposite way so it must be a wiring connection issue

 

That may be it, I'll check and see if there is any electrical signal to the pump when opening the lid. Also, how do I remove the hydraulic cylinder that is attached to the lines and the pump? The lines that are attached to the pump can easily be removed with a hex screwdriver, but I'm having trouble figuring out how the other end that is attached to the cylinder comes off. There seems to be a locking clip over one end of the cylinder (similar to the gas struts that hold the trunk), but I'm not sure how to remove the other end or the cylinder as a whole.

 

So I am at a roadblock here, and hope someone could help me out because I can't find any information regarding this...

I can't find a way to remove the hydraulic cylinder from the trunk. One side of the cylinder has a clip on it, but when I tried removing that it didn't help much. I looked at pictures of the whole assembly removed from the car on ebay, and each end looks to be held in place maybe by a ball joint? See what I mean below:

http://www.ebay.com/itm/00-06-W220-M...dYyC~X&vxp=mtr

I tried pulling on each end with a significant amount of force, without trying to break anything, and had no result. I attached pictures so people can better help understand my situation, and also the torn hydraulic line that I wish to repair. Any help regarding how to remove this would be really appreciated, thanks.

 

Remove the circlip (black retainer) The ball can get seized in the socket and will require some loving force to extract.

 

I've finally gotten the damn thing out. Was stuck, had to use "quite" a bit of force to get it out. And yes, it is held in by a ball and socket. I'm going to go get the lines repaired and will come back with an update.

 

Have you solved the problem?

 

my S600 went to a lot of problems with this. First I had a battery failure, I put the car in storage, and this spring installed a new battery and took the car home. The trunk had no action whatsoever, I had to open it with the mechanical key.

Hooked up DAS, and it gave me a rather implausible fault of trunk angle sensor shorted to ground or battery plus.

cleared the fault, and the trunk promptly unlocked with the fob, but did not lift.
fluid was low (after five years), refilled it and cycled it several times and refilled it again.
All is good now!

 

I have a similar problem that I just noticed yesterday. I'm sort of thinking mine must have a leaking hose. The pump has fluid, new shocks installed less than 4 months ago, and if I push the button on the trunk or door it will pop open but not lift up or close. Might be time to start pulling back that covering for further investigation.

Why couldn't Mercedes just make a trunk like everyone else?

 

good question, but no clear answer. Even the simple electrical system on my E350 is crapping out for the second time in 8 years.

If you pull back the covering, you'll probably find some seepage, but that is easily replaced. I found that forcibly closing the trunk would produce a lot of foam in the reservoir. subsequent refilling and cycling then fixed all the problems.

 

I just pulled out the whole unit for now until I get it repaired later since I'm dealing with another issue right now. Any hydraulic repair shop can do it, and for rather cheap. Yes, it will be quite messy down there in the battery compartment if you think you have a leak.

 

Since with during the battery reinstallation the trunk lid kept falling down on my head, my friend was tasked to hold it up (tough job!).

Ordered 2 new gas springs (left and right are different part#), and installing them took about 5 minutes - use the new ones to identify where to insert a small flat blade screw driver to release the black safety clip, you do not need to remove it).

The old ones were manufacturing dated 2007 and 2008, so they were NOT original, and that indicates a service life of about 5 - 7 years.

The old ones could be compressed easily by hand. the new ones not.
This seems to really ease the work load on the pump, which runs very silently now.

FYI

 

Yeah having good struts is very important, they carry the weight. The hydraulics is just there to open and close, not support it, and it's a HEAVY trunk without the assist springs from the non-power models.

 

I'm having the issue right now that the trunk won't open with the assist.
I don't have any CHF11S handy right now courtesy of FCP Euro's feral monkey packing team, the package was damaged en route.

 

most oReilly and autozone parts stores now carry chf11s

Also note it’s not just the hydraulic ram but also the normal gas lifting struts that fail with age you’ll probably need to replace the gas lifting struts too

 

Yeah, I bought some aftermarket ones that fit but were too strong, so I put one on the motor side and the other I left the stock one.

This worked for the W220 and I just did it in the W215. Both struts had failed.

I should mention, the motor turns on and moves the hood weirdly when closing, but nothing when opening. Its silent.
I'm suspecting an electrical switch issue.

FCP Euro ****ed up my order but they're overnighting a new order that'll get here tomorrow, it should have 2 bottles of CHF11S in it (liqui moly's version).

 

The hydraulic assist system seems to operate backwards. I believe it's trying to open the trunk when I close it, b/c it kicks on but pushes the trunk upwards?
It does work to lower the trunk down.

 

Did you end up finding the solution for the electrical problem?

 

I have the opposite issue with my C 600 trunk, the motor will lift the trunk, but no motor to close it. The problem is in the coiled wiring from the trunk lid to the trunk. It is a common failure item. I also had FCP euro screw my order of CHF 11 S, and they had to send me two shipments. At least I got both of them so I have double the amount of fluid

 

You mean in the wiring harness? Is there a fix?

They hire feral monkeys to package their orders. Now they're overnighting me a not-insignificantly sized package. Idk what on earth their business model is or how it works.