Volkswagen Eos Forum banner

EOS Sunroof failed: Understand why repairs need specialist skills.

489 Views 6 Replies 3 Participants Last post by  voxmagna
After searching the internet and watching videos. Many dive into the sunroof motor with a hex key and try the 'manual emergency close'. When the sunroof is badly jammed, this key and motor shaft isn't strong enough and easily broken. I know how little torque is needed to move my working sunroof, first timers with a jammed roof don't. The next step finds a broken plastic gear in the sunroof motor which can be replaced with a cheap weak copy from Ebay, only for the motor to chew it up again. In reality faults causing jamming are hidden and there is no simple cheap solution for a DIY fix. Do you need a metal gear that won't break? The metal gear won't break but if the fault is still there, even more damage will by caused using one!

The same sunroof design is used on other V.W cars but they change the gear ratio in the EOS motor unit for higher torque because the EOS sunroof is larger and heavier. There's a difficult design decision to provide the high torque needed to overcome friction and drag which varies with use and dryness of seals. The motor unit has an integral electronic controller and circuitry to detect excessive torque V.W calls Pinch Protection. Pinch protection rolls back the glass if there's an obstruction e.g a childs hand. Experience shows pinch protection does not seem to be effective at preventing serious damage when the sunroof jams. MY07 sunroof has never jammed and is still working on the OE plastic gear cog.

IMHO the glass transport system has already failed badly once the jam occurs and there's no alternative but to have the roof top side dismantled and internal parts replaced by a roof specialist. This is tricky work not simple DIY level, because the sunroof frame together with seals for the sunroof and main roof seals are all involved. Anybody thinking they can do this is advised to read the workshop manual first, but don't expect a complete procedure. In a non-cabriolet car with a solid roof, sunroof repairs are easier and carried out internally. The EOS sunroof isn't a drop in module, the roof and seals are designed and built around it. Poor or unskilled work can result in roof seal leaks or an immediate jam and motor gear or other damage(again).

I've already posted what I understand about the EOS sunroof if you search the site. MY07 doesn't have a problem so I can't add photos or detail to the issues I discuss in this post. I've not needed to tear into it, but I have successfully removed the top roof sections, used the V.W sunroof alignment service tool for checks and got everything back aligned and without roof leaks. If you don't like or understand the detail, or choose your own path for a reliable working leak free repair solution, post it here for comment. Somebody has to be first to get the prize! I may be wrong about how it works and fails but everybody is welcome to dig deep and add to this thread with credible answers, photos and solutions.

The high torque geared sunroof motor with its integral electronic motor controller rotates its small output gear which AFIK meshes with the spiral cable or connects into a mechanical transfer box which moves the spiral cables. The rotation movement of the motor gearbox is translated into push pull movement at the sunroof glass frame(and shade?) using the spiral 'octopus' Bowden type cables.

I think the spiral cables at the sunroof end are rotating inside blocks attached to the glass frame each side with hard cut threads working like a worm screw? The spiral cable rotates but doesn't itself move in and out. Otherwise, where would the excess cable go to, so I discount that the spirals themselves move in and out push-pull because there's no space the length of the sunroof.

So here's the first problem: You can't push and pull the sunroof because it's (Threaded blocks?) are attached to the spiral cable and you can't pull them whilst attached. The only way you can move the sunroof manually when the spiral drive is damaged or jammed is by turning the spiral if that works, or disconnect the push pull blocks from the spiral cable. If you accept my explanation to replace the octopus cables anyway, it may be possible to cut/destroy the spirals where they attach to the sunroof frame, then move the sunroof forwards to close? I've never had to try it though! If you use brute force to push and pull, I can imagine the blocks if plastic just get pulled over the spiral 'Teeth' destroying both the block threads, the spiral cables and they will go out of sync. There's the Gotcha because people think sunroof closed, fix the broken motor gears then all will be well. Wrong! Because the sunroof may run out of square then more of the same and worse damage follows.

What we know is some have had sunroof jams which caused damage to the plastic guides. The poster thought the plastic guides being thin were the design fault! V.W sell a replacement sunroof guide service pack. In this example it was left to the dealer to do the repairs at great cost and we know no more.

So here's my take on the scenario: I think broken parts or lubrication are NOT the main cause of the problem, even though the sunroof in most cases is seized. The broken parts are the consequence of other problems made worse by ignoring initial warning signs of impending doom but there's really nothing you can do but teardown the sunroof assembly and replace more parts than you think. Early warning of a failing sunroof are Sunroof pinch protection operates and rolls it back, or the sunroof halts unexpectedly mid operation and aborts a roof operation if that was in progess.

The large heavier EOS moonroof must run parallel between its guides and the only way it stays parallel is if the threaded blocks stay in synchronised mesh with the spiral cable. The width tolerances are very tight because the sunroof has to seal into the aperture and the aperture roof seals are the same seals sealing to the fixed rear top panel. V.W specify a service tool for measuring the sunroof alignment. If a block one side jumps a tooth, the sunroof will be moving out of square and friction problems will get worse as it moves to the fully closed position. This out of square running can cause the plastic guides to get chewed up and put more stress on parts due to increased motor torque. The consequence will be ripped teeth on the nylon gear and/or damage to guides, the spiral cable 'teeth' and possibly the small steel driving gear on the motor gearbox. Damage to the spiral cable may be in one place causing the sunroof to stop at some intermediate point, but once the spiral is damaged anywhere along its length, problems only get worse as this damaged secion moves through the threaded blocks, particularly if sunroof operation is continually repeated on the switch or brute force is used to pull it closed. When there's a warning sign of a stopped sunroof or pinch protection occurs. Only try once to reverse or close it. Same is true of windows.

These are V.W words not mine on sunroof Pinch protection with hidden meaning which explains how you might destroy it:

The sliding sunroof motor is equipped with a force limitation (anti-trap) mechanism. If the sliding roof encounters an obstruction while closing, the sliding roof motor stops and moves the glass panel in the opposite direction.

If the glass panel sunroof is now closed a second time, the glass panel will close again but with higher force.

If the sunroof encounters an obstruction again while closing, it will open again automatically.

If the glass panel is now closed a third time via the switch, the glass panel moves but without closing force limitation.

I.e repeatedly trying to close the sunroof when there's a jam, destroys parts QED!!
AFIK if you wait 10 seconds between each attempt, pinch protection remains active which might reduce more serious damage?

Here's my theory take on the hidden problem which as yet is unsupported or confirmed:
The octopus spiral cables run inside a plastic or ptfe sheath inside steel tubes. Due to limited space the spiral cable runs through some very sharp radius bends. Over time with many turns of the spiral cables and torque to move them (even with slider lubrication), the sharp teeth turns of the spiral cable could wear against inner surfaces of the linings, becoming more oval on bends. The tight fit of the spiral inside the lining would be crucial to holding the spiral cable aligned true and able to transmit high torque. Once the spiral becomes loose inside the lining it could become weaker when torque is applied some distance away at the motor gearbox. This could force spiral turns to distort which when passed through the threaded blocks, cause jamming and further damage. I haven't looked at these linings which are available as spares. Somebody should cut one open carefully along its length and use an eyeglass looking for evidence of internal wear, particularly on bends. If they are using a cheap soft plastic material or ABS, I might consider re-engineering the liners using ptfe if possible which is low friction and self lubricating, or a try a harder wearing material as a substitute? If the radii of bends forming the octopus set can be reduced, that would help but ignore drive for the shade. There's not a lot you can easily do to increase strength of the spiral inner cables.

Therefore it's my opinion that faced with the consequences of an EOS sunroof failure and the high labor cost of skilled roof work for access, the only solution is to replace the spiral octopus cables with their linings, the plastic guide sliders, the threaded blocks for the spirals running inside if that's what they use, the motor plastic gear with an OE quality replacement, small steel output gear if worn or damaged and lubrication.

Everybody seems to want to pour in lubrication without thinking about it. When I measured friction on the sunroof system, I found friction increased when the black blades each side of the sunroof frame pushed the seals apart. They should have considered making those steel blades with a slippery Teflon coating to reduce friction and they are one of the things I keep well oiled with Krytox.

Look after your sunroof and watch for early warning signs of failure, stop using it and accept that only a full teardown replacement of parts to OE standard will put it right. I'm looking at trying an electronic protection device but TBH if it works, it won't solve the problem because the sunroof system is already failing, worn out, and octopus cables and liners and possibly guides and gears will probably need replacing.

See less See more
  • Like
Reactions: 1
1 - 7 of 7 Posts

Given the apparent lack of progress in rectifying the member's problem(s), I suggest the most economic and effective solution is for him to take the vehicle to the acknowledged UK convertible roof specialist repairer CAYMAN AUTO for assessment and repair.

It's already been suggested, but he's not keen on the round trip mileage, or cost and wants to try somebody else.
It's already been suggested, but he's not keen on the round trip mileage, or cost and wants to try somebody else.
A classic case of not realising "the first cost is never the end cost" and the perennial problem of "throwing good money after bad" when trying to find a cheap solution to an expensive and/or difficult problem.

Over the extensive period you and I have been involved with this forum, there have been many examples of Cayman providing an affordable and effective solution to UK Eos owners with roof problems.

I rest my case.......
now that u bring up lubrication, can u link to proper procedure, pls? adTHANXvance;-)
I'm now holding off giving lube advice until I've torn down a complete EOS sunroof system and get a better idea of what's moving, where to, and how beneficial I think applying a lubricant would be. I'm cautious because OEM applied grease lube in some locations shouldn't just 'disappear' and adding excessive (wrong) grease could attract grit and dirt. Plastics sliding on plastic can be naturally self lubricating (Teflon/ptfe is best) but add in sticky grease attracting grit in the wrong places and plastic guides can soon be toast. I've met problems caused by over greasing parts before where the only solution is to strip it all off and start again.

Too many owners of older EOS's are getting serious expensive sunroof failures (and no main roof op.). I'd like to find out why and what might be beneficial to do with mods or maintenance. My gut feeling is only use Krytox, other PFPE lubricant, or a MolyKote silicone product on sliding plastic? The Octopus spiral cables are another issue to think about and I can't wait for V. W to give me answers! I would advise against squirting the wrong stuff around willy nilly and in the wrong places if it mean't a tear down to remove it at a later date. You know how hard it is to get to places in there, think of somebody having to remove it!
See less See more
  • Helpful
Reactions: 1
I'm well inside the shade and sunroof on another EOS with a broken jammed sunroof. The EOS looks like a bird with broken wings at the mo. It has no side roof segments and both the shade and glass are removed plus lots of other bits. This is engineering NOT DIY work!! I was wrong in my previous posts about how it worked: The spiral cables that run inside the steel tubes don't turn, they are pushed and pulled by the motor and gearbox aka the spiral cable is the 'rack and motor drive gear the 'pinion'. Shop manual service procedures are sketchy telling you how to remove or fit a part. But if it's broken and jammed, they say nothing about peripheral parts which need removing.

Looking at the very complex design, there are several ways it can jam and I would put the motor , its gears and spiral cables at the bottom of the list as being the start of trouble but they will fail consequentially. Lubrication: Having got all the bits out now it looks virtually impossible during routine service to lubricate all the parts, and even on this roof some parts that should be lubricated have nothing on them!

The OE grease they used looks like standard yellow LM auto grease, except where I've used white lithium soap aerosol. I shall be cleaning out all the original grease and putting back Krytox GPL 205. That won't be the end because I have a theory about their design and will try a modification to significantly reduce drag. I tested a slider running in its channels lubed with some Krytox and its drag was 6Kg X 2 without any glass! Krytox (the best) gave little reduction in drag and anybody elses attempts at sunroof lube probably won't change much either?

IMHO if you have a motor/gear/cable failure then your sunroof is jamming and only a major teardown will give a good outcome. If you disconnected the motor and shade gearbox coupling and it can't be pulled/pushed by hand, then it needs a tricky engineering level teardown.

Unlike other V.W cars with a similar sunroof design, on the EOS they split the rail track to allow roof side members to move out and in. Once you split a track with plastic parts moving along and past a split, however hard you try to design the 'transition' between two tracks, there's a failure weak point just around the corner.

One thing I've learned so far is a tell tale sign of impending sunroof doom: Always check and ensure the side member front pegs are perfectly aligned as they enter the a A pillar holes. Also, when the roof is lowered into the storage cubbys (fish tanks), check the front pins sit aligned with the rubber buffers and aren't offset to one side or standing up high compared to the other side. The first time damaged plastic parts cause the front pins to not enter the holes and hit solid rubber, the roof pump continues to run and the internal gate guides will eventually break. With the roof open in its service position, the side members do 'wobble', but if either or both are 'Floppy' and the pegs don't align then serious engineering level roof repair work is needed.

Onwards & upwards, I hope this broken bird will fly again one day.
See less See more
  • Helpful
Reactions: 1
1 - 7 of 7 Posts