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Discussion Starter · #1 · (Edited)
Sorry for the length and detail of this, I’d though just to introduce and to upload a PDF to make it easier for working on the car itself, but I guess no attachments allowed due to resource requirements. You can probably PM me with an e-mail and I can send you a PDF if it works better for you.

So, on the one hand if the lock is working OK it’s unlikely this information is needed, but when the lock is not working (typically sort of stiff to use or fully stuck due to age-related corrosion or something else) and the usual solution of injecting a shot of WD-40 or silicone spray doesn’t solve anything, then you are left with replacing the lock assembly or disassembling everything, cleaning and lubing, and then reassembling. In my case, the trunk still locks and opens via the in-cabin trunk release, but the lock itself has been blocked for years, either due to corrosion or due to a period of local pranks where someone had the bright idea to go through school parking lots and inject superglue into locks, etc. I was expecting the superglue prank, so I bought a used but complete emblem-type lock assembly as a parts donor and first dissection example.

My plan was to take apart the used unit but reassemble it with the lock wafers from the original vehicle, so that my original key would work. The unknown factor was how many wafers of the original lock would be destroyed while removing the lock cylinder from the original unit.

Vehicle discussed and shown is 2000 Jetta GLS 2.0 manual. If everything is clean and well lubricated and functional on your car’s lock, then this process of removal and disassembly and reassembly can by performed in an hour or so. But you wouldn’t be doing this work unless something was not quite right or not working all together, and so while your actual working time will be brief, the elapsed overall time can be days depending on how patient you are unsticking the lock itself when we arrive at that point.

Easiest path is to give a $300 bill to the dealership and buy the whole assembly keyed to your vehicle. You can also visit a locksmith and check if they will make the diagnosis and repair for you. But what kind of fun is that ?

WHAT TO DO = Remove, Disassemble, Clean and Check and Lube, Reassemble, and Remount

1 - Remove the lock assembly from the trunk lid. Nothing to this, remove the decorative cover if still in place, unplug the one electrical connection, unfasten one mechanical connection/link, and unscrew three small T25 screws from inside the trunk, and the entire lock assembly with emblem will lift off towards the outside of the vehicle.

2 - Disassemble

Remove the emblem badge by removing a couple tiny Phillips screws on the back side and pulling the badge off from the front.

TIP – because the emblem badge is mounted to the base metal casting in a sort of adhesive sandwich, with one or two rubber-like layers between badge and main casting and between main casting and trunk lid, consider freezing the assembly for 20-30 minutes before separating the emblem badge and gaskets from the sandwich, because the cold will weaken the grip of the adhesive layers, and an easy separation is less likely to damage any of the components such as bending or nicking the emblem itself.

With the badge off and its supporting layer removed, you will discover a small rubber-like collar guarding the key lock cylinder, wedged between the main casting and the emblem gasket or mounting plate. After removing this collar, flip over the assembly and begin to remove all other components.

On the reverse, another gasket to be removed, with a spot of adhesive at the center (skim carefully with razor if sticking), then unclip the small plastic envelope linked with the electrical connection.

Now remove the metal circlip on the lock stem, and right after that a small spring cup, and then the spring itself, taking care to note where and how the ends of the spring are placed on the casting !

After the spring is out, remove next the small inner casting, noting again where and how this small casting aligns with the main casting. To remove the small inner casting, it needs to be lifted slightly and then rotated out of the way of the swinging metal arm attached to the large plastic sleeve.

The main plastic part is a bit tricky as there are two latches to pry up simultaneously, and if your unit is badly corroded or otherwise sticky, it will be a good idea to also pry around lightly on all edges of the plastic to make sure it will slide up and off once the two latches are free.

With the large sleeve removed, there is one more little plastic ring mounted below the metal cup that was removed. Note how it slides into the slots of the main casting and then remove it.

Make sure the lock cylinder is freely working (key goes in and out OK and no wafers are stuck)

If the key will not fully insert, or the lock will not turn with the key fully inserted, then some time will be needed to soak in your preferred rust/corrosion penetrating fluid.

WARNING – do not apply heat to the lock cylinder or assembly in order to free up the stuck lock, otherwise the base assembly will melt rapidly into a puddle due to being made from metal with a very low melting point.

Things to try that might hurry along the lock-unsticking process :

If you have access to a key that is not a flip-key, such as the valet key, consider tapping very lightly on the partially inserted key from time to time, between soaking periods, to try to break the corrosive bond of the lock wafers to the lock cylinder. Lightly and tap are critically important words here, as you can make worse both the lock and the key by pounding long and hard. I don’t recommend it, but it can work if time is critical.

An alternative to the valet key is just a plain old metal strip of the right dimensions. For the typical HAA key form, if you want to make a blank metal strip, the overall dimensions are approximately 0.035 inches thick (20 gauge) by 0.321 inches tall (not quite 1 mm x 8 mm). The overall key width is 0.118 but it’s impossible to fit in a solid thickness due to it would block on the wafers, so the 0.035 is just the center web thickness.

One other alternative is to pick up a “template key” set, which comprises a central rectangular key form (0.035 thick by the way) and then two smaller blades with a lead-in ramp on the end capable of lifting the wafers, which, when all three are sandwiched together, can be used as an HAA key. Locksmiths will have these pieces and this approach is used when decoding a lock and then making a key by hand.

Remove the lock cylinder from the lock assembly by inserting a working key and rotating slightly until the cylinder slides out of the main housing, leaving behind the interlock casting, which cannot slide forward. At this point, the lock cylinder interlock casting will slide out the back of the main housing.

NOTE – it is not possible to remove the lock cylinder without a working key. If you have no key, then one must be made, or the lock must be picked, or the lock must be destroyed.

WARNING – once you pull out the lock cylinder, do not remove the key until you have your hands over a big towel or a shoebox or something to catch all the pieces that may pop out (the 8 brass lock wafers and then one teeny tiny coil spring for each wafer). If you are careful and remove the key slowly with your fingers on the wafers, they may stay in place, provided you do not jostle further the cylinder. Alternatively, for safe storage, you can refit the interlock casting after removal from the main casting, and pull out the key, or at least leave the key in so that the wafers are retained in position.

However, in my case, the answer was “superglued in place or otherwise immovable.” Since I could verify that only wafer one was glued in place, I slowly nibbled away at the housing until I could see the edges of wafer one, pound it into neutral unlock position, and then proceed to lock-pick the other seven wafers until I could remove the cylinder, in order to preserve and to transfer the remaining original lock wafers, hoping one of the ones in the donor unit would match whatever was superglued in position one of the original unit.

While the two versions of lock cylinder and sleeve look very different, dimensionally they match and the HAA key and wafers are a constant, so just to clean and lube and put everything back.

My donor lock assembly did not come with a key, so I went the lockpick route just to see what it was like. Many lockpicks are available on the market, I picked a brand known generally as Lishi, named after the inventor. I chose to learn to lock-pick as part of this project, although for sure once you have the main assembly stripped out, it will be faster and cheaper to have a locksmith do this for you. By way of explanation, how the lockpicking works is that you insert a special tool shaped like the VW key but with two internal levers that you can use to push each of the 8 lock wafers up to their release position, one at a time.

But, it’s not quite so simple as that because you have to put a light rotating tension on the system so that once you lift a wafer to the free position (but without over-lifting it), it sort of wedges itself into that spot so you can go and work on pushing the next wafer out of the way. This sequence is not straightforward, so you end up selecting a starting wafer and then touching all remaining wafers to find the one that will both move out of the way and stay stuck out of the way. Ultimately, the last one will click, and the lock will turn, and out comes the lock cylinder, congratulations and bravo! If you want to understand a bit more about your key and lock system, try www.sidewinderkey.com or sidewinder-key-bitting_by_Greg_Brandt. The MkIV key and lock system is known as an HU66 system and you have the regular key type HAA and the valet key type NAA for your MkIV.

So, assuming you can remove the key without dropping out all the bits, now remove the wafers one at a time, noting the position of each in the lock cylinder (positions go 1 through 8, with position 1 near the key head and position 8 at the tip of the key) and its number (there are four wafer configurations, numbered 1-4, if you see 11-14 they are still 1-4 but are mounted facing the other way). You will want to know this sequence so that you can reassemble exactly once you’ve cleaned and lubed everything. In any case, you have to do the reassembly correctly or you will not be able to reinsert the lock cylinder into the sleeve.

3 – Clean and lube. Do your best to clean and polish each wafer and then use a specialist automotive lock lubricant on the wafers and on the rotating mechanism, etc., so that it never sticks again.
Choice of lubricant is a very opinionated and polarizing topic, so please use whatever lubricant makes sense to you. Two remarks according to my experience and opinion. Do not use WD-40, it is not a lubricant. It’s helpful when unsticking things, but once everything is moving then all traces of it should be removed. Even more so for normal oil or grease, all that is going to do is make things sticky by gathering dirt and dust while it dries out over time. So, look for a dry or non-greasy automotive lock lubricant. Historically this was graphite (dry or in an evaporative carrier), but more recently Teflon in an evaporative carrier or something similar. If no specialist lubricant available, it may be better not to put any lubricant if you have only grease, oil, or WD-40. If still not sure, maybe show your ready-to-assemble parts to a local locksmith and ask.

4 – Reassemble and Remount the unit. You took notes during disassembly, right ?

So, there we are, everything I can think of about this lock assembly that might be of interest, I know I learned a lot. The text seems small and I do not see any options for enlarging it, so I hope the internet takes care of all things like that and it's easily readable now that it's posted.

12 Posts
Discussion Starter · #3 ·
I've been considering doing this to my Golf for awhile now. Is there any way you could upload the pictures to a different host?
Sorry but NO! Like I wrote in the first line, my plan had been a short intro and to upload a PDF of all that. Then I spent more time than I'd hoped to upload to a hosting service (google in this case), upload all the images, try to resize them consistently to something that works in the forum, and then link them all, WHAT A PITA compared to uploading a single file ! So, PM me an e-mail address and I'm happy to send you a PDF of all, or to send you all or whatever pictures you want directly, just let me know which.
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