So I'll start this post by saying that the recommended VW service schedule for the Haldex is 3 years and 40K miles.
At the time of writing this my car is just under 3 years old with a mileage of under 39K but I had the Haldex oil changed by the main dealer when I bought it (allegedly) at 31K for peace of mind so technically, my car isn't yet due for its first Haldex service.... keep that in mind!

Now I hadn't noticed anything untoward with the drive line, no noises or vibrations but it was a little 'jumpy' occasionally around 19mph which I've since discovered is when the 4motion disconnects. However I was looking to do a simply coding change and as usual, did a quick autoscan which threw up this code:


Address 22: AWD       Labels: 0AY-907-554-V1.clb
Control Module Part Number: 0AY 907 554 E           HW: 0AY 907 554 E
Component and/or Version: Haldex 4Motion            0043
Software Coding: 0000005

1 Fault Found:

00448 - Haldex Clutch Pump (V181)
            011 - Open Circuit - Intermittent
             Freeze Frame:
                    Fault Status: 00101011
                    Fault Priority: 3
                    Fault Frequency: 2
                    Reset counter: 14

Never happy to see fault codes being thrown, I decided to investigate what Haldex Clutch Pump V181 was and why it may be experiencing difficulties.  Its function is to provide hydraulic oil pressure to the system and without it, your 4motion car is actually nothing more then a 2wd car hauling about 600Kg of extra metal about, you would think therefore that a fault with the pump would put the MIL light on or at least have some form of text warning on the dash but no, no warning is generated at all which begs the question, how many quattro and 4motion cars are out there running in this state? Worse still is that a failing pump will generate less pressure then expected yet it appears there is no way for the system to detect this so until it fails completely, the clutch will likely be slipping each and every time the rear wheels are driven.

Determined not to let too much wear occur I decided to set about overhauling the entire 4motion system. The Tiguan uses the popular Haldex system manufactured by Borg Warner which for our use is the 4th Generation system or Gen4. Its comprised of the front differential, Haldex unit and rear differential:



Now this is where self-servicing comes into it's own, remember the VW interval is 3 years or 40K for the haldex oil only, they specifically say the filter is 'Non Serviceable' and fitted for life. The differentials are also 'either' 60K or filled for life depending on which bit of the service literature you read which means if you do book the car in for a 4motion Haldex service, you'll get the oil changed and a thank-you receipt only.

So, the parts needed to do a full service on both differentials / transfer box and the Haldex system (Plus the pump):


HALDEX Filter: 1x Part Number 111358


Haldex Oil: 1x VW Part Number G055175A2,


Haldex Pump: 1x VW Part Number OAY598549A, which comes with new mini filter:

 

Differential Oil: 3x 75W/90 Fully Synthetic, I ordered one more for flushing


Next, we need the car up to temperature. You can check the exact temperature of the Haldex box by looking at the AWD controllers measuring blocks using VCDS. In reality a 10 to 15 minute drive will have it up to operating temperature and we are now ready to underneath. Getting access generally isn't that bad on the Tiguan but be aware that you need the car LEVEL to do this job, if you put it on ramps then you won't be able to accurately refill!

Below and at the back, this is the Haldex units drain and fill points (Red arrows) and the Rear Differential drain and fill (Green Arrows)


This is the Haldex ECU, on the rear of this are two multi plugs. One of which is where the pump plugs into:


Here is the Haldex Clutch Pump or V181 in VW Speak and directly above it, the Haldex Filter:


Start by removing the 5mm allen key fill bolt, you always want to make sure you can refill before draining! Then move onto the 8mm lower drain, note for some reason its extremely long!
 


Once drained we can look to remove the filter and the oil pump, both of which are held in with 4mm allen. The filter is above the pump and isn't easy to photograph (hence you get this image instead!). If you are replacing the pump then the connector needs to be undone and the 3 cable clips undone, else it can be slid out enough to facilitate cleaning the mini filter:


With the filter and pump out we can get a look at exactly why you should avoid a main dealer Haldex service! This is the state of the oil filter, pump filter and oil. Remember that oil was allegedly changed just 8K miles ago:






     

This is a shocking state for a low mileage car and clear evidence of why filter change is so important! The crud and sludge is likely clutch material which is a vicious cycle! As the filter gets clogged, the pump generates less power which means the clutch starts to slip and therefore generates yet more material to clog the filters further. There is no monitoring that I can see so it would continue until either the clutches wear out or the pump burns out which, fortunately, is the most likely outcome.

Of course again, if you were to take your car to VW / AUDI because you noticed the Haldex 4motion system not working they would diagnose the pump had failed and replace it without changing the main filter leaving it to just burn out again. I really do wonder just how many 4motions are 2motions...

Anyway, we can now refit everything and fill the Haldex back up. Both the Haldex and Diff's are fill to full meaning you fill them up until the fluid runs out of the fill hole. With the Haldex though you need to get the pump to fill the filter so once you have filled it and the diff's back up, replace the fill bolt and start the car (or use VCDS to activate the pump). Allow it to idle for a few minutes and then undo the fill to top it back up. The Haldex systems takes around 800ml, the diffs are supposed to take 1.2L but in reality seem to take around 900ml.

Finally we can get to the front diff which is exactly the same principle: