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Thread: 8L S3 Haldex (Gen 1) Problems and solutions

  1. #1

    Thumbs up 8L S3 Haldex (Gen 1) Problems and solutions

    Hey guys,

    Ive been lurking for ages, heaps of great stuff on the forums so thanks to all of you, especially those writing up DIY/tech threads. I need to sell my car pretty soon so Ive recently addressed some issues and thought Id give back by writing up my experience. The info on the Gen1 haldex problems is out there but it took a lot of searching and trial and error for me, so this might help someone. Im not sure on forum rules for a noob posting pics/links but Ill try add some at the end of the post.

    word heavy, may bore you to death if youre not interested in Haldex issues. I take no responsibility for any damage caused to peoples cars or parts, only try this stuff if youre fairly confident in your mechanical abilities.

    Intro to Haldex

    (Gen 1) Haldex is a clutch that connects the front-rear driveshaft to the rear diff whenever the car decides it needs rear wheel drive (it always has FWD). The system is operated by a special (read: expensive) oil, which has a pump, and a controller that opens a valve, allowing the oil to press the clutch plates together. The haldex takes signals from long/lat G sensors, ABS/wheel speed sensors, brake switch, handbrake switch, and probably a few other systems. The Gen 1 system was found on 8L quattro models (S3/A3/TT), mk4 Golf AWD, and some other cars such as Volvos and other VAG cars of same era.

    Example AWD scenario

    Try to launch car on slippery surface, front wheels start to spin, car detects this and thinks **** I need rear wheel drive as well, activates the Haldex clutch, car gets more grip and accelerates better. This all happens pretty quick (under 1 second to engage) and if you're Haldex isn't working, the front wheels will continue to spin.

    What happened to my car

    I started to get the locked diff type of symptoms, where any steering at low speed would result in large clunking sensation, such as if driving a car with a locked diff. After I resolved this issue I actually lost my AWD completely. Rather than go through all the details, Ill just summarise everything I did, and if you ever get stuck in the same situation, maybe you can follow this checklist as well. Note that I didnt have access to VAGCOM/VCDS at this point in time, but Id recommend getting this, checking faults, and doing a Haldex test cycle on it.


    • Temp solution is to pull out fuse 31, turning off the Haldex system, effectively giving you permanent FWD only (also turns off traction control)
    • Then, replace Haldex oil filter (PN: 02D 525 558), oil filter sealing ring (PN: N 903 445 01) and tube of Haldex oil (PN: G 052 175 A1). Total cost of $200 from a dealer (can be sourced cheaper, and always ask for a discount from dealers, they originally quoted $240).
    • Now it gets interesting I reinstated fuse 31 to find that I had no AWD!
    • Pulled off Haldex controller (contains the stepper motor, circuit board, hydraulic valve) to have a look, ran some cleaning fluid in it, checked that the valve wasnt stuck. Also opened it up (took cover off) to look for contaminants or smell for that familiar cooked electronics smell. Nothing reassembled, reinstalled.
    • Applied 12V to the Haldex charge pump, using some small female spade terminals and 2 lengths of wire, straight to a car battery. The pump should turn on and whirr consistently (if doesnt turn on or making strange noises, probably dead, pretty common apparently). If its dead, look into the Volvo equivalent pump as apparently they are half the price (Volvo PN: 30783079)
    • Followed the Golf workshop manual to do an electrical test of the system. This allowed me to use a multimeter and check the signals from the handbrake and brake switches, check power for the unit was available, check the integrity of the CAN bus loop (this is what all the ABS, speed, acceleration sensors are wired onto), check the controller. Note that the manual expects infinite resistance on some of the haldex controller pins but I was getting about 2.5kOhms and this was NOT an issue.
    • While doing electrical tests, make sure to check for any corroded pins or sockets on the electrical connectors, and double-check that the earth strap (from rear diff to body) isnt corroded (give it a tug, apparently the bolts sometimes snap off, not so bad in Oz as we dont salt the road).
    • Ordered a new haldex controller gasket (PN: 02D 525 589) Note: my car didnt have one when I last took the controller off, and my model doesnt need one for oil to pass to the correct oil inlets/outlets, but I took a guess and turns out it was probably wise.
    • Removed the Haldex controller again and did a full disassembly and clean. I thoroughly inspected the circuit board for any burned parts or tiny wires. Checked that the stepper motor operated smoothly (these motors are supposed to be notchy (at least 40 notches per revolution, as this is how they work). Remove all of the valve components and inspect for smooth operation etc (WARNING: spring loaded valve, dont let it come flying out). Clean everything, allow any cleaning solutions to dry completely, lightly oil parts and reassemble.
    • Removed the charge pump to clean the filter and test again on 12V (dont run too long without oil, might damage pump, 1-2 seconds will tell you that its OK)
    • I noticed that not much oil came out when I removed charge pump and controller this is a sign that theres no oil (funny that). Somehow my oil had leaked out, possibly because there was a gasket and it fell somewhere as I removed the controller, do yourselves a favour and make sure to clean the whole Haldex unit thoroughly after working on it and check it once or twice afterwards to make sure there are no leaks. Apparently Volvo haldex fluid is also cheaper, but maybe not in Oz, but the Volvo PN is 31367941 (active on demand clutch oil).
    • Topped up with another round of oil (275mL @ $71AUD from Alto VW)
    • AWD!!!

    Now to give it a leather treatment and a polish and put the FS stickers in the window. Sad to see it go but moving overseas to where Audi parts are cheaper. I hope this info is helpful for anybody who gets Haldex issues and cant find a simple solution. Sorry about the wordy post!

    Important links
    VW Golf workshop manual (for electrical testing) -

    How to remove/disassemble charge pump (I only removed, only disassemble if you suspect its rooted) -

    How to test if your Haldex isnt working properly (if youve got performance mods, you should get wheel spin before shifting into second, should be fairly obvious. Maybe not as obvious in stock setup) -


    Ill try to add some to the next post. As Ive only made a few posts, I might not be able to, fingers crossed.

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  3. #3

    Default Pics - 2


    Note the final image with the Haldex controller gasket. These are a crush gasket and are supposed to only be used once. My haldex body has a machined channel in-line with the curved one on the gasket, make sure you install this the right way round. Pro tip: put the bolts through the controller and gasket, then put a rubber band over the bolts and out around the controller body, holding the gasket in place while you install. Before you fully tighten the bolts, break the rubber band and pull it out of the way, then tighten the bolts. There is not much room for fingers in there!


  4. #4


    Hello! Please, tell: what was wrong with AWD at the end of it all? I've got the same problem - kind of "blocked rear diff", and it was some kind of fun during snowy winter)) I supposed that something was stuck inside the ECU. I opened it, cleaned it out, changed the oil and filter, and as a result - I"ve lost my AWD immediately. I thought that a step-motor is dead, changed it, but it didn't help. I have a diagnostic adapter and I can check the Haldex faults - sometimes there is one "mechanical mailfunction", and sometimes it disappears. The test of Haldex via adapter shows that it can not engage, there is no AWD. What was wrong with your system - lack of oil after change? I have a fellow with the problem alike: he had normal working AWD, than he changed the oil and filter, after that he lost AWD immediately. He even had no issues before oil change.
    Thank you for the links - I'll try electrical testing. Sorry for my English)

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