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Audi TT Quattro 225 Haldex Issue

30K views 62 replies 11 participants last post by  Christian_02_225 
#1 ·
Hello, i am new to this forum and have heard positive things about it. I have a 2002 Audi TT Quattro 225 and I love the car despite the usual Audi problems, other than that, the car runs great and there is no major problems with it. My Haldex system does not seem to be performing correctly, I have put it on jack stands and all 4 wheels spun but I get bad wheelspin or power loss from ESP when driving "spiritedly". I know it is engaging but do not think it is providing sufficient torque to spin the wheels from the weight of the car since it did spin on the jacks but does not feel working on the street. I do not know the last fluid change, but there is fluid inside, and considering the car has 170k on it with a rebuilt motor, I expect some problems but would like to at least find out what is wrong with the Haldex since it is a major feature to the car that i am missing out on. Any advice would be appreciated Thanks!
 
#31 ·
Okay so I am going to consider changing the pre charge motor since I have a "hopefully functioning" one on the new one. I attempted to remove it in the past but I could

not get any clearance between the electric motor cover and the driveshaft/ subframe to get it out. Last time I did this, i dont think that I got much fluid back in the unit

when I drained it for the motor removal but my only concern would be that the haldex coupling would be ran with very low fluid for over a month or so, I just don't wanna

spend money on more fluid to add to the existing unit in the car if it could possibly be damaged by running it super low on fluid for a little over a month now. Anyway, would

I just have to remove the driveshaft to get clearance for the motor to come out? I don't really mind doing it now that I have a replacement but I heard that people have

pried the rubber driveshaft cover to get clearance but i do not want to mess anything up. Just let me know, thanks guys.
 
#32 ·
How are you going to know anything if the fluid is low? Maybe it will malfunction because of low fluid as the pump might not get enough to properly charge the system. There is not a whole lot of fluid that goes in there.
Honestly, from your posts, I think you need some guidance. Sounds like you have mechanical aptitude but no way in hell should you be doing these things without someone trying to get you to do it right.
 
#33 · (Edited)
Agreed.

When you do services on the Haldex that require removing the pump and/or controller, you are preparing to purchase a new tube of fluid every time. I made this mistake when I did the troubleshooting on my own car. I did the precharge pump and two controller swaps in rapid succession and ended up going through three tubes in less than a month. Draining/refilling the unit is good practice to ensure you don't run the system dry when you service it.

The people in this thread have made many recommendations about how to go about troubleshooting the Haldex problems on your car, and most are speaking from personal experience. Although what you do is 100% your decision, you've opted to mostly disregard that advice and go your own route.

We want to help and make sure you get the job done right but that requires doing things in a sometimes very meticulous and specific way. When you bought a used MKI TT you nonverbally agreed to buying a car with weird quirks and an uncommon drivetrain system. Owning and maintaining that requires you to sometimes buy fluid when you don't want to or do things more than once to get it right.

We get it - you don't want to waste time, but it took me personally over a year to get the problem solved and now that I took the time to do it I haven't had any problems since. Sometimes you just need to bite the bullet and do it.

Edit: An addition - you can pry the driveshaft cover back with a crowbar/breaker bar or some other sturdy item. I had the same problem with my car and the solution was pretty simple. You can use a fair amount of force on it, too.
 
#34 · (Edited)
Okay, although I might not be the most experienced person working on cars, I am still learning. I think that it is low on fluid because when I tried to use the siphon to put back in the new fluid I just put in the other day. I was not going to buy a whole new tube of fluid if it is not going to function anyway. I know that might not have been the most logical decision but with what I had to deal with at that time, that was my only choice. There is still fluid in there but just not near as much as there should be. If it is not engaging anyway, I do not think that it could do too much harm IMO. I am going to go ahead and try the motor to see if it will fix it. And once again, i know I do need some mechanical guidance, and YES that's why i am here lol. And all I need to know is if driving with a non engaging haldex with low fluid for a little over a month will cause it to completely go out, or should i be safe, there is no binding in the rear end and it drives just like it did before. Thanks guys i really do appreciate your help
 
#35 ·
Okay, although I might not be the most experienced person working on cars, I am still learning. I think that it is low on fluid because when I tried to use the siphon to put back in the new fluid I just put in the other day. I was not going to buy a whole new tube of fluid if it is not going to function anyway. I know that might not have been the most logical decision but with what I had to deal with at that time, that was my only choice. There is still fluid in there but just not near as much as there should be. If it is not engaging anyway, I do not think that it could do too much harm IMO. I am going to go ahead and try the motor to see if it will fix it. And once again, i know I do need some mechanical guidance, and YES that's why i am here lol. And all I need to know is if driving with a non engaging haldex with low fluid for a little over a month will cause it to completely go out? Thanks guys
I would generally not advise running the car with low fluid in the coupling. Even though the clutch pack/controller may not be working properly, the fluid serves multiple purposes. It serves as a hydraulic fluid for pushing the clutches together, but also serves as a lubricant/coolant for the system since it is a wet clutch design. If you drive the car with low fluid you run the risk of damaging the internal components whether or not they are operating the right way.
 
#36 ·
Well i know that it is not good for it regardless hahahaha but do you think it will be okay if i were to just put another full tube in when i do the motor? Oh, and I never really drive the car for really long road trips at a time so I don't think that too much wear could have been caused by heat (just a guess) .... school is 5 minutes away every day, not that school is my only destination but it's not like i am driving for super long periods of time every day. I just want to make sure that it would be worth my time trying the motor. I am probably gonna do it anyway now that i know that you can just pry the driveshaft rather than removing it which was what scared me in the beginning. I have seen a few posts online where people have ran them pretty much dry due to a leak and did not really seem like the haldex grenaded during that process. Much Thanks
 
#38 ·
Naah, it won't hurt a thing. As a matter of fact I recommend you run all your fluids low, drain some engine oil out of it and run that low for a while and same with trans fluid heck even coolant is probably not all that necessary. Best one would be brake fluid, it weighs too much and all it does is slow you down, run that real low as well.
 
#39 ·
Well that's a no brainer, duh!! Weight reduction BRO! I never put fluids in the car, right ? lololol But for real, yes i know it is not the smartest thing to do but I probably am going to get fluid today and possibly going to try to do the motor depending on how I feel. I will let you know how it goes, and YES i have a full bottle of brand new fluid ready to go.
 
#41 ·
No, i got what you are saying but today i am changing the motor and putting a complete bottle of fluid in this time lol. I will let you guys know how it goes. Just to recap to be sure... I undo the 2 allen motor cover bolts, unplug the motor, drain the remaining fluid, pry the driveshaft cover, pull the motor out, and then the reverse. Right? am i missing anything major in the process
 
#42 ·
okay, yesterday I changed the pre charge pump with the one of off my new unit that i got. I was really hoping that the motor would be the trick to fix it but apparently not. I still got the same amount of wheelspin/ power cut as i did before. I tried the rollout test in the parking lot and could hear a bad noise like something was trying to engage and the traction light cut all of my throttle control. I think something internal is just toast in the unit. I do not think me running it low with any fluid caused this because when I did this test about 8 months ago, I heard the same exact sound when doing this test with identical results. I put a completely full new bottle of haldex fluid in the unit and had barely ANY spill out when re inserting the drain plug. Any ideas at this point? There was not any metallic flakes in the fluid that i extracted or anything suspicious that would worry me but at this point i really do not get it. Also, if it was the controller unit, wouldn't it just flat out not work? What do you guys think? :banghead:
 
#43 ·
That noise you hear is sometimes the ESP trying to work the brakes when it thinks something is slipping. Run a VCDS scan, there is also a test for communications with the controller in the VCDS and it will cycle the pump on and off during it's diagnostic of the Haldex..
 
#44 · (Edited)
Okay, that makes me feel a little bit better, I was wondering why the noise was not exactly coming from the back of the car, more towards the front. I will have to find someone with a VCDS or get one. How much could I like make one for? Is it not just a software and an OBD-II to USB cable? I would like to have one for myself but I also heard that the software is pretty expensive. Where can I get the software for the cheapest price? Oh, and also do you think that it could possibly be the controller now? At this point what else is there to replace. I mean could an old filter cause this? I have done the oil changes but have not touched the filter. Could a really old filter possibly cause it to not work like this? Thanks!

Edit: The new unit that I got has a controller too so I could maybe try that? I have read online that a clogged filter could cause a computer malfunction? idk but I really need to get my hands on a VAG-COM
 
#45 ·
Okay, that makes me feel a little bit better, I was wondering why the noise was not exactly coming from the back of the car, more towards the front. I will have to find someone with a VCDS or get one. How much could I like make one for? Is it not just a software and an OBD-II to USB cable? I would like to have one for myself but I also heard that the software is pretty expensive. Where can I get the software for the cheapest price? Oh, and also do you think that it could possibly be the controller now? At this point what else is there to replace. I mean could an old filter cause this? I have done the oil changes but have not touched the filter. Could a really old filter possibly cause it to not work like this? Thanks!
There is enough drag in the system from fluid circulation and friction to allow wheelspin at low speeds when the vehicle is off the ground. The controller doesn't need to work for that result to be observable.

What does happen is that as soon as the input shaft is spinning fast enough to overcome that drag, the wheels stop spinning. This is a mirror image of what happened to me when I was troubleshooting my car, and the solution to that problem was the controller.

You should replace the filter with the fluid every 40k miles. The fluid itself should be done every 20k, if we're sticking to the factory recommendation. This was mentioned by at least two people at the start of this thread and it should have been taken care of as one of the first things you did. You can theoretically replace the filter without draining the Haldex but the whole idea is to do both things at the same time so that that isn't an issue.

VCDS is made by RossTech and should always be purchased through him. You need a laptop/tablet with a full size USB port and a dongle that works with our cars. You can find the connectors on ebay for cheap ($5-10) but you should buy the software from the source. You can get a lite version (good for one install and one reinstall if you change machines) for $90, or at least that's how much it was when I checked last.
 
#46 ·
Okay, and when I do the filter change do I need to get another bottle of fluid? I literally just put in a new bottle last night but without a filter change. Can the filters be cleaned possibly? I mean I have a filter on the new unit I bought and thought that i could maybe salvage that one just enough to test the system in my car. My local VW dealership does not sell the filters so I would have to order one. So in the meantime I could at least try right? and would it hurt the other controller if I installed it with the clogged filter? Thanks
 
#48 ·
Filters can't be cleaned. Don't re-use one off of a salvage rear end as it has the probability of having more miles on it than the one on your car. If you have a way to get the drained fluid back in there, then reuse it but I would suggest using either a filter medium or cheese cloth to get any particulate out of the fluid when you drain it. This will also help you determine if there are pieces of the clutch pack in the fluid suggesting part failure. Win win!
 
#47 ·
Regardless, do yourself a favor and either purchase Ross-Tech VCDS or something comparable. Regular code readers won't see all of the additional details that this software gives you. An example so you understand: if I hook up my car, I can click on each module that has a controller (i.e. engine, brakes, haldex, etc). Once in there, I have many different options such as reading codes, checking readiness or even performing output tests. Output tests are great for activating components that should be actively working in certain situations. Not only will it show absolutely anything to help with diagnosis but the company also provides excellent support through things like their Trouble Code Wiki, which has almost every VW/Audi trouble code, typical effects observed, and potential courses of actions to correct the code. I know I might sound like a fanboy but this single tool, though expensive, took my ability to troubleshoot/diagnose vehicle problems to a whole new level. I've used it to help other VW/Audi owners fix their vehicles as well, for no money of course.

If you'd still rather not spend that money, that's fine however you should use thisLocator to find someone in your area or close-ish. I can't speak for any others but if you were close to me, I'd be over to do a scan and offer any advice I can. Others may want a small fee, which is up to you to decide if it's reasonable. My advice would be to perform one of these two things before throwing anything else at it because the more you change, the more potential for troubleshooting error. You could swap that entire rear end and the issue could be a bad signal voltage or an ESP error causing the issue. Mine right now is a Lateral Accelerometer causing an ESP code. I wouldn't have known that had it not been for VCDS.

Best of luck! :beer: (<----- you mention school and your general sentence structure implies to me that you're on the young side so think of that as a cream soda)
 
#49 ·
I will have to look into that! I would also like to activate stuff like the one click door unlock, and other miscellaneous things. It is also always nice to be prepared at all times too. And YES I would love a cream soda right now lol.
 
#50 ·
I have no idea if anyone is actually going to see this post since it is so old but I finally bought a vag scanner and was shocked to see what came up when I scanned the AWD module. There was a total if 2 codes, The first one was 00526 Brake Light Switch-F sporadic: Implausible signal, the other one was 01155 Clutch sporadic: Mechanical fault, but when I cleared the codes, the 01155 didn't come back but the brake light switch code did. I recently replaced the sensor back last summer because my brake lights and cruise weren't working. The brake lights and cruise control work right now and I really don't know why it is throwing a code if it is working. I feel really stupid for not scanning my car before AS YOU GUYS TOLD ME lol. Tell me what you guys think, and look at my other thread on Cool things to do with Vag Com. Thanks
 
#52 ·
Hmmmmm, well then why do you think that it would throw a code under the AWD module? I did the self-test and I could hear it faintly engaging every time it would cycle so I guess it is mechanically in order. I heard that these particular brake light switches were very bad and always failed.
 
#53 ·
Those brake switches are unreliable as all get out. I replaced mine twice in three years of ownership of my car.

The only thing the AWD test can do for you is confirm if your precharge pump is working. I always felt it was a generally unreliable way of testing the functionality of the Haldex as a whole.

The software won't really tell you what is and isn't working unless you unbolt the controller from the car, in which case you will be able to hear a very audible whining noise from the stepper motor inside if it's functioning correctly. That requires you to completely empty and refill the coupling though and requires a replacement crush gasket for the controller when you bolt it back on.

I previously had an intermittent mechanical fault and the issue ended up being the controller itself. The module can throw codes but some codes can have multiple causes. The troubleshooting continues!
 
#54 ·
Couple of things here. First, order the crush gasket from ECS or your local dealer. The dealer will tell you that there is no gasket as their screens don't show it but if you give them the part # which you can find online they can get it for you.
Second, my controller also failed. After replacing it with a good used one I took the old one apart and found the stepper motor to be stuck, after twisting on the gear with a pair of pliers it freed up and if reassembled should function again. They say that these controllers almost never fail, I think they do but it seems like just the stepper motor gets jammed. If your controller is acting up order the gasket and fluid and remove it, open it and see if the stepper motor wants to turn with your fingers. You might be able to just push on the rod in the opening to get it to free up without opening the controller and have yourself a cheap fix.
 
#55 ·
Haldex REPLY

Okay, back to this thread. I took the car to the local 1/8th mile drag strip this weekend and was only able to get 3 runs in because it was so packed. I raced a 180 TT and completely beat him both times by several car lengths. The track had very good bite and with that, I had TONS of wheel hop on the launch. Not a serious amount of wheel spin off the line but I only had the 2-Step set at 3000RPMs. I ended up running a 9.6 as my best time, I think I could get a 9.4 if I had more time to practice. Otherwise, the car performed flawlessly. The coolant temps never even went over 199 even while idling in the big line. I'm not trying to break the car but I try to keep it safe when running it. I shifted right at 6k every time since peak power is right before that and did not want to over rev the car of course.

Anyway, back to the thread, this brake light switch code is now affecting other areas of the car, such as the cruise control rarely works anymore and the code now shows up in the engine module on the VAG COM, it only started recently. So I have the 00526 Brake Light Switch-F sporadic: Implausible signal in both the AWD module and the Engine module. Also, the AWD module shows the 01155 Clutch sporadic: Mechanical fault code. They all come back after cleared.

I am going to open up my old controller as suggested to see if there is anything unusual inside. Also, when doing the self test, there is the QUIETEST click when I first click the test but when it engages and disengages the pumps and everything, I can't hear anything (noticeable anyway).

Thanks for the advice.
 
#56 ·
Okay so I doubt anybody will even see this but I figured I would give a 2 year later update haha! So since two years has gone by, YES I still have the TT along with a Manual 335xi Coupe! Since the TT doesn't get driven as much, I finally decided to get the triple square bits I needed and went ahead and swapped the whole rear differential assembly with the haldex coupling. By the power of the Lord High Above, I OFFICIALLY HAVE WORKING QUATTRO!!! Doing the rear diff took about 6 hours taking my time and it was well worth making the AWD working after so long! Thanks again
 
#57 ·
How do you know that your Haldex is working? Does it drive differently?
I'm asking because I have had my TT for 9 years and I only use it to commute to work and I live in a desert where it rarely rains and never snows.
With all of the posts I read about peoples Haldex failing, makes me wonder if mine is functioning, maybe I would not know if it wasn't functioning???
It is supposed to rain in 2 days, I think I will try to find a patch of wet grass and hit the gas pedal hard and see what happens...
 
#59 ·
So I knew mine was not functioning properly because even on a dry road, I could floor it in first gear and the tires would just spin..... In the rain it will be super easy to tell if it is working or not, mine used to spin like crazy in the rain, now it does not! I can NOW floor it in first gear in the rain without any noticeable wheel spin!!

To add: I have a N2MB WOTBOX installed (a standalone 2 step launch control/No lift shift module... it simply wires into the pedal switches and ignition wires) and on the first drive after I replaced the rear diff/haldex assembly, I attempted a launch.... that's when definitely could tell the haldex was doing something when my glovebox door flew open upon launching it!

If you find evidence that your haldex is in not working, CHECK YOUR PRECHARGE PUMP first before buying a new assembly like I did. Also of course the basics like the ground strap, fuse, and any obvious wiring issues visually.
 
#61 ·
It rained, I went out and found some wet soaked grass and drove up on it, and I tried to accelerate fast. The car shuddered and the yellow triangle Traction Control warning light flashed a few times, but the tires didn't spin out.
So I guess that means my Haldex is working?!? I have been good about changing the Haldex oil and filter, even though I didn't even know if it was functioning, lol.
 
#63 ·
It's honestly hard to say. Now that my haldex is operating, even on the dirt (in the video) my car hooks and pulls hard even from a launch on 2 step. Before my haldex was working, I could disable the ESP and spin through first gear even on pavement.
 
#62 ·


This is a youtube link to a video showing the functionality of the Haldex system on my car. You can really see the rear wheels kick in when the fronts slip. Feel free to watch!
And the bang you hear is just the 2-Step function (WOTBOX)
 
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