Odd Haldex Issue

Steve Aspinall

Registered User
I had a look and couldn't find the answer to this question. We have lost the rear wheel drive to the wifes S3; just lots of wheelspin and axle tramp from the front wheels when setting off (Nearly new Goodyear F1 Assymetricals). The more confusing part, I took it down to our local garage to get it checked, there are no error codes and when it is raised on a ramp, all four wheels drive, which is obviously at odds with what is happening on the road. The earth strap and fluid has been checked and changed, which made no difference. Any thoughts would be appreciated...

Thanks

Steve :)
 

Jps3290

Registered User
Did they check it with VCDS? Should be showing a code if its a Haldex problem. Most likely the pre charge pump or worse still the Haldex controller.

Have you had the haldex oil and filter changed every 20k to stop it blocking up the pre charge pump??
 

Steve Aspinall

Registered User
Did they check it with VCDS? Should be showing a code if its a Haldex problem. Most likely the pre charge pump or worse still the Haldex controller.

Have you had the haldex oil and filter changed every 20k to stop it blocking up the pre charge pump??

As far as I am aware, yes, but I will double check. Could some garage / commercial equipment miss trouble codes? They picked all other VAG issues up over the last five years on our various Audis, Seats and VWs...

No, we changed it as per the Audi service schedule every 36k, from your comment I guess that was a mistake! Are there ways to check the pre charge pump and haldex controller? Would a fault with them mean you can have drive to all four wheels when unloaded but not when loaded?

Thanks!
 

Jps3290

Registered User
The pre charge pump primes up when the cars turns on which builds up the oil pressure to work the rear haldex clutch so the Rear wheels and engage and disengage when the front wheels detect slip. What usually happens in if the haldex filter isnt changed every 20 k the gunk in the oil clogs up the fine mesh filter on the pump. Sometimes the pump will work fine but when put under pressure it will not get the right flow and hence create enough pressure to engage the clutch.

It should be creating an error visible using VCDS though.

Also within VCDS you can go into the module and run a manual test of the pre charge pump. With the ignition on but without engine started you should hear the pump kick in. The next stage of the test will engage the clutch which you can also hear quiet clearly. As its all electronic the engine doesn't need to be running for the test.

If the traction light is flashing and front wheels losing grip it will be an issue with the Haldex module or the controller.

How old is the car ?

Where abouts in the country are you ?
 

Steve Aspinall

Registered User
The pre charge pump primes up when the cars turns on which builds up the oil pressure to work the rear haldex clutch so the Rear wheels and engage and disengage when the front wheels detect slip. What usually happens in if the haldex filter isnt changed every 20 k the gunk in the oil clogs up the fine mesh filter on the pump. Sometimes the pump will work fine but when put under pressure it will not get the right flow and hence create enough pressure to engage the clutch.

It should be creating an error visible using VCDS though.

Also within VCDS you can go into the module and run a manual test of the pre charge pump. With the ignition on but without engine started you should hear the pump kick in. The next stage of the test will engage the clutch which you can also hear quiet clearly. As its all electronic the engine doesn't need to be running for the test.

If the traction light is flashing and front wheels losing grip it will be an issue with the Haldex module or the controller.

How old is the car ?

Where abouts in the country are you ?

Thank you, that is useful, I will get it to the garage and hopefully they can check it, I have a feeling they may not have an appropriate VCDS so I may need to take it to a VAG specialist.

Yes, the traction light is flashing and the fronts have no real grip.

It's a facelift 2010 model.

We live not far from Shrewsbury! :)
 

Jps3290

Registered User
Yeah same model i have so is a Gen 4 haldex unit. Maybe someone near you has VCDS could run a test on it for you.

Daft thing is you never get an error code or fault warning on the dash for this. When mine failed it was same symptoms as you with traction light flashing when you lose grip. When haldex is working and its pouring with rain I can never get the traction light to come on and its not for testing the cars grip lol
 

ab1702

Registered User
It did turn out to be the haldex pump, now fixed, thanks :)

To prevent this from happening again you need to have the haldex filter changed probably every year or 2.
This doesn't appear in audis service schedule though so you have to do it yourself or get an independent garage to do it.
You can buy the filters off eBay or there is a haldex website.
 
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