WA - mk4 4motion guru?

**Overtaker** · 05-04-2020, 09:53 PM

Hi all - I’ve recently bought a mk4 bora 4motion and am going to need some help with diagnostics on what seems to be the usual haldex issues.

Is there a guru or workshop in Perth that is particularly knowledgeable / helpful that I can contact?

I’m currently running the car in “2motion” with fuse 31 pulled to turn off the haldex. With it in, the car behaves as if it’s got a solid rear axle - a nightmare in car parks.

I’ve serviced the haldex & rear diff. I’ve lifted the handbrake a few clicks and it doesn’t disengage. I’ve seen the list of things that need to be checked - I can’t do it all so want to know where to go so this won’t cost an arm and a leg training up a local shop.

**beale187** · 06-04-2020, 08:43 AM

My first thought would have been to service the Haldex. Do you get any traction control or ABS lights up on the dash?

**Overtaker** · 06-04-2020, 08:56 AM

I had no warning lights and no relevant fault codes. Now that I’ve pulled the fuse the traction control light is showing on the dash.

**beale187** · 06-04-2020, 09:05 AM

Does it only happen at low speed? and more so when turning at low speeds?

You'll definitely need to get it scanned using VCDS (Vag-Com) or similar, but it doesn't always throw a code.

**Perthdisco** · 06-04-2020, 04:59 PM

I’m similarly in the process of working towards a DIY Haldex service here in WA.

I have seen that a key recommendation from the YouTube experts is to remove the motor and clean the filter screen on it. This is a worse place for clogging than the actual filter.

This is not done in a standard VW service which is purely changing the oil and not even the filter which exists on earlier models. VW don’t even have a part code for the filter.

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**beale187** · 07-04-2020, 09:24 AM

Originally Posted by Perthdisco

I’m similarly in the process of working towards a DIY Haldex service here in WA.

I have seen that a key recommendation from the YouTube experts is to remove the motor and clean the filter screen on it. This is a worse place for clogging than the actual filter.

This is not done in a standard VW service which is purely changing the oil and not even the filter which exists on earlier models. VW don’t even have a part code for the filter.

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I have never heard of this on Gen1 Haldex units but it makes perfect sense. Great tip.

**Perthdisco** · 07-04-2020, 09:47 AM

Originally Posted by beale187

I have never heard of this on Gen1 Haldex units but it makes perfect sense. Great tip.

I am no expert for sure only understand that the 2010 Tiguan that I have has the Gen 4 Haldex. This has a removable filter and pump motor.

Not sure the difference on earlier versions. Later versions don’t have the removable filter it seems.

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**Overtaker** · 06-04-2020, 08:24 PM

Hi - which motor needs to be removed? Do you mean the precharge pump?

Anyway I’ve run fault codes again - I’m getting 00526 - brake light switch (F) 27-10 implausible signal - intermittent. (Going back I see this was there when I bought the car and it didn’t seem to be binding then).

I also checked the measuring blocks and saw it is detecting both hand brake and foot brake switches. The pump is running 100% of the time when the engine is running but off when the engine is not running (ignition on).

Clearly this should not be so, but there don’t seem to be any other blocks on the Haldex that are meaningfully measurable.

Should I be checking something else? I know the ECU and ABS control units send signals, but should I be looking here and if so what for?

Or if the pump is always running does that mean the haldex controller is bust? No other options?

**Perthdisco** · 06-04-2020, 08:40 PM

Originally Posted by Overtaker

Hi - which motor needs to be removed? Do you mean the precharge pump?

Anyway I’ve run fault codes again - I’m getting 00526 - brake light switch (F) 27-10 implausible signal - intermittent. (Going back I see this was there when I bought the car and it didn’t seem to be binding then).

I also checked the measuring blocks and saw it is detecting both hand brake and foot brake switches. The pump is running 100% of the time when the engine is running but off when the engine is not running (ignition on).

Clearly this should not be so, but there don’t seem to be any other blocks on the Haldex that are meaningfully measurable.

Should I be checking something else? I know the ECU and ABS control units send signals, but should I be looking here and if so what for?

Or if the pump is always running does that mean the haldex controller is bust? No other options?

Yes the Haldex has a pump motor hanging out of it.

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**beale187** · 07-04-2020, 10:17 AM

Originally Posted by Overtaker

Hi - which motor needs to be removed? Do you mean the precharge pump?

Anyway I’ve run fault codes again - I’m getting 00526 - brake light switch (F) 27-10 implausible signal - intermittent. (Going back I see this was there when I bought the car and it didn’t seem to be binding then).

I also checked the measuring blocks and saw it is detecting both hand brake and foot brake switches. The pump is running 100% of the time when the engine is running but off when the engine is not running (ignition on).

Clearly this should not be so, but there don’t seem to be any other blocks on the Haldex that are meaningfully measurable.

Should I be checking something else? I know the ECU and ABS control units send signals, but should I be looking here and if so what for?

Or if the pump is always running does that mean the haldex controller is bust? No other options?

First thing you need to do is fix the brake light switch code. Link below for a new switch ($15 just do it)
Brake Light Switch - Euro Revolution

The Haldex gets it's signals from the ESP and ABS readings. A few things to check, however you'll need VCDS (VAG-Com) or similar for all.

Measuring Blocks in the ABS module. (ch.04)
Confirm these are all within tolerance. A dodgy YAW rate sensor (indicated by "Rotation Rate" in VCDS) can cause ABS/Haldex issues. This pic was taken when my YAW sensor was fried hence the reading whilst the vehicle was stationary was WAY out.

ABS module (ch.06)
check "Longititude Acceleration"

ABS/Wheel speed sensors (ch.01) - I don't think this is the case for you as no ABS light is coming up but can't hurt to confirm

When stationary make sure they all read "0"
Set up your laptop and phone camera facing the laptop screen. Go for a short drive and confirm readings match the odometer.

imo, if you've serviced the haldex and all of the above is good then my guess is your Haldex controller is fried. In which case you won't always get a DTC.