# Watchout the AWD pump failure



## audinut (Oct 2, 2015)

I found out the pump for Haldex clutch just failed on my less than 2 years old TT with routine VCDS scan right before the second service.

Took it in and Dealer replaced a new pump and all good.

So watch out guys with the quattro system. It's just hard to know cos no error on dashboard at all, only shown in VCDS scan.


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## leopard (May 1, 2015)

Common problem on the mk1+2,nothing has changed then !


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## brittan (May 18, 2007)

The Mk3 uses a Gen 5 Haldex unit compared to the Gen 4 in the Mk2. The biggest difference is that the Gen 5 does away with the hydraulic accumulator used on the Gen 4 and maintains hydraulic pressure using a relief or spill valve.

The Gen 4 unit has a filter but that's denied by Audi. There is no part number for the filter on ETKA and although oil change is in the service regime, a filter change is absent. Almost inevitably that leads to pump failure.
There's no 'haldex fail' warning lamp but typical warning signs include excessive or unexpected front wheel spin, together with the traction control light flashing. There may also be a TPMS warning light. 
Confirmation needs to be, as above, by VCDS fault scan.

I'm not sure yet if the Mk5 unit has a filter: I'd be surprised if it doesn't. A quick check on a parts list shows the oil listed but no filter. The pump looks almost identical to the Gen 4 pump and that has a suction screen.

Much more info on the Gen 4 unit, and its failure mechanisms, here: viewtopic.php?f=43&t=1496866


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## noname (Aug 20, 2015)

graphs don't show any filter...or at least, a removable filter!


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## brittan (May 18, 2007)

There's nothing like a Mk1 (or should that be Mk3) eyeball; so this morning I crawled under the car to have a look at the Haldex unit.

On the Gen 4 Haldex the filter is next to the pump (logically) but on the Gen 5 unit I can see no filter housing anywhere.

The unit has oil drain and fill plugs, as does the rear differential. From an engineering pov I think the lack of a filter is a mistake. The pump looks similar to the Gen 4 one so I expect that it will have a suction screen, which Audi will not clean as part of their service regime.

I may do a DIY oil change in between Audi's service intervals and clean the pump myself. Mind you, it's covered under warranty for now.


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