Coolant leak through EGR valve V6 3.0 quattro TDI

[Audijager]

I Initially posted this in a related thread on the A4 forum (same engine type).

I'm about to receive a hefty bill due to a coolant leak through the EGR valve on my 2010 A6 V6 3.0 TDI (130,000 mostly motorway miles).

it manifested itself initially via a low coolant level warning whilst driving on the motorway and some black exhaust smoke evident when manouvring around the motorway services seeking water. Remaining 65 miles completed, coolant level warning re-appeared just before arrival. Topped up again and next day drove 15 miles to Audi dealership. Plently of action en-route (DPF warning, but only for a couple of minutes, continuous flashing glow plugs warning and reversion to limp mode. Coolant level warning after a while too (engine temp normal at 90 deg at all times).

Pressure testing located the leak in the EGR valve and several EGR parts need replacement. What confuses me is the apparent possibility that the DPF may also need replacement. The DPF was clearly unhappy at some stage, but can anyone here suggest why coolant ingress (which did initially have the correct anti-freeze concentration) could damage a DPF?

[dan2485]

If the EGR cooler has failed then coolant will be getting into the exhaust system (DPF,Cat etc).

[Not_Anumber]

If the EGR cooler has failed then coolant will be getting into the exhaust system (DPF,Cat etc).

Is the EGR cooler still required if the EGR valve has already been blanked and mapped out ? is this something else that could be safely blanked off or will the EGR still get hot and require cooling if it is inoperative ?

[royclark]

Is the EGR cooler still required if the EGR valve has already been blanked and mapped out ? is this something else that could be safely blanked off or will the EGR still get hot and require cooling if it is inoperative ?

I was talking to my son (he is in the car trade) the other day about getting rid of my DPF, he told me not to do it.
Although the MOT requires a visual inspection for the DPF and EGR at the moment, there are plans in the pipeline to include them both in the MOT to be checked that they are functional.

[Audijager]

The DPF did indeed need replacement, because (as dan2485 mentioned) obviously the coolant had run down into the exhaust system from the EGR, what I still can't get my head around is that water and alcohol can be more effective at blocking a DPF than soot! Nevertheless, they ran the static regen after fixing the EGR and it would not regenerate - apparently. What I did find irritating is that there was no regen report to verify the need to replace, do the machines not provide a printout?

[C6Allroad]

If the DPF is old it will have a high ash content and if you add water to this it can solidify into a sludge and dry out like cement thus block the dpf.

[royclark]

If the DPF is old it will have a high ash content and if you add water to this it can solidify into a sludge and dry out like cement thus block the dpf.

I thought that a lot of water was generated as the fuel was burned, so water would be going through the exhaust all the time that the engine is running.
How is it that this doesn't clog the DPF ?

[rowdy-999]

I thought that a lot of water was generated as the fuel was burned, so water would be going through the exhaust all the time that the engine is running.
How is it that this doesn't clog the DPF ?

Smaller quantity, doesn't contain coolant, and is more than likely atomized.

[C6Allroad]

The difference between water vapour produced by combustion and liquid draining into the DPF from a leak?