Mk7 GTD Diesel Fuel Leak

[C2K]

Has anyone else encountered a diesel leak on their GTD? Just wondered if anyone else had encountered something similar, or knew of any faults.

I noticed a stripe on the drive a couple of weeks ago, and totally slipped my mind until it happened again. Fast forward a week and I woke up to diesel dripping off the tank onto the driveway just inboard of the rear right wheel. I had filled the car up the night before. There is a small quantity of diesel sitting on the top of the tank, next to the tank pump under the bench seat, so it can only be the pump or the tank breather but i'm not sure which just yet. As you pull off our driveway there's a left turn onto the street, so the pooled diesel runs off and down the side of the tank at this point.

It is clearly a full tank phenomenon, as both stripes were when the wife left on the first journey after filling up, it just sat around with a full tank overnight the second time. Once some of the fuel is used (call it 2 gallons), the leak stops and the area around the pump and the side of the tank remain dry (well, slimy as diesel makes things).

[C2K]

In the spirit of forums, i'm returning to this to enlighten others.

Given the proximity of the diesel to the pump and the pressure exerted by a head of diesel on a brimmed tank, I had reason to suspect the pump seal. I obtained the following parts and tool

Fuel pump lock ring tool T10202 - from Laser Tools - approx £30
Pump Seal - VW Part no V1K0919133D - approx £18 (was in stock)
Pump Lockring - V1K0201375 - approx £8 (ordered next day)

I followed the workshop manual to remove the diesel connectors (2) and the loom connectors (2). With these removed you can use the tool to loosen the lockring, which as an engineer I have to say is a poor design. The tool engagement onto the lockring teeth is about 2mm at best, yet you are provisioned with 110Nm to undo, on a pump that's sitting at about 15 degrees from horizontal. This has skinned knuckles potential written all over it.

Anyway, with the lockring removed, you can lift the sealing flange of the pump, and slip the old seal off over the head of the pump and vice versa for the new one. this does not require the pump to be taken out, simply the flange lifting. the manual conflicts with itself about leaving the seal dry or lubricating it with diesel over the space of 3 lines. I opted to lubricate the seal on the pump mating face in order to allow it to slide rather than bind during assembly clamping.

I torqued the new ring to 110Nm and the arrow on the lock ring was nowhere near the marker on the pump, so I used a breaker bar instead to get the remaining 15-20 degrees of rotation such that they aligned. Reassembled and the end result is the leak is gone.

My existing lock ring, and indeed the half thread on the tank, are both rusty which is amazing considering they are against the belly of the car. The material is a poor choice, and I have to say the pump fitment and retention was far superior on my old 306 HDi. There was flaked rust all around which i was having to vacuum up to stop them dropping into the tank, but easily collected. I suspect this rust is what has prized the seal apart and facilitated a leak. I would therefore expect others will encounter a leak in this manner, as nobody has ever touched it on my car. I hope this enlightens others.

[Al1040]

Thanks for the update C2K, hopefully I will not need this in the near future but great to have as a reference should it be needed.
Where did you get your workshop manual?

[C2K]

A friend who used to work for me now runs his own business fixing VAGs predominantly. The kinds of jobs garages won't touch like convertible roofs. He has various connections, but if memory serves you can actually subscribe to a service to get that information. He sent me the removal and installation instruction for the pump, hence why I knew the tool number and the torque settings.

It also yielded the cambelt procedure when we changed that. 

[Al1040]

Thanks again, what a great friend to have in helping you out with your issues.