Coolant Migration in B7/NMS

[zeoalex]

Hi All,

I've been working on my girlfriend's car (2014 passat TDI SE) that had some goofy stuff going on - outside air temp failed (MFI reads ---F), intermittent fuel gauge failure (that seems to be more sustained now since it started at the beginning of winter) and a flashing/sustained TPMS light. I swapped the OAT sensor assuming that maybe the other failures were related by needing OAT for correction calculations or something to that effect and obviously that didn't fix the issue.

After spending time reading through the wiring diagrams and noticing that the OAT and the coolant level sensors were on the same ground line back to the cluster, I pulled the coolant level sensor, to check continuity/resistance between the shared ground. To my shock, the collector started dripping. That led me to some further research and finding that coolant migration has apparently long been an issue with VW's with this style of coolant bottle. I went and pulled the fuel pump connector and saw some coolant had made its way back to that connection as well. That would explain the fuel gauge issues.

My question to the class is this - is this something people are seeing on the NMS chassis vehicles? Obviously, this was a huge issue in the early 00's/B5 era, has VW not learned their lesson? Do I have any prayer to get VW to cover this as a goodwill fix, as I can't seem to find a TSB or recall related to this? or am I going to be SOL and have to eat a few grand worth of potential harness repairs?

 

[Jaytechqu]

All connections are sealed. Coolant, water, oil can spill on most connectors In any car and not cause any issues. If you have fluid MITIGATION, meaning fluid leaking from the sensor itself Into it's respective connector, then u get issues. This is in general of course. If you have a prolonged leak directly above a connection, over time it can slowly seep in but not likely u less connection seal damaged.

What fuel pump connector are u referring to tho? So you have any pics?

 

[zeoalex]

absolutely. From what I found, it is absolutely migration from the coolant bottle (which, I believe folks have seen in previous generations, using the same style bottle/sensor).
The fuel pump connector I am referring to is the only electrical connector on the fuel pump. it's a 5 pin connector where I believe pin 1 is power, 2 goes to a shared sensor ground (Ground 410 shared with coolant level sensor, OAT sensor, Windshield wiper level sensor, and cluster module), pins 3 and 4 go back to the cluster/fuel level gauge, and pin 5 is chassis ground in the luggage compartment. Pins 1 and 5 relate to the actual pump functionality, and pins 2,3,4 all relate to the level sensor functionality.

I do have pictures of that connection on both the fuel pump and harness side:

It appears that coolant came down pin 2 and caused some issues off the power pin.

The dealership has done their diag and have found:
- Corrosion in the OAT wiring, but have said that it's from the seal in that harness plug failing and allowing water in.
- Failed fuel pump/level sensor (it all exists within the pump, which to this point has been working without issue as far as I can tell, just the level gauge has been goofy)

During my call with the service advisor, I asked about the fuel pump plug as I believe I had found coolant per the pictures above, and they said that there were no issues/coolant found at that connection, but, they want to replace the pump. I'm wondering if they plugged in the guided fault finding tool and it spit out that the fuel pump is dead due to high resistance or something along those lines. He did say that if they found any signs of coolant, that he would stop everything and call me.

They're going to charge around $1100 to run a new wire to replace the faulty one from the OAT/G17 sensor, replace the fuel pump, and reset the TPMS light.

 

[gforce1108]

absolutely. From what I found, it is absolutely migration from the coolant bottle (which, I believe folks have seen in previous generations, using the same style bottle/sensor).

I drill a hole through the outside of the coolant level sensor and remove the seal on every VW that comes to me. It will leak externally instead of pushing through the harness. It was recommended around here years ago to stop coolant migration.

 

[zeoalex]

yep, that's going to be my plan of action once we get the car back.

For what its worth, I did get a call from the dealer stating that they found fuel in the fuel pump connector (pictured above) which seems extremely unlikely, maybe more unlikely than coolant. The service advisor said that the would send some pictures along of what they found but I have yet to get them.