Brown liquid in my diesel! What is it?

[gaz_123]

If you have a 12v Cig socket > USB adapter with a digital display or a multimeter you can read the alternator voltage with the engine running to prove the alternator.
If the socket voltage is good once the battery is fully charged the alternator is good.
Check for a corroded or loose engine earth strap and or poor battery connections.
If the battery has been discharged very low below 50% SOC (around 12.05V) and/or is 5 years + old it is probably knackered, even if the charged battery voltage is reading 12.6 it may not take a load.
You could visit a battery specialist and have it load tested or you could just replace it if you know it has been repeatedly discharged below 50% SOC and/or is 5+ years old.

Cig socket not working, replaced the fuse ut no luck. However tested the battery terminals with a multimeter when engine is on and its 13.5v - 14v. Battery seems to have been replaced as its not original but unsure when will have to get it tested and look down the electrical fault route/ alternator as nothing else is flagging as a possible cause at hhe moment. I would let it run until something else fails however it going into limp mode on a motorway irritates me

 

[JumpShip]

A cheap OBD reader will show you live data .

 

[DXX]

I would disconnect the battery and see if it discharges first before spending £ on diagnostics.
As @JumpShip points out Carista or similar will be cheaper than a garage diagnostics session.

 

[gaz_123]

A cheap OBD reader will show you live data .

Yeah we have one now but the code hasnt appeared since getting it, at the weekend going to take it for a very long drive as only seems to be appearing on the motorway

 

[gaz_123]

I would disconnect the battery and see if it discharges first before spending £ on diagnostics.
As @JumpShip points out Carista or similar will be cheaper than a garage diagnostics session.

Good idea i shall do that over the weekend

 

[JumpShip]

Your OBD reader will be able to show live data so you can watch the battery voltage along with many other things in real time as you drive .

 

[gaz_123]

Your OBD reader will be able to show live data so you can watch the battery voltage along with many other things in real time as you drive .

Yeah we have been last couple of days but doesnt help when its a smart alternator so looks like its dropping to 12.5v when driving at certain points but apparently its normal

 

[gaz_123]

Yeah we have been last couple of days but doesnt help when its a smart alternator so looks like its dropping to 12.5v when driving at certain points but apparently its normal

Apparently only charges when needed to and not all the time when accelerating to save fuel

 

[wayney999]

I had the same issue with fuel last year, while driving to DisneyLand Paris in June. I’ve got a T6 2.0 TDI DSG. Died on the motorway outside Paris and cost a fortune to get it home. I had new injectors fitted prior to this in the January.

When my mechanic was doing diagnostics after getting it back, we founds exactly the same water/fuel problem in the fuel filter. It ended up needing new injectors, HPFP, fuel filter etc.

When the injectors were being removed, the third one was stuck solid, with a kind of rust/corrosion around it. I think the copper washer was also distorted (perhaps bad installation?)

I was losing coolant prior to it packing up, and since the second lot of injectors it’s still losing coolant.

Could Coolant have got into the fuel system from a poorly seated injector? Or is this not possible?

 

[DXX]

Not possible for coolant to migrate to the fuel system. It is possible for somebody to mistakenly put adblue in the fuel tank though.
I would get the coolant leak fixed asap no matter how small, if definitely won’t get better and it is highly detrimental to the engine right up the point of hydrolock in the most serious case.
There’s a big thread on the Forum regarding `loosing coolant’, not often an easy diagnosis but it has to be done.