Warrior193

Hello, welcome to the forum. Do I assume correctly that you have a PHEV? Are you saying that you are unable to get the ICE to run, and it's running only in EV mode?

Hello, welcome to the forum. The contents of the bag (or capsule) if fitted are Silicate, and this was fitted to the coolant expansion tank for extended coolant life and corrosion protection for the engine. The problem comes from the bag splitting and releasing silicate granules into the cooling system, blocking small channels - especially in the heater matrix. AFAIK, the problem only appears with the bag (if fitted) - later vehicles had a plastic capsule insert fitted instead of the bag. Even later vehicles dispensed with the silicate insert - I believe this may have been when coolant was changed to G12evo.

Given the highly hygroscopic nature of DOT4, I doubt there is such a product as 'long-life' brake fluid.

Apologies, I missed your reference to new plugs.

Hello, welcome to the forum. What is the mileage? Do you know when the spark plugs were last replaced?

Spotting air in the braking system is very easy - the pedal will be 'spongy'

Are all the front ADAS systems still working OK?

The 55% health is only part of the story though - the voltage dropping through the floor while the engine is being cranked will be what is causing apparent spurious DTCs. That's pretty bad for a battery less than 2 years old! Internal resistance is fine, so that's not the problem. Can you show a cranking test result on that too?

Which instruments will presumably be flagging that the battery is failing and should be replaced? If that battery is only 19 months old, is it still under warranty? If so, I'd be looking to submit a claim on it.

I mean what is the alternator output? - measured at the battery terminals with the engine running. A voltage as low as 7.96 is far too low under any conditions - was this while the engine was being cranked? It is little wonder that fault codes (DTCs) are being thrown!

9.6 volts is too low and is a strong indication the battery is failing. What is the charging voltage? Total failure can be sudden and leave you stranded. At the very least, you will be chasing phantom fault warnings - remember what happened to the Boy who called Wolf once too often.

The drain holes are concealed under the seal on the door and are prone to blockage - gently insert fingers between the folds of the seal at the bottom of door and run them along it.

The very first thing to do if odd, and sometimes seemingly random errors are indicated on these vehicles should be to give the battery a through test, including at a high load.

If it is a genuine fault indication, I'd say definitely yes - I'd have thought that driving with any braking system fault that could result in sudden loss of braking force would be a no. I once tried rolling a vehicle down a gentle slope with the engine off, and was shocked at how I literally had to stand on the brake pedal with full weight to get any braking - this was at less than 2MPH!

I believe engine block and head are aluminium. Has the coolant concentration been maintained in service records?

AFAIK, it should not be the case for the Mk4 - but there was an issue with the 'Mit Silicat' insert in the coolant expansion tank of earlier Mk3 models splitting, causing blockages, especially in the heater matrix.

Hello, welcome to the forum. If you have the folding type key fob (like penknife) - flip out the key blade, insert a coin or something similar into slot and twist, battery cover will pop out.

Good morning Giedrius, welcome to the forum. Can you describe what is puzzling you?

Controlling RPM is not important when regenning a GPF - ensure vehicle is in ICE mode, disable coasting, get engine fully up to normal temperature, get up to speed and back-off throttle several times (probably ideal going downhill)

If the expansion vessel is correctly sealed, there should be no (or negligible) evaporation from what is a closed system. Yes, the H2O content of the coolant will boil-off sooner than additives, but should not be lost from the system. I'd suggest checking that the cooling system is actually pressurising (and holding pressure) when it heats up.

^^^See above.

GPF regens differ from DPF and do regens during throttle-off overrun. Get up to speed in ICE mode and allow to run down, best would be on fairly steep down-slope.

Re. the fuel filter, AFAIK that is the case. It does suggest that picking up a load of contaminated fuel could end up being very expensive!

To clarify - the water pump replacement reference is for TDIs only.

I don't understand - 'as soon as it connects the car starts' - as soon as what connects?