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CriticalCommonCooling

BMW M5: S63TU4 Coolant Expansion Tank Cracking in the Hot-V — Injector and Coil Damage

S63TU4 Coolant Expansion Tank Cracking in the Hot-V — Injector and Coil Damage is a common cooling fault on the BMW M5 on the 2018–2023 cars, and we rate it critical. Putting it right costs $400 to $6,000 at New Zealand independent workshop rates. Below is what goes wrong, the symptoms to notice on a test drive, where to look, and what to ask the seller before you hand over any money. It is one of 6 documented faults on the BMW M5.

Vehicle
BMW M5
Only on
Bi-Turbo / twin-turbo / BMW M
Engine
S63
Years
2018–2023
Fuel
petrol
System
Cooling

This page covers the BMW M5 as a model. Some faults only affect particular engines or build years — enter a plate below to narrow the list to one car.

All BMW M5 faults6 documented faults on this model

What you are looking at

A single common-rail diesel fuel injector photographed against a plain background.Example of the part — not this vehicle

A common-rail diesel injector. Contamination damages the nozzle at the tip.

Panoha · CC BY-SA 3.0 · Wikimedia Commons

What goes wrong

The F90 M5's plastic coolant expansion tank sits in the hot valley of the 4.4 twin-turbo V8 and is known to crack along its seam. Because it leaks directly onto the fuel injectors and ignition coils below it, what starts as a coolant leak can short coils, kill injectors and in bad cases damage the ECU. BMW revised the tank part in late 2020, so pre-revision cars that still carry the original tank are the ones to check hardest.

What you would notice

  • Coolant level warning or repeated top-ups
  • Coolant smell from the engine bay after a run
  • Misfire together with a coolant loss
  • White crusty residue around the centre of the engine

How to check it

Where to look. Centre of the engine bay — expansion tank in the V between the cylinder banks

With the engine cold, look into the valley between the cylinder banks with a phone torch for crusty pink/white coolant residue around the tank and on the components below it — residue there is the fault in progress. Check the coolant level and ask how often it needs topping up. Ask whether the tank has been replaced with the revised part and for the invoice. If a workshop inspection is possible: pressure-test the cooling system and inspect the tank seam directly.

Parts involved: Coolant expansion tank, Fuel injector.

What it costs to put right

$400 to $6,000 at New Zealand independent workshop rates. That is for this job on its own, not for the car.

An estimate, in NZD, for the repair as normally carried out. What a specific car costs depends on which part has failed and what it damaged on the way — treat this as the floor for a negotiation, not a quote.

Ask the seller

  • “Has the expansion tank been replaced with the revised part?”
  • “Does it ever ask for coolant between services?”
  • “Any misfires alongside coolant loss?”

Now check the BMW M5 you are actually looking at

Everything above is true of the model, and it is free. What it does not tell you is whether THIS car has been looked after: its odometer history and whether the reading has ever gone backwards, whether there is still money owing on it, whether it has been reported stolen, how many owners it has had and what it is really worth today. That comes from the official records for that plate. Enter the plate for the free details, or get the full history and a market valuation from $13.49.

Not sure what you would be paying for? See what a full KickTyres check includes.

Where this comes from

The failure described above is documented in published sources — owner forums, technical service bulletins, recall notices and workshop write-ups — held in our fault database. The inspection instructions and the cost estimate are KickTyres’ own interpretation of them, and it is a starting point for an inspection rather than a manufacturer statement.

BMW M5 buyer questions

Is s63tu4 coolant expansion tank cracking in the hot-v — injector and coil damage serious on a BMW M5?

We rate it critical and common on the BMW M5. The F90 M5's plastic coolant expansion tank sits in the hot valley of the 4.4 twin-turbo V8 and is known to crack along its seam. Because it leaks directly onto the fuel injectors and ignition coils below it, what starts as a coolant leak can short coils, kill injectors and in bad cases damage the ECU. BMW revised the tank part in late 2020, so pre-revision cars that still carry the original tank are the ones to check hardest.

How much does it cost to fix on a BMW M5?

$400 to $6,000 at New Zealand independent workshop rates. That figure is for this job on its own. A car showing the symptoms on this page is usually worth either walking away from or negotiating down by at least the repair figure.

Which BMW M5 years are affected?

Our research records this fault on the 2018–2023 BMW M5. Build dates move around, especially on imported cars, so treat the range as the years to look hardest at rather than a guarantee either way. The official records tell you the exact build and first registration date for the car in front of you.

How do I check for it before I buy?

With the engine cold, look into the valley between the cylinder banks with a phone torch for crusty pink/white coolant residue around the tank and on the components below it — residue there is the fault in progress. Check the coolant level and ask how often it needs topping up. Ask whether the tank has been replaced with the revised part and for the invoice. If a workshop inspection is possible: pressure-test the cooling system and inspect the tank seam directly. Look here: Centre of the engine bay — expansion tank in the V between the cylinder banks