The N55's Pierburg electric water pump is a known failure around 100,000 km, and the thermostat and expansion tank follow right behind. We replace all three in one visit at your home.
BMW's N55 turbo six doesn't have a belt-driven water pump — it uses an electric pump made by Pierburg, computer-controlled to move coolant exactly when and how fast the engine needs. Clever engineering with a known expiry date: these pumps reliably fail around the 100,000 km mark. The electronics or the pump motor give out, often without much warning — sometimes a logged fault code like 2E22, sometimes intermittent overheating, sometimes a sudden red temperature warning on the highway with a perfectly full cooling system.
The supporting cast fails on the same clock. The thermostat on these engines is an electrically heated unit in a plastic housing that becomes brittle with age, and the coolant expansion tank is another plastic part living under pressure and heat cycles. The classic N55 cooling story is replacing the pump alone, then being back for the thermostat three months later, then the cracked tank after that — three labour bills for parts that all share the same corner of the engine.
The symptoms before total failure are worth knowing: coolant level dropping with no visible leak (the pump can weep internally and tanks vent past their caps), no heat from the driver-side vents at idle, and overheat warnings that come and go. Any of those on a 2011–2016 N55 points the same direction. Because an electric pump can stop entirely without a noisy death rattle, the first definitive symptom is sometimes the one that strands you.
If your BMW is doing any of these, this is the likely cause:
An electric pump doesn't fade gracefully — when it quits, coolant flow stops completely, and an N55 at highway load without circulation overheats in moments. Aluminum engines take heat damage fast: warped heads, crushed head gaskets, and on a turbo engine, a cooked turbo as a bonus. A pump that's logging faults or letting the temperature wander is announcing its retirement; the difference between replacing it scheduled and replacing it after a roadside overheat can be the head gasket job that costs multiples of this repair.
Yes — this is a regular mobile job for us. The pump access is tight but fully workable in a driveway, and the critical part — the electronic coolant bleed with a scan tool — is equipment we bring. Half a day, and the car is verified at steady operating temperature before we leave.
The pump itself is a precision electronic part priced accordingly, the access hours are real, and dealers add the thermostat and tank as separate book-time line items at their rate. Done together, the three parts share the same drain, access and bleed. We quote the complete cooling refresh as one flat price before any work starts — pump, thermostat, tank, coolant, bleed, done.
Because they're the same age, the same brittle plastic, and the same labour to reach — and they're the two parts most likely to put you right back in an overheat situation months after a pump-only repair. Replacing them with the pump costs you parts only; replacing them later costs the whole job again. If yours are genuinely recent or already updated, we skip them and the quote reflects it.
It's the most common explanation on this engine. The pump can weep internally where you'll never see it, and aging expansion tanks vent coolant past the cap as vapour under heat — no puddle either way. We pressure-test the system during diagnosis, so you'll know exactly where the coolant is going before we replace anything.
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