Cooling Overhaul for a Mini Cooper S in OE Supplier

A cooling overhaul: the Mini thermostat housing and water pump, which are both known failures and are both behind the same covers.

We are an independent parts supplier. We are not BMW AG or MINI, we are not appointed by them, and BMW and MINI are their trademarks. What we sell are parts that fit those cars, described as such. Every listing states the chassis codes and engine codes it fits, the production date range, which quality tier you are buying, the labour time the job actually takes, and whether the part needs coding to the car before it will work. Where a part is only made in plastic by the factory and fails because it is plastic, we say so and we offer the metal one.

Specification and fitment

• Fits: Mini Hatch R56 R55 R57 F55 F56 F57 and Countryman R60 F60
• Engine: N42 N46 N52 N53 petrol, N20 N26 B48 petrol, N54 N55 B58 turbo, M54 six cylinder, N47 N57 diesel, and N14 N18 on the Mini applications
• Production dates: 2000 to 2019 depending on chassis. These cars change mid production, sometimes twice in a model year, and two cars built four months apart can take different parts. Send us the last seven digits of your VIN with the order and we check the part against the build record before anything is dispatched. It takes us two minutes and it is the difference between a part that fits and a return.
• Quality: made by the firm that supplies the vehicle manufacturer, in that firm's own box rather than a dealer box. Identical part, identical line, no dealer margin, and this is what we would fit ourselves
• Part number: cross referenced to the original equipment number for your VIN and confirmed before dispatch. We do not publish a single number against a listing that covers several build variants, because that is how people order the wrong part
• The failure this addresses: Almost every cooling failure on these cars is a plastic part doing a job that heat makes plastic bad at: a water pump with a plastic impeller, an expansion tank that splits at the seam, a thermostat housing that warps. The electric water pump on the N52 and N54 typically goes between 60,000 and 90,000 miles and takes the head gasket with it if you keep driving. If yours is original and the car has done 70,000, it is not a question of whether.
• Labour time: three to five hours, and an hour more where the radiator comes out
• Coding: no coding, but the adaptation values want resetting with a diagnostic tool afterwards or the car will run on the old learned figures for a while. On the electric pump engines the pump is recognised automatically but the adaptation should be reset
• Also needed: coolant to the correct specification, which on these cars is a specific blue or the later green and they must not be mixed, plus new hose clips and O rings throughout
• Torque: plastic housing bolts are torqued low and in sequence. Overtightening a plastic thermostat housing cracks it on the bench, which we have all done once
• Weight: approximately 18.2 kilograms
• Warranty: three years or 36,000 miles, whichever comes first
• Vacuum fill: these systems are filled under vacuum, not poured in. An air lock in a BMW cooling system will cook a head gasket while the temperature gauge reads normal, because the sender is in the coolant and the coolant is not where the air is
• Do the lot: a cooling system is a set of plastic parts of the same age. Replacing the pump alone on a 90,000 mile car buys you eight months and the labour twice
• Uprated: the metal impeller and aluminium housing versions are available and are what we would fit
• Warning signs: a sweet smell, a low coolant warning that comes back, a heater that blows cool at idle, or a white crust at a hose joint

What arrives

• the water pump and thermostat
• expansion tank, cap and level sensor
• every hose in the circuit and new clips
• coolant to the correct specification
• O rings and gaskets throughout
• a vacuum fill and bleed guide

Fitting

Three to five hours. Fill under vacuum. An air lock in one of these systems will destroy a head gasket while the gauge sits in the middle, because the temperature sender is measuring coolant and the problem is the air. If you do not have a vacuum filler, have it done.

Which version to buy

There is only one real decision here and it is whether to replace the plastic parts with plastic or with metal. The factory used plastic because it is light and cheap and it lasts about a decade, which was long enough for the warranty. On a car you intend to keep, the metal impeller pump and the aluminium thermostat housing cost about two hundred pounds more and remove the failure rather than resetting its clock.