Power Steering Cooler, aka "Cooling Coil" or "Steering Loop". Like the Pressure Hose it has a metal pipe with swaged fittings that are prone to leaking. On older models there is no cooler and this hose runs back to the reservoir. This hose runs the fluid out of the rack and into the steering cooler. Manual steering is not recommended unless you have a vintage 2002 or E21 with skinny tires.į. The power assist comes from the hydraulic fluid pushing on a piston which moves the rack. In this way, power and manual steering racks function the same. Turning the steering wheel turns the pinion shaft and the pinion teeth mesh with the rack teeth to move the rack side-to-side. The pinion is the steering shaft and it meets the steering rack at an angle. ![]() Steering Rack, aka "Hydro Steering Box". Most BMWs use rack-and-pinion steering. It's easier to replace the entire line with a new OEM or BMW part than to try and repair the line.Į. These swage fittings are the most common area for PS leaks on your BMW. These fittings are compression crimp-style swage ("swedge") fittings that are very common in the automotive world. Unfortunately it has a lot fittings where rubber hose meets metal line. The hose has extra length so the system can have more fluid capacity. At either end is a hard metal line secured with a bolt and copper crush washer. The PS pump is usually driven from the same serpentine belt as the alternator and water pump.ĭ. The internals of a PS pump are quite simple but the bearings can become dry, requiring the complete replacement of the pump itself. As with any other rubber hose, this one will leak at some point from either dry rotting or swelling from over-saturation.Ĭ. These clamps are crimped into place and cannot be re-used so we recommend getting the appropriate premium traditional clamps if you're ordering new hoses. Crimped hose clamps attach it at both ends. Supply Hose, aka "Intake Manifold" or "Suction Pipe". A rubber hose running from the reservoir that supplies the power steering pump with fluid. The filter is not serviceable so it's a great idea to replace the reservoir at some point.ī. Also inside is a filter that will trap metal and other foreign particles so they do not reenter the system and cause damage to the pump or rack. You can top off or refill your fluid in this container (make sure you use the correct fluid - see below!). This sits at the top of your engine bay, usually on the driver's side. Power Steering Reservoir, aka "Oil Carrier". This is typical for all BMW hydraulic power steering system hoses.Ī = Fluid Reservoir | B = Inlet Hose ("Intake Manifold") | C = Power Steering Pump | D = Pressure HoseĮ = Steering Rack | F = Return Pipe | G = Fluid Cooling Pipes ("Cooling Coil") | H = Return Hose ("Radiator Return Line")Ī. This is for an E46 M3 but nearly all BMWs using a belt-driven PS pump will have a similar hose layout. Below is a diagram showing a typical hose layout. Factory BMW hoses are reinforced rubber with metal fittings except where the hoses attach to the reservoir with hose clamps. ![]() On later cars one of these hoses is actually a metal cooler that sits in the airflow and cools the fluid after it leaves the rack. We'll explain the layout and function below.Īll hydraulic systems will have 4-5 hoses/pipes that carry hydraulic fluid from the reservoir, to the pump, to the rack, and then back to the reservoir. However, looking at the power steering system on your car can be intimidating with many hoses crisscrossing the engine bay. Preventative maintenance such as fresh fluid and replacing leaking hoses will help prolong the life of the rack. Steering racks are expensive and replacement can be very invasive. But millions of hydraulic power steering systems are still on the road today and they need to be maintained. Several major advancements have been made since the original 1970s power rack-and-pinion systems and BMW is now all-electric. In concept, modern BMWs are no different than the power steering systems from 40 years ago - turning the steering wheel rotates a shaft, which slides a toothed rack with assistance from a hydraulic pump or electric motor, pushing and pulling on the tie rods at each wheel to point the tires in the direction you want to go. BMW Power Steering System, Rack, Hoses, and LinesĪside from a few exceptions, BMW uses power-assisted rack-and-pinion steering on every model.
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