Hydro Unit (AKA Hydraulic Pump) - BMW E46 3-Series

The core deposit ($200 out of the $725 that you are paying) gets refunded in full if the matching core is returned within 90 days and it has not been subject of severe abuse (such as damage from DIY repair attempts, or parts on the outside of the pump obviously broken by external forces).

Seals inside the pump get upgraded, and design flaws get rectified. Pumps rebuilt by Top Hydraulics perform better than brand new ones, and Top Hydraulics' seals will far outlast those in brand new pumps. The pump we are shipping to you may not be perfect cosmetically, because it has been used before. We do our best to clean up or polish out external blemishes, but what really matters is what's inside the pump.

The most common failure symptom on used BMW E46 hydro units is a gradual loss of pressure and power. There are various possible reasons for gradual power loss inside the pump/hydro units, ranging from degrading electric motors through pump pistons wearing out and check valves bypassing, to pressure regulators failing, or even hydraulic fluid seeping into the electric motor. Top Hydraulics will check that all these components meet or exceed factory specs and exchange or upgrade them if necessary. Bench testing includes all valve functions, pressure test, flow test, extended load test, and test for leaks, to make sure that factory specs are exceeded before the pump ships back. Beware when purchasing used pumps that those may actually be units that are still pumping, but are not able to complete the convertible top's opening or closing cycle without manual assistance.

Some of these pumps have external leaks (you may find the foam casing soaked in hydraulic fluid). The most common source for external leaks on these pumps are the port seals. Port seals are tiny seals of special shape that are sealing the hydraulic lines when they are plugged into the pump. The port seals are behind brass bushings. These bushings are pressed into the pump housing, and they are made to 1/100 mm precision. Any DIY repair attempt would destroy the bushings. Top Hydraulics replaces the original port seals with an improved version made of Viton, which has practically unlimited shelf life. Before assuming that the pump is leaking externally, check the hydraulic lines going into the pump to make sure they are dry.

The fill plug is a metric (5-mm) Allen bolt. It is the one closest to the level marker on the reservoir. Make sure to have a fitting 5-mm outside hex wrench, so that you do not strip the inside hex of the plug. Please drain the fluid through the drain plug before shipping the pump to us, unless you have a hard time getting the fill plug open.

Removal of the pump from the car is easy - this is "plug and play":

1) Remove panels inside the trunk to create access to your pump, located in the forward left corner of your trunk.

2) Remove the single bolt that mounts the pump in its foam cover against the car's chassis.

3) Pull the pump out of the protective foam housing, and unplug it from the main wiring harness.

4) Rotate the two retaining discs that hold all hydraulic hoses. Rotate counter-clockwise some 10-15 degrees, until the hoses can be pulled out. No need to loosen or fasten any bolts for this - the plates will simply click into place. No need to mark the hose locations - each hose has a number printed on it near its metal fitting, and that number matches the number engraved on the retaining disc.

5) Drain the hydraulic fluid through the fill plug (it is good to replace old fluid, anyway), replace the plug, disconnect the remaining wires from the motor and the solenoid, wrap the pump in a large garbage bag, then inside another one, box up well, and send the pump to Top Hydraulics.

You can save some money by using Mercedes fluid 0009899103 or FeBi 02615 - they are fully compatible with your BMW 3-Series cabriolet hydraulics. Fill the pump through the fil plug. The fluid level is supposed to be within the round level marker on the reservoir when the convertible top is down. Do not overfill the reservoir. Adjust the fluid level after the top has cycled a few times. Give the pump motor a break (to cool down) latest after three complete cycles or 2 minutes of running time.

The official BMW part number is 54347025595 (or 54 34 7 025 595); p/n 8 234 530 or HB70346-002 are usually printed on the pump. Fits model years 2000-2006. If you have an early model year (2000 or 2001), then you need an adapter p/n 54347076030 (or contact us and we will provide the pump that matches the original equipment in your car, without the need for an adapter).