BMW Z4 E89 Convertible Roof Motor & Hydraulic Pump Replacement
The folding hard top is the best and worst thing about the E89 Z4. When it works it turns the car from coupe to roadster at the press of a button. When it doesn't, you get a red light on the roof button, a bong from the dash and a roof parked halfway between the two, often in the rain.
The hydraulic pump under the boot floor gets the blame for most of these failures, and sometimes rightly. But a reconditioned pump is around £500, water damage in the boot can push the bill into thousands, and several of the things that stop the roof cost nothing or a few pounds to fix. So this guide works through it in the order you should: how the roof decides whether to move, the cheap causes to rule out, and then the pump swap itself.
How the E89 roof works
Everything is run by the convertible top module, which lives in the right-hand side of the boot. It drives the hydraulic pump, the valves, the boot lid soft-close and an electric locking motor that latches the roof to the top of the windscreen frame.
The pump itself sits in a recess in the boot floor, next to the battery, in a foam carrier. BMW quotes it as producing 150 to 200 bar, feeding four cylinders that move the roof panels and two that move the boot lid section.
The part that catches people out is the checking. Thirteen sensors (five Hall sensors and eight microswitches) watch every stage of the sequence. If any one of them reports something unexpected, the module stops the roof where it is. That's why a single corroded sensor can look exactly like a dead pump.
Check these before you buy a pump
BMW's own operating conditions for the roof explain a lot of the "it worked yesterday" faults. The roof will only move if:
- The luggage partition is fully down. If the divider in the boot isn't in its lowest position, the roof won't open. Press it firmly down at both sides and clear anything pushing against it.
- The battery is above 11.5 volts. The roof can pull up to 40 amps, so a tired battery that still starts the car can stop the roof mid-cycle. Run the engine while you test it. If the battery is ten years old or more, change it (a 70Ah AGM on these cars) and register it to the car.
- The car is stationary. Cars built from April 2012 will operate the roof up to 40 km/h (about 25 mph); earlier ones need to be stopped.
- It hasn't been cycled too many times in a row. The module locks the roof out after five back-to-back operations and if the hydraulic fluid gets too hot. If you've been testing it repeatedly, give it a rest and try again.
Then look at the faults owners on the Z4 forums report again and again:
- The two salmon-coloured relays on the pump. Their contacts wear every time the roof moves, and they fail without warning. Green or burnt-looking contacts are the giveaway. Two relays cost a fraction of a pump, so renew both if there's any doubt. While you're there, check the connector block feeding them for corrosion.
- Microswitches on the horizontal cylinders in each rear wing. These switch unreliably with age and usually give intermittent faults first, often the roof failing to lock.
- The Hall sensor on the right-hand side of the roof coupling lock. It corrodes and splits, usually with no warning. A common sign is the roof stopping as the boot lid section opens or closes.
- Boot lid soft-close switch wiring. The flexing wires to the microswitches either side of the boot lock break. The lock then won't latch, or keeps trying to, and the roof refuses to start.
- Tired gas struts. If the boot lid or roof section drops on opening or struggles on closing, the struts are the likely cause rather than the pump.
If the roof buttons themselves seem dead, the wiring runs from the centre console back to the module, so it's worth reading our Z4 centre console guide before pulling the boot apart.
Symptoms and the likely cause
| What you see or hear | Most likely cause |
|---|---|
| Nothing happens, red light and bong | Partition not down, low battery, or a sensor/microswitch reporting a fault |
| Pump whirrs but the roof doesn't move | Low fluid, a burst hose or line, or a failed valve; the motor itself is still running |
| No pump noise at all | Failed relays, corroded connector, or a motor killed by water |
| Roof stops partway, works on a second try | Intermittent microswitch or Hall sensor, or battery voltage dropping under load |
| Roof stops as the boot section moves | Right-hand coupling lock Hall sensor, or boot lid soft-close wiring |
| Water or damp foam under the boot floor | A leak that will kill the pump if it hasn't already |
Why the pump fails: water
When the pump really has died, water is nearly always behind it. It sits at the lowest point of the boot, and any leak finds its way down to it, sometimes along an electrical cable. The usual sources owners find:
- Rear light clusters that weren't sealed properly after being replaced. Some replacement units use fewer fixings than the originals, leaving a hole in the body open to the weather.
- Perished rear ventilation flaps (BMW part 64226909340, one each side). They can be changed from inside the boot without removing the bumper.
- Seal joints around the boot opening.
A leak often shows only after heavy rain or a car wash, so it's easy to miss. Fix the leak before you fit a new pump, or the new one will go the same way. A cheap habit worth getting into: lift the boot floor each spring and check that the foam around the pump is dry, especially at its right-hand end.
Parts and part numbers
| Part | BMW number | Notes |
|---|---|---|
| Hydraulic unit (pump and motor), Z4 E89 | 54377309634 | Replaces the earlier 54377220798, used from January 2009 to June 2013 |
| Hydraulic fluid for the roof | 54340394395 | 250 ml bottle; BMW lists it for the Z4 E85 and E89 |
| Rear ventilation flap | 64226909340 | Two per car, a common leak point |
Always check against your VIN before you order. You'll see other "Z4 roof pump" numbers on parts sites that actually belong to the E85 soft top or the 3 Series and 4 Series convertibles, and they won't fit an E89.
Specialists also sell reconditioned units, and some offer just the motor. The motor bolts onto the hydraulic block, so if the block, hoses and valves are fine, swapping the motor alone is the cheaper route. Reconditioning firms say the replacement doesn't need coding to the car.
We couldn't find a published torque figure for the pump fixings from a reliable source, so take that from BMW's repair information (section 54 37) rather than guessing.
Safety first
Do the work with the roof fully closed and latched, the ignition off and the key away from the car. The system runs at up to 200 bar and the roof mechanism is strong enough to trap fingers, so never reach into it while anyone could press the button.
The pump has two brass valves on top. Owners describe opening one with the 6 mm Allen key from the glovebox tool kit to move a stuck roof or boot section by hand. BMW treats emergency operation as a workshop job, so only try this if you understand what it will release.
Tools and parts
- Trim tools for the boot floor and battery cover
- Socket set and Torx bits
- Replacement hydraulic unit or motor, matched to your VIN
- BMW roof hydraulic fluid (54340394395)
- Towels and absorbent cloths, plus a wet/dry vacuum if there's standing water
- A battery charger to keep the voltage up while you test the roof
Removing the old pump
- Close the roof fully if you can, switch everything off and lift the boot floor and battery cover. You'll see the battery with the pump beside it in a foam carrier.
- Look at the foam before you touch anything. If it's wet, you've found your problem, and you'll need to find the leak as well as replace the pump. Check the polystyrene box on the right that houses the roof module for water too.
- Remove the bar that runs across the battery and pump.
- Lift the pump out of its foam carrier and rest it on top of the battery so you can reach the connections.
- Unplug the electrical connector. The wiring is delicate, so take a photo first and ease the connectors apart rather than pulling on the wires.
- Motor only: undo the two bolts holding the motor to the hydraulic block, disconnect its power lead and lift it off. The hydraulic side stays sealed.
- Complete unit: move the hydraulic pipes across to the new unit one at a time, so none end up on the wrong port. Have cloths ready for spilled fluid.
Fitting the new pump
- If the foam carrier was wet, take it out and let it and the boot well dry fully, which can take a couple of days. A new pump sitting in damp foam won't last.
- Fit the new motor to the block with its two bolts, or connect the hydraulic pipes to the new unit one by one, each to the port it came from.
- Reconnect the electrical connector until it clicks home, and check the relays and their connector are clean and secure.
- Seat the pump back in its carrier and refit the bar across the battery.
- Check the fluid level and top up with the BMW roof fluid if any was lost. Follow BMW's procedure for the level check and any bleeding.
Final checks
With a charger connected or the engine running, leave the boot floor out and cycle the roof open and closed. Watch and listen around the pump for leaks, and check the roof finishes each movement cleanly with a green light, not red. Remember the module will lock you out after five cycles in a row, so pause between tests. Once it's consistent, refit the floor and cover.
This second video is useful for seeing the pump area and the connections before you start:
Troubleshooting
- New pump runs but the roof doesn't move: check the fluid level first, then the hoses and the lines in the rear roof shell. Those lines and the sensor wires running alongside them fatigue with age and can split.
- New pump does nothing: go back to the relays and their connector before suspecting the new unit.
- Roof works for a while, then fails again: the leak hasn't been fixed. Recheck the rear lights, the ventilation flaps and the boot seals.
- Random roof faults alongside other electrical oddities: suspect the battery before anything else. If the car is also slow to crank, see our Z4 starter motor guide.
Most E89 roofs that stop working can be fixed without a new pump, and the ones that do need a pump usually got wet first. Check the partition, the battery, the relays and the sensors, find any leak, and only then spend money on the hydraulic unit. For more on the car, see the rest of our BMW Z4 guides.