BMW Z4 Convertible E85 – Top reasons why the folding roof system does not work

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bmw z4 cabriolet folding roof

Are you experiencing folding roof problems with your BMW Z4 Convertible?

The BMW Z4 E85 Cabriolet is the first generation of BMW Z4 roasters, produced between 2002-2008.

This cabriolet has great body control and sharp handling and with the option for a four or six cylinder engine, contributes extra pace and a purr from the engine for your roof down ride.

The Z4 has a super-fast soft top cabriolet which opens in ten seconds and a surprising amount of boot space, the BMW Z4 E85 offers something for all convertible lovers.

In this blog we will share all you need to know about the BMW Z4 E85 including common faults, best bits and the important maintenance measures to be taken to keep the cabin dry and the roof working.

Cayman Auto Services BMW Roof Specialists

BMW Z4 E85 Hydraulic Pump Fault

As any passionate cabriolet owner knows, keeping the front and rear drains clear is vital for the preservation of parts within the convertible roof system. The function of the drains is to carry any water through the bodywork of the car and out of the bottom, keeping the interior, cabin and boot areas clean and dry. It is too easy for the dirt and debris to build up within these channels, causing blockage. This leads to water leaking into the vehicle, and with essential mechanical components beneath the roof frame, this can be detrimental to your cabriolet roof operation.

The BMW Z4 E85 is a shining example of this – when the rear drains become blocked, water builds up into the bodywork, particularly on the passenger side where the essential hydraulic pump is located. For this reason, failure of the hydraulic pump is a very common fault on the BMW Z4 E85 – it becomes water damaged and requires replacement.

Unfortunately, replacing the hydraulic pump is not a cheap repair, yet it is an essential part of the roof system – without your hydraulic pump operating correctly, you can kiss goodbye to those wonderful top-down rides.

This design flaw is an inevitable feature, hydraulic pump failure is an avoidable pain. Maintenance is the key to keeping the convertible soft top alive and well, especially in temperamental British weather, where it can be wet in the morning and you want to drop your roof down by the afternoon!

The most important thing is to have your drains cleared on a regular basis, something that can be usually done by your usual service garage. The correct way for this to be carried out is by using a pressurised airline to blow the dirt through, leaving your drains squeaky clean. Some opt to DIY at home using long pieces of metal wire to push all of the dirt out- although this is not something we would advise.

This is often an ineffective method of getting rid of that pesky dirt, and if something were to get stuck whilst rummaging around in there, you will have a much bigger problem on your hands! This can result in damage to the drain system, piercing the channels and then requiring repair and replacement.

BMW convertible common faults

How can I tell if my BMW Z4 Convertible pump has failed?

Often the pump will start to show signs of failure through water ingress before the component eventually ceases to work at all. This can result in a slower than normal roof retraction and closure and the pump can become noisy in operation.

Often the roof will not open, however most BMW Z4 cabriolet owners are unaware there are 2 motors that operate that the roof system.

The first motor drives the top lock latch mechanism, which locks and unlocks the roof to the windscreen. This generally will operate and the driver will hear this motor working where the soft top lifts away from the windscreen. Simultaneously, the windows drop a few centimetres ready for the convertible roof to retract. Usually it is at this stage that the roof will go no further as the motor at the front then switches to the hydraulic system to power the roof down.

This is a sure sign that the hydraulic pump has failed.

How to check your BMW Z4 E85 drains

If reading this far has sent you into panic, don’t worry! There is a simple and effective method to find out if your drains needs clearing on your BMW Z4 E85. All you need to do is open your roof, pour water down the rear drains and see if the same amount of water exits the drain hole at the underside of the vehicle.

If the same amount of water exits on the rear channel, you know your drains are free from build-up and will work correctly.

If you pour water into the channels of your BMW Z4 E85, and there is little exiting from the underside of your vehicle, you have a problem on your hands. The reason water isn’t flowing out is because there is an obstruction of sludge and dirt preventing this.

This is where the design flaw is apparent. The hydraulic pump of your BMW Z4, a pricey part that is key for the operation of your cabriolet roof system, is located in an area that is not waterproof! When a pump becomes water damaged, it requires replacement. What’s more, if you do not have your rear drains cleared regularly, don’t expect a new pump to last too long!

Cabriolet roof specialists will advise to keep your drains clear to preserve the warranty on the new pump. See the video tutorial below if you fancy giving it a go at home on your BMW Z4 e85;

Relocating the Hydraulic Pump for the BMW Z4 E85

One idea amongst the BMW Z4 E85 community is to attempt to rectify BMW’s error in judgement and compensate for the design flaw, with regards to poor choice of placement of the hydraulic pump.

Some owners wish to relocate the pump into the boot area away from its’ usual position under the roof frame. This way when the drains fill with water and fill the area where the pump is located, if the hydraulic pump has been relocated, the theory is this should eliminate the problem of a water damaged hydraulic pump.

Though this sounds like a good idea, you may end up causing more problems than you solve.

Here is why Cabriolet and Soft Top Roof Specialists would not recommend relocating the hydraulic pump:

Reasons not to locate the Hydraulic Roof Pump

Firstly, relocating the pump makes the roof operation terribly noisy. There is no sound deadening effect and the cabriolet driver will hear the pump quite loudly in operation.

Secondly, the combined loss of boot space and the fact the pump has nowhere to mount as it was not designed to be there make for practicality and aesthetic issues.

Relocating the pump will not negate the need to keep a check on the drains – the blocked drains will still result in water entering the void where the pump was originally located and overflow into the passenger compartment which can then result in damp carpets and airbag and warning light electronical failures.

Essentially, rather than relocating the pump, just have the drains cleared every six months at your local service garage to avoid complicated and expensive cabriolet roof repairs. Maintenance is key for keeping your cabriolet roof system alive, especially when you own the BMW Z4 E85.

How Do I close my BMW Z4 Roof System Manually?

In the unfortunate event that you cabriolet roof system malfunctions, you will need to manually operate the roof system to the closed position.

Often cabriolet owners with failed roof systems see this function as an alternative to the electric operation of the roof system. This manual procedure should be regarded as an emergency close procedure only as overuse can damage further components – opening the roof using this procedure is not advised.

The hydraulic roof system is a pressurised unit and requires release of this pressure to enable manual closing. Without this release the roof system is very difficult to manoeuvre as you have resistance within the system.

Please see our video for help with release of the hydraulic pressure to operate the pressure release system.

Once this is disengaged the roof can then be manually lifted following your guide in your driver’s handbook. You should have 4mm cranked Allen key stored in your tool kit that locks the top locks closed. If the hydraulic pump has failed you should not need this tool to lock the system.

How to clean and maintain the Soft Top of your BMW Z4 E85

The soft top of the BMW Z4 E85 also requires care and attention. Due to material and the age of the vehicle’s fabric, the roofing system can become porous over time. Much like you often see with waterproof jackets.

This is because the fabric can lose its water repellence and any water that sits on top of the fabric will eventually seep through the cabin or boot area. This can lead to a number of issues including wiring corrosion, motors and pump damage, water ingress, smell, rotting carpets and sloshing noises.

Therefore it is important to clean and protect your roof to prolong its life and maintain its water resistance.

A number of expert products can be used to remedy this. You should always clean all your roof at once, as spot cleaning can lead to dark patches. Use a soft dry brush to clean away the dirt and then apply a product such as using Renovo’s ‘Ultimate Fabric Soft Top Cleaner’ as instructed.

Once clean you should also seek to protect your roof. Using a similar product such as Renovo’s ‘Ultra Proofer can re-establish the waterproof weather barrier of the roof, reinforce the UV barrier and protect against mould and mildew.

BMW Z4 E85 or E89?

The BMW Z4 E85 actually has a newer, hard-top version with the production years 2009-2016.

BMW did make alterations to overcome the drainage issue within their newer E89 model, so the hard-top version does not experience the issues already discussed with drainage and water flooding to all important hydraulic pump. Though there are many factors to be considered when deciding which model is best for you.

Let’s start with the E89. This adaptable cabriolet comes with a range of engines to choose from. Starting with a 2.0 Litre without outputs of 181 BPH or 242 BPH and ranging to a 3.0 Litre engine offering outputs of 244 BPH, 302 BPH and 335 BPH. So, similarly to the E85 – we are spoilt for engine choice.

The E89 features a turbo charged engine whilst the E85 takes an old school approach with a naturally aspirated one. Further, the E89 features a twin turbo and updated navigation. The E89 is both a coupe and convertible – designed to keep you cosy in the winter and living your cabriolet dream when the sun shines. It claims to morph from convertible, yet sporty cruiser to an outright performance car, though the E85 tends to make for a sharper and nimble ride due to its reduced weight from the soft top roof system. Essentially, the BMW Z4 E85 is one for the old school lovers, whilst the E89, equipped with tech and gadgets is a great choice for the modern day driver.

Related Questions:

What diagnostic equipment do I need to diagnose a BMW Z4 Roof Fault?

Correct diagnostic equipment is crucial to identify faults and failures within all modern vehicles, and the BMW Z4 E85 and E89 are no exception. Most common garages have a generic diagnostic tool and although they are effective for diagnosing standard vehicle faults, they do not communicate effectively to the Cabriolet Roof System.

To diagnose the BMW Z4, we would recommend Autologic or BMW ICOM, along with a strong level of expertise and analytical skill from the technician – generally at Cayman Autos we can find the fault within an hour.

bmw z4 e85 cabriolet drainstop
BMW Z4 E85 Cabriolet Drainstop.

How do I modify the drains on the BMW E85?

At Cayman Autos, when we replace the BMW Z4 Hydraulic Pump, we modify the drains and pump housing to help prevent water damaging this component again should the drains become blocked. The drains as they stand have restricted ends, or filters which are designed to stop insects and bugs crawling up the drains into the vehicle in countries where poisonous and deadly creepy crawlies are a problem.

Luckily in the UK this is not something we need to worry about as these vehicles suffer the consequences of rain water and leaves! We modify the drain holes and remove the restricted ends, which allows water, debris and sludge to drain through freely.

Can I use a refurbished a hydraulic pump on my BMW Z4 E85?

The simple answer is it is unwise to use them – to replace the hydraulic pump on a BMW Z4 E85, the entire cabriolet roof needs to be removed to access and completely service the drains. This is a very labour intensive job, so for this reason it is beneficial to replace with a part that is unlikely to fail. Second hand parts or refurbished units that undoubtedly have been exposed to water will usually fail in a short time. Spending money on the labour to fit these parts is not cost effective and we would always recommend replacing the unit with a genuine BMW pump.

Can I replace the Electric Motor only on the Pump Unit?

Some customers visit the workshop when they have fitted only a used motor to the roof system rather than replacing the entire hydraulic pump. The electrical part of the system is obviously damaged by water and replacement of this unit alone can get the roof working again, however the pump unit also gets damaged by water. Replacement of only one component of the damaged system results in a very slow and sluggish operation – not ideal and frustrating for the owner. This can result in the roof needing to be removed again to replace the entire system when this faulty historically water damaged part fails again.

Here at Cayman we can help you with all of your BMW Z4 E85 Cabriolet roof problems

We hope you have found this blog useful for the common BMW Z4 E85 roof problems that many of our Z4 Cabriolet owners experience.

Having a convertible roof system can be the envy of all our friends, however not quite so fun if the sun is shining and the roof is not opening.

At Cayman Autos we have a high level of customer service and turnaround for quick, efficient and cost effective roof repairs. We have customer travel from all over the UK and internationally for our expertise and knowledge together with the most up to date diagnostic equipment.

The correct diagnosis for your Cabriolet fault is paramount and can save customers time and money on unproductive and ineffective repairs. Please check our testimonials and reviews on Google Facebook & Trustpilot to give you the confidence to make the journey to our workshop. We carry many parts in stock and aim where possible to diagnose and repair the very same day. We look forward to helping you with all of your Cabriolet Roof Faults.

Thanks for reading Top Reasons why the Folding Roof System does not work. If you require some assistance from the team at Cayman Autos, Contact us today on 01737 761599 or visit us at 51 ORMSIDE WAY, REDHILL, SURREY, RH1 2LG.

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