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      09-10-2019, 07:55 PM   #1
Donkman
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2005 BMW Z4 2.5L Top not working

OK, When I push the button to lower the top it unlocks but does not lower it. I hear the motor in the back spinning but nothing move. What could it be?

Thanks in advance guys..
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      09-11-2019, 02:37 PM   #2
JAS1169
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After pushing the top down button and the top just stops moving. At that point is the top easy to move manually or very firm?

Have you used the hydraulic pump by pass in the trunk, will the top move freely once this is engaged?

Note: If the red by-pass is engaged & the top doesn't move freely manually do not force the top down only because you may not be able to get it closed again.

Generally, given that you can hear the motor running but, the top isn't moving it means that your hydraulic fluid within the system is low and you have a leak in either a hydraulic line or hinge lifter.
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      09-12-2019, 10:38 PM   #3
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Push up on the roof to see if it will retract when/after the top unlocks.

If it does... lubricate the locking position roller on each side. Use a good quality penetrating and lubricating oil... not WD40.

When the top is unlatched it is at its weakest point/least able to retract if there is resistance at the latching point. There is/are correct word to describe in physics terms but it's been 50+ years since I took physics in school.

I'd lubricate the rollers anyway as it's needed. If the rollers don't "roll" it creates significant resistance in the retraction/closing of the convertible top.

Think crane... the further the boom is out and the shallower the angle the smaller the weight it can lift. At a certain point the righting moment goes negative and the crane tips over. The locking arms are the end of the boom and when there is too much resistance it's the same as the crane reaching the end of its ability to right itself/lift a weight.
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      09-25-2019, 08:34 PM   #4
Donkman
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Quote:
Originally Posted by JAS1169 View Post
After pushing the top down button and the top just stops moving. At that point is the top easy to move manually or very firm?

Have you used the hydraulic pump by pass in the trunk, will the top move freely once this is engaged?

Note: If the red by-pass is engaged & the top doesn't move freely manually do not force the top down only because you may not be able to get it closed again.

Generally, given that you can hear the motor running but, the top isn't moving it means that your hydraulic fluid within the system is low and you have a leak in either a hydraulic line or hinge lifter.
The top moves freely when it stops moving. When I press to go up, motor sounds but nothing moves, but is free to lift up manually.
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      09-26-2019, 08:39 PM   #5
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ok, your issue has to be one of two things.

Check to see if your Emergency by-pass is engaged. It"s a little red handle in the trunk on the drivers side. There's actually a video on youtube on it.
If your very lucky it's this and simply dis-engage it.

However, since your total top movement is simply unlocking at the windshield and stopping dead with the motor still spinning away, it's highly likely that you have hydraulic pressure failure caused by either a bad hydraulic line or hinge lifters.

Unless your by-pass is engaged (or jammed up at the motor) the hydraulic pressure in the system should make it very difficult to move the top. However, you can move your top manually which means you have no hydraulic fluid in your system because it leaked out at the location where it failed.
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      09-27-2019, 07:01 AM   #6
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Quote:
Originally Posted by JAS1169 View Post
ok, your issue has to be one of two things.

Check to see if your Emergency by-pass is engaged. It"s a little red handle in the trunk on the drivers side. There's actually a video on youtube on it.
If your very lucky it's this and simply dis-engage it.

However, since your total top movement is simply unlocking at the windshield and stopping dead with the motor still spinning away, it's highly likely that you have hydraulic pressure failure caused by either a bad hydraulic line or hinge lifters.

Unless your by-pass is engaged (or jammed up at the motor) the hydraulic pressure in the system should make it very difficult to move the top. However, you can move your top manually which means you have no hydraulic fluid in your system because it leaked out at the location where it failed.
In the past I would have said that this is a hydraulic motor failure. I hope though that you are right - topping up the fluid seems a lot easier and cheaper than replacing the motor.
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      09-28-2019, 02:46 PM   #7
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O/P advised twice that after the top releases from windshield it stops dead, yet he can hear the motor running. Since he can hear the motor operating it means there isn't motor failure.

Unless the O/P has himself moved, or purchased a Z4 which had it's Convertible top motor/pump relocated to the trunk it is impossible to top off hydraulic fluid only because you can't reach the motor/pump without either pulling the top or pulling the motor out thru the trunk.

The z4 uses a high pressure hydraulic system for it's top and would drain out quickly.
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      10-18-2019, 09:43 AM   #8
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Thanks to all for the info. I started to get at the Hyd. Motor thru the trunk but stopped short when I reached my hand on it but could not remove the connections on it. Looks like I have a manual top now.

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      10-21-2019, 09:31 PM   #9
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Yea, I'm glad you stopped. Generally, pulling the motor is only done when you have motor failure. In your case, after the top is released from the windshield you can still hear the motor running, which means the motor is good but, you have little or no hydo pressure.

This lack of hydo pressure can be caused by either a broken line or a failed hinge lifter. However, it could also be caused by the emergency release system within the pump being jammed.

When you have these potential issues the only way to really trouble shoot it is by taking the top off the car to determine the problem area.

The potential repair cost by BMW of the broken line or the jammed emergency release would be very high. However, the cost of replacing only one hinge lifter would be very, very costly.

Having a manual top is ok. Maybe someday if you keep the car long enough you'll really fall in love with it and want it done. However, time and $$$ will tell.
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