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  #1  
Old 03-27-2020, 05:58 AM
Kentuckyduck Kentuckyduck is offline
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Mein Auto:
Convertible roof still malfunctioning after new motor

Good morning, all. I have an '06 Z4 3.0i that I bought used last year (only 53k miles!). The car was in pristine shape and had no mechanical issues.

Toward the end of the fall, the hydro pump began to make an extraordinary groaning noise during the final portion of the roof latching process. Within a few weeks, the motor began to struggle to raise, and then shortly later to even lower. As the weather was turning cold, I decided to put off the repair until spring. In the meantime, I did a lot of research and learned the propensity of the convertible top motor to fail due to corrosion if the drain well got clogged. Not knowing the history of the vehicle for the previous 13 years, I figured that was the case.

I ordered a new hydro pump, which was installed Monday. I've used the same mechanic for more than a decade. He was originally a Honda-certified, but left a dealership and formed his own import repair shop. He's worked on many BMWs in the past so I felt comfortable using him.

To our surprise, the drain well was clean and the old motor looked brand new. Still, as we're talking about an '06 here, the motor still could've just worn out, right? The fluid level in the old motor was just slightly lower than that of the new motor so we figured we didn't have a fluid issue, either. He also said there was no evidence of a leak at the pump and the lines all looked perfect--no corrosion.

Upon replacement and reassembly, the new pump pushed the roof at the normal speed but intermittently groaned excessively. Uh oh....

Having read that a new hydro pump will self-bleed over the first few cycles, we held out hope that the noise would magically disappear.

Now here we are 3 days later. Road into work with the top down, celebrating 60 degree weather. When I went to close the roof, I got the loud groaning noise and the roof stopped halfway up. I had to (gently) pull the roof as I held the button to finish the closing cycle.

Any ideas what the heck is going on here???
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Old 03-27-2020, 06:07 AM
Tom Broderick Tom Broderick is offline
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These are mysterious automobiles, similar problem

Sent from my moto z3 using Tapatalk
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Old 03-27-2020, 10:08 PM
Andyz4 Andyz4 is offline
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When I replaced my top motor and moved it to the trunk, it worked great initially but after a few weeks it started sounding funny and stalling like it had air in the system. Also the hydraulic fluid was low so I thought there was a leak somewhere. But after topping up and cycling a few times it's been fine since, and the oil level has stabilized (easy to check in boot location), so it was just air in the system which was displacing the oil. If you can, have your fluid level checked and corrected (but do not overfill). I believe it is at highest level with top down. Also very important that the oil reservoir is vertical to the pump to eliminate any possibility of air inclusion. Hope this helps.
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Old 03-28-2020, 08:00 AM
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dc_wright dc_wright is offline
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Mein Auto: '06 Z4 3.0si, '11 128CiC
Sounds like you've got some binding in the top frame or you've got an issue in one of the lift cylinders. Lubricate all of the top frame pivot points with white lithium grease and see if that frees up the movement of the top.
Usually with low fluid, you hear the pump motor speed up when it hits an air pocket. If there's no air in the lines or the lift cylinders, the level in the reservoir doesn't change because you're moving fluid from the top of the lift cylinders to the bottom to raise the top and opposite to lower it. That's why there's two hydraulic lines to each of the lift cylinders.
If lubricating the top frame joints doesn't free up the movement, then you may have a bind issue internal to one of the lift cylinders.
You could also have an issue with the release valve in the pump where it's traveling too far in the closed position and partially blocking flow where it's not supposed to.
I had a failure of that type on one of my pumps where the relief valve actually broke into two pieces internal to pump housing. Initially the release was open and the pump just ran free, then the broken piece shifted and completely blocked a flow passage and the pump would only run for a short time and you could hear how labored the motor was.
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Old 04-07-2020, 07:03 PM
dguard8326 dguard8326 is offline
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Following with great interest. My 2007 that I picked up last July, failed in a similar way - the red-blinky light after getting stuck half way up. I tried the simple, easy to get to things rear tray switch. Schwaben scan tool shows a dead short. I removed the top and expected a boat anchor in the driver's side well but instead found a pristine BMW motor and pump. Judging the slight corrosion on the hydraulic lines and the pristine condition of the motor, labels, etc it seems that it was replaced recently.

The top runs through its full range on the garage floor with no problem. Wondering if it might be the CVM module but finding very little on diagnostics
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Old 04-10-2020, 11:55 AM
Kentuckyduck Kentuckyduck is offline
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Thanks everyone for the replies. Your suggestions prompted some experimentation on my end. After a brief hiatus due to a hectic work schedule, I was able to fiddle with the roof yesterday. I discovered something; I just don't know what it means!

The roof had been down for a week. Attempting to raise it brought an immediate groaning noise out of the hydro pump and the roof was slow to move. It came to a halt less than a foot up. I was able to use one hand to help it along as I held the up button with the other. The pump seemed to be straining and continued with its extraordinary groaning noise, which sounded like a clutch slipping. One it got past the apex, I went to the trunk and released the Bowden cable. It moved easily, with just a slight bit of resistance as it released pressure. From that point, I manually brought the roof to a fully closed position, which was achieved without any resistence. I then lowered the roof halfway back. Nice and smooth. Brought it back closed. Nice and smooth. Lowered it completely. Nice and smooth. Opened and closed a half-dozen times. No resistance beyond the weight of the roof. No unusual catching or hitching. Lo and behold, on the 7th try, after a foot-and-a-half it came to an abrupt halt. No grinding, no rubbing, no noise whatsoever. It was as if someone put a firm hand on the roof from the other direction. No noise, no grinding. Just stopped. I had my daughter hold the roof in place while I went back to the trunk. The emergency release cable was still in the "out" position, so I reinserted it and pulled it back out. Lo and behold, there was slight resistance so pressure had clearly built up in the system as I was manually manipulating the roof. Once the pressure was released, it moved forward another foot then hit resistance again. Moved the cable back and forth another time and the release of pressure allowed the roof to completely close.

So I've clearly got a hydraulic pressure issue. I'm guessing I'm not getting the system fully pressurized, which is leading to the groaning/slow operation.But was is the source? I know the system is "self-bleeding" but at what point? There's no evidence of leaking fluid, and the reservoir of the old hydro pump still had fluid in the reservoir. The pump motor doesn't race, which is indicative of air in the system, right?

Others have suggested a faulty hinge. If that was the case, wouldn't the top twist as it raised, with one hinge operating properly and the other sticking?

Thoughts, anyone?
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Old 04-10-2020, 04:42 PM
Stinger22 Stinger22 is offline
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I have sorta the same. Was working had had a new motor and after couple of months it struggled to complete and close and then would not raise or lower. I can hear the motor but not raising or lowering. I went into the trunk and turned the release valve to release pressure on the system and now I just use the key fob or the insert into door and press or turn until I hear the latching motor release or close and just lift or lower manually and the use complete the cycle so the latching motor latches it. It doesn't take much effort and I can do just as quick can even do from inside the car by I usually do from the outside.

Last edited by Stinger22; 04-10-2020 at 04:43 PM.
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2006 z4 3.0i, convertible, hydro pump


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