Z4 Roof issue

[celticrider]

So after 20 minutes, bypassed, roof dropped to 1 .5 “ from the plastic cover where the lock was.
Another 15 minutes any it’s about 1 .25”
Keep in mind it’s about 40 degrees,oil thicker?
By the way I’m using CHF 11S oil
Was recommended by the rebuilder of the cylinders.
I’ll send some pics little later

[celticrider]

Found one thing holding the roof up
1/2 or so.
The socket I had in the shelf switch was rubbing on the window not letting it settle flat.
Not it is laying perfectly flat and the gap at the roof to plastic is 1” now!
Gaining!!!

[tekoo]

Regarding the baseline hydraulic pressure at idle; most factors influencing this idle pressure are constant except for 3 factors that are modifiable;

1- Hydraulic fluid viscosity
2- Counter resistance the roof is facing during opening and closure
3- Relief valve pressure settings

Relief valves in the hydraulic system act like a fuse would in the electrical system. Relief valves allow the pressure to escape out of the hydraulic system when it reaches a maximum predetermined safety level. This prevents bursting of the different hydraulic components (e.g hydraulic lines, cylinder seals ...etc) but more importantly prevents severe damage if a human body part or object gets entrapped or caught in the roof during pump operation. Relief valve safety pressure can be set close or higher from the normal maximum pump operational/idle pressure depending on the amount of risk someone is willing to take. Setting the relief pressure too high increases the baseline hydraulic pressure at idle and may cause the cylinders/hinges to be springy. On the other hand, setting the relief pressure to low causes the pressure to escape at normal pump operational/idle pressures and compromises the pump/cylinder function!
For safety reasons, all hydropneumatics systems have relief valves. The relief valves have to be located somewhere where 1- the released hydraulic fluid/pressure can return to main reservoir to prevent spillage/loss of fluid and 2-the main input and output fluid channels are covered and should be oriented in a direct ion that would aid in easy gas release during pump operation (vertical).

The only structures that fit all these pressure relief valve criteria in the Z4 E85 roof pump are the 2 valves we see in the hydraulic fluid reservoir! The only way to reset these valves if something alters their screws from factory spec is via using a pressure gauge while the pump is running (not an easy task)! This is why I stress against touching these valves unless its a last resort before throwing the pump in trash! When you alter these valves you are messing up with the 1- maximum allowed SAFETY pressure in the whole hydraulic system, 2-safety of human beings during pump operation; 3-the safety/integrity of various hydraulic system components even at idle!

[tekoo]

In regards to hydraulic fluid viscosity and the difference between BMW factory recommended Febi fluid (BMW # 54340394395) and Builder recommended Pentosin CHF 11s fluid:

You will have to compare the viscosity and other physical characteristics in product datasheet
http://www.pentosin.net/specsheets/pentosin_chf_11s.pdf
https://partsfinder.bilsteingroup.co...db02615_GB.PDF

In regards to counter resistance against roof mechanism, we will have to inspect and eliminate any restrictions/blockages that could interfere with a smooth movement of the roof while performing its functions!

[tekoo]

Found one thing holding the roof up
1/2 or so.
The socket I had in the shelf switch was rubbing on the window not letting it settle flat.
Not it is laying perfectly flat and the gap at the roof to plastic is 1” now!
Gaining!!!

Good work! Keep looking we are not too far!

[celticrider]

Where did you locate that information on the valve?
I scoured the internet and other than the post from the UK that was it.
That’s wild. If it comes to it later, any way to get the operating pressure?
I have gauges for testing.
I wouldn’t touch them unless I knew the specs, and like you said as a very last resort.
The lowering cylcle definitely appears weaker and has since we’ve owned it.
It takes twice as much power to lift than lower.
You can attest to that when you move the roof with the bypass engaged.

[tekoo]

Where did you locate that information on the valve?
I scoured the internet and other than the post from the UK that was it.
That’s wild. If it comes to it later, any way to get the operating pressure?
I have gauges for testing.
I wouldn’t touch them unless I knew the specs, and like you said as a very last resort.
The lowering cylcle definitely appears weaker and has since we’ve owned it.
It takes twice as much power to lift than lower.
You can attest to that when you move the roof with the bypass engaged.

like I said in my prior post; pressure relief valves are the equivalent of fuses in the electrical system. It is a very well know concept. You can google pressure relief valves if you want more info!

The design information for our Z4 hydraulic pump is no where to be found online and everyone is confused and transmitting wrong info.

My conclusion is based on my personal evidence-based approach, logic and limited testing! However I have a very high confidence interval!

Just the fact that the convertible top module is programmed not to allow motor/pump operation if the vehicle is not stationary is the biggest evidence these are pressure relief valves!

If the vehicle moves with roof halfway closed/open and catching/hitting against wind ->significantly elevated counter-resistance to the hinges/hydraulic system -> significantly elevated hydraulic system operational pressure ->Operational pressure approaches the upper max/safety limit (preset relief pressure reached and perhaps exceeded) -> hydraulic fluid squirts out of the 2 valves and keeps squirting (as long as the vehicle movement /abnormally high resistance is maintained) ->hydraulic fluid completely drains out of the system overfloats and either leaks out or bursts the reservoir!
This is why BMW prohibited roof operation while vehicle is moving!

If significantly high pressure levels where rapidly achieved prior to complete bleed of the fluid out of the system -> hydraulic lines can reach burst pressure (~750 PSI) and burst or cylinder seals balloon and burst!

[tekoo]

If you would like to test this theory; connect direct 12 volt power to the motor harness (bypassing the vehicle's computer/safety control) while driving against wind or while an object is positioned in the field of the moving roof mechanism (tree branch or something) and watch the fluid reservoir getting filled with fluid!


As you can see, when I object to something I usually have pretty good logic/reasoning behind it! Not that I have to be correct as it may appear!

[celticrider]

XxAttachment 640868Attachment 640866Attachment 640869Attachment 640867these are pics of the roof in stowage position when it normally goes down electrically. Other than the front of the roof definitely being higher than yours,I’m thinking the rear doesn’t look much different. The glass sits perfectly flat
it never took much effort to get from here to when it locked when we were using it last summer,basically if you turned around in the seat and pushed with your palm it would lock. Not right but that’s what it worked like. So my question if the pressure was low on one valve causing it to be slow to raise of windshield,could it cause it to be too slow to reach the lock? Having said that you say the roof should go to the lock position on its own without power.

[celticrider]

I have lots of experience in relief valves,only on larger scale.
I’ve been a heavy equipment mechanic for 35 yrs, but on large equipment, 100 GPM and 10,000 PSI ,same principle however
No hydraulic system operates without a relief valve.
It is the only protection for the whole system.
However, my experience has always said not to adjust blindly.
Having said that, it is a adjustment screw that could have backed out or not set right from the factory.

[celticrider]

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These are the pics from my earlier posts for some reason went on as attachments and wouldn’t open.

[tekoo]

XxAttachment 640868Attachment 640866Attachment 640869Attachment 640867these are pics of the roof in stowage position when it normally goes down electrically. Other than the front of the roof definitely being higher than yours,I’m thinking the rear doesn’t look much different. The glass sits perfectly flat
it never took much effort to get from here to when it locked when we were using it last summer,basically if you turned around in the seat and pushed with your palm it would lock. Not right but that’s what it worked like. So my question if the pressure was low on one valve causing it to be slow to raise of windshield,could it cause it to be too slow to reach the lock? Having said that you say the roof should go to the lock position on its own without power.

Before you start getting excited about valves and confuse yourself please understand there are 3 different pressures:

a)Idle baseline pressure when motor is not running
b)operational pressure aka motor/pump running pressure
c)Maximum/safety pressure aka relief pressure

In the same hydraulic system, each one of these pressures has a different value.
The idle pressure is predetermined by all the constants (hydraulic line elasticity & recoil pressure, cylinder seal recoil, roof mechanism resistance, roof weight, hydraulic fluid viscosity, total length of the hydraulic lines, narrowest caliber of the connectors/banjo bolts/fittings ..etc).
The operational pressure is usually the sum of the idle pressure + the max pump flow pressure + if any; additional pressure encountered from increased counter-resistance during operation
The relief pressure is THE ONLY pressure that is settable by these valves and does not affect the operational and baseline/idle pressure in any way UNLESS the set value of the relief pressure approaches and overlaps with the operational/idle pressure value that are determined by the other circuit variables. In which case the pump would be venting/leaking out the fluid through the relief valves even at low non-threating pressure levels. This would be pretty dysfunctional and inconvenient as you can imagine.

Logic tells us;
1-the pump idle and normal operational pressures have to be within range of the normal hydraulic line pressure ratings (i.e. within ~200 PSI limit in the Z4 E85 specifically).
2-the relief pressure value has to be lower that the hydraulic line burst pressure (less than ~750 PSI in the Z4 E85 specifically).
3-the relief pressure can not overlap or be too close to the normal operational pressure to prevent unnecessary fluid leak and system dysfunction.
4-the relief pressure has to be set at a value that would allow room for occasional transient non-life threatening increase in operational pressure (e.g power supply fluctuations, changes in roof weight during operation rain/snow/wind, mechanical frame/fabric abnormalities and resistance etc.).
5-Relief pressure can not be set too close to the hydraulic line burst pressure either to allow safety window for hydraulic line quality variations and decaying of hydraulic lines as vehicle ages.

Conclusion:
1-Relief pressure has to be set somewhere between 200 nd 750 PSI but perhaps somewhere around 550-650 PSI
2-Relief pressure only affects the circuit when safety limit is approached
3-Relief pressure resetting can be a remedy for abnormally elevated operational/idle pressure but not for low overall operational/idle system pressure Unless various burst pressures are not of concern or the maximum settable relief pressure is still lower than the lowest burst pressure in the system).
4-Relief pressure set value is a sensitive and critical value that has to be very accurately calculated and calibrated!

Hope this makes understanding the relief valves more clear!

[tekoo]

B2B5A8CF-20A1-4F67-90D9-0242A3DE32CC.jpg4A624CB2-BF98-4414-B83A-4459591DC5C8.jpg7EAE9FF5-74AC-4EA3-80F0-0D4851D0A8F2.jpg1C4D490C-A424-4196-987D-5936834B7425.jpg

This looks way better than before. I think at this level there is really little if any room for improvement. I mean we are talking about 1 cm or 1/2 inch maybe difference between your roof and mine now.

2 things I have noticed from these images:

1-The link circled in the image below is what seems to be affecting the current front roof height I doubt if this is adjustable. All we can do is perhaps clean these joints/links and lube them to make sure they extend and bend to max allowed range.

roof 5.jpg

2-The rear roof clearance with the trunk body is much smaller than mine. It's almost as if the roof is pushed back as a unit towards the rear of the vehicle.

[celticrider]

I am assuming those pressures are a guess as you said there is no available information.
One way to test is to test the know circuit that is working and compare to the one that isn’t

[celticrider]

Any recommendations for lube.
There is white grease in the joints now.

[tekoo]

I have lots of experience in relief valves,only on larger scale.
I’ve been a heavy equipment mechanic for 35 yrs, but on large equipment, 100 GPM and 10,000 PSI ,same principle however
No hydraulic system operates without a relief valve.
It is the only protection for the whole system.
However, my experience has always said not to adjust blindly.
Having said that, it is a adjustment screw that could have backed out or not set right from the factory.

EXACTLY the point that I was referring to in the above posts and in the past when I mentioned the guys from the other forum don't understand/realize the risks or even functions of these valves.

Testing and adjusting these valves requires not just a pressure gauge but also progressively increased pressure and intact hydraulic fluid circuit. Something that can not be achieved easily (if you take the reservoir cover off to access the valves you would have no hydraulic fluid in the system to test the pressure! not to mention how difficult it will be to progressively increase pump pressure above normal operational values!)

I can assure you none of the average Z4 owners would be able to perform these tests/resets at home without additional professional tools and creative testing environment! So all the B.S. you hear/read about 'I have done lots of these valves' is either invalid or a disaster if true and was performed blindly!

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I am assuming those pressures are a guess as you said there is no available information.
One way to test is to test the know circuit that is working and compare to the one that isn’t

The Z4 hydraulic lines pressures (operational and burst pressures) are accurate and confirmed info based on the hydraulic line diameter and pressure ratings (stamped on the hydraulic lines).

The relief pressure value range is my personal estimate!

[tekoo]

Any recommendations for lube.
There is white grease in the joints now.

I would 1) clean the joints well, 2)use a spray lubricant first so it can reach and penetrate the difficult to access areas, 3) follow that with silicone grease or any similar grease for long-term effect and to prevent drying/evaporation

[celticrider]

Ok.
I’ll get the hinge joints done 1st and then tackle the valves later.
The only way to safely do it is out of the car and use the working functional side as the proper pressure. We know that the lift side works properly.
It’ll mean some making of test fittings and removal of the reservoir, adjust and refill every test. I’ve did worse, but not on my own equipment!

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I’ll post what happens, if works, maybe save someone a pump replacement.
Thanks again for all your help and patience

[tekoo]

Please keep in mind If the pressure relief valves where the culprit in your pump the pump would have not responded to banjo bolt swap or any other interventions short of adjusting the valve pressure!

I would leave the valves out of this until the pump is completely dysfunctional and changing the banjo bolts, cleaning the pump and cleaning the joints have failed.

You already have a working pump 99% of time. I am hoping replacing the banjo bolts and a thorough clean to the pump centrifugal part will suffice!

[tekoo]

Also the pressure in your system is anything but low; as evident by the springy roof and the 15-20 minutes it takes for roof to drop with gravity.

Turning the screw of the pressure valves clockwise compresses the spring of the valve elevating the relief pressure set point and vice versa.

Now if you recall the screw in our pump are set closer to the very outer/superficial end of the valve! So basically close to the lowest relief pressure set point possible! In other words there is only room for increasing the relief pressure setting which is probably the opposite of what you would want to achieve!

[tekoo]

My theory is that one of your banjo bolts was over torqued blocking its entry hole against inner pump frame-> elevating the operational pressure to approach the relief valve preset pressure—> fluid was being diverted back into reservoir (via the relief valve) instead of moving through the banjo bolt to the hydraulic line. So yes the valve was involved but not because there is a problem with it. It was involved because there was a fluid obstruction in the system!

[celticrider]

Yes valve will be an absolute last resort

[tekoo]

Also keep in mind that eventhough we have knowledge of the hydraulic line functional and burst pressures, we have no idea about the equivalent pressure limits of other circuit components (valves, seals, nozzles ..etc). We also lack any info about the motor power and the load it is able to handle!

[tekoo]

By the way; when you lubricate the links be careful not to let the fluid drip on the fabric. It will be very difficult to clean and can cause permanent color changes/blotches. Perhaps you should just stick with the grease and avoid the liquid lube completely!

[tekoo]

In regards to the roof stowage/ front roof height, there is only one additional BMW recommended solution left to consider. However I am not sure if it is worth a shot as it involves altering with the factory pre-set main pillar height (see image). It is also not clear how this affects the roof stowage. The only reasonable explanation is that it would create more clearance at the main link by sliding the frame slightly away from link? Or perhaps it could pull the whole roof more forward and away from trunk to increase rear clearance with the trunk if needed?

roof 3.JPG

If you decide to play with it; I strongly encourage you to mark the current position/distances so you can reverse the action if needed

roof5.JPG