Elevating roof hydraulic pump repair

[oak]

Hi.

My '07 T5 California has an issue with the elevating roof. Symptoms are that the roof opens fine, but when lowering it only lowers one side. Concluded the problem is with the hydraulic pump unit since when I swapped ram hoses between left and right on the pump side, the symptom moved to the other ram.

Since the pump itself is generating hydraulic flow, it appears that something is wrong with either a canal, restrictor, or some kind of flow balancing mechanism. Given that there are few moving parts, I find it unlikely that anything is actually physically damaged or worn. I reckon it is a fair chance that something is either stuck or clogged due to contamination. Given that the price for a new pump is hideous, I decided to try a partial disassembly and then try to rinse the housing.

Status is that I have disassembled all the parts that can easily be disassembled (some springs/balls and a couple of sliding pistons). Left in the block are some pressed in sleeves, and what looks like calibrated adjustment valves. I have not touched anything of this.

I think I will try to submerge everything in a fluid in an ultrasonic cleaner. That should hopefully loosen any trapped contamination. Then rinse/flush somehow afterward. The question I have is what kind of fluid can be used? Since some parts are left in the block It is difficult to ensure all cleaning fluid is properly flushed out. Ideally, it should be compatible with the hydraulic fluid (which is 150GBP per liter by the way).

Any suggestions?

 

[westfalia]

@TripleBee is at the same stage as you with his old pump.

The question I have is what kind of fluid can be used?

That sure will have to be a special fluid so the seals
don't get damaged.

 

[oak]

Can't really see any seals in the manifold. It seems to be purely metal parts like sleeves, balls. springs, spools.

I was thinking maybe I could place it in normal tap water with a small amount of dishwasher detergent, or maybe a small amount of isopropyl alcohol? This should evaporate and not leave any residue. Could heat the manifold in an oven or similar for a few hours to aid evaporation.

Only think I am sceptical about is that some parts might develop rust.

 

[oak]

A couple of pictures of the current state:

 

[darrenjane]

The photos are helpful. Watching with interest as am in exactly the same position.

 

[westfalia]

Yes, this could be really helpful.
We just need @TripleBee to come with a bit of info.

I thought he had one in with a hydraulic repairers but i might
have got that wrong.

An alcoholic cleaning agent would be my choice as, like you say it will
evaporate.

 

[oak]

I have spent some time trying to understand how the pump/manifold is working. I measured the placement of all the drilled holes in the manifold block and drew it up on a CAD program to create a 3D model. Some of the holes I exact depth or wher it intersect other features, but for many of them the depth is just an educated guess based on what I though makes sense. It might very well be mistakes in the model.

From the 3D model I tried to derive a hydraulic diagram. But I have no knowledge about hydraulics (except for what google has taught me over a few hours of reading). The diagram is a bit messy but and i don't know if it makes sense (I cannot say I fully understand how it is supposed to work. The red arrows are assumed/possible flow path when lowering the roof.)

If anyone with more hydraulic experience would like to take a look and give some feedback I think it would be helpful.

 

[oak]

All the letters in the schematic are referenced to letters to the external ports on the manifold according to the picture below.

Pump in and out port is actually int the center of the big circular feature. I have not drawn that detail.

Here is what I believe the various components are:
A = 3 way Spool valve
B = Ball check valve
C = Pilot operated check valve? Side 1
D = Directional valve for pump flow? Side 1
E = 3-way spool valve
F = Emergency close valve
G = Directional valve for pump flow? Side 2
H = Pilot operated check valve? Side 2
I = Adjustable restrictor or ball check valve
J = Adjustable restrictor or ball check valve
K = Pilot operated check valve
L = Pilot operated check valve
M = Ball check valve
N = Ball check valve
O = suction pipe
P = adjustable restrictor or ball check valve
Q = adjustable restrictor or ball check valve

Ram connection ports:
RF = Right Front
RB = Right Back
LF = Left Front
LB = Left Back

BTW, I have tried cleaning the manifold as good as possible using brake cleaner (isopropyl alcohol basically) in combination with compressed air. I don't know if it helped or not but could not see any obvious debris exiting from anywhere.

 

[szczota81]

All the letters in the schematic are referenced to letters to the external ports on the manifold according to the picture below.

Pump in and out port is actually int the center of the big circular feature. I have not drawn that detail.

Here is what I believe the various components are:
A = 3 way Spool valve
B = Ball check valve
C = Pilot operated check valve? Side 1
D = Directional valve for pump flow? Side 1
E = 3-way spool valve
F = Emergency close valve
G = Directional valve for pump flow? Side 2
H = Pilot operated check valve? Side 2
I = Adjustable restrictor or ball check valve
J = Adjustable restrictor or ball check valve
K = Pilot operated check valve
L = Pilot operated check valve
M = Ball check valve
N = Ball check valve
O = suction pipe
P = adjustable restrictor or ball check valve
Q = adjustable restrictor or ball check valve

Ram connection ports:
RF = Right Front
RB = Right Back
LF = Left Front
LB = Left Back

BTW, I have tried cleaning the manifold as good as possible using brake cleaner (isopropyl alcohol basically) in combination with compressed air. I don't know if it helped or not but could not see any obvious debris exiting from anywhere.

View attachment 60433

Really good job. Two questions - what's the reason of the holes plugged by metal boll
Do you know bleeding procedure of this system? My oil level is changing significantly. There has to be some air.

 

[oak]

Hi.

The plugged holes are due to the manufcturing process. The way to create the internal cavities/channels is to drill them from one of the side and then plug them.

Strange I would get a post in this thread right now, as I just came in from reinstalling my pump after cleaning and reassembly, and IT WORKS . I could not be happier right now.

I did not really find any fault with the pump, so I did not have much hope that it would work really. But it did, so I guess the most likely cause was what I believed from the start, some debris that made one of the spools get stuck. From what I know now after the reverse engineering it was most likely the G spool (ref.the drawing)

When I get some time I will update my schematic and description posted earlier as it contains some mistakes. Hopefully it can prove helpful for others.

Sent fra min SM-G975F via Tapatalk

 

[oak]

Correction, E spool

 

[oak]

Bleeding is (according to Elsawin) done by several open/close cycles with the reservoar fill screw only partially screwed in (so that air can vent).

In my car the reservoar oil level is always higher when roof is closed. If I fill to between min/max while roof is open it will overflow out of the fill screw when lowering (don't ask me how I know). This makes sense as the cylinders are retracting when closing so the total hydraulic volume becomes less forcing more fluid into the reservoar.

 

[szczota81]

Bleeding is (according to Elsawin) done by several open/close cycles with the reservoar fill screw only partially screwed in (so that air can vent).

In my car the reservoar oil level is always higher when roof is closed. If I fill to between min/max while roof is open it will overflow out of the fill screw when lowering (don't ask me how I know). This makes sense as the cylinders are retracting when closing so the total hydraulic volume becomes less forcing more fluid into the reservoar.

That is a secret!!! Reservoir screw has to be screw partially only

Oil level in my Cali is constantly different. Sometimes is almost full sometimes is between min/max.

I started investigation due to roof sagging and I discover really low oil level. Previous owner idiot did something and I know that right ram which is sagging was disconnected by him. I added oil and sagging appear form time to time only right now but there is a problem with oil level. In my opinion there has to be some air on the right system. Am I right?

One more question. How big oil level change is between roof close and open? Is it min in open condition and max in close condition?

Can you send me a CAD model of this pump?

 

[oak]

Attached are pictures of level open vs closed.

System is supposed to "self bleed" so not sure what is going on in your case.

 

[oak]

What format would you like the CAD model in?

 

[szczota81]

Attached are pictures of level open vs closed.

System is supposed to "self bleed" so not sure what is going on in your case.

View attachment 63025

View attachment 63026

Is not too low?? The pump may sucks the air.

 

[oak]

The pickup pipe is almost touching the bottom of reservoar so I approximate it will not suck air until the hydraulic level is about 1 cm.

Sent fra min SM-G975F via Tapatalk

 

[WelshGas]

The pickup pipe is almost touching the bottom of reservoar so I approximate it will not suck air until the hydraulic level is about 1 cm.

Sent fra min SM-G975F via Tapatalk

Just a point of information. I presume the Min/Max marks relate to when the roof is in the Down position?

 

[oak]

Yes that is what I figured out as I tried to fill to between min/max when open and then it overflowed when closing.

But Elsawin does not not say anything about the roof position when checking the level.

Disclaimer, this is just based on observations of my car. For all that I know it might not be typical, but at least it works perfect and I believe what I see makes sense.

Sent fra min SM-G975F via Tapatalk

 

[szczota81]

Ok Then i will bleed my system with partially open bolt.
Because different oil level can be due to air in the system.
i will post the results here.

 

[szczota81]

Done!
Oil level constant and on right level.
Thx for this tip.

 

[oak]

Does your level change open vs closed as mine?

Sent fra min SM-G975F via Tapatalk

 

[szczota81]

Yes Between close / open has to be different.

But before bleeding the oil level was different at close condition between different openings.

 

[snow85]

Hi from Basque Country. I'm new here. He had a problem last weekend with pur roof and VW workshops too busy to solve it. We had changed pistons and roof is now blocked. We think we need to bleed system to unlock it but no idea of which screw we have to touch (we already fullfilled pump). Can anyone help us? Thanks

 

[snow85]

I have spent some time trying to understand how the pump/manifold is working. I measured the placement of all the drilled holes in the manifold block and drew it up on a CAD program to create a 3D model. Some of the holes I exact depth or wher it intersect other features, but for many of them the depth is just an educated guess based on what I though makes sense. It might very well be mistakes in the model.

From the 3D model I tried to derive a hydraulic diagram. But I have no knowledge about hydraulics (except for what google has taught me over a few hours of reading). The diagram is a bit messy but and i don't know if it makes sense (I cannot say I fully understand how it is supposed to work. The red arrows are assumed/possible flow path when lowering the roof.)

If anyone with more hydraulic experience would like to take a look and give some feedback I think it would be helpful.

View attachment 60425
View attachment 60429

View attachment 60430

View attachment 60428

Hi, just wondering to know how I could bleed (take air off) from pump. Dont't know exactly which screw I need to touch. Thanks