Failed vanos test post Beisan

[eacmen]

How hard did you crank down on the hub bolts? Compression of the spring washer that much seems unlikely.

Do you have a photo of the back side of where the hub bolts thread into? You should be seeing those bolts protrude as much as the gap you’re seeing between the hub and the disc.

[maupineda]

What's the theory??

Hub pressing into beisan disc causing bad shaft/inner hole alignment? I am trying to think of how the hub would come into play in this regard.

So let me first share some dimensions from the oil pump disc and VANOS unit shaft (measurements taken with digital caliper), so they are close and good for reference only, not to assess tolerances, just the base dimension.

OE Disc height is 20.15mm from the center to the machined groove, and 20.00mm there after
OE Disc piston holes are 9.03mm
OE Pistons are 9.00mm
OE Disc ID is 26.09
Pump Shaft OD is 26.07
Pump Shaft height is 20.50mm

Below are some facts we need to keep in mind

Pump disc as installed is bottomed out to the VANOS unit aluminum casting
The pump disc pistons outer race does not bottom out, nor contact the washer retained by the large c-clip, it just "floats" and spins on the roller bearing
There are ~3mm of clearance between the outer race and the washer
The pump piston side holes are centered on the disc relative the the 20.00mm height, not the 20.15mm

So based on the above, and with the VANOS unit out of the car, the disc and piston racer can move along the pump shaft axial axis up to the point the race is stopped by the washer and c-clip.

Now let's see some photos for ease of explanation

Pump Disc Installed, Space between piston outer race and washer / c-clip



Based on the dimensions, with the OE disc, the shaft protrudes 0.35mm.



Another fact I was missing is that inside the piston holes we have the spring cups, and they have much smaller holes than the holes on the shaft, so the entire aperture is not used / needed for the pump to work, so some offset should be fine. I could not accurately measure the location of the shaft holes relative to its height, but my engineering mind tells me by design they should all line up, or have a very minor offset.

Now here comes the thought I had when looking at my car yesterday with the valve cover removed. We all know the exhaust hub and the disc are in contact, this is evidenced by the marks we always see on the OE disc, and the image below



When I looked at my car yesterday I was surprised to see so much separation, as I do remember my car originally was as per the image above. I did not measure the gap, but is in the range of 2-3mm (Beisan Disc).



what the above means is that the disc can move fore / aft (driver perspective) as the pump operates affecting pump efficiency, this also tells me I have way too much preload on those cup washers, as by design, the hub and disc should be in contact.

the above for sure would be a problem for response time, as the cup springs have too much preload and the same pressure will actuate the cams slower. I am not 100% sure how much the above has an impact to the pump efficiency (assuming all else is to spec), but for sure there is an assembly deviation. so it is KEY to be able to torque those hubs to spec, or there is just too much preload, and in the case of the exhaust hub, separation from the disc allowing axial movement.

So perhaps BMW was not as stupid, and the tab sizes and play relative to the disc were necessary to reduce binding forces as the disc is limited by the casting on one side, and the hub on the other. this is just a thought.

Lastly, I firmly believe the unit has an oil jet that provides oil so the steel disc does not eat through the aluminum, and the step in height is just for that oil to flow out. I think this is an important feature.



So, there you have it, it could be that the issue has a tie to an assembly problem due to the lack of proper tools to torque those hubs appropriately,

[sapote]

Could be reflection of light

[Cubieman]

It does look higher than the shaft. You will be able to see if the hub is pressing on the disc or not, and it should not press on.
BTW, I see the hub tabs already "dent" the disc holes just a few miles.

This was a shot before install. Must just be machining marks you see?

[sapote]

Place a thin paper between the hub and disc and pull the paper after the Vanos bolted down. Torn then tight.

[sapote]

It does look higher than the shaft. You will be able to see if the hub is pressing on the disc or not, and it should not press on.
BTW, I see the hub tabs already "dent" the disc holes just a few miles.

[Cubieman]

FWIW here is two shots of my vanos with original disc and beisan disc. I am most likely leading myself into thinking I am seeing the besian disc as thicker based on these photos as I am trying to reach for any possible answer.
It appears that the beisan disc MAY be sticking up beyond the shaft whereas the OE disc is even or "flat" to the shaft.
I know I am reaching here, it will all be disassembled on a bench soon enough..

Edit: Looking at these pictures even closer I think I am simply seeing the inner ring of the beisan disc (different colored material) as a beveled edge right near where the oil drop is. It appears to me to be a beveled edge protruding up past the shaft but upon closer inspection it looks like it could just as well be the inner ring (bushing?) of the disc.

I'll post when I have something more concrete to present, sorry.

[sapote]

Raj sent me a re-drilled OE disc and will be here Monday, I plan to get right after it Monday night after work. The history of the disc being sent is unfortunately unknown to me, I sure wish I had MY disc.

Take a good pic of the inside center hole with the "cleaned circle" before install the disc.

[sapote]

Hub pressing into beisan disc causing bad shaft/inner hole alignment?.

This is possible. If the after market hub is thicker than OE then the tabs could bottom on pump disc pushing it forward (driver view). This would force the disc pistons off the grooved track (on the roller bearing inner race), reducing the pistons working stroke and lower the pump efficiency.

[sapote]

Is NOT the feed valve. Otherwise you would also have low pressure at higher rpm also. That valve rarely fails and is there just to avoid chocking the VANOS pump.

I'm curious why the pump needs the infeed valve. The higher engine oil pressure should help to fill the VANOS pump pistons faster, so why limited the infeed pressure?

One reason I think is that the pump was designed to provide 115 bar at engine rpm range [870 to 8000rpm] at the infeed X psi (X is regulated by the infeed valve to less than the engine Constant Pressure valve). This is to avoid the pump working too hard (loading on the EX cam) at higher engine rpm for nothing as the exceed pressure will be relieved by the 115bar valve anyway.

[Cubieman]

I changed my spare VANOS seals today and assembled the disc. I also had to change the valve cover gasket as it was leaking and while doing so I noticed a very interesting difference of how the hub is placed relatively to the disc, which is very different to how it was before I did the VANOS rebuild. This drove me to a different theory on why I may have low pressure!!

What's the theory??

Hub pressing into beisan disc causing bad shaft/inner hole alignment? I am trying to think of how the hub would come into play in this regard.

[maupineda]

I changed my spare VANOS seals today and assembled the disc. I also had to change the valve cover gasket as it was leaking and while doing so I noticed a very interesting difference of how the hub is placed relatively to the disc, which is very different to how it was before I did the VANOS rebuild. This drove me to a different theory on why I may have low pressure!!

[maupineda]

I want to to get it working and not take it apart again if possible. I will try to make myself change only the disc first as it is important to find root cause.

Raj is very sure that the OE disc will not change anything except to make pressure possibly even lower and response times worse.

Is NOT the feed valve. Otherwise you would also have low pressure at higher rpm also. That valve rarely fails and is there just to avoid chocking the VANOS pump.

[Cubieman]

So are you going to install a used good OEM disc?

Raj sent me a re-drilled OE disc and will be here Monday, I plan to get right after it Monday night after work. The history of the disc being sent is unfortunately unknown to me, I sure wish I had MY disc.

[sapote]

So are you going to install a used good OEM disc?