Failed vanos test post Beisan

[Cubieman]

* loose pistons in disc side larger holes causing leaky pump.
* tight piston in disc side small holes and cannot moving fast enough.
* new solenoid plate leaking (don't know if it has old or new plate)
* VANOS 2 pistons new seals were twisted when installed causing leak around the seal?

New plate seals were installed and I definitely took my time with installing the main vanos piston seals, although I still may have made a mistake.

So the seals around the 2 vanos pistons have a direct effect on amount of oil pressure produced when measured at the vanos line?

If 100bar is the benchmark then something is seriously wrong here.
I understand it won't be bang on 100bar as the vanos unit has some miles on it (67K), but 60% down is quite substantial.

EDIT:
I recently had an exchange over eBay with a person who rebuilds vanos units and also has a shop that focuses on S54/S62/S85 vehicles, they told me that the pump disc would be item 8 or 9 on a list when troubleshooting a low pressure vanos unit. I am trying to fully understand how this system builds, and more importantly, HOLDS its pressure.

Thanks guys, you have been more than helpful.

[maupineda]

Cold start was right at 100bar, it was slightly higher than 100bar for a brief time period before the vehicle went into closed loop and the idle dropped.
It then got down to 40 bar when up to temperature, wow that's low.
I talked to Raj over the phone and he is pretty confident that my low oil pressure is due to the oil pump disc shaft wearing.
I did not take a pressure reading before disassembly so I cannot say if this is the case or not.
Raj is of the opinion that my oil pressure was the same or likely worse before the new pump disc was installed due to his disc having tighter tolerances in regards to pump cylinders.
He thinks my worse vanos response times are due to the new seals having to get set. He thinks my response times will improve by 200 city miles. I am at about 125 city miles post install at this point.

Raj gave me this gauge and is going to help me out to figure out the root cause. Man, this is super disappointing to me.

Cold:


Getting up to temp: (Settled about here temp wise after 20 min)



After vehicle was up to temp. I hit the throttle of few times to see what the pressure did.

At 1500RPM (DIS test RPM) gauge read approximately 78 bar.

At 2000RPM gauge read about 82 bar

This is exactly my very same case. And we did the same, and we both have low miles, in my case even lower. I am not sold that the shaft is worn out

[maupineda]

* loose pistons in disc side larger holes causing leaky pump.
* tight piston in disc side small holes and cannot moving fast enough.
* new solenoid plate leaking (don't know if it has old or new plate)
* VANOS 2 pistons new seals were twisted when installed causing leak around the seal?

He passes leak test, so the seals must be ok, or DIS would report this as the car would not hold the set camshaft position.

the only other thing would be a leaky restrictor valve.

But they OP was fine before the service, so there is one element left, and that is the disc.

i changed the restrictor valve in a quest for a solution but since then I have not measured the pressure again. But I am 90% sure it will not fix the pressure issue.

[Rosie]

I am trying to fully understand how this system builds, and more importantly, HOLDS its pressure.

Page 22 of this Doc:-

http://www.billswebspace.com/MS54B32TrainingModule.pdf

The pressure is “held” in the accumulator.

[Cubieman]

Page 22 of this Doc:-

http://www.billswebspace.com/MS54B32TrainingModule.pdf

Good reading, thanks!

[sapote]

If the solenoid plate was leaking wouldn't that result in an external leak (if anything)? How would that result in low pressure?

Internal leak, such as solenoid valve leaking.

[Cubieman]

Internal leak, such as solenoid valve leaking.

So a new valvebody would be the only fix for that correct?
Unfortunately from my searches I have found one cannot simply buy the valvebody. You must purchase the valvebody/solenoid pack/regulator as one, quite an expensive endeavor to troubleshoot. But it is what it is and I am bound and determined to fix this.

[sapote]

the only other thing would be a leaky restrictor valve.

You mean the one between VANOS and head? If this valve is leaking then increasing the rpm will not increase the vanos pump pressure much as the engine oil pressure doesn't change much as it has the constant pressure relief valve.

[Shonky]

Maybe the accumulator then? Have you seen this before and after video? It shows the right 100 or so bar but it dies off much quicker when the engine stops before replacement.

Before:

https://youtu.be/CmOuDd525Ys

After:

https://youtu.be/rGqweBmz4bg

[maupineda]

You mean the one between VANOS and head? If this valve is leaking then increasing the rpm will not increase the vanos pump pressure much as the engine oil pressure doesn't change much as it has the constant pressure relief valve.

No, I meant the valve that holds the filter. I should’ve used “pressure regulator valve” term instead. But since his pressure is at 100 when cold, i have second thoughts this can be the solution.

hence why I keep coming back over and over at the pump as the culprit. Before the service he had good numbers, so he more than likely had good pressure.

if you guys read the thread of how to measure pressure you will find there was another case in the UK with the same problem. I messaged that user and he was failing VANOS test also, he ended up buying another used VANOS and that fixed his pressure problem and he was able to pass the test. I am not saying this is the solution for the OP as he was fine to begin with (i don’t buy his VANOS shaft is the issue). If we take the elements from a fishbone for root cause analysis based on how the VANOS creates and holds pressure you have

VANOS valve body - unlikely as he was fine before and passes leak test
Pistons seals - unlikely as he passes leak test rather good
Oil Pump Disc
oil pump shaft - unlikely as the shaft is steel, the disc has what seems a brass bushing. Similar to a rod bearing interface, the bearing goes first (soft), not the crank race (hard)
pressure regulator - unlikely as it keeps pressure at 100 when cold so it seems to be doing it’s job

For slow time response issue

Solenoid pack - is a possibility but not likely, this could be the problem if he had good pressure and still slow times.


If it was me I would start ruling out the easy and “cheap” first

1. try another pack
2. try another pressure regulator

i am dealing with the same issue, and I have done 2 above, just need to stop being lazy and measure again 😝

[maupineda]

Page 22 of this Doc:-

http://www.billswebspace.com/MS54B32TrainingModule.pdf

The pressure is “held” in the accumulator.

The accumulator is more of a capacitor, is a nitrogen filled damper that stores oil at pressure, when the VANOS actuates, pressure inside the VANOS lowers as the oil volume capacity in it increases, the accumulator provides oil at pressure to fill the added volume. It does not play a role in oil pressure capacity from the pump.

[maupineda]

The OP and I have the same setup, low mileage (mine is lower at 43k), and new disc. this is with oil at 95C. in my case my car reaches 80bar at 2k rpm, and I can reach 100 at ~2.8k

the below is with a new pressure regulator valve in place, so now we know that would not be the solution.

If what Beisan is saying is true, and his disc has tighter tolerances, well, that may actually play against the performance of the VANOS instead of improving it.

The OE disc has 9.03mm holes, and the pistons measure 9.00, sot here is a 0.03mm clearance, so that discussion about some pistons being 0.003mm larger, does not matter, 0.003mm would fit in the 0.03 OE clearance several times.

also, FWIW, the ID OE disc measures 26.09, and the shaft is 26.07, so they have 0.02mm clearance, and the shaft and OE disc have zero signs of wear on the races, so again, I don't buy the theory that we have worn out shaft at these low miles

Lastly, the car drives fine, I would lie if I say something does not feel right, but I don't have dyno charts or anything to support feelings with data. in my mind this is why there are so many happy customers, because very few have done before and after testing, and the car drives normal, and someone with a crappy leaky VANOS will for sure see an improvement, but what if I were to drive a brand new S54? who knows LOL

[sapote]

OP, after shut off the engine how long does it take to drop from 40 bar to 20 bar?

[Cubieman]

OP, after shut off the engine how long does it take to drop from 40 bar to 20 bar?

That information I did not record, I do however have a recollection of the oil pressure dropping quickly when a relay was heard clicking about 4-5 seconds max after engine was shut down.

[sapote]

Based on this video it should take about 2 minutes to drop from 40bar to 20 bar. Too short time could mean big leak from the disc (center hole has too much clearance), or bad accumulator. If it is a known good ACC then we can say the leaking disc is the cause.
https://nam3forum.com/forums/forum/m...pressure-tests

The sure way is to remove the disc and check it alone (no pistons riding on roller bearing) on the center shaft: rock the disc around and one should not feel any plays.
To check the pistons fit in the disc: slide the piston in with no spring and it should feel zero plays when rocking the piston radially, then with finger seals off the piston exhaust small hole, pushing the piston in and it will bounce back as compressed air is not leaking. If air is leaking then the hole is too large for the piston. Piston also should slide smooth and freely.