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Discussion Starter · #1 ·
Hi guys.
I hope you’re well,

I have a reoccurring fault with my M5 and it’s doing my head in!

fully rebuilt s85
vanos pump pressures are perfect. Oil is debris free.
When I removed the cam gears they basically fell apart due to my locking tool snapping. So I rebuilt them back together, set everything up as per bmw workshop manuals.

Anyway. All back together, runs lovely but intermittently flags a warning for 271b
Cam timing control exhaust bank 1.

when I watch live data on cold start all values are very similar on live vanos timing. Including the exhaust bank. However after about a minute it bottoms at 117.8 degrees and barely moves over 118.00 indicating a possible mechanical failure. On thevanos test it stops at 0 degree mechanical angle, whereas bank 2 exhaust sticks at 87
951704


I switched solenoids and fault still remains.
do you guys think this is a vanos unit failure or the actual cam gear? Tried vanos bleed tons of times. This is the only thing holding the car back. No knocks,rattles etc.
Timing was checked with oem tools and was within specs after 10 crank rotations

thanks for all of your help!


951703
 

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A tip from Jim comes to mind: are solenoid wires swapped? Green wire (colder) goes to intake, red (hotter) goes to exhaust.
 

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Discussion Starter · #6 ·
Hi guys.
Managed to do a swap over tonight.

fault still persists. Limp mode with the exhaust bank 1 vanos control 271B fault. If the cars running and I try to clear the fault it doesn’t clear. I have to stop, clear the fault on the car, start the car and the faults gone for about another 30 seconds. Within those 30 seconds the timing is the roughly the same as the other bank 2 exhaust.

when I start the car it runs beautifully, no issues at all. When I drive the car it’s perfect. It’s only when I allow the car to come back down to idle it jams at 117-118 degrees on vanos timing on that bank. As soon as it does that and the reduced power mode is active, if I Rev it the values barely move by .2

Just to confirm it’s already had with the rebuild

full bottom end rebuild with new vanos pump and high pressure line
4 x new solenoids
Oil is COMPLETELY clear of all debris. There’s not a single bit of metal in my oil.

Has anyone got any other ideas?

Thank you for your help.
 

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Your plunger seals on your vanos unit could be going. Unfortunately, there is no way to replace it that I know of. Essentially, need a new vanos.

Good vanos:

Bad seals:
 

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if the seal of the actuator is defective he would have a leak but he didn't claim any leak the OP mentioned that the pressure is perfect.
What was the Vanos pressure?.
You can isolate one bank from the other with extra connection to verify a leak on that side but I doubt if there is no leak from the beginning.
Did the Vanos been working before the overhaul?.
Post the fault details.

Monitor this in the morning when the car sat overnight: view Vanos values before startup then start the car, do you see the exhaust cam advance to 95 degree right after startup then as the cold start progress do you see them retard to the value you mentioned 118 or they are stuck at 118 since the beginning of the startup.

When the gears have split and put back together, did you re tensioned the spring back on the exhaust gears, which gears have split, the exhaust, both banks, the intake, or all.

Leak only explain no solenoid movement if no electrical malfunction, or actuator jammed but necessarily leaking.
 
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