Anyone want to explain VANOS?

[Sully]

As the title states, I'm really just curious what VANOS is and what makes it different from systems on other cars or non-VANOS cars. Does BMW use it in all their cars or just older ones. So who wants to learn me some knowledge about VANOS.

Also if you know the leading causes of failures of VANOS systems, I would like to know that as well. Does it require regular service maintenance and should it be checked or is it like an ignition coil meaning it just goes when it goes, and then you replace it.

[JustinG]

ITS LIKE VTAK FOR BMWS YO!!!

[Sully]

Why then have I never heard an excuse for wrecking a BMW be, "VANOS kicked in, wound up ass first in ditch"

[CaptainHenreh]

ITS LIKE VTAK FOR BMWS YO!!!

This is exactly correct.

[Mike]

Why then have I never heard an excuse for wrecking a BMW be, "VANOS kicked in, wound up ass first in ditch"

because it's usually broken.

[Jake]

To expand on Justin's oh-so-eloquent statement, it's variable valve timing for BMW motarzz, yo. It was introduced in 1993 on the M50 motor. The M50 is either an M50B25 (pre-93) or an M50B25TU (93+). The "TU" stands for Technical Update and TU = Vanos. From there on out, a lot of their newer motors got Vanos when they were refreshed. The 3/5 series badged as a 2.3L or 2.8L (323, 328, 528) is an M50 that's been tuned slightly differently for more/less power (and by "tune" I mean more than just a chip, tweaked might be better word choice).

I don't know what goes into fixing Vanos, or what the common issues are really. I know there are rebuild kits. Oil runs through the solenoid for it, so I guess there's a seal in there that can need replacing.

[Kaan]

To expand on Justin's oh-so-eloquent statement, it's variable valve timing for BMW motarzz, yo. It was introduced in 1993 on the M50 motor. The M50 is either an M50B25 (pre-93) or an M50B25TU (93+). The "TU" stands for Technical Update and TU = Vanos. From there on out, a lot of their newer motors got Vanos when they were refreshed. The 3/5 series badged as a 2.3L or 2.8L (323, 328, 528) is an M50 that's been tuned slightly differently for more/less power (and by "tune" I mean more than just a chip, tweaked might be better word choice).

I don't know what goes into fixing Vanos, or what the common issues are really. I know there are rebuild kits. Oil runs through the solenoid for it, so I guess there's a seal in there that can need replacing.

Oil/solenoid + variable valve timing? das ist vtec. i hate when vtec is broken!

[D_Eclipse9916]

On the road right now, but theres single vanos and dual vanos. And its very different than hondar VTEC. Its based on advance, not on "dual cam profiles". Your car has single vanos (on one cam, the intake), S54s had dual vanos (both cams). If I get some time tonight when I get to VIR ill write out what it does, but it simply adjusts the cam timing based on load (a combination of throttle position, revs, gear).

Why you need to rebuild it is mostly the seals (bmw rubber/plastic goes brittle), or you can get a build for it to make the gears more "efficient" (less drag), but thats almost useless.

[D_Eclipse9916]

PS- look up the different VTEC.

[Kaan]

On the road right now, but theres single vanos and dual vanos. And its very different than hondar VTEC. Its based on advance, not on "dual cam profiles". Your car has single vanos (on one cam, the intake), S54s had dual vanos (both cams). If I get some time tonight when I get to VIR ill write out what it does, but it simply adjusts the cam timing based on load (a combination of throttle position, revs, gear).

Why you need to rebuild it is mostly the seals (bmw rubber/plastic goes brittle), or you can get a build for it to make the gears more "efficient" (less drag), but thats almost useless.

ok this makes more sense now. honda must have stolen this idea because the "new" i-vtec also does the vanos timing thing as well as the old change the lobes...

If your vanos is broken, it probably just makes the car feel slow. if its "leaky" you just arent getting all the timing.

DJ do you know if the computer is reading this and not throwing in the ignition timing advance due to pressure loss? i'm assuming something is keeping the ignition timing down because if it wasnt, there would be a lot of bmw kids crying about how vtec broke their shit.

[Sully]

If I'm at idle and put pedal to floor I get a huge lag and it almost stalls sometimes, is this my bad coil pack not keeping up or could it be vanos?

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[Kaan]

Check your packs by unplugging them one at a time. If the car idles the same after you unplug one and doesn't die ... That one is probably bad.

[Sully]

Oh I know which coil it is...number 6. I think that's the far back...the problem is its not constant so the unplugging doesn't work, it usually acts up while I'm driving and can't stop to unplug em...the lag happens almost all the time though if I really floor it from idle but maybe it lagged even the day it was new :dunno:

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[Steve85]

Lag is a result of the misfire in cylinders #7 and 8. :p

Seriously though, may want to check fuel pressure. If it's low, clogged filter, failing pump, etc. it may not be able to react quickly to the sudden increase in demand. Someone around the club should probably have a fuel pressure gauge, maybe even available for rent at AZ. Hook it up, tape it the windshield, drive and observe. You can probably even duplicate the load without driving just by power braking. It's another one of those quick and easy tests that eliminates several components at once.

[SlimKlim]

I just dealt with a intermittent bad coil on mine. I'm pretty confident that's the problem you're having, the best way to check is to find someone in town with a 96-99 M3, 328i, an E39, etc etc that you can borrow a single coil out of. Swap it in with the one you suspect is the culprit and take it for a quick test drive. I'd do that before going into the fuel or anything else, just to save you a whole lot of time.

It sort of sneaks up on you when they fail like that. This summer my car was just ever, ever so slightly stuttering when i let the clutch out, or losing power if I gave it a lot of throttle. The last time my coils failed they FAILED. With them 100% dead it was easy to figure it out, but when the one went out this time I was going through the MAF, the ICV valve, searching for vacuum leaks and running down a dozen other dead ends before I came back to the coil.

One indicator of VANOS getting old is a grinding/clacking sound on start up (e39 M5s get this baaaad), or a weird sound returning to idle (mine does this sometimes I think). A car with a bad VANOS unit will feel off, and less powerful, but it should still run okay. Its just not advancing the timing to give you more power higher up in the rpm range. I think mine makes noise but it still runs strong and I can tell when vanos does its magic around 4k. Rebuilding it is on my long, long list of things to do, but not planning on it anytime soon.

[Jake]

Read this post about coils on my friend Jeff's E34. It was like night and day. His motor has Vanos and I have no clue if it works properly or not. Misfiring type of stuff is coil packs. His got progressively worse, much like Joey's.

Also, I wrote this before I diagnosed the problem as coils:

Now for the window regulators (shipping soon) and to diagnose the rough idle and slight misfire while running. She shudders pretty bad around 2,000 rpms, and the idle will randomly dip a few hundred. I kind of remember putting the coils back on the plugs, and seeing one of them look a bit melted. That'll be where I check first.

[Steve85]

Ahhhh...this is a problem that has existed. I thought this was a new issue. AKA - "I know I have bad coil, but now it's also doing this other thing"

Yes, replace known bad parts before diagnosing other driveability issues.

[Sully]

The lag is just something I am curious about with the explanations of VANOS. This thread is to educate me on what my car has. I don't think my VANOS is actually going or gone. I plan to do coils soon.

[SlimKlim]

Yeah I think your VANOS is okay. I've never heard of bad VANOS causing any catastrophic problems, just a slight loss of power, some seepage and some weird noises. I want to rebuild mine eventually, but I have no idea how much is involved. I've seen someone do it on an E39 M5 and it looked like a nightmare, a buddy of mine did it on his M50B28 and said it wasn't too bad.

[CaptainHenreh]

Yeah I think your VANOS is okay. I've never heard of bad VANOS causing any catastrophic problems,

Except when the solenoid disassembles itself inside the cylinder head.