[ewicky]

Update: I received some good info about the operation of VANOS and advice on timing over on my post at n54tech.
The timing now appears to be confirmed correct. What's worse is my oil filter looks like a glitter bomb. Engine damage is deeper than I feared!

Hello e90post!
TL;DR I have the valve cover off and am trying to verify the engine timing.
How does one verify the timing if the VANOS actuators can rest the cams a significant amount off in either direction? Is the VANOS supposed to return to a position with spring power? Center, advance, or retard?

Full Story:

I recently purchased an 08.2007 335xi A/T with 111k miles. Clean vehicle history report and, from what I can tell, stock.

After about a month of ownership (and 1000 miles), and running just fine, it suddenly made a few bad noises as I was approaching a stop and the engine struggled to idle for a few seconds before dying. About a mile before the breakdown, the 1/2 engine power/limp home/SES lights were illuminated, though the engine was still running totally smooth (but without boost). I was planning on checking codes once I got home from work but the car died too soon.

I put the car in N and attempted to restart it, but the engine cranking was very labored, and quickly depleted the battery. With a jump, I can crank the engine, but it struggles. It will technically start, but makes noises, sputters and dies. Any throttle input results in an even quicker stall. Loud squeaking noises can be heard that seem to coincide with when combustion has been attempted by the engine (doesn't squeak at first when cranking). I pulled the car up on a flatbed trailer and brought it to the garage.

A compression check shows all cylinders are within about 5% of 105psi, which is lower than the approx. 160-170psi I've gathered the engine should be. This leads me to believe the valve timing is very off, such that the pistons aren't compressing for their full stroke. My fears of a stuck, broken, or crashed valve (it is an interference head design) or of a single blown piston ring seem unlikely since all cylinders have comparable compression.

My current theory is the squeaking noises must have been combustion leaking out of valves that are erroneously open.

VANOS is an obvious suspect, though sifting through many reports of VANOS problems has led me to believe a timing error this bad is not within the operating range of motion of the VANOS system.

I removed the valve cover to do a visual inspection of the VANOS/timing sprockets and timing chain. Nothing alarming, other than the cams aren't synced. This is somewhat to be expected, as the VANOS system can have the cams in any number of positions, within a certain range.

Where I am stuck at now is: With the engine rotated to TDC, how to check the cams' positions after that. According to the BMW repair instructions, you should be able to put the special tool on top of the cams and that means it's timed (the special tool just holds level both cams). However, that doesn't seem to account for the operating range in the VANOS.

Anyone with experience timing the cams, replacing the timing chain, or otherwise gone this deep in the engine please set me straight.

Also, are the VANOS actuators held on by the single stretch bold, and is the rotational torque transferred simple by that? No spline or index? Is it possible for them to slip, then, without the timing chain skipping a link?

Thanks for your time and consideration. Be patient; I'm new! 2nd BMW; 1st post, 1st time this deep in an engine.

PS I've been searching like crazy the last couple days and have read plenty of DIYs, looked at plenty of photos, and have TIS up and running. I'm still stuck. I took a video of what the engine sounded like when attempting to crank, but I'm not sure what the forum-preferred method of uploading a 95MB file is...

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[buly34]

Have you pulled out the VANOS solenoids? I had issues with mine last year and replaced them both. It took care of my problem and hasn't come back since. There are ways to clean them out also, but considering mine were original and the car had 130k I opted to just spend the $ to get a fresh set. Goodluck

[ewicky]

Originally Posted by buly34

Have you pulled out the VANOS solenoids? I had issues with mine last year and replaced them both. It took care of my problem and hasn't come back since. There are ways to clean them out also, but considering mine were original and the car had 130k I opted to just spend the $ to get a fresh set. Goodluck

Thanks for the suggestion.
I have pulled the solenoids. I have no way to know they are good for sure, but when the engine isn't running, I can't see how they could actuate the VANOS. They rely on oil pressure to turn the cams, of which there is essentially none when cranking.

[buly34]

Originally Posted by ewicky

Thanks for the suggestion.
I have pulled the solenoids. I have no way to know they are good for sure, but when the engine isn't running, I can't see how they could actuate the VANOS. They rely on oil pressure to turn the cams, of which there is essentially none when cranking.

I know there are DIY guides on how to clean them out, maybe try that

[Flyboy161]

Try this:
http://5series.net/forums/diy-do-you...enoids-118718/
Cleaning procedure with pics. Apparently in the Bentley manual as well

[flyingspirit55]

Wicky, sorry to revive an old thread, did you get to the bottom of this? Was it vanos or something else?