540i P1346 and P1347 cyl 3 misfire after timing chain guides + vanos

[geargrinder]

Bummer Joe, just catching up on this thread. Holidays = sporadic and erratic forum monitoring.

Did you wash your valve covers thoroughly after they came back from the powder coater? Gotta make sure no abrasive is left from blasting on the undersides! I really doubt that'd manifest as seizing a valve guide, but just sayin'. Gotta do that.

Was the flywheel lock-pin in the entire time the chain was off? Was engine ever turned at all while the chains were out?

[joekitch]

yup, CW left the flywheel lock in there and the cam locks on while the he was doing the vanos. during that time (about a week) is when i did the valley pan gasket bit.
and again we timed the engine once he came back and did the various timing checks after the chain went back on. I don't really understand how it -could- have gotten out of time

[JimLev]

IT'S OUT OF TIME?
Did I miss something, how did you determine that?

[joekitch]

i mean, if the valve is actually bent, i can't think of any other cause aside from being out of time that makes much sense.
thing is i don't understand how it could have possibly gotten out of time. Heck, CW left a zip tie on the left side chain guide when he took the tensioner tool off so it'd keep the chain from skipping a tooth on the crank while i put the engine back together, and i took that zip tie off only right before putting the actual tensioner piston thing in.

One thing to note is i recorded most of the entire procedure, i think i'll go back and review the footage around putting the chain tensioner piston back in, as well as the footage right as i was starting the car, look for the chain possibly skipping a tooth or bent valve sounds. i'm certain there were no sounds of that but eh, recording > eyewitness testimony?

[Mach540]

Just thought of a goofy idea you could try.

Rotate the engine about halfway back on the compression stroke and feed a bunch of rope down into the cylinder. Then turn it to compress the rope........ maybe, just maybe, you could push the exhaust valve back up if it is just a stuck valve.
Might be enough to get it working again.

I've done this to hold valves in place whilst changing seals.

What's the chances of a broken valve spring not bringing the valve all the way back up? Anybody seen that before??

[joekitch]

oh yeah the rope trick, i forgot about that !
ill probably need to pick up some actual cotton rope , i imagine nylon stuff will turn into stiff stuff in the cold and not coil .
not to mention it might work well for soaking up oil too, yay .

im also going to try doing quick blasts of full pressure air through the leakdown hose to hopefully blast sludge or obstruction out of the exhaust valve into the exhaust to let it close

[geargrinder]

Its almost impossible to 'skip a tooth' on these things, even with some slack. What happens is you CAN have slack that isn't pulled over to the tensioner side, and then when the 'infinitely adjustable' sprocket and VANOS are tightened they won't be truly fully in time (hence the recommend to 'turn 720 and re-check multiple times ') but the guys who say "it SKIPPED TEETH" are talking bollocks IMO. Short of an impossibly freakish broken/worn parts situation that can't happen, as proved by the way you need to slide the sprockets on with the chain on etc. etc. and can't just loop the chain on with the tensioner out...

I gotta say... knowing the expertise help you got on this job, and that all parts are new etc. and engine ran well beforehand... bit of a head-scratcher.

[StRaNgEdAyS]

If it was a timing issue that's bent the valve, all the exhaust valves on that bank would be similarly bent

Sent from my G8141 using Tapatalk

[joekitch]

If it was a timing issue that's bent the valve, all the exhaust valves on that bank would be similarly bent

that was my thought as well, but i remember reading a few instances of a single bent valve on one cylinder happening occasionally due to chain issues
or i might have misread

I gotta say... knowing the expertise help you got on this job, and that all parts are new etc. and engine ran well beforehand... bit of a head-scratcher.

i know right? i should be really mad about all this, considering how long it took me to get the whole thing done, but as this new evidence rolls in i'm much more baffled than anything.

i'll going to dry the piston dome tonight, look for valve strike marks, and then do the rope trick. wish me luck ?

[joekitch]

ok yeah just reviewed my go pro footage of both the first crank without the fuel pump, and the first actual start.
absolutely no sounds to indicate a bent valve, no metal on metal contact noise or clanging, and the misfire began immediately as it began to ran so it didn't develop afterwards

its looking more and more like this rope trick to shove the valve back into a seal is going to work

[joekitch]

this just gets weirder by the second
did the rope trick...didn't work, cylinder still has no compression. i actually really tried to jam the rope in there and use a breaker bar on the engine bolt to really push the rope up
in fact i did it twice...
still, didn't work

HOWEVER the rope did a really good job of soaking up oil, so much so that i did another piston dome inspection and found pretty much no signs of valve damage.
i mean, i know what valve damage looks like, and nothing on this piston looks like that (the cutouts with the little bit of oil in them are the exhaust valve cutouts)

cylinder 3 piston dome dry-ish.jpg

my last ditch effort will be to put the engine all back together and run rislone through it as well as some seafoam through the vacuum line that comes off the intake boot
that line being #8 in this image

71DE6GtUwDL._SX355_.jpg

just do that for a while, use the whole seafoam bottle and all the rislone and let it run at temp.
after that, do the rope trick one last time
and if that doesn't work.....just pull the darn cylinder head because at that point it'll just be like screw it

[joekitch]

and here's the first start from almost two weeks ago now.



i'm just not hearing any sounds of valves in distress

[geargrinder]

that was my thought as well, but i remember reading a few instances of a single bent valve on one cylinder happening occasionally

Thats usually from a hand-crank whack I think. Somebody tries to turn motor over with chain off or out of whack and it hits resistance, they push a bit harder, bend the one but not the others.

[Mach540]

How flexible is your bore scope? Can you drop the piston down some, tie a string to the end of the scope, slide it in and pull on the string to get the scope to look straight back at the valves??

[joekitch]

How flexible is your bore scope? Can you drop the piston down some, tie a string to the end of the scope, slide it in and pull on the string to get the scope to look straight back at the valves??

it's more a question of borescope diameter. folded back on itself it's too wide in diameter to even get through the spark plug hole
although one crazy idea would be to drop it through the fuel injector hole with the intake valves at full open and push the scope past the valve opening with the mirror attachment, might juuuust be able to see the valves bottom-on

however that's all moot by now, i just did a full rislone AND seafoam treatment (bottle of each, damn that seafoam smokes) and there was no change in behavior. cylinder 3 stayed dead weight the entire time.
also there's a nice ticking sound along with it too, sounds an awful lot like other youtube videos of engines with bent valves running

it's really audible at 0:17

[JimLev]

Your scope won't fit thru an open intake valve.
Do what Mach said thru the plug hole, should work.
Last resort, pull the exhaust manifold off and look in that way.

[joekitch]

Your scope won't fit thru an open intake valve.
Do what Mach said thru the plug hole, should work.
Last resort, pull the exhaust manifold off and look in that way.

yeah, exhaust manifold's gotta come off for a head removal anyway, might as well peek while i'm there.
interestingly, i tried to loosen a few of the nuts this evening, they're really hard to get to with a wrench and i was expecting them to be seized hard but they actually turn pretty easily. huh

[JimLev]

I used a 3/8' ratchet and a short extension. Might have got at a few from under the car.

[Mach540]

it's more a question of borescope diameter. folded back on itself it's too wide in diameter to even get through the spark plug

Don't think you understand what I meant.

Put the scope into the cylinder, and THEN pull on the string to fold the scope over. Should be enough room inside the cylinder to bend around.

[joekitch]

Don't think you understand what I meant.

Put the scope into the cylinder, and THEN pull on the string to fold the scope over. Should be enough room inside the cylinder to bend around.

ooooh, an interesting plan...
i'll have to use some strong tape for the string, and some strong string, it's one of those semi-rigid neck borescopes so it takes some force to bend

[joekitch]

man, taking off those exhaust nuts was a pain, and the studs came off with the nuts on cyl 4
also the downpipe nuts were so seized i had to stop for the day and let them soak in PB.
with the header out of the way i can do more borescoping, and feel which valve is leaking air by hand with a leakdown by just putting my finger over the seated valve through the exhaust port

[JimLev]

If you do remove the head with the cams installed you'll need to rotate the cams to get your socket down to the head bolts. That's what those rounded notches are for on the cam between the lobes.

[joekitch]

exhaust header off
put my really bright work light down into the spark plug hole while looking at the exhaust valves, could see some light peeking through BOTH valves that i couldn't see on cyl 2 valves
leakdown while sticking my hands in the hole was inconclusive about which valve was leaking, so it's probably both of them

so yeah, looks like the two valves were bent super super slightly, just enough to zero compression. weird

[Mach540]

Fudge!!

Well, at least you now know.......

Now use a vice grips to rotate 'em 180 degrees and bump them again... That'd oughtta straighten 'em out.

[joekitch]

this is actually pretty concerning.
thing is, if the timing was PERFECT and it still bent a valve. how do i know it won't just bend whatever new valves i put in there? what's causing the bend? are CW's timing tools off?