Timing chain noise/crankshaft will not fully rotate - Update: Success! mostly...

[evbrad2002]

Son was driving car on a rather long trip when he started intermittently losing power and getting some shuddering at highway speed.  Thought it was a bad plug or ignition coil so pressed on.  Upon arrival at my house noticed a rather loud timing chain noise.  Popped in a new tensioner the next day to no avail, still had the timing case noise.

While trying to sort out the timing chain noise, pulled valve cover (removed plugs) and started off rotating the crankshaft clockwise to get to TDC to check timing marks.  Made a full turn plus with no issues.  However, I realized that I was looking for the alignment arrows on the gears in the wrong place so rotated past TDC about 1/3 turn.  I then stupidly rotated counterclockwise to get back to TDC and  moved past a minor bind (chain did buckle slightly - moved a tooth?), then nothing, full stop.  Then attempted to turn clockwise but only made it about a 1/4 turn before hitting another full stop.

So, am I fully screwed here?  Suggestions?  Any good sources for used M42's?

[DesktopDave]

I'd be hopeful that you didn't bend anything.  You might be mistimed now, though.

I'd pull both front chain cases.  Definitely check that lower idler gear - it's problematic.  The later M42 and M44 replaced it with a deflection rail.

I have a used M42 sitting on my driveway, LOL.  I was planning on rebuilding it to install in my sedan.

[evbrad2002]

Thanks for your quick reply.  I was intending to use the starter method to free the crankshaft bolt.  That's out now.  So what are your suggestions for getting the crankshaft bolt removed?  Thanks!

[DesktopDave]

You can still use the starter method.  I'd remove the cams to ensure that the valves are all closed.  Then the only thing you'd need to worry about is the cam chain...and the small bit of rotation from the starter bump likely won't cause any trouble.

[evbrad2002]

Wow, removing cams sounds daunting.  Doing the timing guides is new territory for me as it is.  can you direct me to a quality DIY for cam removal/install that will keep me out of trouble?  Again, thanks for your help!

[DesktopDave]

Wow, removing cams sounds daunting.  Doing the timing guides is new territory for me as it is.  can you direct me to a quality DIY for cam removal/install that will keep me out of trouble?  Again, thanks for your help!

I haven't done it on an M42, couldn't find a pictorial guide either.  Remove the cyl cover, it should be pretty obvious.  IIRC, you just unbolt the gears, then remove the bolts from the cam bearing caps and lift the cams out.  They sit in alu carriers that also seem easy to remove.  Don't mix up the caps once you have them off - it's best if the caps and cams stay matched.  The bearings wear together to make a perfect match.

If you're even remotely nervous, buy or download the Bentley BMW E36 manual, they detail the whole procedure.  The E30 manual is good too, but I've heard it doesn't have a section on the M42...only the M10 and M20 motors.  They also have a table that specs torque values for all those fasteners, very useful.  Money well spent.

[evbrad2002]

Ahhh, yes!  I actually have a Bentley E36 Manual that I purchased years ago for an M3 I had.  Totally forgot the M42 was included in this manual.  Thanks!  I'm concerned I may have buggered the engine anyway so nothing really to lose in diving in with manual in hand...might even learn something...

[DesktopDave]

Ahhh, yes!  I actually have a Bentley E36 Manual that I purchased years ago for an M3 I had.  Totally forgot the M42 was included in this manual.  Thanks!  I'm concerned I may have buggered the engine anyway so nothing really to lose in diving in with manual in hand...might even learn something...

That's the spirit!

[mabeer]

Sorry to hear of your troubles.  You've got to be careful with the cams.  They are hollow grinds and brittle.  The valve springs exert quite a bit of pressure and if done incorrectly you run the risk of fragging your cam.  The Bentley talks about a special tool.  I found this youtube video to be very helpful when we pulled ours.  It's not an M42 but it's still apllicable to us.   http://www.youtube.com/watch?v=12CTLgtaV9A

I followed the video and it's a piece of cake really, not bad at all.

Let's hope it's just an idler pulley or chain rail that gummed up the works.  I don't have a spare engine but I do have cams and crank in very good condition and some new VW lifters if you need anything.

[evbrad2002]

Sorry to hear of your troubles.  You've got to be careful with the cams.  They are hollow grinds and brittle.  The valve springs exert quite a bit of pressure and if done incorrectly you run the risk of fragging your cam.  The Bentley talks about a special tool.  I found this youtube video to be very helpful when we pulled ours.  It's not an M42 but it's still apllicable to us.   http://www.youtube.com/watch?v=12CTLgtaV9A

I followed the video and it's a piece of cake really, not bad at all.

Let's hope it's just an idler pulley or chain rail that gummed up the works.  I don't have a spare engine but I do have cams and crank in very good condition and some new VW lifters if you need anything.

Thanks for your help!  Yes, hoping for the idler pulley or chain rail, which brings up a question...if the crank is not turning due to idler pulley or chain rail, then crank's still going to have a stop in it even with the cams out, right?  So would not be able to loosen the crank bolt using the power bar/starter method.  Suggestions?

[mabeer]

Maybe  this http://www.pelicanparts.com/cgi-bin/smart/more_info.cgi?pn=TOL-3034-2&catalog_description=&Crank%2520Pulley%2520Securing%2520Tool%252C%2520For%2520M%2532%2530%252C%2520M%2534%2532%2520and%2520M%2535%2530%2520Engines%252C%2520Each%2520%2520

and then a lever Archemidis would be proud of.

If you have access to one of those inspection scopes take a look around the idler sprocket and crank sprocket (my kids named their cats sprocket and crank long ago but I digress) and see if there's something wedged  in there that could be fiddled out with one of those grabber things.

***disclaimer*** I've only got my engine apart and not back together yet so take my rookie advice as just that.  There are plenty of wrenchers with much more experience that will come to your aid.

[evbrad2002]

what position should the crankshaft ideally be in to ensure pistons are lowered to avoid contact with the valves?  That is, where should the little notch on the tooth be in relation to the timing mark arrow near the oil filter housing?

Also, did you find the "sweet spot" for the cam behaved the same way as that shown in the video for the M3?  And, did you have a helper hold the camshaft still or were you able to do that without help?

[bmwman91]

When the arrow in the oil filter housing is pointing at the notch in the toothed crank wheel, things are at TDC. As long as you turn the crank ~90 degrees from there, the pistons will be at the middle of their travel and well away from the valves.

One of two things is going on here.
a) When you rotated the crank CCW, the chain loosened and jumped some number of teeth when it got bound up on the (stupid) lower plastic guide. The "stop" you feel is pistons touching valves. It generally takes 2+ teeth jumped to get to this, at least in my experience.
b) When you rotated the crank CCW, the chain loosened and is getting all bound up on the (stupid) lower plastic guide. Is the tensioner piston still installed? Basically, you never ever really want to rotate the crank with that tensioner piston out. Turning things CCW with it out is an even bigger no-no.

You can try taking the cam sprockets off and rotating the cams so that no valves are fully opened. That might buy you enough clearance to turn the crank further and try the starter trick on the damper bolt. You'll probably also need to try pulling up on the chain to get it properly engaged with the crank sprocket if it is binding in the lower plastic guide.

Before doing anything, try draining the oil and see what all is in it. If you have lots of aluminum shavings, then the idler sprocket most likely snapped off of the timing case (been there myself). If you see some ball bearings, then the idler sprocket's bearing blew out (also been there). The latter situation seems most likley and it has happened to a lot of folks. The idler setup is junk in the original M42 motors. I HIGHLY recommend swapping in an M44 timing case. You need to make sure to use M44 oil pump gears, and you will need an adapter bracket for the crank position sensor (I know that Metric Mechanic can probably sell you one). I had the bearing fail on my idler sprocket. So I replaced the thing ($170 part!!!) and then a year later it snapped off of the timing case entirely. The casting probably got damaged when the bearing blew out.

Also invest in a magnetic oil pan drain plug. Turner Motorsport sells one, and it is worth its weight in gold. I had one in there when the bearing blew, and all 6 balls were neatly stuck to it.

[evbrad2002]

Thanks so much for your detailed reply bmwman91.  Very helpful.

[mabeer]

Thanks so much for your detailed reply bmwman91.  Very helpful.

There are plenty of wrenchers with much more experience that will come to your aid.

See?  Told you.  You're in the right place!