Need advice from experience for an M42 rebuild

[JonsE30]

Do you mean the bolt should be in the center of the bolt slot of the cam gear? The square edges at the rear should be flat relative to the angle of the head casing? These are the dowels it’s probably hard to see but it without taking the front timing cover off, but with respect to the angle of the head casing the dowels are sitting at between 7 and 8 o’clock. The right gear maybe sitting more like 8 o’clock. Sent from my iPhone using Tapatalk

[roguetoaster]

Bolts should ideally be centered, or as close as you can get to the center of the slot. It's not likely to be perfect without a cam locking tool, but don't sweat it. Remember, this feature adjusts actual valve timing.

The square bits on the backs of the cams should be flat relative to each other. As in, put a ruler across them and there should be little to no daylight visible. Start with aligning the squares and see where this puts the bolts in the slots. You may have it right on.

From memory I believe the dowels are in the right place presently, and IIRC the arrow pointing up achieves this. The one on the intake side does not matter as the cam sensor does not read it.

[JonsE30]

got it. i will readjust the camshafts and the gears and post the pics as soon as possible.

[bmwman91]

Yeah, the cams are visibly off in the photos if looking at the rear ends. I have also just used an adjustable wrench on the square ends to turn the cams and a small straight edge to visually verify that they are parallel after adjustment.

In your case, the intake looks advanced and the exhaust retarded. It's hard to tell if it is a whole tooth off, but with any luck they are just at the limits of their travel in the sprockets' slots.

[JonsE30]

here is my plan of action: is this right?

remove the water pump, crank sensor and front timing cover so i can remove the gears, then remove the bearings caps, level the edges at the rear of the cam, reinstall the caps, then reinstall the cam gears aligning the dowel and arrow markers.

[bmwman91]

Ha man, no way. That is far too much work!

You just need to leave the flywheel locked at TDC as you showed in the photo, remove the valve cover (which I think you already have) and loosen the 4 bolts holding each cam to its sprocket. Get an adjustable wrench on the back of the cams to set the ends parallel with one another (and you are at least close since the faces that need to be parallel are the ones with the 2 small holes in them), and tighten the 4 sprocket bolts again.

Then remove the flywheel locking pin, turn the engine 3-5 times by hand, lock the flywheel again and double check that the cams are still parallel. It is normal to find them just a little off, so you might need to tweak them once more. If so, turn the engine again and check until they stay aligned.




The arrows and dowels on the sprockets are themselves almost irrelevant. They are good for a rough visual check to make sure you are in the ballpark, but the 3 things that actually matter are the flywheel lock pin and the 2 back faces on the square cam ends. That's it. Now, if you were off by a whole tooth you MIGHT be able to still get those 3 things aligned and be at an extreme end of the slots in the cams, but it would be fairly obvious since the factory configuration had the bolts centered in the sprockets. So anyway, if you do the steps above and find that the bolts are bottoming out in the slots when trying to get the rear edges parallel, then you need to remove the sprockets because they are off by a tooth. You can fix that in-place without pulling the upper timing cover, but it is a pain in the ass and you DEFINITELY want a magnet on a stick to prevent a bolt from falling in...it becomes a much bigger project at that point! You might be better off pulling the upper cover, but then you may need to replace the thermostat housing gasket again (most local parts stores can get Elring or Victor Reinz ones in 24 hours).

[JonsE30]

I loosened the front four bolts of the gear on the exhaust cam and tried to use and adjustable wrench to rotate the cam so I can level it with the squared off edge of the intake cam but It stopped. And I didn’t want to turn it more because I didn’t want risk snapping or breaking anything. Is this the resistance from the lobes pressing on the lifters? Should I just rotate with a little more force?

[roguetoaster]

Just to add, the cam bolts can be undone and somewhat tightened with a flat wrench, so no need for that other stuff.

You are at the checking and adjusting phase, so don't go back to disassembly unless you absolutely have to.

[roguetoaster]

There can be a lot of resistance when turning the cams as you have no mechanical advantage and you have to compress the valve springs. Use your best judgement and see where valves are in their travel relative to piston position to inform you if something may be wrong.

[bmwman91]

I loosened the front four bolts of the gear on the exhaust cam and tried to use and adjustable wrench to rotate the cam so I can level it with the squared off edge of the intake cam but It stopped. And I didn’t want to turn it more because I didn’t want risk snapping or breaking anything. Is this the resistance from the lobes pressing on the lifters? Should I just rotate with a little more force?

Some resistance is normal, and it may well feel sort of sticky. Also, it looked like both cams were off, so you will need to mess with both at the same time to get things parallel. Just be sure to lay some sort of straight edge across them to check that they are parallel...it can't be done reliably just by eyeballing things.

[JonsE30]

Those techniques all worked! I loosened all the front bolts that let me re-adjust the gears by a tooth or two. I squared off the edges of the rear of the camshafts then tightened everything down. I then hand cranked as recommended then lock flywheel again to remeasured. I had to do this a few times for those micro re-adjustments. Once I got it to stay flat after a few tries I slapped everything back on then tried to start and she fired up and she sounded “normal” without that clacking/slapping noise. There was light “steam” or light smoke coming from the head, but not like black smoke. Is this like the rebuild lube burning off or is something more serious? No white or black smoke was coming out of the muffler and when I gave it some gas the muffler sounded normal. For a maybe about 30 seconds or so it was rough idling but not dying, then a check engine light came on. I did the stomp test and it came with a 1215 which I read is the MAF sensor. Is this related to the rough idling? But this is means the engine rebuild is OK? Now it’s these other maintenance items to address outside the engine rebuild?

[bmwman91]

Well, there is at least some good news in there.

When you say that smoke was coming off of the head, where did it look like it was coming from? If you used gasket sealers then maybe those had some volatiles flashing off. Did the smoke stop after a little while, or was it continuous?

1215 can be a number of things, and usually not the AFM. The most common one is a big vacuum leak. Did the rough idle last for 30 seconds and then stop, or did it stall?

[JonsE30]

I tried starting it again and I didn’t see any more smoke. The car idles and catches itself but it doesn’t die. I let it run a little to get temp up but not too hot to check for any leaks. I found some seeping from the lower timing cover. Near the water pump and a/c compressor error. So I gotta deal with that too. Sent from my iPhone using Tapatalk

[bmwman91]

Well, I would say to warm it up and run a compression check just to rule-out the worst case scenario. Do you hear anything at all like a burble noise or bellowing noise? I am all too familiar with what a bent valve sounds like, and there is a somewhat distinctive sound when compression is lost. Another video could help, although the sound is usually low enough in frequency that phone mic's probably don't capture it well.

Otherwise, I'd say it could be vacuum leaks, or a bad sensor connection somewhere. Did you possibly mix up the coolant temp sensors? The grey connector goes on the one toward the front of the engine and the black one that is not part of the same branch goes on the rear one (the one on the same branch is for the oil pressure switch...I mixed those up once and got a real scare).

Also, did you happen to notice a single-wire connector that was unplugged up on the wire loom on the firewall and plug it back in? If so, it needs to remain unplugged and it has been the cause of some people's troubles in the past.

[JonsE30]

Link: https://youtu.be/GuDuuvjzSow Here’s what it sounded like yesterday after readjusting the timing. Wire on the firewall is unplugged. I will need to check tomorrow morning on the plugs under the intake.