(Yet another) M42 top end refresh and engine reseal (mid-2021)

[bmwman91]

Yeah, strange, I have used that same stuff for years and never had a splatter issue. I use it the same way that I use spray paint...continuous flow over each pass, making multiple light passes with a little overlap. In the case of this stuff, to avoid putting it on too heavy, I hold the nozzle pretty far from the gasket. A lot of the spray blows away, which is a waste, but it ensures a very thin and even coating.

To be honest, I am not even sure how much additional sealing the spray will provide here. One of the key things that I like about the spray is that I can easily stick the gasket into place. Paper gaskets generally won't leak as long as they are installed as intended on smooth, clean surfaces.

[econti]

I use Hylomar which brushes on instead of a spray, might be a good option if you keep having issues

[jsnppp]

Some progress tonight. More to come this weekend.

Installed the cams in the head. Step by step:

Spring caps/covers in the cam tray:




Flipped the head on the side to install the cam tray (otherwise the spring caps/covers fall out):


Flipped the head back right side up. Layed the cam in. Tried to keep it in TDC position (furthermost right lobes pointing slightly up):


Assembly lube on each cap:


Caps on and 11mm nuts on finger tight.Was generous with assembly lube.




Then walked down the bottom row of the 11mm nuts, left to right, each turned 1/4. Went back to the left and did the same across the top. Repeated until the cam was tight.

With diagram - we tightened 1, 2, 3, 4, 5 each 1/4 turn. Then tightened A, B, C, D, E 1/4 turn. Note that sometimes the next nut in the sequence is loose because the nut prior pushed the cam down. If that happened I tightened it finger tight again and then turned it 1/4. Then returned back to 1, 2, 3, and then back to A, B, C, etc. Repeat ad naseum until complete. Torque on the last step.


Repeated on the intake side. We then installed the cam sprockets, only loosely to get them off the table.


I'm a bit concerned about the next step to align the camshaft with the head. Right now the cams are as near vertical as they can be, but they won't hold at perfectly 90 degrees. My first thought was that I would move them with a wrench when the chain is on. I then read on one of the links that you risk bending a valve that way.

So, I ordered the least expensive cam alignment tool I could find ($50 delivered).e will back off the caps, install the tool and then tighten them up again.

Tomorrow we reinstall the front case (and install muffler, carpet, etc.).

[82eye]

beauty work man.

[jsnppp]

beauty work man.

Thanks! Lets hope it runs after all this :-)

[jsnppp]

All we did today was clean the timing case and the engine block. Then installed the muffler.. Tomorrow we will get it done!

Hey bmwman91 - I was looking at the timing cover and know that the idler gear is a failure point. I'm assuming the threaded insert that the idler bolt is tied to has material failure from the cyclic loading.

It occurred to me that I could fill the area around the back of the threaded insert with JB Weld and perhaps reduce motion/stress. It's almost like a cup.

[bmwman91]

I would not touch a single thing in that area. The coefficient of thermal expansion of epoxies (45-65 ppm/degC) is going to be significantly higher than that of aluminum alloys used for engine castings (~25 ppm/degC), so it'll just put more stress on things. More than that though, the yield strength of JBW (~28 MPa tensile, ~12 MPa adhesion) is basically negligible compared to the timing case aluminum (140-210 MPa), so if the casting were to start failing, it would probably only buy you an extra few seconds at most.

In my case, the failure was likely due to a small nick in the casting which was a result of the original idler sprocket blowing out its bearings. If you do not see any dents dings or cracks anywhere at the base of the mount boss or in the gussets, then it is probably OK. If there is a hairline crack, it might not be visible without the full chain tension bearing on the sprocket. Because of that, I always recommend the post-93 M42 timing case (or M44, but that requires a custom adapter for the crank position sensor) which eliminates that awful sprocket. Now, that is just me being paranoid. MOST M42's on the road have the original sprocket in there still and have had no problems. Numerically, very few M42's see the timing case fail entirely.

[jsnppp]

I would not touch a single thing in that area. The coefficient of thermal expansion of epoxies (45-65 ppm/degC) is going to be significantly higher than that of aluminum alloys used for engine castings (~25 ppm/degC), so it'll just put more stress on things. More than that though, the yield strength of JBW (~28 MPa tensile, ~12 MPa adhesion) is basically negligible compared to the timing case aluminum (140-210 MPa), so if the casting were to start failing, it would probably only buy you an extra few seconds at most.

In my case, the failure was likely due to a small nick in the casting which was a result of the original idler sprocket blowing out its bearings. If you do not see any dents dings or cracks anywhere at the base of the mount boss or in the gussets, then it is probably OK. If there is a hairline crack, it might not be visible without the full chain tension bearing on the sprocket. Because of that, I always recommend the post-93 M42 timing case (or M44, but that requires a custom adapter for the crank position sensor) which eliminates that awful sprocket. Now, that is just me being paranoid. MOST M42's on the road have the original sprocket in there still and have had no problems. Numerically, very few M42's see the timing case fail entirely.

Excellent point on the epoxy material property differences. The idler wheel is new now and I didn't see any nicks or cracks so we will go with it. It's funny that BMW chose to leave that cup instead of using solid material. On our other 318is I will search for a late M42 timing case or M44 as you say.

Today is the day we start bolting things up! Just noticed something on that the torque settings image we are referencing. I believe the author has specified the order of the tightening with the 1, 2, 3, 4, etc. The first time we did it I started at the big 17mm and then just cross patterned the order. This time we will use the order listed.

[jsnppp]

Got a lot done. Some dark alleys that took me a bit to recover from but all seems well now.

I had to reread some of the links listed on the first page in order to answer some of my questions. I am firmly convinced that no matter what I do it's going to leak. So many threads start with "I did it 100% perfect and it still leaks". Will see.

My dark alleys:

• Spraying two gaskets (timing case + timing case cover) and dropping them on the ground. Twice. Each. I was paranoid it would pick up a microscopic rock and so had to wipe and review both sides of each. What a pain.
• Mistakenly writing M8 when it was M6 and starting to torque to 22NM vs. 10NM. Thank goodness I stopped b/c it didn't feel right. I fixed the page one where I had mislabled. Yikes.
• Getting the gaskets to line up - for some reason either one side or the other would shift.
• Big one --> I absolutely could not find two of the long M8 bolts that hold the timing case cover. Looked everywhere for almost an hour. Then looked at the other 318is and one of the linked pages and realized that the two bolts were part of the AC bracket. This was great but then had to pause and clean the greasy AC bracket, etc. Was driving me nuts.

Here are some action photos.

Lower case on, timing rail on, crankshaft pulley (I just put some assembly lube and slid it on, hope this is ok).




When I first put on the timing chain:



After I tied it up with a (loose) zip tie. I hope timing chains are non-directional.



Having to verify gasket was centered properly in each hole:



How it looks now, with AC bracket on. Also loosely fit the water pump.

[bmwman91]

Good progress! I am sure that the lower part will not leak since it sounds like you were OCD-level meticulous lol.

As far as I know, the main leak source is the joint where the profile gasket butts in with the upper & lower covers on the passenger side. The driver's side is less of an issue since it is "uphill" although oil could wick out. Basically, get a utility knife and trim any overhanging paper gasket ends that protrude visibly past the end of the lower cover.The upper gaskets are a little tougher...you could try trimming them a little short. Then before installing the profile gasket and upper cover, shoot RTV into the butt joint so that it fills any and all openings where things come together. If the upper gasket was trimmed short, the RTV can fill in under the upper cover at the bottom. My suspicion is that people put the joint together with RTV, but it only ends up on one side of a gasket tail.

Remember that, ideally, you will compress the front profile gasket. I think that I have written out the procedure before. Basically, put the upper cover on with the bolts not-quite finger tight so that it can slide vertically without dragging the gaskets around. Then put the valve cover on without its gasket and use the proper length M6 bolts to draw it down and act as a clamp to force the upper cover to be flush with the cylinder head. Then go ahead and tighten the cover bolts in a few passes (finger tight, a bit more than finger tight, then final torque).

[jsnppp]

Good progress! I am sure that the lower part will not leak since it sounds like you were OCD-level meticulous lol.

As far as I know, the main leak source is the joint where the profile gasket butts in with the upper & lower covers on the passenger side. The driver's side is less of an issue since it is "uphill" although oil could wick out. Basically, get a utility knife and trim any overhanging paper gasket ends that protrude visibly past the end of the lower cover.The upper gaskets are a little tougher...you could try trimming them a little short. Then before installing the profile gasket and upper cover, shoot RTV into the butt joint so that it fills any and all openings where things come together. If the upper gasket was trimmed short, the RTV can fill in under the upper cover at the bottom. My suspicion is that people put the joint together with RTV, but it only ends up on one side of a gasket tail.

Remember that, ideally, you will compress the front profile gasket. I think that I have written out the procedure before. Basically, put the upper cover on with the bolts not-quite finger tight so that it can slide vertically without dragging the gaskets around. Then put the valve cover on without its gasket and use the proper length M6 bolts to draw it down and act as a clamp to force the upper cover to be flush with the cylinder head. Then go ahead and tighten the cover bolts in a few passes (finger tight, a bit more than finger tight, then final torque).

Thanks bmwman91. I plan to follow your steps for the profile gasket. I'm not convinced it won't leak but I'm doing my best to be OCD on this. (like others)

I'll take some photos of the gasket next to make sure that I'm trimming it properly. I'm not sure I understand what to take off..

But yes good progress, can't wait to get the head on and start getting closer to turning the key. Being pulled in a few directions with work and house projects at the moment..

Jason

[jsnppp]

Question on trimming the timing case to cover gasket prior to installing profile gasket. I'm thnking that it's these three locations.



I'm thinking I should trim it back across the entire top, like this:



Will be a bit challenging now that I have it already installaed. I'm thinking an extremely sharp razor blade, just enough to score it, then bend it apart. I don't want to scrape the head.

Thoughts?

[bmwman91]

Actually, that won't leak out of the engine. The case-to-block gasket can be left as is. It is the gaskets that go between the case covers and case + head which can be the issue as far as I know. I have some fairly boring meetings I will be stuck in at work, so I will try to sketch up a diagram to show the issue as I see it.

[jsnppp]

Actually, that won't leak out of the engine. The case-to-block gasket can be left as is. It is the gaskets that go between the case covers and case + head which can be the issue as far as I know. I have some fairly boring meetings I will be stuck in at work, so I will try to sketch up a diagram to show the issue as I see it.

Ah, got it. So the profile gasket(s) are what needs trimming? Curious as to what to trim on this. If you posted elsewhere and I've missed it, let me know! But I'd welcome a diagram.



~~~~~

I had another thought regarding installation.

Instead of installing the head and then installing the front top timing cover (and using valve cover to push it down to level with washers), how about bolting (w/ proper torques) the front top timing cover to the head with gaskets on the bench first? Can then make the top cover perfectly aligned with the top of the head.

Then as a unit install the head + cover on the existing bottom half. The benefits of this is that it's a uniform push across both sides of the profile gaskets, including the famous butt joint. I'd still use sealant in that area.

Feels like there would be less motion this way and less opportunity for shifting.

Thoughts?

~~~~ EDIT ~~~~

Ok, so I just sanity checked my proposal. It won't work as I wrote it b/c you wouldn't be able to pass the timing chain through if the top cover is already mounted.

What COULD be done however is to install profile gaskets with sealant in the butt joints, lay the headgasket on, lay the head in place (possibly lifted slightly), route the timing chain, then bolt on the front timing cover in place at exactly the correct height with the valve cover.

Can THEN bolt up the entire head + top timing cover on top of the block and profile gaskets...

My focus on this remains figuring out a way to uniformly press on the profile gaskets so that it does not shift.

Thinking out loud here.

[bmwman91]

Yeah, good point. Pre-installing the upper cover properly would simplify some things for sure.

The profile gaskets themselves are fine and I don't trim those. It is the skinny paper outer perimeter gaskets that I am referring to.

I need to think about it a bit more, but it might also be better to skip the cover gaskets entirely and just RTV the covers on. That would eliminate the tiny little gaps that I suspect result in oil seepage. Anyway, I'll see if I can make some diagrams later.