m42 timing case replacement

[the_thryll]

I have an e30 with an M42. I am planning to replace the engine's timing parts (guides, chain, gears, tensioner). After removing the old timing parts, I was hoping to swap in a late-model M42 timing case and its unique timing parts. Is it possible, however, to replace the timing case without removing the head or messing with either oil pans?

My first concern is that I will need to loosen the entire upper oil pan (after removing the lower oil pan) in order to access and remove the 5 bolts that screw into the base of the timing case. My second concern is not being able to adequately seal base of the new timing case without replacing the upper oil pan gasket. My third concern is that the new profile gasket may get squeezed and damaged during installation because the head is still on the engine. (BTW, big thanks to Balleristic31, bmwman91, and many others on here for their invaluable advice on the late-model M42 timing-case topic).

[bmwman91]

You can definitely do it without pulling the head, but you do need to unbolt the upper oil pan (which means removing the lower pan). There is definitely no way to swap cases without taking one or the other off, and since the upper pan bolts into the timing case, the lower pan must come off no matter what.

The upper pan does not need to be removed entirely, which is good because you have to jack the engine up a questionable amount to get it out without removing the crossmember. However, that means it is a bitch to replace the upper pan gasket since you have to slide it into position and not get it full of dirt and shit. If you plan to seal it with RTV, it's a messy pain in the ass to try to smear it where it needs to go.

Getting the timing case back in with the head on is a nerve-wracking chore, in my experience. You have to slide it in with the new profile gaskets which are relatively stiff and need to be compressed in order to get the timing case up and high enough to slide onto the crank properly. It is somewhat easy to "roll" the gasket, which is not OK. I have lubed the profile gasket with some appropriate silicone RTV (high temp, resists oil & coolant) to help things slide, and I also had a sheet of 0.005" brass shim stock between the head & timing case + profile gasket to help act as a lead-in aide. Getting the sheet back out involved some crazy pulling with pliers through the opening where the kidney grille sits (was removed). Using RTV as the lube does impose a time limit on the installation though...take too long and it isn't going to lube much lol.

Honestly, having done a couple of head jobs on the M42, I say just pull the head. You should be able to have it decked for under $200 at a competent machine shop (can't skip this), and it wouldn't hurt to have the head disassembled & cleaned anyway. This also makes installation of the timing case into a breeze. Just my opinion though, I am not sure what your budget and schedule look like.

Which timing case are you going with? I believe that the 1994-95 M42 timing cases had the updated design that got rid of the idler sprocket. The M44 case is another option which has a larger capacity oil pump, BUT there is no bracket for holding the crank position sensor and you would need to buy one (~$100). Also, make sure to use the right timing case gasket for whichever case you go with...verify in RealOEM which gasket corresponds to which year M42/44 engine. Finally, replace all of the little parts in the oil pressure relief valve system that lives in the timing case...plunger, spring, circlip, etc. There was a design update since the original was prone to seizing.



Also, when you put in the new long driver's side guide, make SURE that you have the updated top screw to go with it. The original guide had an M6x40 socket cap screw holding the top of the guide to the head. The updated one requires an M6x45 screw, and if you use the old 40mm one, it will strip and lots of bad things will happen. To be honest, I have seen that top hole in the head strip on MANY occasions even with the proper 45mm screw, so consider installing an M6x1 helicoil or Timesert up there while things are apart.

[the_thryll]

You saved me from starting on a job that is much more involved than I had initially thought. If one wants to replace the timing case, certainly sounds like the smartest option is to remove the head first. I need to read more, and then decide if I can handle all the steps required to replace the gaskets for both oil pans, head, and removing and reinstalling the head. This job may be more than I can handle right now, skillwise and timewise.

I think I picked up the correct fillister-head screw (07119919629) for the driver-side timing guide. The timing case I got was on a 1994 318i. Since I got my car 4 years ago and fixed the odometer, I've put 25,000 miles on it, and the engine has always run smooth (*knock on wood). But my engine's actual mileage is unknown, (def > 125,000), and so my chief motivation here was to prevent future problems on my daily driver by installing new timing parts and the timing case from the 94 318i.