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M42 Cam Gears - inspection request

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    M42 Cam Gears - inspection request


    I am planning on performing timing chain maintenance which will include gears, rails, chain etc. Car is 1991 318is (12/1990 build), engine has 146K miles. Since M42 cam gears are NLA, only way I might be able to get them would be if someone had a spare pair and would be willing to sell them. There are lots of posts out here, some saying that cam gears need to be replaced every time you perform timing chain maintenance, others state that it depends on the condition of gears. Since gears are NLA, this becomes a bit of a problem. I have taken valve cover off to inspect the gears. I would like someone to take a look at the pics and give me their opinion if I should hold off with maintenance until I find a pair of new gears or if my gears still look OK, and I could go head with timing chain maintenance. I am attaching a link to a post that has some info about cams wear.

    Thank you in advance for your help

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    Last edited by gooseman; 12-20-2019, 06:50 PM.

    Any input would be appreciated.



      The gears are probably fine. If you had chipping, edge wear, or just a bunch of wear at the base of the gear/chain roller mesh point then you would want to replace them.

      You should replace the idler as the plastic gear components are a big unknown, and often present no symptoms before failure. Also look for cracks at the mounting boss for the idler.

      As to the crank sprocket, I have a sneaking suspicion that it will be fine if the cam gears are anything to go off of.

      Ne sure to really inspect/flex your crank trigger wheel as these are all seemingly on the way out as of now.


        Thanks roguetoaster for your input.

        Based on various post on this forum and others, I have come up with a list of parts I am planning on replacing. I would appreciate If anyone could go over this list and confirm If I missed anything or maybe even take some parts off the list as they might not be necessary.

        Also, I have seen some post where Yamabond is used instead of paper gaskets. Is this still a valid recommendation or something else should be used, or maybe I should stick with paper gaskets.

        Timing parts

        #1 - 11311247160 - Timing Chain
        #2 - 11211247338 - Crankshaft Sprocket (maybe, based on inspection as per rougetoaster recommendation)
        #4 - 11311721887 - Cam Sprocket x2 ( maybe, If I am able to find a new pair, otherwise I will keep existing as they are still in good condition)
        #6 - 11311247470 - Timing Chain Guide Rail
        #7 - 11311721419 - Timing Chain Rail
        #9 - 07119919629 - Intake Side Chain Guide bolt ( updated style to work with new guide rail)
        #11 -11311727569 - Deflection wheel
        #14 -11311727342 - Chain Tensioner Guide Rail
        #17 -11311743187 - Chain Tensioner
        #18 -07119963355 - Chain Tensioner washer
        #20 -11311721641 - Timing Chain Rail, Upper Slide Rail

        #3 - 11141439570 - Front Crankshaft Oil gasket
        #4 - 11141247837 - Gasket, Top of Lower Chain Case ( Profile )
        #7 - 12141727220 - Camshaft Position Sensor O ring
        #15 - 11141721802 - Gasket Set, Lower Front Chain Case Cover
        #16 - 11141721919 - Gasket Set, Upper Front Chain Case Cover

        #2 - 11511714519 - Water Pump seal
        #6 - 11537511580 - Thermostat, 88 Degree
        #7 - 11531721218 - O Ring, Thermostat 60x3mm
        #8 - 11531721172 - Gasket, Thermostat Housing

        #3- 11121721876 - Valve Cover gasket
        #4- 11121721476 - Spark Plug Chamber gasket x3
        #5 - 11121721475 - Spark Plug Chamber gasket - lollipop shape
        #9 - 11121721879 - Valve Cove Seal Washer x15

        Thanks again for any input
        Last edited by gooseman; 12-21-2019, 11:48 AM.


          You'll want the updated bolt for the intake side chain guide. Bmwman had a few posts on it in this section.

          Get a new camshaft position sensor o ring, and valve cover bolt grommets too.

          You will want to replace the crank seal as you will be removing the lower timing case.

          Consider coolant hoses since you will have the radiator out. There are three to do.

          You can use any quality sealer instead of the timing case front gaskets, or you can use the gaskets plus sealer, just not the gaskets alone. Remember to seal the joints/interfaces of the components, but don't overdo it.

          If your crankshaft sensor has cracks or other issues you should have a new one on standby as it's easy to slightly tweak the old brittle line and cause a no start or odd operating condition. Be aware, some new sensors are not exactly the same and may require non-stock wire routing.

          I have a new set of cam sprockets if you really want to buy them, but you don't need them IMO.


            Thanks again for valuable info roguetoaster

            I have edited previous post and added below parts as recommended. Please confirm that I got correct part # ( maybe this list can be useful for the next person).

            #9 - 07119919629 - Intake Side Chain Guide bolt ( updated style to work with new guide rail)

            #7 - 12141727220 - Camshaft Position Sensor O ring

            #3 - 11141439570 - Front Crankshaft Oil gasket

            #9 - 11121721879 - Valve Cove Seal Washer x15

            My coolant hoses have been recently replaced, but I will add them to the parts list later for reference.

            Also, I have read that a new crank bolt might be required as it is not supposed to be reused. Any input on this ?


              Not going to spend the time checking your part numbers as it's your project to do, but the crank bolt should be fine to reuse.

              Be certain if you do use gaskets and gasket maker that all bolts are hand installed and that the gasket isn't pinched around the perimeter before you tighten. To be clear, no gasket maker on the rubber gaskets except at the edges/ends of the timing case upper to lower case seal.


                Yeah, crank bolt can be reused no problem. It is not a torque-to-yield bolt.

                As rogue said, be careful with sealants. In my experience, it is very easy to wreck a gasket job with gasket sealer. Basically the uncured sealant acts as a lubricant for the gasket, and will push/slide the gasket itself out in places as the parts are bolted together. This goes for the M42's paper gaskets, anyway. I think that the later M42's and M44 had a coated metal gasket which probably did not need sealer, and it would not move around in bad ways even with sealer.

                When I do use a gasket sealer, I use Permatex High-Tack Spray A Gasket (funny smelling red stuff), and I apply it LIGHTLY; enough to make the gasket uniformly reddish, but NOT dripping or running, and not enough to look super glazed over. Even this stuff will allow gasket shift if used too heavily. After spraying, I let it cure for 15-20 minutes (in ~70°F weather, longer if colder) before assembly. During assembly. I pop it into place and then slowly clamp / bolt down the mating part, tightening each one progressively in 4-5 passes (light finger tight, finger tight, hard finger tight, 50% final torque and then 100%). Also visually check the part of the gasket that sticks out and make sure that it has not shifted.

                Yeah, it may seem overkill, but at least for the thermostat housing, oil filter housing, oil pans and timing case covers, you really do want to do it this way to avoid leaks (or worse). I've had enough leaks due to NOT doing things this way in the last 20 years that it is worth it to me to take the extra few minutes.


                  I have collected all the parts and finally got some time to perform timing chain maintenance. So far things have been going well taking it apart. I stopped at the point where I need to remove AC compressor bracket in order to get to the lower timing case cover. Can I remove AC compressor with the the bracket or do I need to first remove the AC compressor and later the bracket. Do I have to disconnect any electrical wiring from the AC compressor? What would the best way to remove AC compressor bracket to get to the lower timing case cover?


                    You have to do the four bolts that hold the compressor to the bracket first, and you'll want some way to hold the compressor once it's off so the lines aren't too strained. Then you can remove the other 6 or so bolts for the bracket. You can leave the electrical connection and refrigerant lines in place. It's a truly annoying system to service.

                    When you reassemble, be very careful to not over tighten the bolts for the compressor as they are going in to aluminum (same goes for all of the timing case and valve cover bolts). Also make sure to put your crank sensor/wire back in place before you reinstall the compressor bracket, because if you don't you get to remove the entire thing again!


                      Thanks rouetoaster, I was able get the bracket off and then removed lower timing case cover.

                      After removing a chain and rails I was able get to a crank sprocket. I took some pictures after I removed it for further inspection. Can I reuse this crank sprocket or should I get one?. I am attaching a few pictures.

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                      Last edited by gooseman; 06-29-2020, 05:41 AM.


                        Pics didn't make it.


                          Pictures have been fixed.


                            It does not look terrible. But, it is either some old/original design, or the rubber seats disintegrated over time. If you look at pictures of a new one, you'll see the difference. I am not sure how important those are, but since it is all apart it might be a good idea to replace it.


                   seems to have the best price for an OEM one.


                              You should be fine to run it, and I look for edge chipping or wear as the main indicator of if/when to replace sprockets. I really don't know the intention of those rubber rings on the sprocket as I haven't personally installed one with them.