Announcement

Collapse
No announcement yet.

Strange Oil Leak

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Strange Oil Leak

    After only about 200km after a complete engine rebuild my engine starts leaking between engine and gearbox, but only under certain conditions. The engine needs to be warm and it has to be shut off. As long as the engine is running, there is no oil loss. When I only drove for about 30km, no oil loss. But when I drive a little longer and then shut the engine off, the oil starts dripping out after a few minutes. It stops dripping quite soon once it stands. The oil can be found between engine and gearbox, it comes out black there (guess that comes from dirt in the bell housing), and there are only a few drops with clean engine oil in the far back and right of the engine in the area between engine block and the reinforcement plate. When checking the oil I can see that the oil loss can not be that big. My first idea was the upper oil pan gasket, but then I guess the engine would be a lot messier and the amount of oil loss bigger. Also the other parts of the engine are dry. So the other idea is the RMS. My theory is, as long as the engine is running, it seals just enough also due to the slight vacuum in the crankcase. Once it stands, it starts leaking esp. When the oil is hot. Is this plausibile? The other idea would be the gearbox but then I guess the oil would smell respectively and the gearbox would be really dirty and the oil would come out also and especially when the car is running. Any other thoughts? Would like to give the workshop some ideas and also would like to avoid that e.g. The RMS will be replaced and the problem still remains. And the mess is to big to just ignore it.

  • #2
    A new RMS should be mounted slightly further in, towards the front of the car so that the sealing lip rides on a part of the crank that has no wear on it. The old seal will have worn a ridge into the surface where a new seal cannot seal.

    If the engine builder fitted a new seal, ask him 'you did put the new seal at the same depth as the old seal, right?'
    If he answers "yes, of course", you know the reason why it's leaking...

    If he's paying attention/listening closely to what your asking and he has put the seal slightly further in, he will answer " no" and give you the above reason.

    The flywheel bolts need a thread sealant on them otherwise engine oil will wick past the threads into the bell housing but to be honest I think that would take a very very long time before you see a drop outside at the bottom of the bell housing.

    Comment


    • #3
      Just keep in mind, once the oil runs through the bellhousing and gets really dirty, it is very difficult to tell engine oil from gearbox oil. It is at least as common for the transmission input shaft seal to develop a leak as it is the RMS.

      Comment


      • #4
        I recommend putting a dye in the gearbox, taking it for a couple of long drives and inspecting the leak with the proper light to illuminate the dye. If it lights up with the light, your leak is from the gearbox. If it does not, your leak is from the engine. The input shaft of the transmission is know to leak if the pinion shaft bearing is bad, or in extreme cases if the case of the transmission is worn. As Hardtailer and Ironhead have detailed above, the RMS can be the source of the leak if it wasn't installed properly. I'll add that the type of RMS also matters. Some have double seal lips on them and I've found those to be less susceptible to leaks. I did have an engine once that leaked from the RMS right from the start after a full rebuild, and it was set in further than the prior RMS. I replaced it and that one leaked too. Put in a third and viola, no more leak. Go figure.
        Ron ///Man

        • '91 Gr-A Former CiBiEmme / Ravaglia - Sold
        • '90 M3 Faux EVOII Alpineweiss 36K Orig Owner - The Queen
        • '91 M3 Faux EVO III Brilliantrot Euro Driveline - The Rocket
        • '91 M3 Faux Gr-A Club Racer DM - The Alter EGO
        • '89 M3 M3T / ITR Club Racer
        • '94 Spec E36 - Eh....
        • '09 M3 - Tarmac Terrorist
        • '04 330Xi Sport 6 Speed - Snowmobile
        • '07 530 Xi - Highway Star
        • http://www.imwcarparts.com/e30-m3-parts.htm


        Comment


        • #5
          With a rebuilt engine and no work on the transmission, the first 'guess' where the oil leak is would be the engine.
          Larry

          Comment


          • #6
            Thanks for your answers so far. I will first go figuring out if I can exclude the tranny by putting dye in the tranny oil. It is of course possible that the oil is coming from there since I really can not see a significant lower oil level on the dipstick and also there is quiet some oil leaking out the bellhouse immediately when I just shortly park in my steep driveway with the nose facing down.

            Comment


            • #7
              Short update: It is engine not gearbox oil and I now looked at the oil trace thoroughly. Since the engine is very clean after the rebuild I can follow the oil back. So the highest point where oil can be found is the seam between the crankcase and the upper oil pan. The gasket (the cork gasket) also looks a little wet on the right hand side. It seems that the oil follows the seam to the back, some of it (clean drops) come down at the screws from the pan and the reinforcement plate, and some dirty stuff is coming out of the bellhouse. So I guess that the upper oil pan gasket is not holding the oil back as it should. Strange is that this appeared not directly after the rebuild but after approx. 200km. So I think that the bolts of the upper oil pan need to be retightend. The oil loss is not very big and oil seems to come out shortly after shut down of the engine. While running, it is not marking the street. The upper oil pan has also bolts on the inside, right?

              Comment


              • #8
                Originally posted by weisen View Post
                Short update: It is engine not gearbox oil and I now looked at the oil trace thoroughly. Since the engine is very clean after the rebuild I can follow the oil back. So the highest point where oil can be found is the seam between the crankcase and the upper oil pan. The gasket (the cork gasket) also looks a little wet on the right hand side. It seems that the oil follows the seam to the back, some of it (clean drops) come down at the screws from the pan and the reinforcement plate, and some dirty stuff is coming out of the bellhouse. So I guess that the upper oil pan gasket is not holding the oil back as it should. Strange is that this appeared not directly after the rebuild but after approx. 200km. So I think that the bolts of the upper oil pan need to be retightend. The oil loss is not very big and oil seems to come out shortly after shut down of the engine. While running, it is not marking the street. The upper oil pan has also bolts on the inside, right?
                Use sealant instead of the cork. Toyota gasket maker or hondabond are great

                Comment


                • #9
                  I can't believe how bad the OEM BMW gaskets for the S14 are. If you use them dry without a coating of some sort of sealant, your freshly rebuilt engine is almost guaranteed to leak somewhere.

                  I agree with Adam. Ditch them and go with a chemical gasket of your choice. There are about a dozen such products, and they all work well.

                  Comment


                  • #10
                    I had the same issue with a rebuilt motor. Was the upper oil pan gasket. Also had the same sort of trail where it was near the back of the motor and I thought it was RMS.

                    Comment


                    • #11
                      Originally posted by Ironhead View Post
                      I can't believe how bad the OEM BMW gaskets for the S14 are. If you use them dry without a coating of some sort of sealant, your freshly rebuilt engine is almost guaranteed to leak somewhere.

                      I agree with Adam. Ditch them and go with a chemical gasket of your choice. There are about a dozen such products, and they all work well.
                      Do you install it completely without a gasket and solely use the sealant or do you coat the gasket with sealent?

                      Comment


                      • #12
                        Originally posted by weisen View Post

                        Do you install it completely without a gasket and solely use the sealant or do you coat the gasket with sealent?
                        I use no gasket at all, except for the head/valve cover gaskets.

                        Comment


                        • #13
                          Originally posted by Ironhead View Post

                          I use no gasket at all, except for the head/valve cover gaskets.
                          You're the reason why I did the same when I resealed my engine 2 years ago. Not a single drop since. It was shocking lol

                          Comment

                          Working...
                          X