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M50 chirping noise... oil pump? Help!

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    M50 chirping noise... oil pump? Help!

    I'm 2 weeks away from my next LeMons race, and I finally got the M50 swap in my E30 mostly buttoned up, so I fired it up and let it run for a while. The car was idling fine for a few minutes until I started hearing a chirping/bearing type sound from the front of the engine. It started all of a sudden and kept going. It sounded similar to a bad alternator or water pump bearing, so I figured it might be one of the belt driven accessories, To eliminate them I pulled the belt and fired it up again. The noise was still there. Not good. I put the belt back on, and the noise went away for a while, then came back. Pulled the belt off again, was there again. Oil pressure is good - 50-60 PSI at idle according to my VDO gauge, and it sounded good otherwise.

    It seems to be coming from the bottom end, and was loudest at the bottom end of the oil pan. When I originally got the engine, I pulled the oil pan off, replaced the pump nut with one that has safety wire, and put it back together because everything looked nice and clean. So based on this. I thought maybe the safety wire was hitting something?

    So I decided to pull the oil pan, which meant pulling the subframe and front suspension, then pulling back the G260 trans.... luckily we cheated and were able to just pull the trans far enough back to access the last two bolts without pulling the whole thing from the car. Got the pan off and found nothing unusual. The oil looked clean, pulley and nut were still on, chain appeared to be okay. I didn't plan on pulling any main bearing caps off but I suppose I could. I considered replacing the oil pump until I learned that it was over $200 (I work for a parts distributor and that's my cost!).

    Backstory on the engine - I got it from another former LeMons car which crashed. Engine has about 170K on it and went through two races without issue. I drove the car before buying it and parting it out for the engine and it was fine. I swapped the G250 for our original G260, but everything else (other than typical gaskets and stuff) is what came with the engine.

    Does anyone have any clue what this could be? To say I'm frustrated is an understatement. With the amount of time and effort I've put into the car, and given that I basically only have one weekend left before the race, I'm on the verge of a meltdown. I don't have time to completely pull apart the engine. I'm at the point of just putting it together, crossing my fingers, and hoping for the best.

    Help!
    The Homer: Powerful like a gorilla, yet soft and yielding like a Nerf ball.

    #2
    Try getting it to op temp see if it persists
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      #3
      Got the car all put back together, only to find the same noise. Here's a video:



      As you can see there is no belt on the engine. It seems to come and go. It it loudest right around the crank pulley. At one point it got really loud, so we shut down the car, then fired it back up and went away.

      As a last ditch effort, we decided to just shoot some spray lubricant behind the crank pulley, and to our amazement it got quiet and has stayed quiet ever since. I actually got the car put together and took it on its maiden voyage with this engine - the first time it has moved under its own power in a year and a half, and it seemed just fine. The noise never came back.

      I'm really stumped and not thrilled about the prospect of racing this car for 24 hours straight without knowing what the problem is, but at this point I think I have no choice. I'm going to spend the next couple of weeks getting the car finalized (needs a new windshield, exhaust, and I have to wire up new lights) and hope for the best.
      The Homer: Powerful like a gorilla, yet soft and yielding like a Nerf ball.

      Comment


        #4
        my bet is you ditched the AC pulley and didn't use shorter bolts so its rubbing on the front main seal housing?

        AMIRIGHT?!

        Rebuild kits for M50 pumps are 60 bucks. Inner and outer rotor. You should take the pump apart.
        Past Car : E30 S50 6 Speed 5 Lug 3.73
        Current : Z3 S50 OBD2 (Smog Legal) 6 Speed BBS RN Dual Ear Diff
        ___________________________________________
        BNB Designs
        Engine Swaps, Fabrication, Innovation, General Repair
        Richmond CA
        Julian 848-248-8029

        Comment


          #5
          Originally posted by jrdeamicis View Post
          my bet is you ditched the AC pulley and didn't use shorter bolts so its rubbing on the front main seal housing?

          AMIRIGHT?!

          Rebuild kits for M50 pumps are 60 bucks. Inner and outer rotor. You should take the pump apart.
          Oh snap.... you may be onto something.... I did ditch the secondary pulley on the front of the crank. What damage could that have done? I'm guessing it would be self clearancing after a while though.
          The Homer: Powerful like a gorilla, yet soft and yielding like a Nerf ball.

          Comment


            #6
            That's gotta be it. The car ran for a good long time with no issue so I'm hoping the front seal is okay. I really don't want to have to pull the crank pulley.

            I haven't had a chance to look at the car yet today, but I'm hoping the worst that happened is that the outer edge of the front crank seal bore was machined off.


            The Homer: Powerful like a gorilla, yet soft and yielding like a Nerf ball.

            Comment


              #7
              The crank pulley is very easy do not worry my friend.

              The main crank bolt only holds the steel flange to the crank.

              The pulleys are attached with 6 bolts to the flange and they torque to 16 - FT LB.

              Generally it only scores the outside of the housing, just remove the ACC Belt, the 6 polts and inspect.

              If I remember correctly with AC pulley is M8x16 - 10.9, without M8x12 - 10.9.
              Past Car : E30 S50 6 Speed 5 Lug 3.73
              Current : Z3 S50 OBD2 (Smog Legal) 6 Speed BBS RN Dual Ear Diff
              ___________________________________________
              BNB Designs
              Engine Swaps, Fabrication, Innovation, General Repair
              Richmond CA
              Julian 848-248-8029

              Comment


                #8
                I didn't think about that. I still won't really be able to see behind the crank flange, but at least with the pulley out of the way it'll be easier to inspect the damage. I'll buy some shorter bolts from a hardware store.

                Thanks for chiming in, I never would have thought about that being the issue. I only wish I would have known about this before unnecessarily pulling apart half of the car!
                The Homer: Powerful like a gorilla, yet soft and yielding like a Nerf ball.

                Comment


                  #9
                  Oh and the bolts are M8X18 per Real OEM. I will get some a few mm shorter.
                  The Homer: Powerful like a gorilla, yet soft and yielding like a Nerf ball.

                  Comment


                    #10
                    How many laps will they give you for an M50 swap?

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                      #11
                      I was waiting for that question. Our car has $200 residual value from the last race, and we bought the whole running/driving M50 swapped car (with a wrecked body) for $250. I sold the shell for $25, and my old M20 for $100, so technically we're up to $325 LeMons budget. Of course I've shelled out plenty for maintenance items, materials, etc., but we're legally within budget.

                      Having said that, I won't be surprised if we get some laps, and while I don't want any, I don't mind. I've been busting my ass working on the car so much lately that I'll just be happy if we get on the track, let alone do well.
                      The Homer: Powerful like a gorilla, yet soft and yielding like a Nerf ball.

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