Announcement

Collapse
No announcement yet.

M42 cracked head? Blown head gasket?

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

    M42 cracked head? Blown head gasket?

    Here's some background info that I tried to sum up without leaving anything out:

    Bought a 91 318i a few months ago. Timing chain guide was disintegrated so I replaced all the timing components. Started up. Took it for a test drive, everything checked out. Drove it to work a few days later (8 mile trip) it began overheating on the way back. 3/4 mark was the highest right before I turned off the highway. The built in reservoir leaked coolant and probably wasn't properly bled. Ordered a new radiator and bled it properly. Gauge was a tick past halfway until I cleaned the ground terminal for the temp gauge on the cluster. It read a few ticks under half way ever since.

    Now at some point in time. Not sure if it was before or after overheating, it would have a rough start every time I started it when it was cold. I also eventually noticed coolant level was getting lower. Put the two together and you know where this is going. So pulled the spark plugs, all brand new, #2 was yellowish. I put a snake camera down there and sure enough there was coolant covering 25% of the cylinder, and this is with the motor mounted at an angle.

    I can't see any white smoke come out ever. No bubbles in the reservoir. No milky oil. Saw a small puddle of coolant in my garage but it could've been from refilling the reservoir. I do keep noticing a puddle in this cavity between the alternator and the block. It seems to be dirty coolant. No oil.

    I'm just trying to figure out if this is a cracked head or a blown headgasket. I don't want to take it apart if it's a cracked head as it's my only mode of transportation right now. I've been driving it like this for 2 maybe 3 months now so I doubt it's going to fail on me abruptly. Replacing a head gasket on the weekend wouldn't be a problem for me.

    Thanks for reading this (tried to keep it short, I swear..) and TIA for any input you guys might have

    #2
    Something tells me you should pull that head over a weekend and take a look. My bet it would be a failed head gasket. I would however check very carefully on the block and see if the wall doesn't have a crack between 2&3.

    Good luck man that sounds like no fun!
    Parts Collector and Former Houndstooth interior junkie.

    Comment


      #3
      Originally posted by Gerta View Post
      Something tells me you should pull that head over a weekend and take a look. My bet it would be a failed head gasket. I would however check very carefully on the block and see if the wall doesn't have a crack between 2&3.

      Good luck man that sounds like no fun!
      This x100. By wall Gerta most likely means valve seat area to coolant passage when you pull the head.

      Comment


        #4
        Originally posted by Gerta View Post
        Something tells me you should pull that head over a weekend and take a look. My bet it would be a failed head gasket. I would however check very carefully on the block and see if the wall doesn't have a crack between 2&3.

        Good luck man that sounds like no fun!
        Yeah that would be the surest way to do it. Just afraid I'd find a crack and then it's game over from there and I wouldn't have a car to drive until I find a new head. Think I'll do the tranny swap in the 635 first so I can have something to cover my ass while the e30 is out. I've been putting this off for weeks and the more I think about it the more I lean towards it being a head gasket. Fingers crossed

        Originally posted by roguetoaster View Post
        This x100. By wall Gerta most likely means valve seat area to coolant passage when you pull the head.
        That's what I assumed. I've read the 2nd and 3rd exhaust valve seats to passages are prone to cracking on these and probably many other bmws



        Appreciate your thoughts and advice.

        Here's the #2 cylinder for laughs. This is what gets me to work everday

        Click image for larger version

Name:	IMAG0066.jpg
Views:	1
Size:	23.0 KB
ID:	7176839

        Comment


          #5
          ^ Dude. You need a bilge pump stat!
          Parts Collector and Former Houndstooth interior junkie.

          Comment


            #6
            There's no way I'm gonna take the time to pump that out every time I go for a drive.

            I just have to refill the reservoir once a week. That's about 12oz or so. Not bad...?

            I think I'll swap in a nv m50 and then figure out what to do with the m42

            Comment


              #7
              If it was mine, I'd pull the head and do a gasket. Because it's "probably" the gasket,
              and if it was, I'd feel stupid for driving around with a bad gasket and eventually
              wrecking the motor.

              If it WASN'T the gasket, I'd still bolt it all back together and drive it, and not
              feel so bad about trashing a motor that's already junk.

              That's me. Done that a few times now. Usually it works out.
              Occasionally, it doesn't.

              t
              now, sometimes I just mess with people. It's more entertaining that way. george graves

              Comment


                #8
                You're probably right. Well I don't feel any power loss or anything else out of the ordinary, can't be THAT bad. I have an m50 nv waiting to take its place now.

                I also have a 635csi with a blown trans and a getrag 265 ready to go in but I'm thinking I'll graduate from the b34 to b35 while I'm at it. Currently everything is removed from that so it's getting there.

                Give it a month tops and I'll be done with the m42. Maybe save it for another project since I already have $ invested into it. It's great for its size and weight

                Comment


                  #9
                  Very very late update: as of the other day, 1/15/16 my car is beginning to misfire at high rpms. Think it's safe to assume its cyl. #2 that is misfiring. In other words words, I put 15k miles on it without addressing the issue and drove it pretty hard on long road trips until now. I have a m50nv that needs work before using it and my 635csi is on the backburner almost road ready. I'll do a compression check when I get back home then tear it all down and inspect it and just maaaaybe I'll finally replace the HG if nothing is cracked. Call me craz I know. This m42 is a trooper and I just want to see how far it can go

                  Comment


                    #10
                    As far as E30 engines go the M42 is pretty fragile. Head is probably warped, maybe cracked, if the head gasket is blown. As you said before, M42s are prone to head cracks.

                    IG @turbovarg
                    '91 318is, M20 turbo
                    [CoTM: 4-18]
                    '94 525iT slicktop, M50B30 + S362SX-E, 600WHP DD or bust
                    - updated 1-26

                    Comment


                      #11
                      If you don't want to bother with disassembly you should definitely do a compression test. That will narrow down the cylinder and be certain that you have a HG leak or cracked head. Even if your head isn't cracked and it was just a blown HG you should definitely have the head checked to make sure it isn't warped, just something to think about.

                      It will be better to do this sooner than later! Good luck. :)
                      The fun never ends :-?

                      89 318iS
                      R.I.P 89 325i coupe
                      89 335iC

                      Comment


                        #12
                        Yep. I'm not too excited about the head being warped cause I'd really rather not spend the time completely disassembling it to get it decked. If and only if it's just a blown HG then I will go through with the repair. And I'd be really surprised if it isn't warped at all. Is there a tolerance to warpage? I'm willing to take a little risk since I'd imagine it's either a hit or miss and should last just fine if it works

                        Comment


                          #13
                          I'm willing to bet it's not a bad gasket but rather a cracked head. I've had the exact same thing happen to two m42s and both were cracked heads not gaskets.

                          -NICK

                          Comment


                            #14
                            my head had a nasty crack and cylinder #3 was filled with coolant even worse. the crack is visible on the head from a couple feet away, its pretty gnarly. FWIW a headgasket takes about 6 hours if you know what youre doing. good luck!

                            Comment

                            Working...
                            X