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Continued issues after head gasket replacement -- cracked block?

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    Continued issues after head gasket replacement -- cracked block?

    I've got a 1990 325i with 255K on it. Ever since shortly after I bought it, I've had issues with overheating at idle. After replacing the entire cooling system, I had no improvement. One day while driving home, the car suddenly took a turn for the worse -- I had to keep it above 5K rpms to prevent it from overheating very rapidly.

    Out of other options, I changed the head gasket. When I removed it, I found a leak between cylinder 2 or 3 (forget which) and a coolant passage. Had the head pressure tested and shaved .007." Installed the gasket, torqued the bolts, etc. After that, it ran like shit. Exhaust smelled strongly of gas, very rough surging idle, and stalled out if left to idle for more than a minute or so. Also, there was an oil leak that left oil puddling on the top of the front exhaust manifold. I ruled out vacuum leaks with a can of starter fluid. The engine also had piss-poor compression (all between 145-155 immediately before I started the job) that was not consistent between cylinders.

    I figured I just screwed it up, never having done anything this complicated before. So, I finally got a chance to redo it. I did everything twice as carefully, and had no problems along the way. I started the car and it had the same set of issues. Trying to diagnose it, I again didn't see signs of vacuum leaks, and didn't bother checking the compression. A mechanic that I sometimes go to for advice said there was an outside chance that the block was cracked.

    This seems like one of the few remaining possibilities, if not the only one left. Anyone ever had this happen before? Anything else to check before I invest in a new block/motor?

    If I do need a new block, what sort of options do I have? I'm thinking it's between a new i block, a M50 swap, or a super-eta block. From what I'm reading, the M50 swap is going to take more time, experience, and money than I've got. I'm also seeing a lot of stuff saying that the 2.7i combination is too expensive for the money -- however, these all seem to be opinions from people going from e->i, not vice versa -- is it worthwhile to get the super-eta block if I already have the rest of the i stuff?

    #2
    If compression is low across the board, I wouldn't readily suspect a cracked block.

    Valve timing is good?
    -Dave
    2003 Lincoln Towncar | 1992 BMW 325iC | 1968 Cadillac Deville

    Need some help figuring out the ETM?

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      #3
      Perfect -- I not only checked it with the timing marks, but lined up the cylinders and the valves by inspection at TDC 1 before reassembly.

      edit: I don't recall the exact figures I got from the compression test -- they were low (120s, 130s) across the board, but some (IIRC, those with the leaking oil among them) were extremely low (80ish)

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        #4
        Are you sure the head is good? Almost sounds like the head warped (due to overheating) and a valve is sticking or something.

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          #5
          Originally posted by NitroRustlerDriver View Post
          Are you sure the head is good? Almost sounds like the head warped (due to overheating) and a valve is sticking or something.
          I think he would have had the job done by a workshop.

          Originally posted by yoda634 View Post
          Had the head pressure tested and shaved .007." Installed the gasket, torqued the bolts
          Is it possible that the block's surface is warped?
          Did you check it with a straight edge before installation of the head?
          Is it possible that the PO did anything to the compression on the motor? ie: changed pistons to something other than stock?
          ///Monstrosity. (OO≡≡[][]≡≡OO)

          Aside from showing yourself to be offensive, lacking experience and ignorant in the ways of business, you're also illiterate and imprudent. Beyond that, your sense of liability is severely impaired.

          Comment


            #6
            Originally posted by NitroRustlerDriver View Post
            Are you sure the head is good? Almost sounds like the head warped (due to overheating) and a valve is sticking or something.
            The machine shop said it was in excellent shape, so I'm guessing no warpage.

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              #7
              Originally posted by Doughnut View Post
              Is it possible that the block's surface is warped?
              Did you check it with a straight edge before installation of the head?
              Is it possible that the PO did anything to the compression on the motor? ie: changed pistons to something other than stock?

              It guess is possible that the block is warped, but from an uneducated mind, that doesn't seem to make any sense. That's a thick piece of iron to be warping. No, I didn't check it with a straightedge. I didn't know to do that.

              It's highly unlikely that the PO did anything to the compression. He maintained the car, usually with OEM parts, and that was the extent of his involvement.

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                #8
                subscribed.

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                  #9
                  The odd compression numbers and running characteristics could be a sign that the camshaft isn't correctly timed. It is also possible that the running problems are aren't related to the head and that you have an intake leak. The definitive test for an intake leak is to have a smoke test done.
                  The car makes it possible, but the driver makes it happen.
                  Jim Levie, Huntsville, AL

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                    #10
                    I'd bet damn near anything that the camshaft is correctly timed. I checked that as thoroughly as one possibly could, several times.

                    Tell me more about this smoke test?

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                      #11
                      A smoke test is where the intake is pressurized with smoke filled air. Any leaks become immediately obvious.

                      I'd highly suggest doing another compression test. You say that before ever pulling the head you saw 145-155 across all cylinders. You should see very similar numbers now and if you don't something related to the head or cam isn't right.
                      The car makes it possible, but the driver makes it happen.
                      Jim Levie, Huntsville, AL

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                        #12
                        I would do a leakdown test in a quiet place as your next step.

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                          #13
                          I just bought a 90 325i with 170,000 miles. The car overheated and it has a lot of the same problems you describe. I'm going to change the headgasket, have the head checked/fixed, and other belts, gaskets etc. I pray to god I don't end up in the same situation as you...
                          sigpic

                          Comment


                            #14
                            Originally posted by Manfred View Post
                            I just bought a 90 325i with 170,000 miles. The car overheated and it has a lot of the same problems you describe. I'm going to change the headgasket, have the head checked/fixed, and other belts, gaskets etc. I pray to god I don't end up in the same situation as you...
                            Let me know what you find out. I did the head gasket twice and got the same symptoms, so unless I'm completely inept, something else was wrong, and I still don't know what.

                            I'm putting a new engine in the car, but I plan on continuing to troubleshoot this one after it's out. It's been a damn nightmare. I've replaced every single component of the cooling system except the expansion tank -- everything from the water pump to the expansion tank cap, and I think the head gasket blew while chasing the problem around.

                            Good luck!

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