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  • Engine rebuild question

    Hi,

    I have been reading this forum for many months and this is my first post.

    My engine has approximately 156000 miles and I am considering a rebuild. Now, through searching the archives, I am under the impression that no one would recomend a rebuild unless the engine was blown. Mine, however, runs fine. I've not done a compression test, but it start, runs, pulls hard, doesn't make more than the required amount of noise, etc. My reason then, is that nearly every seal or gasket has something oozing past it. Also, under hard acceleration there is a bit of a cloud behind me, leading me to believe the valve seals could use some attention. And, to top it all off, I'm not sure if the chain has been done, so I'd like to take car of that. Nothing really to be considered "major", but annoying none-the-less.

    My question then is this... Do I leave well enough alone, and just do the chain? Or should I do a "minor" rebuild. Don't laugh, I know "minor" sounds foolish. Ideas?

    Thanks in advance!

    Jay

  • #2
    Jay,

    It all depends on the budget you want to spend. If you are going to take the head off, and do the timing chain, you would be wiser, to do an entire rebuild. Best thing would be to do a compression test and copare to other postings, or post your results, then make your decision. The smoke on acceleration could either be oil or your car running very rich so some more info would help.
    E30 M3 for the Road
    & one for the Track &
    a S14 2002 for fun

    Comment


    • #3
      What color is the cloud? Usually a light-colored clound under acceleration is your rings; when you see it under engine braking it's probably your valve seals. A dark cloud means the mixture is overly rich.
      Do a compression test, it doesn't take much time and will tell you a lot.

      If you can do the work yourself, you can replace the chain/guides/tensioner and all seals. Might as well do the oil pump and rod bearings, too. Should cost less than 1000 if you price-shop.
      But if your compression is bad or you need a valve job, you'll obviously need more expensive internal work.

      Comment


      • #4
        I firmly believe that if you are going to replace the timing chain, so much work is involved in doing that you might as well overhaul the entire engine.

        I personally believe it is a myth that the timing chain needs to be replaced at a certain interval. A timing chain, and this is true on pretty much all engines, is designed to last for the life of the engine and only be replaced when the engine is rebuilt.

        Some say you can replace the timing chain without pulling the head. Maybe so, but doing it that way I think you are virtually guaranteed to wind up with oil leaks around the timing chain cover, particularly at the head junction.

        Once you have stripped the engine basically down to a short block for the timing chain replacement, at that point I think it would be false economy not to do the complete rebuild.

        The oil leaks you are having point further to the wisdom of a rebuild. You could certainly just live with the leaks, but who wants to?

        Engines usually don't just "die" and need to be rebuilt. Compression and power gradually drop, leaking increases, more oil is burned, etc. Whether your engine is at that point is for you to decide. But don't tear down the engine just to do the timing chain.

        Comment


        • #5
          Re: Engine rebuild question

          Originally posted by bmwmpower89
          Now, through searching the archives, I am under the impression that no one would recomend a rebuild unless the engine was blown.
          Not really true. It's a lot cheaper to rebuild your motor before it self destructs.

          What people generally say is that it doesn't make sense to rebuild the motor unless you know there is a potential problem. In general these motors are pretty tough.

          Comment


          • #6
            Yes, leave well enough alone...unless you feel the engine should be rebuilt and want to have peace of mind. If it's smoking and consuming more oil than recommended then you're engine sounds like it's getting tired. I wouldn't JUST replace the chain and tensioner though. I'd do so only with a rebuild. Do a leak down test and see what kind of condition it's in and go from there. Don't worry about leaky gaskets at this point. With that kind of mileage on old gaskets you can expect some leakage. Do a full rebuild. I would start thinking about what kind of rebuild you want to do (ie 2.3/2.5, cams, headwork, custom pistons).

            88 M3 - LACHSSILBER/M TECH
            89 M3 - ALPINEWEISS II/SCHWARZ
            85 323I S52 - ALPINEWEISS/SCHWARZ
            91 M TECHNIC TURBO - MACAOBLAU/M TECH


            Comment


            • #7
              Re: Re: Engine rebuild question

              Originally posted by bmwmpower89
              Now, through searching the archives, I am under the impression that no one would recomend a rebuild unless the engine was blown.
              Originally posted by Mick
              Not really true. It's a lot cheaper to rebuild your motor before it self destructs.

              What people generally say is that it doesn't make sense to rebuild the motor unless you know there is a potential problem. In general these motors are pretty tough.
              Sounds like something i might have said...however the question was different. IMO, I don't see the need to go to a 2.5 if you have a perfectly fine running 2.3. This situation is different. A compression and leakdown needs to be done to see what (if any) problems exist.

              Comment


              • #8
                I rebuilt mine (2.5) at 170K. IMHO if you have the means, go for the rebuild - especially if upgrades are planned. My car is a hundred more times fun to drive now. Big difference between a stock, tired 2.3 and a built 2.5...
                2000 Porsche Boxster S - Daily Driver
                1995 Porsche 993
                2001 BMW 530iA Sport (hers)
                2004 Ford F-150 FX4
                2005 KTM 450EXC (More fun than all of the above)

                Gone:

                1988 BMW M3 2.5 EVOIII Replica
                1985 BMW M635CSI
                2001 BMW M3
                1988 BMW 325is (E30 M3 springs, steering, Konis, etc) - my favorite BMW - missed.

                Comment


                • #9
                  You've come to a pretty slippery slope, because it's hard to decide when enough is enough.

                  1. You could just replace the timing chain and the gaskets that are leaking. I'm in that camp that you don't _need_ to replace the chain at a set interval, but I have nothing to back that up with.
                  2. You could also go in a do rod bearings and a bunch of other internals. However....
                  3. If you want to replace the rings at that mileage, you are probably going to have to re-bore the block and get oversized pistons in place.
                  4. But if you are already boring the block and buying new pistons, maybe you should also get a new 2.5L crank too along with some 2.5L pistons in place of the oversized 2.3 pistons.
                  5. And with all that displacement, it would make sense to refresh the head, replacing the valve guides and seals, maybe recutting the valve seats.
                  6. While the head is off, maybe it is a good time to port the head. Afterall, the 2.5 could use the additional breathing.
                  7. And to best take advantage of the ported head, some 48mm throttle bodies would be nice. Maybe an Alpha N (or something) kit too.
                  8, 9, 10, 11, 12, 13...... use your imagination.


                  Personally, I think once you crack it open you may want to go up to 4 (5 if you are having valve train issues.)

                  Comment


                  • #10
                    Originally posted by Chris F.
                    You've come to a pretty slippery slope, because it's hard to decide when enough is enough.

                    1. You could just replace the timing chain and the gaskets that are leaking. I'm in that camp that you don't _need_ to replace the chain at a set interval, but I have nothing to back that up with.
                    2. You could also go in a do rod bearings and a bunch of other internals. However....
                    3. If you want to replace the rings at that mileage, you are probably going to have to re-bore the block and get oversized pistons in place.
                    4. But if you are already boring the block and buying new pistons, maybe you should also get a new 2.5L crank too along with some 2.5L pistons in place of the oversized 2.3 pistons.
                    5. And with all that displacement, it would make sense to refresh the head, replacing the valve guides and seals, maybe recutting the valve seats.
                    6. While the head is off, maybe it is a good time to port the head. Afterall, the 2.5 could use the additional breathing.
                    7. And to best take advantage of the ported head, some 48mm throttle bodies would be nice. Maybe an Alpha N (or something) kit too.
                    8, 9, 10, 11, 12, 13...... use your imagination.


                    Personally, I think once you crack it open you may want to go up to 4 (5 if you are having valve train issues.)
                    Everything state here is what I would say. I agree also that you only would have to go to five. Less would be a waste of an opportunity to take care of it once and for all. I would say six is not far out of the question either. Seven and on is completely for the fun factor, and really does not have anything to do with building a reliable motor. If cost is going to be a factor here, buy the best parts you can and only go up to say three or four. Making horsepower is great, but making reliable horsepower is better.
                    1990 e30 m3

                    Comment


                    • #11
                      Your oil leak problem *could* be related to the "PCV" hose from the valve cover to the intake, make sure that's clear and clean. Loosen your oil fill cap with the motor running, you should be able to feel the vacuum holding the cap on, if it wants to blow off in your hand you need to look at the PCV hose.

                      I would suggest doing a compression test, wet and dry, and do a leakdown test, before taking things seriously apart.

                      The smoke under acceleration may or may not have anything to do with the state of wear on your engine. As previously noted, valve guides cause smoke under deceleration.

                      A rebuild is expensive enough that you dont' want to do it "for the hell of it".

                      150K miles is not *that* high a mileage for a modern motor built to the standard that the S14 was built to. But if it's bee abused or poorly maintained, it might be tired.

                      Comment


                      • #12
                        Hi Jay,

                        Quite a bit of good advice here. As others have said, get leak down and compression tests done before proceeding. That will tell you were the engine is at, health-wise. Something else to consider is the real cost of a 2.5 rebuild, especially given the Euro-dollar rate. Plan on a minimum of $8k, using new parts (e.g. crank, pistons, gaskets, T-chain, oil pump) and your block, head, valves. Perhaps budget constraints will help you make a decision.

                        I'm in Colorado too and just rebuild my engine to a 2.5. Perhaps I can help with in-state resources, few and far between that they are. Send me a pm if interested.

                        -Dietrich

                        Comment


                        • #13
                          Most of the standard oil-leaks can be fixed easily (though time consuming) without opening up the engine.

                          From my experience, the common oil-leak points on our engines are (In no particular order - just as I remember them):

                          Sump gaskets
                          oil filter housing to block
                          oil pressure switch
                          oil temperature switch
                          oil pressure relief cover (on filter housing)
                          crankcase ventilation system (the black plastic tube below the starter motor)
                          cam cover
                          rear cam carrier plate (at the back of the engine close to the bulkhead)
                          distributor to head
                          oil cooler pipes

                          Probably a lot more...
                          Steve
                          Scottish Cecotto

                          Comment


                          • #14
                            Originally posted by SteveM
                            From my experience, the common oil-leak points on our engines are (In no particular order - just as I remember them):

                            Sump gaskets
                            oil filter housing to block
                            oil pressure switch
                            oil temperature switch
                            oil pressure relief cover (on filter housing)
                            crankcase ventilation system (the black plastic tube below the starter motor)
                            cam cover
                            rear cam carrier plate (at the back of the engine close to the bulkhead)
                            distributor to head
                            oil cooler pipes
                            I think you _have_ to add the timing chain cover to that list, even if it approaches the "opening up the engine" category.

                            Comment


                            • #15
                              Rebuild it before it goes ka-boom... I'm not saying that's imminent, but, you never know... I can tell you from looking inside many S14's, after 120K or so, the bores are pretty scuffed and out of round, the small end of the rods are very worn, as are the exhaust (and probably intake) valve guides. If an aggressive chip is in the car, most likely rod bearings are showing signs of wear and the top ring lands on the pistons may be ready to fracture too.

                              I don't mean to be an alarmist, but, north of 150K is a bunch of miles for a car that might get driven shall we say "spiritedly" ???


                              Ron ///Man Checca
                              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


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