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Yet another S14B25 rebuild thread

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  • Don't take this the wrong way evo 3....but I think you are over-thinking things a bit here.


    • Youíre probably right, but since the moment I dismantled that plug, I wanted to understand the chemical reasons why this corrosion happened, compared to other fasteners in aluminium engine parts - thatís just how I am :-) I agree however that this material selection topic is not really M3 related anymore :-)


      • Originally posted by evo_3 View Post
        Youíre probably right, but since the moment I dismantled that plug, I wanted to understand the chemical reasons why this corrosion happened, compared to other fasteners in aluminium engine parts - thatís just how I am :-) I agree however that this material selection topic is not really M3 related anymore :-)

        No worries about "off-topic" or anything like that....I just think you might be over-complicating things...for your sake....


        • Maybe the connector was never "really" tight and there was an oxygen atmosphere coupled with the coolant not being changed for many years lead to a very acetic mixture which ate away at the threads. The M42 had this problem with the profile gasket. Numerous other cars with aluminum parts have corrosion problems near the water pump.

          Once you get it fixed, I suggest you stick to low phosphate anti-freeze.


          • Sounds like a possible scenario - it must certainly have something to do with the presence of water without anti-freeze (or too long replacement interval). Maybe one of the previous owners thought that anti-freeze is not required in a summer car, who knows...

            I always use BASF Glysantin G48 on BMWs, which is phosphate free, so that should be fine.

            I called my engine shop today and will bring them the engine tomorrow. Will keep you posted.



            • This rear head outlet corrosion has been a known issue for a while.

              If you are not completely over the whole thing already, there were some threads here on from way back about the galvanic corrosion that takes place in the plug.
              If I remember it centered around when Jefrem made an S14 head plug kit (pre-dating AKGs version).

              A few people discovered the problem when they went to install Jefrem's kit.
              Reading those was the main reason why I have never taken them out of my own heads.
              FWIW, even Prodrive (or the PO to me after Prodrive) had the rear head outlet simply capped on my Gruppe A car.
              jimmy p.
              87 E30 M3 Prodrive British Touring Car
              88 E30 M3 Zinnoberot - Street
              88 E30 M3 Lachsilber - Race (#98 SCCA SPU)
              92 E30 M Technic Cabrio - S14 POWERED!
              98 318Ti M44, Base - Morea Green
              04 Ford F350 - V10


              • Thanks a lot for this information Jimmy - I did some research on and was able to find out that Brendan had just the same issue with his engine - that's probably one of the threads you were referring to (post #489):

                Yesterday, I did dome research on the thread dimensions of this fitting and on how much the thread in the head was really damaged. The original dimension of this thread is M36x1.5, not M36x2 as stated above. According to this table, the maximum inner diameter of an M36x1.5 nut thread is 34,676mm. On my engine, I measured a diameter of approx. 35mm on the damaged thread, which means that around 0.3mm have been shaved off during the extraction of the fitting. The minimum outside diameter of an M36x1.5 bolt thread is 35.73mm, so that I would still have some "overlap" of the inner and outer threads after a thread repair.

                Today, I brought the engine to the machine shop, and they told me that they had exactly the same issue on an S14 rebuild some time back. On that engine, they were able to repair the threads sufficiently well by recutting them with a tap and then they installed a new fitting with a thicker paste-like thread sealant. I suppose something like this: The good news is that they have the suitable tap available, so they will try the same repair method on my engine. Also, after visual inspection, they were not too concerned about not being able to repair my thread in the same way. They will work on my engine in the next few days - I'll inform you about the outcome.


                • Thanks a lot for your advise on the oil pump and cylinder head fitting issues, all problems are now solved:

                  Cylinder Head fitting

                  My engine shop was able to repair the thread without any problems. Luckily it seems that the thread in the cylinder head was just completely "filled" with the shaved off male thread of the fitting. We reinstalled the fitting with a new o-ring and a quite viscous type of thread sealant, so this problem is now luckily solved.

                  Oil pump to conrod clearance

                  As mentioned above, I decided to use the new oil pump and machine the housing to use a countersunk bolt on the location where I had low clearance with the #1 conrod. Some photos of the machining progress and the result are attached. With this method, I reached an additional clearance of 4mm, while the original "non DTM" S14B25 solution provides for 3mm additional clearance, so I should be fine now. I will post photos of the resulting clearance once the pump is installed.

                  Oil pump internal clearance

                  Following Dave's advice I measured the internal clearance of the oil pump gears inside of the housing (on the new pump), which turned out to be exactly 0.002", so I decided that no sanding of the housing would be required. The photos of the measuring process are attached to this post (I placed a flashlight behind the straight edge to see the remaining clearance)

                  My VAC oil pump upgrade kit arrived yesterday, so that will be the next step before reinstalling the pump in the engine.

                  The next open point on my checklist is the necessity to install adjustable camshaft gears due to the machining of the head and the block. The head was machined by 0.11mm and the block by 0.07mm, so 0.18mm or 0.007" in total. The camshafts are now installed with the original gears (A100 gear for the exhaust cam) and the camshaft positions look just like before: with the crankshaft at exactly TDC, the inlet gear is visually spot on while the exhaust gear is slightly retarded (due to the A100 gear). I have absolutely no experience with adjustable cam gears, so I would be interested to hear your opinion on this.

                  Again, thanks for all your help.



                  • After a long time of inactivity for professional reasons (again), Iím back and have worked some more on my engine the last few weeks. The engine is now completely assembled and installed in the car.

                    Iím now only waiting for my new oil cooler to arrive (the old one still looked nice but had a quite nasty dent in one of the channels, so I ordered a new one for >400Ä...) and then Iím finally ready to start up the engine.

                    I just have one last point which I would like to validate:. During the engine rebuild, the cylinder head was machined by 0,11mm and the block by 0,07mm, so in total 0,18mm are missing. The cylinder head gasket which I used is a stock S14B25 head gasket. Would this kind of machining typically require the installation of adjustable cam gears?

                    When setting the crank visually to exactly OT, the intake camshaft visually also sits perfectly on its OT mark. The exhaust cam is slightly retarded due to the installed A100 cam gear. What do you think, should I just run it like this, or would it make sense to look into adjustable cam gears?

                    Thank you in advance!



                    • What you are looking at is 0.18mm in relation to the circumference and the angle.

                      If we are talking a diameter of 120mm...

                      120*3.1416= circumference of 377mm

                      377/360=1.04mm per degree.

                      in the case of a 120mm cam pully 0.18mm of centre to centre reduction is equal to 0.19deg.

                      Don't worry about ti.
                      Sport Evo No.47

                      My Sport Evo Restoration


                      • Thank you for this calculation Steve, this makes sense and it explains why I see absolutely no difference on the visual OT marks.

                        Another question which I just thought of is related to the cooling water hoses. I replaced all the hoses and hose clamps by new ones, with the exception of the return hose coming from the heater. The reason is that the new hose supplied by BMW (part # 64211374908) has a simplified routing compared to the original design (see attached photos). The new hose can be installed in this location without a problem, but it is then interfering later during the airbox install, so I had to use the old hose. Is there any alternative hose which can be used here, or is there a way to install it without creating an interference with the airbox?

                        Thank you.


                        • I am wondering if the hose you have been supplied is incorrectly labeled, and was intended of use on a M3 with the additional water pump ďthermostat regulatorĒ.


                          E30 M3 1987
                          Mini Clubman GT
                          BMW E36 323 Msport
                          Toyota Corona
                          KTM 200EXC
                          Honda CB50 (1979)


                          • Thanks for your input on this Dave.

                            I donít think that the hose was incorrectly labelled, because the hose which I received looks exactly like the ones on the photos I found on google for the part number 64211374908 (the one which should fit in my car according to realoem).

                            However, the photos that show up on google when I search for the part number 64211381541, which is the hose for the S14 with thermostat regulator according to the link you sent, looks like the hose which was originally installed in my car.

                            In order to compare how this hose looks like in other cars I googled some engine bay photos and found this one. Here the hose looks exactly like the one which was originally in my car (and the thermostat regulator one discussed above), and not at all like the one I received, part number 64211374908.

                            I think I will order the hose 64211381541 to see if it fits. It would nevertheless be interesting to see which hose others received for their rebuilds.



                            • Here is the photo found online:


                              • Finally after all this time, my S14 came back to life this week. The engine started immediately at the first crank (after the usual procedure of first building oil pressure without spark plugs and fuel injection), but it was running at very high idle (around 1400-1500 rpm) and with quite some misfires. Given that the engine was not fine tuned yet, I let it heat up to complete the filling of the cooling circuit. Also at operation temperature, the idle had not changed, so I tried adjusting it, but the turning of the main idle adjusting screw however did not have any effect. I then found out that the idle control valve was not buzzing at ignition key in position 1. I checked the resistance values on the ICV against the specs which I found here on the forum (1-2: 20,6Ohm / 1-3: 43,1 Ohm / 2-3: 22,6Ohm and the spec says 20/40/20 Ohm) and the wiring to the ECU and all seemed fine to me, so I went ahead and opened up the ECU to check for burnt ICV transistors. The transistors looked fine at first look, but when I checked the backside of the PCB I found that the circuit going from the Transistor to Pin 34 of the ECU connector was very slightly damaged, but just enough to interrupt the circuit (see attached photo). Also I found out that the original transistors (type ON588) were already replaced by one of the previous owner to the recommended replacement type BDX53A. However, it seems like the previous owner overlooked a slightly (but not completely) burned circuit on the board, which then developed into a complete failure now after my engine rebuild (the engine ran without any idle issues before disassembly).

                                I read all the threads about ICV failures here on the board, and the consensus seems to be that when such a failure occurs, the ICV and the transistors should be replaced. Given the price of 500Ä of the ICV, and considering the good resistance values of my ICV, would it still be recommended to replace it? I don't want to be cheap on this, but from what I read on the board, the typical failure mode of the ICV valves is when the resistance starts to go down (ending up in a short circuit?) and not slightly higher than spec.

                                I have already ordered the transistors online (0,30Ä / piece) and will repair the ECU as soon as I have the parts. In order to avoid the ECU damage to happen again, I read that it's possible to install a 3A fuse in the ICV power supply line coming from the main relay. I attached an extract of the electric circuit diagrams where I marked the wire in which I intend to install the inline fuse holder. Is this the correct location for this fuse?

                                While I wait for the parts to arrive, I wanted to prepare the different steps to get the injection-related components set up. This is what I intended to do:

                                1) Short-circuit the TPS connector on the engine harness and set the idle speed to approx. 880rpm
                                2) Setup the fuel mixture with the AFM adjusting screw, using a voltmeter connected to the black wire of the disconnected O2 sensor (target value 0.5V if I recall correctly)
                                3) Synchronize the throttles by adjusting the bypass screws using manometers
                                4) Have the fuel mixture fine adjusted at a workshop using a CO meter

                                Is this sequence ok or would you recommend to do it differently?

                                Thanks for your comments.