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Thread: Another M60 Vaccuum Leak

  1. #1
    Join Date
    Nov 2009
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    Another M60 Vaccuum Leak

    I have replaced the intake manifold gaskets on this 1995 530i 3 times for the 10 years I have owned it. In those 10 years I have only replaced the water pump and thermostat once. So I decided to work on it this weekend, replace the water pump, thermostat, the knock sensors and the manifold gaskets including the throttle body and pcv gaskets.

    Before jumping into the job, I noticed the intake boot was completely torn and was letting unfiltered air in. Strange since the car did not idle bad, it was not perfect but it was a sliiiight rough idle that one can easily attribute to bad motor mounts.

    Anyway, I order the intake pipe and begin to tear down the intake and cooling system. I foolishly forgot to order intake gaskets and throttle body gasket. For whatever reason, it thought I had them on hand. No matter, I'll replace the pcv gasket and the both orings on the metal tube that runs under neath the manifold. I ran into issues trying to put the new water pump because the SAP metal pipe is running right infront of it and making it difficult to place the water pump. So I loosen it by removing the nut connecting it to the SAP valve(?) That is infront of the passenger side head. Then I lift the pipe that seems to be connected somewhere in the driver side. Hard to tell but I am assuming it's the exhaust? Either way it gave me good clearance and I was able to put on the water pump with no issues. I then lower the pipe and tighten it up back up to where it meets with the other end of the pipe.

    After reinstalling everything, the car ran with a high idle and it would have a hunting idle. It would rev itself and then eventually after 30 seconds it would stall. Weird, but I assumed it was the intake manifold gaskets and throttle body gaskets being worn and the intake pipe (fixed it with black tape as a temp fix). So just to verify, I buy a cheap cigar and blow it into the manifold (removed MAF) from the SAP vacuum line behind and the brake booster line infront of the manifold. Smoke came out of the intake manifold gaskets and the throttle body. Great, I'll wait for the parts.

    I get the parts yesterday and I install the manifold and throttle body gaskets plus the gaskets that come with the new intake pipe.

    Same problem, but now I have a check engine code 1215 for MAF. Car hunts for idle for about 30 seconds and then it just stalls.

    I assume I installed the gaskets wrong or something so I use the cigar method again and there is no smoke coming from anywhere. Once I removed the cover on the intake pipe, a bunch of the smoke came out.

    So I figured coincidence on the bad maf? I replaced it with a used b30 maf unit I had and the check engine stayed on. Same deal, stalls after 30 seconds if I don't hold the gas pedal. Run the car with the maf unplugged, same deal, it stalls after 30 seconds. I figured it's a bad idle control valve? So I put in a used idle control valve I had laying around but I think it belongs to my 95 525i since the number on the ICV says 268(?) While the original one that came with the 530 came said 292 I believe. No difference.

    I was parked on the street and I needed to move it so I dont get a ticket so I held the gas and put it in gear and moved it to another spot. Car struggled and made a loud knocking noise, assuming it is misfiring horribly.

    So now I am at a loss. I've done this job several times and I have never experienced this issue. I read other threads about MAF code could also mean that the computer does not like the air/fuel mixture and it does not necessarily mean the maf is bad. It was running fine before the job but I can't see how it ran better with a completely torn intake boot and old gaskets than now with new parts.

    Is it possible that when I pulled the metal pipe for the SAP that I messed something else up? Even if it created an exhaust leak, I don't see it causing a stall. Unless the system is extremely sensitive. But shouldn't the SAP be closed after the initial cold start and it would no longer cause a vacuum leak? At this point I have no idea what else to do.

    The only thing I did not replace is the pcv but I remember replacing it with a meyle unit about a year or two ago. I don't see how it can cause this stalling issue though. Esp if I don't see smoke coming out of it.

    Car has b40 intake manifold, throttle body and maf since 2015.

    Apologies for the long post but I feel like every bit of info helps. Also written using my phone.

    Tl;dr: Car can't hold idle and stalls after replacing intake manifold gaskets, throttle body, pcv gasket, intake pipe and associated gaskets, replaced all hoses connected to manifold and orings for the metal pipe under manifold. 1215 code and replacement used maf does not change check engine light or car performance. Possible SAP issue?

  2. #2
    Join Date
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    The PVC Plate has those plugs in the back, if they deteriorate will cause a vacuum leak. I think anyone with this motor should religiously replace this PVC Plate as the manifold collects a lot of oil and the oil deteriorates the diaphragm or cause it to get stuck. This engine would benefit from a PVC Delete and a oil catch can setup, but I am under CA SMOG and this setup will not pass emissions. For those who live in a state that allows for catch can setup, you should consider this upgrade as an efficient way to deal with this M60 engine flaw.

    Another culprit for vacuum leak is the oil cap, this needs to replaced as part of regular maintenance. Also the Brake Booster might be causing this vacuum leak and will NOT show up on a smoke test.

    I suspect possible brake booster leak, since you seem to have covered most of the connections on the engine except for PVC Plate & Plugs and smoke test didnít identify any further leaks. If it turns out to be the brake booster, just have it rebuilt as a new one is almost impossible to find and if you do find it will be way over priced.

    Good Luck on your vacuum leak hunt.
    Last edited by E34 Lives; 05-22-2022 at 02:50 PM.

  3. #3
    Join Date
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    I appreciate your reply. I replaced the pcv cap in the back when I was replacing everything. I gave it another go earlier today and I could not find any vacuum leaks. I had someone start the car and I disconnected the hose that connects the intake manifold to the brake booster and blocked the hose connected to the manifold. It did not make any changes in idle. So i figure the brake booster is fine.

    I did the smoke test again with a cigar and it doesn't come out anywhere.

    I disconnected the battery and reconnected the other maf I had laying around. I no longer get a MAF code when I immediately start the car, now I get a 1253 code which seems to be for fuel injector number 3? I reseated the electrical connection. The car still runs the exact same. Hunting idle until it just stalls. I don't see how a fuel injector can just go bad and not give any symptoms after a week and some change of working on the car. I disconnected the battery again and after reconnecting, the same check engine comes on immediately and gives code for fuel injector 3.

    I drove the car (holding gas pedal and brake pedal at the same time while putting it on drive) a few blocks and when I accelerate it sounds like loud knocking. I am assuming these are misfires? I hear no knocking when the car is idling or when I rev the car when it's not in drive.

    I replaced the ignition coils with known working used bremi coils I had laying around. No change. I found some oil in the ignition coil for cylinder 8. I ordered valve cover gaskets for both sides seeing as they seem to be shot. No other ignition coil/spark plug had oil. I did not replace the spark plugs but I have a brand new set I was waiting to put in. I may just do it next time I work on the car.

    When I rev the engine while it is struggling to idle I hear a faint hissing sound. Not sure if it's just the suction of the intake manifold or an air leak. I cant trace the sound, it seems to be coming from the middle of the manifold. The smoke test showed absolutely nothing.

    Waiting on the pcv valve in order to replace it. At this point, I am running out of ideas. Do the intake manifold on these cars crack easily? I did not drop the manifold when I had it out to replace the gaskets. Can a vacuum leak cause such loud knocking/misfires when the car is being driven?

    Did some of my wiring go bad somehow? Bad cam position sensor? Bad dme?

  4. #4
    Join Date
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    I'd smoke test the crankcase too. I found a leak in one of my M62 timing covers that way (using a cigar). The leak let it pull air in through the CCV system.

    The cigar method can work, but it might not. If you can't find the leak, you might want to get it professionally smoke tested.

    And lean mixtures can come from too little fuel, bad MAF, etc., not just too much air.
    Last edited by R Shaffner; 05-25-2022 at 07:16 AM.

  5. #5
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    Since its been 7 months, id assume and hope that you found the issue. Can you share what it was and how you found it?

  6. #6
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    Quote Originally Posted by Hogg View Post
    Since its been 7 months, id assume and hope that you found the issue. Can you share what it was and how you found it?
    To be honest, i haven't fixed it yet. It is a back up car and its been sitting. I still turn it on once every 2 weeks so the battery doesn't die but it still has the fluctuating idle and stalls after the secondary air pump turns off unless you give it gas. I want to take it to get a professional smoke test but i broke my arm a few weeks ago so that put a further stop to fix the car. Once i am back and able to work on the car i will update.

    If it matters, the only thing i have not replaced and i feel may have fell off when i had the manifold off is the oring for the air intake temp sensor. Not sure if that can cause such a big vacuum leak but its been on my mind. I've replaced every single gasket that can cause a vacuum leak on the car besides that one.

  7. #7
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    What was the fix for this issue?

  8. #8
    Join Date
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    My money is on brake booster if smoke test does not show leak, which it will not in a brake booster leak. To test, at idle with car in drive on open road where you can safely pump brake aggressively, do this and if engine cuts out then you found your leak.

    Another is the manifold bolts, each have an individual gasket that holds down manifold, if they are old then they might not compress down enough, but a smoke test will identify leak in this case.

    Curious to see what was the cause.

  9. #9
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    Apologies for the delay in replying.
    I ended up taking it to a BMW indy and he smoke tested it and find a very very tiny leak on the manifold gaskets. Despite the gaskets being new, he replaced them again and smoke tested and found no other leaks.

    He ran diagnostics on everything and could not find the problem. He checked compression and stated all numbers were healthy and within spec, switched maf with a known working one, switched dme with a known working one, ran tests on auto tranny to see if torque converter was bad, and other tests I can't remember off the top of my head since it's been about a year. Basically, he could not find the problem. He said he's been a bmw mechanic for decades and could not figure it out and it has him and his mechanics stumped.

    He did say maybe it was a wiring harness issue since he cant think kf anything else but he does not have a spare and would be an expensive part to buy new without confirming its actually bad.

    What I ended up doing was disconnecting the wiring harness on the top of the manifold where it connects with the wiring harness to the dme and other computers. It was stuck and after tinkering with it I was able to get it free, cleaned the contacts and reconnected it. The car idles much better and does not fluctuate as much as before. I am thinking that the wiring harness is bad somewhere and somehow. I managed to get a wiring harness from a 530i from the junkyard but have not installed it due to time.

    The car runs, doesn't die on idle nearly as much as it did before but I've been barley driving it until I can get the harness fixed.

    Will update once I have the free time to replace wiring harness.

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