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Thread: Blown upper rad hose knock sensor codes oil leak, all related?

  1. #1
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    Blown upper rad hose knock sensor codes oil leak, all related?

    Ok so i have a 97 740iL, the other nite my check engine light comes on, car seems to be running fine & im not far from home so i go there. Popped the hood to scan it and notice my upper rad. hose is split open. So i scan and get P0325 knock sensor circuit or sensor 1 circuit malfunction. Im also noticing a strange sound from inside intake, kinda sounds like a liquid dripping onto an extremely hot surface, lots of popping and sizzling sounds, so i pull the air box and MAF off and open the butterfly and smoke starts to come out. Smells kinda like burnt plastic. Then i notice alot of oil under the intake and down the front of the engine and on the left frame rail right under oil filter housing. So i clear the code and replaced the upper hose, did a little research and read the oil separator valve often causes the type of oil leak i have. I see that you can test this by pulling dipstick out while engine is running and check for vacuum and/ or whistling sound, rough idle so i do this and yes definitely got all those things. So thats probably going to be my oil leak. I go to order the osv and on the way check engine light comes back on, this time p0330 knock sensor bank 2 circuit malfunction and there seemed to be a lot of coolant leaking out from under the car but i really couldn't tell from where. I obviously have multiple issues, so my questions are could it be as simple as knock sensors (dtc's) and osv (oil leak) and possibly valley pan (coolant leak)? If so why did a different knock sensor code come up and not both the previous and the new one? Thanks in advance to any and all help, it is greatly appreciated

  2. #2
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    The knock sensor errors are from overheating the engine (did you notice the temperature gauge going into the red?). The PCV is on the back of the manifold (the OSV is right inside the engine) - neither cause external oil leaks - only blue smoke from the exhaust. More info on PCV/OSV here:

    https://www.meeknet.co.uk/e31/BMW_M6...entilation.htm

    If you have oil leaking externally from the engine then it isn't the PCV - it's something else.

    My best guess is that you have overheated the engine causing multiple problems - but sort the coolant and oil leaks first and take it from there.
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


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  3. #3
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    [QUOTE=Timm;30126424]The knock sensor errors are from overheating the engine (did you notice the temperature gauge going into the red?). The PCV is on the back of the manifold (the OSV is right inside the engine) - neither cause external oil leaks - only blue smoke from the exhaust. More info on PCV/OSV here:

    https://www.meeknet.co.uk/e31/BMW_M6...entilation.htm

    If you have oil leaking externally from the engine then it isn't the PCV - it's something else.

    My best guess is that you have overheated the engine causing multiple problems - but sort the coolant and oil leaks first and take it Temp was 210°F when p0325 occurred and 169°F when p0330 occured. And i read from multiple sources (doesnt mean its true though) that the vacuum, rough idle, and whistling sound being present at dipstick tube when engine is running is an indicator that the osv or ccv has gone bad, and i definitely have all three present when i pull dipstick with engine running. Thanks again for your help as these cars are new ro me.

  4. #4
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    I do have some of those symptoms, poor pick up under light acceleration, poor idle/misfire, high oil consumption. But none of those trouble codes.

  5. #5
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    Did you overheat the engine?
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


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  6. #6
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    No like i said freeze frame says coolant temp was 210°F when p0325 occurred and 169°F when p0330 occurred and the gauge was reading normal no steam or nothing to indicate overheating when i opened the hood, except after p0330 occured (i drove the two blocks to my house after i saw CEL) after turning off the engine, there was some coolant expelled from somewhere that i noticed on the ground, which i believe came from possibly the valley pan or wherever my coolant leak is. other than that, nothing to indicate overheating. And the gauge wasnt even in the middle yet when i arrived
    at home (169°F temp from ff data at time dtc was set ).

  7. #7
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    You say no but symptoms indicate yes.
    Sorry, but in my opinion YES, the engine was overheated.

    Now let's verify who is correct by performing a cylinder leakdown test,
    combined with a cooling system pressure test. Post back with results.

  8. #8
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    So just an update for anybody with these symptoms curious on the cause. So I replaced all the knock sensors, valley pan, osv, thermostat (sensor was leaking), all the hoses, and all new gaskets where needed. Valley pan fixed coolant leak, osv gasket had failed and was the cause of my oil leak, and one pair of knock sensors had a knick in the insulation exposing the wiring, and the other had oil seeping out of where the wire goes into the sensor, so those i believe were the causes of my two knock sensor codes. Its been about 6 weeks since replacing everything and I drive the car everyday, all the leaks are gone and have had no codes return. Thanks

  9. #9
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    That's great news!
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


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  10. #10
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    Quote Originally Posted by Spuddd View Post
    all the leaks are gone
    No such thing with these engines!
    But congrats!

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