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Thread: Oil in Coolant - Not head gasket related

  1. #1
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    Oil in Coolant - Not head gasket related

    I have a 2004 325xi. The other day the low coolant light came on and when I looked in the expansion tank the coolant was an oily/off white color. My first thought was the head gasket however the engine oil is at the proper level and color (no coolant mixing). In addition there is no maple syrup smell present nor any white smoke in the exhaust. The car has also never had a cooling problem or overheating in all the time I've owned it (bought 7/2011 with 70k, now has ~172k).

    To add to this the other day when I was driving home I noticed what appeared to be a slight delay in the auto transmission shifting. I can't really tell what type of oil is being mixed however I've tried flushing the system a few times and it keeps coming back. I don't really live near any BMW shops so I was hoping to try to diagnose/fix the problem myself if I can.

    My question is this: On the 2004 325xi I assume the transmission has a cooler on it. Where is it located and is there a way to check it for leaks? Also on the transmission itself I've been told they're "sealed" units so is there any way to check the transmission level or to see if coolant is getting in there?

    Thanks in advance!

  2. #2
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    I believe only auto transmissions have a cooler:

    dZPILGI.png

  3. #3
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    Yes it is an automatic. Thanks for the diagram I'll have a look at it this afternoon.

  4. #4
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    Be very careful because plastic bracket around that corner of the radiator is very brittle and usually breaks the second you touch it. Same goes for the little automatic transmission thermostat that sits below the expansion tank. ATF Heat Exchanger mentioned in the image below is a "layered" aluminum block with hoses going in and out (could be seen on the image in my previous post).

    coolant flow.jpg
    Last edited by Mless5; 11-17-2017 at 11:06 PM.

  5. #5
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    Your transmission is most likely getting coolant contamination also. Coolant is VERY BAD for your transmission. The friction material in the clutch plates will absorb the coolant/water mix and swell causing all kinds of problems. Transmission cooler is probably cracked internally creating a leak between the two fluids/systems. While driving the trans fluid pressure is higher than the cooling system pressure so trans fluid will enter the cooling system. When you shut off the engine, trans fluid pressure drops to zero but the cooling system is still pressurized for a while. Coolant is entering your transmission then. Heat exchangers crack sometimes due to the heat cycling and having two fluids with two different temperatures flowing through the cooler. If this is your problem you will need to replace as much of of the transmission fluid as you can with either multiple drain/fill or a flush. Clean inside the pan and replace the filter too. Only other possible way to get oil in the cooling system is a head gasket problem or a cracked head or block or any of the other problems that happen when you overheat an m54 like pulled out threads in the block for the head bolts. Oil analysis of a sample of the stuff that is floating in your reservoir should tell you what it is. After the problem is fixed the oil in the cooling system can be cleaned out by draining the block and radiator running water and dawn dish soap in the cooling system. Depends on how much oil is in the system but you may need to do this a few times. Follow with a few fill/run/drains with water only. Then obviously fill with the proper coolant mixture. Good luck you are up against a possibility of an expensive problem.

    Sent from my SAMSUNG-SM-G870A using Tapatalk

  6. #6
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    To add to what Randy has written, don’t drive the car. Don’t start the engine. Have the car flatbedded to a reputable shop. Try www.bimrs.org. Also, google “BMWCCA #####” where “#####” is your zip code. That’ll give you the link to the local chapter of the BMW Car Club of America. Check the website for shop recommendations.

    The tranny will need a complete fluid flush. Luckily, your tranny was made by GM of France. How do I know? You have an “x” E46. BMW installed only GM trannies in that version of the car. So, the fluid (Dex3) is relatively cheap. The tranny fluid filter will have to be changed also as will the tranny fluid cooler. The cooling system will need to be flushed with a cleaner to remove EVERY trace of tranny fluid. It’s a good idea to bring the cooling system maintenance up to date, too.

  7. #7
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    Thanks for the replies everyone. My next question before I dig into this is with the transmission fluid - is there a way to check it without disconnecting everything? I'd like to see if that's contaminated too (as I assume it is). The connections on that transmission cooler unit seem very brittle, and before I go breaking something I wanted to know if there was another way to check.

  8. #8
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    You’re going to have to replace a bunch of parts. Sorry, even quality German plastic gets brittle over time and heating cyles. I guarantee that the tranny fluid is contaminated as is the engine coolant. If you plan on keeping the car you’ll have to see the costs and efforts as investments.

  9. #9
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    This is a common issue on some of the Mercedes of similar era where the radiator internals fail and let coolant and trans fluid mix. Ive never heard of this issue on an E46 though, you will probably need to replace the radiator and thoroughly flush both the cooling system and transmission.

    When i have repaired the Mercedes ones in the past i run a mix of dish soap and water in the cooling system and take it for a short drive. Then i flush it out and repeat if necessary, once all the oil is out i do one final flush with just water, and then proceed to fill it correctly with coolant.
    Current:

    - 09 335i MSport, FBO.
    - 98 Euro M3, Estoril Blue
    - 04 M3, Carbon Black, 6 Speed Coupe
    - 06 M5, Black on Black, Full Leather.
    - 73 3.0CS, Tagia Green, 5 speed M30b35 converted

    Ex's: 1984 325e, 1988 325IX, 1992 525I, 1995 540i/6, 2002 330i, 2005 330xi, 1992 850i, 2003 330i #1, 2003 330i #2, 2002 330ci, 2004 330ci, 2007 328CI, 2007 335i, 2001 M3, 2006 M5 6 speed

  10. #10
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    So I've been taking the coolant system apart to get access to the transmission cooler. So far it's been a fairly straight forward process however I'm having a very difficult time getting these quick connect hoses off of the cooler itself (the lines coming from the transmission). Is there a trick to these? They seem like they want to break off however I don't think that will solve anything.

    On a positive note (if there is one) I also opened up the oil filter to check on the engine oil in there and there's no sign of coolant present, so I'm even more confident that it's not engine oil that's been mixing in.

  11. #11
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    Quote Originally Posted by SilverArrow04 View Post
    So I've been taking the coolant system apart to get access to the transmission cooler. So far it's been a fairly straight forward process however I'm having a very difficult time getting these quick connect hoses off of the cooler itself (the lines coming from the transmission). Is there a trick to these? They seem like they want to break off however I don't think that will solve anything.

    On a positive note (if there is one) I also opened up the oil filter to check on the engine oil in there and there's no sign of coolant present, so I'm even more confident that it's not engine oil that's been mixing in.
    There is actually a special tool to release them. Its possible but can be tricky to seperate them without it. You need to press the plastic ring into its housing while pulling the pipe out.

    https://www.amazon.com/Assenmacher-S.../dp/B002UBO1WA
    Current:

    - 09 335i MSport, FBO.
    - 98 Euro M3, Estoril Blue
    - 04 M3, Carbon Black, 6 Speed Coupe
    - 06 M5, Black on Black, Full Leather.
    - 73 3.0CS, Tagia Green, 5 speed M30b35 converted

    Ex's: 1984 325e, 1988 325IX, 1992 525I, 1995 540i/6, 2002 330i, 2005 330xi, 1992 850i, 2003 330i #1, 2003 330i #2, 2002 330ci, 2004 330ci, 2007 328CI, 2007 335i, 2001 M3, 2006 M5 6 speed

  12. #12
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    Quote Originally Posted by randy72877 View Post
    Your transmission is most likely getting coolant contamination also. Coolant is VERY BAD for your transmission. The friction material in the clutch plates will absorb the coolant/water mix and swell causing all kinds of problems....
    So I've removed the connections and a LOT of coolant came out confirming that it was a faulty transmission cooler. Due to the large amount of non-ATF liquid that has been in my transmission and the fact that I have no idea how long this was going on for (Last coolant check was beginning of the month. I've driven maybe 150-200 miles since) is there any special transmission flushing I should be doing? I've read a few forums on here describing the procedures however I'm not sure at this point if I should bring it into a shop to do.

    Thanks for everyone's help so far. I would provide pictures if I could figure out how.

  13. #13
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    The car is going to have to go to a tranny shop to flush the tranny. Sorry. Basically, the tech attaches the hoses that run from the tranny to the tranny fluid cooler to a machine. The machine has two tanks: fresh fluid and, at the start, no fluid. Fluid is pumped through the tranny. Now, I don’t know if the machine does the pumping or if the tranny does it. I’m sure a reputable shop has seen the mixing of coolant and fluid before, so the tech should know if a mild detergent is added to the fluid initially.

  14. #14
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    You have 2 options. Take the car to a shop for a true flush, which as mentioned pumps fluid through the transmission while it is operating(make sure you are clear that you need it flushed, many shops dont flush as part of a transmission service, they just drain and fill with a new filter).

    The other option is to fully drain the transmission and the torque converter, then fill to spec with a new filter. Drive it for a short time and then repeat the process. After the second flush you should be fine.
    Last edited by legoman67; 11-22-2017 at 12:15 AM.
    Current:

    - 09 335i MSport, FBO.
    - 98 Euro M3, Estoril Blue
    - 04 M3, Carbon Black, 6 Speed Coupe
    - 06 M5, Black on Black, Full Leather.
    - 73 3.0CS, Tagia Green, 5 speed M30b35 converted

    Ex's: 1984 325e, 1988 325IX, 1992 525I, 1995 540i/6, 2002 330i, 2005 330xi, 1992 850i, 2003 330i #1, 2003 330i #2, 2002 330ci, 2004 330ci, 2007 328CI, 2007 335i, 2001 M3, 2006 M5 6 speed

  15. #15
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    So as an update in the past 2 weeks I fully flushed the coolant, replaced the transmission fluid cooler, and flushed out the transmission myself ($35 for a new kit + ATF vs. $460 at the local shop). The car runs and drives normal again however I have one minor issue with the gear indicator on the instrument cluster. All of the sudden it goes blank (ie. the letter P, R, N, or D) will disappear. Its sporadic and doesn't happen all the time, and not at all when in manual/sport mode however prior to this mishaps it never occurred. Any ideas what could cause this? When I replaced the pan gasket and filter I saw a ton of wires and I was extra careful not to touch anything. I'm not sure what could've caused this however it is extremely irritating.
    Last edited by SilverArrow04; 12-01-2017 at 08:26 PM.

  16. #16
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    That occurs when the EGS doesn't know what gear the transmission is in. I would suspect the gearshift position sensoir which is on the side of the transmission.

  17. #17
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    After sitting for a week the car seems to be back to normal including the gear position indicator. Thanks for everyone's help on this.

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