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Thread: M54 2.5 litre high oil consumption. Swap for M52?

  1. #1
    Join Date
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    M54 2.5 litre high oil consumption. Swap for M52?

    Hi all, I have an 03 E46 325 which has been using around a litre of oil every 500 miles and I understand this is a common problem. I have now developed a misfire on no 5 cylinder and on checking compressions there is 130/140 psi on all cylinders except no 5 which only has around 40psi. The generally low compressions and badly fouled plugs pretty much explain the oil consumption and 40psi on number 5 explains the misfire. I'm considering swapping the block and cylinder head from a twin vanos M52 engine into my car as these don't appear to suffer the same problem. Has anyone out there done this or know if its feasible as I'm wary of fitting another M54 which may have the same oil consumption issues. Any help would be very much appreciated.

  2. #2
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    The excessive oil use could be a bad CCV (have a crank case pressure check run) and the low compression on that cylinder could be a valve problem (a leak down test will tell). Both of those are problems than can be fixed.
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

  3. #3
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    Hi Jim, many thanks for your speedy reply. The CCV and all hoses have been changed twice in the last 2 years to no effect and I've used BG 109 compression restorer followed by BG MOA oil treatment twice in the last year, again with little effect. As the compression is low anyway on the other 5 cylinders, combined with the filthy spark plugs and black, oily tailpipe I've pretty much decided to give up on the original engine now and am interested in contacting anyone that may have already replaced an M54 engine with an M52 engine in their vehicle as they don't appear to have the same oil consumption problem.

  4. #4
    Join Date
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    Why would you want to do that?

    Trust me, you dont. Your M54 had a problem, tons of M52TU's have problems too. Replace it with an M54. This swap is a downgrade power-wise and everywhere-wise plus what are you going to do when you sell it? Hey great news potential buyer, my 2003 BMW has the engine from a 1999 because I didnt want to deal with a little oil consumption!

    Get it fixed or buy an M54 tested to be in good condition. You are knowingly driving on a car with low compression while complaining about oil consumption??? What?

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  5. #5
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    My dad's E39 525i has pretty high oil consumption too. Suspect it may be the ccv, but it's clean under the valve cover, except for some reddish residue on the cover. OP, with 40 psi on one cylinder, it is pretty clear your engine has a problem. Do a wet compression test and find out what is leaking. Adding the oil to the cylinder may even unstick your piston rings.

  6. #6
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    Hi BB, Part of my problem is that the car is only worth £2k max and I don't have the money to throw at it. I can pick up a used engine for around £400 (M52 or M54) & fit it myself. The question of fitting an M52 came around because there is one for sale locally which is still in the car and can be heard running. I don't mind the slight drop in power or any resale issues as I'll probably run it till it dies anyway so my main concern is whether the M52 block and head will accept all the M54 ancilliaries. The misfire on No 5 only started around 10 days ago and was diagnosed as a faulty coil. I fitted a new coil which made no difference and that then led me to check the compression for the first time. BTW I re-checked the compressions yesterday with a new gauge (mine was very old and hadn't been used for around 20years!) and No 5 is 50 psi, all the rest are ok at 170/180. Until the misfire started I'm pretty sure now that the compressions were ok.
    Thanks for taking the time to reply!

    - - - Updated - - -

    Hi DYL, I did a wet compression test on no 5 yesterday and it didn't improve so I'm thinking there is a leaky valve. I'm still looking down the second hand engine route though as even if I get the head fixed I'll still have the oil consumption problem.

  7. #7
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    The later I think 99 M52 was the "M52TU" which was more compatible with the M54.

    It will fit in place and everything, if you plan on dropping the whole longblock engine in then it should be no problem. Regarding ancillaries, perhaps realoem would be of greater assistance there (looking up part number for alternator, for example, to see what models/engines it fits on)

    Id be curious to see what your cyl 5 looks like. Plan on tearing into it if you swap it out?

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  8. #8
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    The one I've found is an M52TUB25. It's in a '99 MOT failed (120k miles) car that can still be driven and I intend to do compression test before buying it. And a big yes to a stripdown of the old engine as I want to see the state of the bores/rings and also the valve guides/seals. I've done hours of reading about the oil consumption issues with the M54 engine and there doesn't appear to be a definitive answer. I really appreciate your input, thanks again!

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