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Thread: Elusive 300Tdi engine noise

  1. #1

    Elusive 300Tdi engine noise

    Hoping you can help...

    Vehicle is a manual 95D1 300Tdi.
    Noise is difficult to accurately describe; a bit like rattling a sack full of empty glass bottles together. Very frustrating. The noise is quite loud at light loads, eg cruising at 70km/hr. Its harder to hear under heavy load and at idle. And very hard to hear under no load - ie revving engine whilst stationary and whilst it is cold. It disappears completely on over-run.

    I could have created the noise when I recently replaced the timing belt. I cannot be certain because prior to changing the belt, the vehicle was my wife’s daily drive and she probably wouldn’t have noticed the noise. Its the third time I've changed the belt (did not experience this noise on the previous belt changes).

    At first I suspected that I've got the pump timing too far advanced. I used a new pin kit that comprised of a pin to lock the pump and bolt with a pip or nipple on the end to screw into the bell housing and lock the flywheel. I rechecked the timing and it was advanced; looking up the bell housing hole the flywheel slot was about one slot width away from the center. Which was weird because I used the pin to lock it in place. I then check the diameter of the pip or nipple on the end of the bolt and it measures 6.1mm. I try inserting a 6.1mm drill into the flywheel slot and its way too big. So I found why my timing was advanced - the pin did not engage in the slot, just on the edge. So much for the timing pin kit I purchased that was advertised as a 300Tdi kit!

    So I set the timing by eye; centralising the slot in the bell housing hole. A test drive indicates that the noise has reduced slightly but is still there. I then retard the timing about a slot width and this resulted in a loss of power, a slight reduction in the noise again but its still there. So maybe the noise is not caused by the pump timing. I've since reset the timing back to where it should be and had the timing cover off again to double check the cam timing (match cam sprocket with arrow behind it) and it looks spot on.

    I've also checked the tappets and looked for exhaust leaks. They are good. I don’t think it's big end bearings since the oil pressure is fine and the engine was fully reconditioned 150,000km ago.

    If there is a problem with the injector pump, could it result in such a noise and how do I check it? I think the pump is original - done around 380,000km. Any other things to check?

    The vehicle still runs fine. Power is good. I've been waiting for more clues to present themselves; however, it seems the mystery is set to continue.

    Thanks in advance,
    Taz

  2. #2
    Join Date
    Apr 2007
    Location
    Prospect SA
    Posts
    2,137
    Taz

    I had a very elusive noise also.

    Not till I took it to a mate who only works on Mercs that he got out his stetoscope(spelling?).
    He found that a couple of the fuel and other fluid lines were touching and at certain times made a horrible inconsistent tapping noise.
    He seperated those and no more.

    They were situated near the steering columm over the RHS wheel arch.

    I thought noise was clutch or tappets also.

  3. #3
    Join Date
    Dec 2007
    Location
    South East Tasmania
    Posts
    10,711
    My Defe used to have the same noise and the problem was thet the pump was not delivering enough fuel and pressure to the #3 cyl.
    I replace all the injectors and the pump (second hand) and the engine runs like a dream.

    Try to get a injector that you know it is ok and use it to test each port on the pump. If all the delivery in all the ports is equal and looks good, then test each injector.

    All the problems was cause by dirty fuel!
    Justin adjusted the pump as well and now have heaps of power and the economy is fantastic.

    Cheers

  4. #4
    Join Date
    May 2007
    Location
    Safety Bay
    Posts
    8,266
    Vacumn pumps can rattle like a mungrol. Pat

  5. #5
    Quote Originally Posted by PAT303 View Post
    Vacumn pumps can rattle like a mungrol. Pat
    Thanks Pat. I forgot to mention that I did the old screwdriver-to-the-ear trick on the vacuum pump and its quiet.

  6. #6
    Join Date
    May 2007
    Location
    Safety Bay
    Posts
    8,266
    I wish mine was!!. Pat

  7. #7
    Join Date
    Dec 2008
    Location
    Kenya
    Posts
    258
    Check the air filter housing is properly clamped down and that the rubber grommets holding the whole assembly to the bracket on the engine are good...?

  8. #8
    Join Date
    Jan 1970
    Location
    Moruya Heads/Sth. Coast, NSW
    Posts
    6,566
    Check the idler/adjuster (compressor) bearings and the fan bearing in the timing cover, are the tensioner and timing idler bearings OK, Regards Frank.
    What Goes Around, Comes Around.
    94 Disco 300TDi Auto, with the Lot
    93 Disco with the lot, Gone
    78 Series III 109, Diesel.
    Toyota BJ 40, Gone
    Ford Bronco WOW, Gone
    Toyota 4Runner RIP
    F100 4WD, Unbelievable, Gone
    Suzuki Brilliant, Gone

  9. #9
    Quote Originally Posted by Panya View Post
    Check the air filter housing is properly clamped down and that the rubber grommets holding the whole assembly to the bracket on the engine are good...?

    Thanks Panya. Yes I read your earlier thread and checked that just in case, but to no avail.

  10. #10
    Quote Originally Posted by Tank View Post
    Check the idler/adjuster (compressor) bearings and the fan bearing in the timing cover, are the tensioner and timing idler bearings OK, Regards Frank.
    Thanks Frank.
    By idler/adjuster, do you mean those for the timing belt? If so, yes they were renewed with the belt. And I replaced the surpentine tensioner bearing and air/con belt tensioner bearing. I havent replaced the fan bearing in the time cover; however, it seems OK.

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