Cat 6NZ oil leak

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by W Bench Farms, Jan 21, 2022.

  1. W Bench Farms

    W Bench Farms Light Load Member

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    I have a 6NZ Cat in a 95 Freightliner FLD120 with a bad oil leak. Seems to have gotten worse over the past couple weeks. Problem is that I can't figure out where it is coming from. It is on the driver's side, behind the air compressor. Doesn't seem to be the front cover, although I know these motors are known for that. Air compressor has been replaced. Oil feed line was not, but doesn't look to be from there. Seems to be worse when loaded or under a hard pull. No blow by and no smoke out the exhaust. I'm wondering if it could be coming out of the head gasket? No oil in the antifreeze, or antifreeze in the oil. Getting ready to send it to somebody, but checking if anyone else has seen anything like this. Will try to get some pictures.
     
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  3. LameMule

    LameMule Heavy Load Member

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    Pics or it's not real...
     
  4. W Bench Farms

    W Bench Farms Light Load Member

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    Oct 16, 2017
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    Hard to tell from the pictures but it's well oiled.
     

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  5. LameMule

    LameMule Heavy Load Member

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    I'd wash it then take it for a spin and see where that BP spill is originating from.
     
  6. lwlevens

    lwlevens Medium Load Member

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    Yep spray it down with some good cleaner let it idle and start looking for oil coming out somewhere.
     
  7. W Bench Farms

    W Bench Farms Light Load Member

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    Oct 16, 2017
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    Done that several times. Seems to not leak when idling. Leaks more when under a pull. Have someone going to take a look hopefully soon. Just wondering if anyone has seen these leak somewhere other than the front cover. Not ruling that out completely, but looking at other options.
     
  8. W Bench Farms

    W Bench Farms Light Load Member

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    Oct 16, 2017
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    Still haven't pinpointed this oil leak, but what would be the chances of it leaking from between the head and block? Seems to be worse when loaded or heavy. Had a week of light loads and hardly any leak. Last week was 75k+ and went through a good bit.
     
  9. spsauerland

    spsauerland Road Train Member

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    Spacer plate gaskets seem to leak worse when engine is working harder
     
    Goodysnap Thanks this.
  10. W Bench Farms

    W Bench Farms Light Load Member

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    Oct 16, 2017
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    That's what I thought as wondering. Finally got a hold of a mechanic that does a lot of Cat work. Said the spacer plate is an issue. Said cat issued an update on the gaskets and also now uses a sealer. He's about 3 weeks out, but looks like it's going to the shop. Also said that the left side is where all of the oil returns, and that's where my leak is. Can't see any other places it can leak, so hopefully that will fix the problem. Was wanting to put it in to run the overhead, so I guess we'll take care of that also.
     
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