Oil mixing

Discussion in 'Street/strip 400/430/455' started by Miguel, Sep 8, 2021.

  1. Miguel

    Miguel New Member

    Hi guys! A short question: gearbox ATF oil level goes down (with no drops on garage or street floor) and motor oil level raises up. How is it possible? Someone tells me about the vacuum transmission modulator which can suck trans oil into the intake manifold: but such a big quantity (about 2/3 liters in 2.000 kms...) without any motor issue (only blue smoke from exhaust)?
    Thx in advance
     
  2. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Oil sucked into the intake from a leaky vacuum modulator diaphragm would be burned in the cylinders usually producing white smoke. There might also be some shifting symptoms. Pull the vacuum modulator and point the vacuum nipple down. If any ATF comes out, replace the modulator.

    That would not cause an increase in engine oil level. Make sure your engine oil isn't being contaminated with fuel. Smell the oil on the dipstick. If it smells of fuel, suspect a leaky diaphragm in the fuel pump. Change the fuel pump and oil.

    The only other possibility is coolant leaking into the oil, but that would produce a milk shake looking emulsion. I am assuming you would have noticed that.:)
     
    bostoncat68 likes this.
  3. 436'd Skylark

    436'd Skylark Sweet Fancy Moses!!!!!

    Are you checking the engine oil after the car has sat for awhile? Its normal for a BBB to drain the filter back into the crankcase after sitting overnight. The dipstick will indicate overfull until the engine is started and the filter is full again.

    As far as the transmission fluid check the engine coolant. I've seen the internal cooler fail and mix the trans fluid into the radiator. Usually that makes the engine overheat as well though.
     
  4. Miguel

    Miguel New Member

    Thank you guys for quick answers!
    Btw I got off the modulator and it seems faulty because some ATF dropped out either from the nipple and the vacuum pipe connection (just ordered a new one).
    But never thought about fuel pump... infact while engine is running, with a weak diaphragm, a good amount of gas can be drained into the crankcase.
    Other reasons are out of speak, motor oil is very fluid but not "milkshaked", and the radiator was redone and tested 6 months ago.
    I'Definitively I'll change the fuel pump too, with all new rubber pipes.
     

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