1. Thank you for visiting HeavyEquipmentForums.com! Our objective is to provide industry professionals a place to gather to exchange questions, answers and ideas. We welcome you to register using the "Register" icon at the top of the page. We'd appreciate any help you can offer in spreading the word of our new site. The more members that join, the bigger resource for all to enjoy. Thank you!

1999 7.3 Powerstroke Oil In Coolant

Discussion in 'Trucks' started by Birken Vogt, Jun 25, 2019.

  1. Birken Vogt

    Birken Vogt Charter Member

    Nov 30, 2003
    Grass Valley, Ca
    Just picked up another Ford 7.3 Powerstroke, 1999. It was cheap and worth it just for the components. But we will most likely use it as-is.

    Has 203,000 on the odometer and a slight amount of oil in the coolant reservoir. I mean a ring around the liquid level of black oil but none floating. The PO showed a shop write up for a HEUI pump and injector cups so they decided to sell instead of repair.

    But we are not sure how they came to that conclusion.

    We are hoping oil cooler or something like that. No evidence of coolant in oil on the dipstick or filler cap. Truck starts easy and drives strong and clean except maybe minor black haze on the first real romping up a hill but I think it cleaned up after a short drive. Rail/ICP pressures normal on scan tool.

    Thoughts on the correct way to diagnose this?
  2. Tenwheeler

    Tenwheeler Senior Member

    Dec 16, 2016
    Totally different vehicle but I later found out it had been low on water. Someone grabbed a used oil jug and filled it up with water and dumped in the hole.
    I would probably replace the oil cooler and flush it out. Run it and see what happens.
  3. crane operator

    crane operator Senior Member

    Mar 27, 2009
    sw missouri
    I had a external oil leak at the oil cooler on my 2001. My mechanic didn't change the one gasket on the neck, and that's where the leak was, so we had to take it back apart. On reinstalling the second time, I dropped off one of the seals on reinstalling the "tube". I fired it up, and after about 10 seconds, the radiator looked like Mt. Vesuvius, it was erupting oil like nobody's business.

    The third install was the good one. We rinsed and refilled radiator, dishwasher detergent and everything, and I still have a little oil scum now and then on the top of the coolant tank. I suck it out with my little hand held suction, and have learned to live with the worry every time I check anti-freeze, when I see a little oil in the radiator.
  4. GregsHD

    GregsHD Senior Member

    Sep 26, 2014
    Self Employed HD Mechanic
    Mahood Falls, BC
    Pretty common for the seals on the cooler core to pass oil into the coolant, (same cooler as DT466 NGD) you'll see the compromised seal when you pull it apart.

    Seal kits are fairly inexpensive if you buy it in the Navistar bag!
  5. Nige

    Nige Senior Member

    Jun 22, 2011
    And once you’ve located & fixed the problem there is nothing like a good dose of Cascade dishwashing detergent to get the oily residue out of the system. Some systems may require a second dose but it will clean out all the oil leaving nothing behind.
  6. thepumpguysc

    thepumpguysc Senior Member

    Mar 18, 2010
    Master Inj.Pump rebuilder
    Sunny South Carolina
    Get a cooler delete kit & a box of Cascade..