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Thread: Oil smells like gas, oil leak at #4 exhaust manifold

  1. #1
    Member
    Join Date:  Jan 2017

    Location:  Rockwall, Tx

    Posts:    96

    My VIN:    10686

    Oil smells like gas, oil leak at #4 exhaust manifold

    Just rebuilt the engine on 10686 and got her to fire up for the first time. I had some issues with getting it to fire but those seem to have worked out, it will fire now with no plug swap and idles. Idles a little high but that can be worked out. As the engine is heating up i notice its smoking, smoking more than running rich or something. I shut it off and notice a black oil film type substance all over the drivers side header. It looks like it was push out and a higher compression, it mainly runs off of the bottom rear exhaust mainfold bolt. These are new headers with new gaskets and new studs, i did notice they needed to be tightened down some more so I did, but once that oil got warm it started blowing out again. I also noticed that when I removed the oil filler cap it smells like gas. Why or how would gas be getting into the oil, im sure no matter what a small amount gets in there but I just need some direction. the rings on the pistons are new, the liners are new, the pistons are new high compression ones. did i some how blow my rings when i kept turning the motor over trying to get it to start? Or do you guys thinks there is a hole in one of the exhaust mainfold studs, I did pull on the headers some when installing the exhaust, wonder if I stripped out the studs near the back on # 4.

  2. #2
    Member
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    My VIN:    10686

    So after thinking about it I used assembly lube on the pistons to install them. Now knowing better I wouldnít do that again. I wonder if this is the piston blowing and pushing that assembly lube out of the liner and the ring not seating until itís all gone.


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  3. #3
    Senior Member OverlandMan's Avatar
    Join Date:  May 2011

    Location:  Rowlett, TX

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    My VIN:    5482

    Curious if you rebuilt the motor yourself or outsourced. What's the history on the motor? Did it run prior to the rebuild and if so, what justified the rebuild?

    Your follow-up theory sounds plausible, though admittingly I've never run into this nor have I rebuilt my PRV.

  4. #4
    Member
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    I did the rebuild myself, the motor had 100,108 miles on it before i did the rebuild. The reason it was pulled was to replace all the gaskets, when I opened it up to do the heads it looked really bad had big "rocks" of electrolysis in the water jackets i. I elected to just rebuild it with new pistons, liners, rings, bearings, etc. My crank shaft was way out of spec so i sourced another one that was good. I had the heads redone and ported, they did new valve springs as well. I will admit through my amateur engine build skills i didn't think about coating those pistons with assembly lube when i installed them. I even put more on the liner walls to keep it from rusting/provide lubrication as i turned it over by hand when setting the cams. I'm going to remove the exhaust manifold in question tomorrow to investigate and see if maybe i punched into the head some how, i seriously doubt it. i will say i did some pulling on those new headers, maybe i did something there? one would think it would just strip the stud out not pierce the wall on the head? maybe it cracked it some how? who knows, after some investigation i may try to run the engine and see if it is the oil that is indeed burning off and being pushed out. I also have another leak i need to address but that one is from the pressure sender and very obvious and minor.

  5. #5
    Delorean Guru
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    It can take a while for the rings to seal up especially if you are using synthetic oil. For the break-in you should use a straight weight mineral oil and I use a can of Marvel Mystery Oil. Run it for 500-1,000 miles and then you can go to a synthetic oil. If the motor oil smells like gas it probably has a lot of gas in it from cranking and not running. All of that fuel got sprayed into the motor and wound up in the oil. If you have a lot you should change the oil. Do a baseline compression test now and in 1,000 miles. Get a pressure gauge on the oil and note the pressure. Watch the oil consumption for a while and pull and "read" the plugs. Can't explain your oil leak by the exhaust unless it is the valve cover leaking?
    David Teitelbaum

  6. #6
    Member
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    I used joe Gibbs 15w 50 conventional for break in. The assembly lube that was all over the cylinders was semi synthetic Lucas, I agree with the oil change. I flooded the cylinders so badly that the plugs were wet when I was first attempting to crank. I pulled them all and let everything dry out. I am going to get new plugs soon. After I worked the firing issue out I pulled a plug from each side the were a powdery Black indicating a rich mixture so I will fine tune that. I still feel that the piston is seating and having to push all that damn assembly lube out and itís blowing it out the exhaust port. Like I said Iím going to pull the header to investigate and see whatís up.

    My other thought was do you think the plugs next to the exhaust port could be bad? Iím referring to those Welch plugs on the head. I guess thatís what they are called.


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  7. #7
    Delorean Guru
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    Assembly lube disappears quickly but til the rings seat you can get some blow-by. If you didn't disturb those large plugs, they should not be leaking. If it is running to rich lean it out. Get through a few heating/cooling cycles and check for more leaks.
    David Teitelbaum

  8. #8
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    Sounds good


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  9. #9
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    Got her running, heat cycle 2 times, then ran it a 2500 rpm for about 10 mins. No smoke, now we are back to having hot start issues.... couldnít get it started after it got to temp. Fans ran and cooled it down nicely though. I also left my damn o2 sensor wire unhooked and melted it on the exhaust lol. Iím sure that sensor is done anyways after the rich running condition. The exhaust was running terribly rich, Iím also going to put new plugs in the others are fouled form all my start attempts. Before reaching temp you couldnít start it no issue


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  10. #10
    Delorean Guru
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    Check rest pressure and if it doesn't hold up the fuel accumulator is probably bad. Confirm with the "plug swap".
    David Teitelbaum

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