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Thread: oil on two pistons, harder to start after driving

  1. #1
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    oil on two pistons, harder to start after driving

    Mate has a rebuilt SR20, done around 600 miles after rebuild (new chain, tensioner, gaskets, piston rings, pumps, ported head) and noticed there is some oil on two pistons, other two are dry. There was also some oil in the lower part ob the intake manifold for those two cylinders.
    Compression is the same as at the beginning, 150 150 148 148, he has changed OEM valve stem seals with supertech ones, but the problem is still there on those two cylinders after 10 min of running. What is the next thing he could look at, maybe valve guides? The engine has done 120k miles and the rebuild was done as a precaution, there was nothing wrong with it.
    The hard starting when warm is probably from the oil leaking onto the pistons and when it starts, it fires up on 3 cylinders for a second or two, then the 4th one joins in.

  2. #2
    Guest hooky's Avatar
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    If its sat in the intake manifold, Maybe its pulling oil through the intake to rocker cover (crank-case evacuation) breather pipe?

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    Wouldn't that be on all 4 cylinders and not just two?

    Here's a video of the intake ports on the offending cylinders:
    https://www.youtube.com/watch?v=YlSd...ature=youtu.be

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    Guest hooky's Avatar
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    Ahh I see, I assumed you meant the intake manifold.

    It does look as if the oil is running down the valve stems, so valve guides/stem seals would seem a good guess.

    Did this just start happening after the rebuild? it could just be faulty stem seals or incorrect fitment?
    Last edited by hooky; 12-06-2015 at 16:17.

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    Started happening after the rebuild. Stem seals were replaced again a couple of days ago with supertech ones, but it's no better so it probably can't be that then.

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    Guest ANDY black s13's Avatar
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    Possible them two cylinders suffered oil control ring damage when installed,and possibly scored the bores slightly as they went in,
    would need to get a micro camera or some thing in the plug hole to inspect the bores for tell tale
    vertical oil lines from the oil control ring not sealing properly and inspect the bores
    may have a ring land/piston issue on them two? were they new pistons/rings or just rings on old pistons
    if stem seals are good not much else can cause oil in the bores,
    No evidence of mixing of coolant and oil I guess
    just my ideas of possibles

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    Thanks for these ideas!
    Only the rings are new OEM ones, pistons have done 120k miles, could bad oil rings cause oil to stay on top of the pistons, as it seems like it's coming from the top? No signs of a headgasket problem either or any strange water / oil usage or smoke.

  8. #8
    Guest ANDY black s13's Avatar
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    Quote Originally Posted by igralec View Post
    Thanks for these ideas!
    Only the rings are new OEM ones, pistons have done 120k miles, could bad oil rings cause oil to stay on top of the pistons, as it seems like it's coming from the top? No signs of a headgasket problem either or any strange water / oil usage or smoke.
    It could if the oil control rings are not controlling the oil from getting there as the pistons are moving pretty fast
    so every stroke its weeping past,it must be smoking pretty badly if there is oil in the chamber ,but you say no smoke?
    I can't see it getting in there from the top,if the chamber was cracked (from over heating they can crack around the spark plug holes)
    but if anything like that was the case you would have very low compression readings,were yours is good for compression

    could be unburnt fuel and engine breathing fumes have mixed and puddled in the plenum runners you have noticed and think its pure oil?

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    Guest S15_SAM's Avatar
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    Need to do a leak down test really, compression test is only one small diagnosis. Leak down is much more accurate.

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    here are the leak down test results:



    so that and compression seem to be ok, what else can it be then?

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    Member alanjuggler's Avatar
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    were the valves / guides measured when it was rebuilt?

    if the valves and / or guides are worn, no amount of new valve seals will fix an oil weep.
    white '94 s13 200sx scrapped - mapped to 1.45bar. OS giken box, garrett GT2876R, 950cc injectors, ORC twin plate, nistune. 349bhp/325lbft @ 1.3bar CA18DET
    white '96 s13 180sx - type g with more kouki bits - RB25DET, GTR steel twin turbo conversion, RB26 crank & rods. 2.6L VVT twin turbo, SR20 OSG box, OSG STR twin plate clutch, Z32 ECU w/ nistune.

    current status: 180 a bit broken but to be repaired.

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