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Leak Down test results.....What next ????

Discussion in 'Engine & Transmission' started by Ian and Shelley, Jun 26, 2019.

  1. Ian and Shelley

    Ian and Shelley Active Member

    Messages:
    347
    Location:
    Umina Beach
    Hi all


    I have a 1976 Bay with I think original engine heads etc etc..

    The Clutch needs some work so while the engine is out I am considering doing necessary engine work?

    Compression test results gave the following

    Cylinder 1 - 100 psi
    Cylinder 2 - 95 psi
    Cylinder 3 - 75 -90 psi ( sometimes 75 psi and sometimes 90 psi)
    Cylinder 4 - 100 psi

    Leak down test results as follows

    Cylinder 1 - 25%
    Cylinder 2 - 20%
    Cylinder 3 - 35%
    Cylinder 4 - 20%


    Cylinder 3 again the weakest....

    I ran out of daylight and will re test 3 in more detail.but think most air was escaping through oil filler tube which I assume could mean worn pistons / rings?
    Some air could be heard through carburettor...
    No air leaking through exhaust...

    IF Worn rings would you expect high oil usage? (Engine does not use any oil.??:)

    All thoughts and suggestions on recommendations and repairs most welcome
    (A VERY Limited budget on this project so please consider most economic options)

    Is anything REALLY required or keep as is?


    Thanks
     
  2. KahunaKombi

    KahunaKombi Super Moderator Staff Member

    Messages:
    22,221
    Location:
    Bracken Ridge, Qld
    What type of inlet manifold gaskets do you have ? - metal or bakealite (efi ones).
    Had the bakealite ones with twin Dellortto's on Igor (why ? :rolleyes: well only the engine builder knows that) and LHS one cracked causing a leak down this led to dropping the engine and a new set of rings - didn't appear to be using any (extra) oil. Replaced the inlet gaskets with the metal ones ;)
    Leak down will cause rings to wear and so as your tests are showing compression loss and so time to look @ checking them out replacing rings and checking pistons and barrels for damage.
     
  3. Ian and Shelley

    Ian and Shelley Active Member

    Messages:
    347
    Location:
    Umina Beach

    Thank you for your advice..

    I have standard metal inlet manifolds..
    New rings could be the answer...?
    From the results could we assume the heads are OK? Until we get them off and examine?

    Lots of unknowns here of course,

    I am trying to ascertain potential repair costs, don't want to start pulling the motor out, have it pieces and run out of Kombi funds when its running just fine at the moment
     
    Mr Beckstar likes this.
  4. cbus

    cbus Well-Known Member

    Messages:
    13,517
    Location:
    sunshine coast
    My thoughts.
    Real mechanics thoughts welcomed :)
    Oil rings shown as ok but you may ?? have a weak compression ring in #3.
    Did you repeat test with some oil sprayed onto bore?
    This would go be an indication of compression ring wear.
    Also it's quite common to have a fair bit of blow by in an older engine without major issues
    Was it similar for each cylinder.

    Assuming correct timing position on test it may seem to be an inlet valve not sealing on #3.
    I would pull that head and check/ lap the valve.
    Wouldn't worry about ring unless it is proven to be the main issue.


    Retention both heads.

    Check condition of adjusting screws.
    A long shot that excessively worn one may be messing valve adjustment measurement.
    Judge by additionaly listening to it while operating by hand and compare to others of same setting.

    Newish purchase?
    A few oil changes with a cleaner may help as may a lifter free up type additive.??
    Not magic solutions but sometimes clean things enough to make a difference.
    But in your case I would attend to the possible valve seating issue and be happy to just drive for a while longer.
     
    Last edited: Jun 26, 2019
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  5. tintop

    tintop Well-Known Member

    Messages:
    986
    Location:
    Canberra
    Hi Ian, yeah, from what you've written, number 3 appears to be your weakest (warm engine results are usually highest - all cylinders in the same ballpark is a good goal)....maybe a stuck ring or carbon buildup around a valve - which you may be able to free up by pouring stuff down the carbies or adding to the oil (not sure what's on the market nowadays)...or it could be worn rings, burnt valves, loose seats but I wouldn't jump to that conclusion.

    To decide what to do, I would use your results along with other factors, for example:
    • budget
    • driveability
    • oil consumption
    • oil colour
    • oil temperature
    • excessive oil from breather
    • oily spark plugs

    Patrick
    P.S. you could check if the variable compression is due to a loose seat shifting around by getting it really hot then listening for a ringing noise and probably some popping on deceleration
     
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  6. Ian and Shelley

    Ian and Shelley Active Member

    Messages:
    347
    Location:
    Umina Beach
    Thanks everyone, bloody good forum

     
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  7. Ian and Shelley

    Ian and Shelley Active Member

    Messages:
    347
    Location:
    Umina Beach

    Thanks Patrick
    P.S. you could check if the variable compression is due to a loose seat shifting around by getting it really hot then listening for a ringing noise and probably some popping on deceleration

    I have noticed I get popping and backfiring on deceleration / idling down hill when engine is cold ( goes away once at operating temp

    • budget - UNSURE
    • driveability - ALL GOES WELL, STARTS GOOD NO SMOKE AND HAPPY DRIVING
    • oil consumption - NIL - NO OIL NEEDED SINCE LAST SERVICE (1500KM AGO)
    • oil colour - CLEANISH
    • oil temperature - 70 - 90 C URBAN AND 100C ON HIGHWAY
    • excessive oil from breather - WILL CHECK BUT NONE OBSERVED
    • oily spark plugs - NO OIL SOME CARBON
     
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  8. Ian and Shelley

    Ian and Shelley Active Member

    Messages:
    347
    Location:
    Umina Beach
    Thanks !!!

    THERE is a noisy-ER knocking from Cylinder 3 side of the motor, have not determined where exactly but will try a listening screwdriver and see what I can locate...

    I will try the oil cleaner / carbon removing stuff, definably worth a try
    I will recheck valve cleaernces today and compare and thenl repeat the test with oil in the cylinder and compare results
     
    Mr Beckstar likes this.
  9. rstucke

    rstucke Well-Known Member

    Messages:
    1,902
    Location:
    Wamberal NSW AUS
    I'm assuming your using the leak down tester properly
    engine warm
    compressor pumped up but not running
    cylinder to be tested at TDC firing stroke and engine locked(top gear manual, bracket on ring gear auto)

    If so then listen in 3 places during the test with a short piece of garden hose

    carby on that side with the throttle wide open for inlet valve leaks
    exhaust pipe for exhaust valve leaks
    Oil breather (top of motor) for leakage past the rings

    10% or less leak is good
    10% variation or less is good
     
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  10. Ian and Shelley

    Ian and Shelley Active Member

    Messages:
    347
    Location:
    Umina Beach

    Yes.... and NO !

    Engine was warm
    Compressor on but not running
    TDC for tested cylinder BUT ENGINE NOT LOCKED... Will repeat with engine locked !!!!

    Thanks
     
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  11. rstucke

    rstucke Well-Known Member

    Messages:
    1,902
    Location:
    Wamberal NSW AUS
    The engine tends to rock down to BDC if not locked
    If the engine doesn't turn when testing then locking it isn't necessary
     
    Last edited: Jun 26, 2019
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  12. Ian and Shelley

    Ian and Shelley Active Member

    Messages:
    347
    Location:
    Umina Beach
    Another question...

    I am rechecking valve clearances and have flowing engine info for exhaust and inlet valve settings...

    From reading other posts and website info...I understand Exhaust valves are on the Exterior / outer side of the head with inlet on the inner side.....

    However....Haynes manual has a diagram showing inlet (numbered 31) the outer side and exhaust valve (numbered 32.) on the inside.

    Can someone please confirm which location of inlet and exhaust valves is correct???

    Thanks

    rps20190518_150914.jpg

    rps20190626_171258.jpg

    rps20190626_171209.jpg
     
    Last edited by a moderator: Jun 27, 2019
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  13. tintop

    tintop Well-Known Member

    Messages:
    986
    Location:
    Canberra
    exhaust on the outside...that sketch was trying to show the valves for the cylinder towards the front
     
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  14. Ian and Shelley

    Ian and Shelley Active Member

    Messages:
    347
    Location:
    Umina Beach

    Thanks....confused by diagram
     
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  15. KahunaKombi

    KahunaKombi Super Moderator Staff Member

    Messages:
    22,221
    Location:
    Bracken Ridge, Qld
    Get an idea on price for a ring set - https://www.mickmotors.com.au/category-pistons-cylinders-26.aspx
    As mentioned I had leak down in only 1 cylinder but chose to do all 4 as the engine was out and didn't want to have to go through it again if something was thrown out of "whack" with doing only one cylinder or 1 side (sort of like a brake cylinder scenario - do one and expect the other side to blow not long after).
    You'll also get to know if your cylinders are standard size or over -sized which mine were & that led to another issue with sourcing an oversize set of rings - barrels, pistons etc all ok but did all relevant gaskets and seals which were in a kit in the above link.
     
  16. Barry

    Barry Well-Known Member

    Messages:
    5,995
    Location:
    Abbotsford NSW
    See if you get a “honing?” Tool to redo the cross hatching of your cylinders if you re-ring
     
  17. Ian and Shelley

    Ian and Shelley Active Member

    Messages:
    347
    Location:
    Umina Beach
    Great....looks like it's time for me to.get busy on the tools and start pulling things apart.....good times!!
     
  18. Ian and Shelley

    Ian and Shelley Active Member

    Messages:
    347
    Location:
    Umina Beach
    Hi.


    Retested compression test and leak down today both wet and dry...

    Dry compression....better results..

    1 - 100
    2 - 90
    3 - 95 (adjusted and corrected valve clearance)
    4 - 95e

    Dry Leak results - strangely worse than last week...
    1 35%
    2 35%
    3 40%
    4 -35 %

    Wet compression

    1- 110psi
    2- 95 psi
    3- 100 psi
    4- 110 psi

    Wet leak down

    1- 10%
    2- 25%
    3- 20%
    4- 20%

    Wet test results are much better all round..

    What assumptions should I take from these results...?
     
  19. rstucke

    rstucke Well-Known Member

    Messages:
    1,902
    Location:
    Wamberal NSW AUS
    It's a worn engine but not rooted
    I would keep using it.
     
  20. Ian and Shelley

    Ian and Shelley Active Member

    Messages:
    347
    Location:
    Umina Beach
    We are planning to do some long drives and road trips over summer to festivals etc across NSW...would you be concerned to take this engine a long distance..just slow won't be pushing it hard...
     

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