Engine issues seeking advise

Discussion in 'Flat Fender Tech' started by willysgatorjeep, Jul 29, 2015.

  1. Jul 29, 2015
    willysgatorjeep

    willysgatorjeep #showmeyourwillys

    Bagdad AZ
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    45 MB frame with flat head out of a 48. 5.38 w/ stock tires.
    Tail pipe blue smoke that smells like oil and gas. Oil in the radiator coolant and knocks when hot under a load.

    Head gasket, bearing, rings, valve seats...

    I was thinking of compression test first.
    Then a leak down test to attempt to find weakness.
    Leading into pulling the oil pan, head and Pistons to get a visual?
    Replace bad bearings, Ring swap and head gasket in the jeep and call it a day?
     
  2. Jul 29, 2015
    timgr

    timgr Jeepin' Nerd Sponsor

    Medford Mass USA
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    Yes, do a compression test.

    You can test dry and wet. Run your test without any special preparation, then run it again after you add a spoonful of motor oil to each spark plug hole. If the readings improve significantly, that indicates worn rings.

    Do your compression test and report back here with the numbers, before you set up for a leak-down test.

    Oil in the coolant is bad. Oil can't get to the coolant except through a bad head gasket or a crack. But before you pull the head, do as much testing as you can and write down the results.

    What's your oil pressure, at cruise and at hot idle?

    The MB came with 4.88 gears. If you have civilian axles (or a civilian Jeep), they would be 5.38s.
     
  3. Jul 29, 2015
    willysgatorjeep

    willysgatorjeep #showmeyourwillys

    Bagdad AZ
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    Compression
    w/out oil 90 80 100 75
    w/oil added 100 85 110 85
    I will drive it tomorrow to work and get the oil psi info
     
  4. Jul 29, 2015
    PeteL

    PeteL Member Sponsor

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    That's definitely on the low side all round.

    Oil in the coolant? If there is coolant in the oil, too, that's gonna hurt things like the bearings.

    Blue smoke? You might want to consider that your valve guides could be worn/loose too. Add a manifold vacuum test to your list.

    Knocking under load? Check the timing.
     
  5. Jul 29, 2015
    tarry99

    tarry99 Member Sponsor

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    Looks like there is a few weak cylinders.........not really sure what the cranking compression should be on that flat head as I believe the compression ratio is only about 6-7 to 1... I would leak it down and see if you can find either an Intake or exhaust valve that may be leaking...........In either case your only off 15 to 20 % over all between the cylinders......10% is considered OK not the end of the World but with only 60 HP it might be!
     
  6. Jul 30, 2015
    timgr

    timgr Jeepin' Nerd Sponsor

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    In theory, you can calculate the psi you should see. P1 V1 = P2 V2. So at 6.48:1 compression ratio (per Wikipedia) that's 6.48 atmospheres pressure at full compression. 1 atmosphere = 14.7 psi. 6.48 * 14.7 = 95 psi. So your readings seems a little too high, but I'm not sure what to attribute that to - maybe heating of the air when compressed? Let's say that the 100/110 cylinder (#3?) is ideal, then the worst cylinder 75/85 is down 25%... that's quite a lot. Typically when you have one bad cylinder, it's a "burnt" exhaust valve, but I see two low cylinders, and they are not adjacent - ie not due to a bad head gasket. You did do them in order, ie 1 2 3 4 or 4 3 2 1 and wrote them down that way?

    If you had bad rings, the cylinders would be uniformly down on compression and all would come up more with the oil.
     
    Last edited: Jul 30, 2015
  7. Jul 30, 2015
    45es

    45es Sponsor Sponsor

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    FYI: Per the War Department Technical Manual TM 9-803, with plugs removed, "the standard pressure is approximately 110 pounds at cranking speed. Maximum variation between cylinders must not be more than 10 pounds". This was for the MB / GPW engines but I doubt anything was changed in the following 3 years after the war.
     
  8. Jul 30, 2015
    willysgatorjeep

    willysgatorjeep #showmeyourwillys

    Bagdad AZ
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    Compression numbers are in order, cold, all plugs out and full throttle.
    reg says 45MB, front dana 25 and rear dana 27 full floater with removable axles. 5.38 w/ lockright front and rear. Climbs anything.
    Woke up late to drive the jeep into the mine. Freeport Bagdad AZ open copper pit. I drive in 4 miles to get to the entrance and 6 miles in side the gate on the left hand side.
    I will check timing and get oil psi numbers later today and drain the oil for coolant.
    What should the timing be?
    Runs super fat, plugs black black. carb rebuild also or is there an alternative carb replacement?
    How do a preform a manifold vacuum test?
    Should I do a cylinder leak down test?
    I plan to rebuild anyways, should I keep testing or just tear it down? any ideas on the rebuild cost?
     
  9. Jul 30, 2015
    willysgatorjeep

    willysgatorjeep #showmeyourwillys

    Bagdad AZ
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    Dude at the machine shop said the engine is so simple there is no way to get oil in the coolant. Wants $20 a cylinder, $90 to mill the top and $240 for valve seats/guides. I don't know.
    Oil psi at 50 on the gas, and 15 at idle. Not much flat ground. About 30 or so off the gas.
    Pickin up a master rebuild book this weekend at grandma's.
    Going to keep testing to diagnose w/carb rebuild and plan to pull the engine after labor day.
     
  10. Jul 30, 2015
    PeteL

    PeteL Member Sponsor

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    A cheap vaccuum gauge hooked to a port directly on the intake manifold will tell you a lot about the engine condition. (Don't attach to the vacuum-pump line, or a ported vacuum on the carb.)

    Many of them have diagnostic notes right on the dial, or google it. http://www.classictruckshop.com/clubs/earlyburbs/projects/vac/uum.htm

    Don't have the specs for a flathead, but timing probably is around 5ยบ BTDC like the F-Head.
     
    Last edited: Jul 30, 2015
  11. Jul 30, 2015
    Glenn

    Glenn Kinda grumpy old man Staff Member Sponsor

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    Never thought about it but, if the engine is pumping oil it seems like it could get in the coolant because of a bad gasket.
     
  12. Jul 31, 2015
    tarry99

    tarry99 Member Sponsor

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    No oil that I know of near the head block sealing surface and that is the only place where coolant gets sealed by a gasket ...........oil below that area yes , cracked block may be the only way to get oil mixed with water in the crankcase.

    $20 a cylinder to hone? Seems OK $90 to mill....the block and head?....$240 valve job and knurl the guides? What about the crank and rods.......both may need attention.......Grind the crank and recon the rods.......If it needs to be bored that will be extra + a new set of pistons............Camshaft and lifters + bearings + rings , oil pump and timing gears and gaskets and a good boil out before assembly.......It adds up!
     
  13. Jul 31, 2015
    willysgatorjeep

    willysgatorjeep #showmeyourwillys

    Bagdad AZ
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    Yes, it does add up. Gave up asking more cost questions over the phone when he told me oil can't get into the coolant from the head.
    First thought was a crack.
    Off to see the family this weekend. When I'm back, I'll hook up a vacuum gague and run it. Then get the oil drained looking for coolant.
    Drain the radiator and pressure check.
     
  14. Jul 31, 2015
    timgr

    timgr Jeepin' Nerd Sponsor

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    If you have a cracked block, repair of that falls into the "heroic" category for most engines. Usually it's way cheaper to find a better core engine and work on that. But finding a good core L134 might not be so easy ...
     
  15. Jul 31, 2015
    PeteL

    PeteL Member Sponsor

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    Your original post said "knocks under load." I took that to mean you meant pre-ignition, which relates to timing.

    BUT - perhaps you meant bearing knock? Bad bearings will point you more toward a rebuild. But your oil pressure seems good, which argues against bad bearings. Get down under and listen to different parts of the engine with a stethoscope (or dowel, etc). You may be able to to locate the area and nature of mechanical noises.

    Smoke in the exhaust/running rich? Black could merely be a carb adjustment. But blue smoke is more likely oil = bad rings/valve guides. White smoke means water (gasket or crack).

    Oil in the coolant... Are you sure? Are you losing coolant? Burning a lot of oil? Radiator ever 'boiling over' after a hard run? A hydrocarbon snifffer test can reveal if there is exhaust gas in the radiator.

    The symptoms as first described could mean anything from fairly minor tune-up, to a a full rebuild. You may need to systematically define the issues better before tearing it down.
     
  16. Aug 3, 2015
    willysgatorjeep

    willysgatorjeep #showmeyourwillys

    Bagdad AZ
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    Last edited: Aug 3, 2015
  17. Aug 4, 2015
    PeteL

    PeteL Member Sponsor

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    Set the points before you time it.

    The plugs look fuel-rich, but not oil burning.
     
  18. Aug 4, 2015
    Glenn

    Glenn Kinda grumpy old man Staff Member Sponsor

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    I agree, I would expect them to be oily looking. Exactly how much oil does it use? How many miles before you have to add a quart?

    In 1980 when I bought my CJ5 it used about 3 quarts in maybe 60 miles. It ran good and had good power actually, but the oil rings weren't up to the job anymore. Didn't knock either, no bearing or oil pressure issues until it go too low of course. Needless to say people would pass me holding their noses. :D

    I didn't drive it very long before deciding it needed a rebuild of course.
     
  19. Aug 4, 2015
    Wenaha

    Wenaha Member

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    If you get a crack in the block (which is common enough on these motors) you CAN get oil in the coolant. Do you have coolant in the oil?

    Commonest place to find a crack is on the block below the distributor. The heads can also crack, which can result in coolant be ingested through the cylinders.
     
    Last edited: Aug 4, 2015
  20. Aug 5, 2015
    willysgatorjeep

    willysgatorjeep #showmeyourwillys

    Bagdad AZ
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    Distributor was loose. Oops, I actually never checked it since I got it running. The timing was way off and the points gap was short.
    Carb rebuild after work and test drive.
    Planning on a 15-40w oil. Should I run a zinc additive or a diesel oil?
     

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