1. Registration trouble? Please use the "Contact Us" link at the bottom right corner of the page and your issue will be resolved.
    Dismiss Notice

Knocking Noise - F134

Discussion in 'Early CJ5 and CJ6 Tech' started by Kevin D, Feb 16, 2019.

  1. Feb 16, 2019
    Kevin D

    Kevin D New Member

    Monroe, NY
    Joined:
    Jan 24, 2009
    Messages:
    36
    was plowing the other day and started hearing knocking noise. Noise was more present under load. Noise is not apparent when engine is cold. Once warmed up you don’t hear noise at idle but you can hear it when the engine is revved up. Noise sounds like a rod bearing to me but does not disappear when ignition wires are removed one at a time . Oil pressure is 10psi at idle and 40psi at about 3000 rpm. Compression tested 2 of the cylinders. Both about 90-100 psi. I couldn’t test the other two yet because plow pump is in the way of plug removal. Checked ignition timing- checked ok. Any ideas before I go further.
     
  2. Feb 16, 2019
    47v6

    47v6 junk wrecker! 2023 Sponsor 2022 Sponsor

    USA
    Joined:
    Oct 25, 2006
    Messages:
    5,798
    Pull off the pan and find the bad bearing.
     
  3. Feb 16, 2019
    jpflat2a

    jpflat2a what's that noise?

    Hermosa, SD
    Joined:
    Jul 30, 2003
    Messages:
    8,513
    Camshaft timing gear is fiber type; can sound like a rod bearing.
     
    Vanguard likes this.
  4. Feb 16, 2019
    73 cj5

    73 cj5 Not ready for the junkyard yet

    Clinton, Mississippi
    Joined:
    Jan 10, 2014
    Messages:
    2,137
    check the mains while the pan is off.
     
  5. Feb 16, 2019
    SIDSCJ

    SIDSCJ Jeep addict

    14th State
    Joined:
    Jun 25, 2004
    Messages:
    1,189
    I plowed with my F-134 for two years with that same knock.
    Ended up eventually tearing the motor down and found all the rod bearings were about gone.
    Could grab each rod end and move it on the crankshaft.
    It still ran well enough to plow.
    Is it only under load, when in gear, or can you hear it in neutral when revved up?
    Is this just a "plow rig", or do you drive it on the road?
    Run it, winter isn't over yet....
    What weight oil do you run in it?
     
  6. Feb 16, 2019
    Kevin D

    Kevin D New Member

    Monroe, NY
    Joined:
    Jan 24, 2009
    Messages:
    36
    Noise is present after warm up when engine is revved up in nuetral and especially present when pushing snow under load.

    Given that the noise just started all of a sudden, I thought if it was a rod bearing it would have been isolated to just one. But My diagnostics of pulling one ignition wire at a time did not isolate the noise.

    I’m running 10w-40
     
  7. Feb 16, 2019
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
    Joined:
    Aug 10, 2003
    Messages:
    23,596
    Jpflat2a knows a lot about these Jeeps. Check the camshaft gear.

    With an F134, the stroke is very long, which makes the piston velocity high and the force on the rod bearings high. You should worry about rod bearings if you have a knock. However, if you have a bad rod bearing, in my experience the oil pressure goes away very quickly. Oil pours out of the hammered rod bearing. Also, it gets worse fast. So if it bangs and you still have oil pressure and it does not get worse fast, maybe it's not a rod bearing.
     
  8. Feb 16, 2019
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Hills of NH
    Joined:
    Aug 3, 2003
    Messages:
    9,754
    Stethoscope, wooden dowel, or a long screwdriver held to the ear is my "go-to" to find the source of engine noises. Hell of a lot easier than pulling the pan.
     
  9. Feb 17, 2019
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Hills of NH
    Joined:
    Aug 3, 2003
    Messages:
    9,754

    Rod knock tends to come and go as it is loaded or unloaded.

    Mains are more of a steady rumble.
     
  10. Feb 17, 2019
    70cj5134f

    70cj5134f Member

    East Tn
    Joined:
    Aug 18, 2018
    Messages:
    749
    Under load is a sign of rod bearing.
    Add some stp, or Lucas, and keep your ears open, and wait until snow is over?
    Or even better, change oil, cut filter open, go through it with a magnet?
    Then add the stp(2 bottles) and maybe use 50wt oil?
     
  11. Feb 17, 2019
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Hills of NH
    Joined:
    Aug 3, 2003
    Messages:
    9,754
    Okay but bearing metal is non-magnetic.

    And good luck cranking a cold engine with 50 -weight in it.

    That said, I've babied old F-heads with bad bearings by limiting the rpms, and sometimes just throwing in some undersize bearing shells.
     
    47v6 likes this.
  12. Feb 17, 2019
    47v6

    47v6 junk wrecker! 2023 Sponsor 2022 Sponsor

    USA
    Joined:
    Oct 25, 2006
    Messages:
    5,798
    Standard set of mains are 100 bucks. Rods are 13 bucks a rod set from rock auto for standard size. I would pull the pan, pull off the main/rod bearing caps to see if hey are undersize and if they are all the same undersize or standard, slap it all back together, order the bearings and change em out when they come in. You don't need to pull the engine to do this work. Maybe it is just the fiber cam gear too. They are 50 bucks. You will need a puller.
     
  13. Feb 17, 2019
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
    Joined:
    Aug 10, 2003
    Messages:
    23,596
    Dick Datson has a story in one of his books about repairing rod bearings by the side of the road. One of the Dads from my Scout troop was a mechanic for the city, and he and my Dad went hunting in his 50s Chevy truck. They also had a delay to replace rod bearings by the side of the road. Both of these vehicles have forged steel cranks - a Studebaker V8 in Datson's case, and a 235 Chevy six.

    I was not there for the Chevy repairs, but Datson describes his repairs in the book. He took the pan down, undid the rod and cleaned the journal with crocus cloth. I believe he hitched to town and bought the parts, and repaired the engine where the car was parked. I will dig out the passage if you guys are interested ... none of his books have indices, and they are basically collections of old newsletters and articles, so it could take a while.

    I think the moral is - forged steel cranks are tough. Most modern cars (including the 225, 232, 258, 304) have cast iron cranks because they are much cheaper to make than forged steel. A cast iron crank's hardness is pretty close to the bearing material, and bearing failure takes out the journal as well as the bearing material. Not necessarily so with steel.
     
    dane71 and Bowbender like this.
  14. Feb 17, 2019
    47v6

    47v6 junk wrecker! 2023 Sponsor 2022 Sponsor

    USA
    Joined:
    Oct 25, 2006
    Messages:
    5,798
    In many manuals where bearings are the shell type that are replaceable, pulling off the bearing cap and turning out the upper bearing, then turning in anew one is speced out. If you do have a bad bearing, its not spun or the journal is not destroyed where it needs welded and cut, replacing the bearing is a cheap and effective way to get a lot more life out of your engine. Face it, if its wrecked, you can't make it worse.

    An old school mechanic can repair things without a machine shop and total teardown. These jeeps were originally designed for mil spec where they were to have loose tolerances, battle field repairable and to be reliable.
     
    ITLKSEZ likes this.
  15. Feb 17, 2019
    70cj5134f

    70cj5134f Member

    East Tn
    Joined:
    Aug 18, 2018
    Messages:
    749
    Yea ,and I've heard of using leather to get the noise to stop,lol.
    Just trying to get through winter, then he needs to do it right!
    These engines are over built and under powered, it should be hard to trash one
    if u stop it in time?
    Might be lucky and find a bad lifter, or cam gear, might be time for an overhaul?
    Im sure, back in ww2, all kinds of makeshift repairs were done?
    The thick oil and a keen ear should get u to spring?
    Surely not more than a couple more snows are coming?
    Good Luck!
     
  16. Feb 22, 2019
    Kevin D

    Kevin D New Member

    Monroe, NY
    Joined:
    Jan 24, 2009
    Messages:
    36
    Thanks for the info. It was mentioned a few times that my problem may be a bad cam gear. Short of removing the front cover are there any tricks for diagnosis?
     
  17. Feb 22, 2019
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
    Joined:
    Sep 21, 2002
    Messages:
    12,367
    The only thing I can think of that might help would be to check the timing to see if it's quite erratic....at least you could start there.
     
    47v6 likes this.
  18. Feb 22, 2019
    70cj5134f

    70cj5134f Member

    East Tn
    Joined:
    Aug 18, 2018
    Messages:
    749
    Get it so u can c the valve train, through oil fill or remove valve cover.
    Place a socket on the crank, and just try to barley nudge it, rock in both derictions.
    If theirs play in the chain, or gear, the crank will move a bit and the valves won't.
    Do this for 2 reveloutions, so u get all way round the cam.
    I had a 1980 Chevy monza, and it knocked like a rod.
    Wife had a 80s Pontiac, both 4cyl gear driven cams, it also knocked loud.
    Never repaired either, just kept driving. Neither ever broke down.
    But that damn noise was hard to get used to.
     
  19. Feb 22, 2019
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
    Joined:
    Sep 21, 2002
    Messages:
    12,367
    F-heads are gear to gear, so no chain, thus the reason for the fiber timing gear=quieter. Haven't experienced a bad timing gear so I can't comment on it making noise other than throw out an idea.
     
    47v6 likes this.
  20. Feb 22, 2019
    47v6

    47v6 junk wrecker! 2023 Sponsor 2022 Sponsor

    USA
    Joined:
    Oct 25, 2006
    Messages:
    5,798
    So, should he ignore the knocking noise or rebuild it the right way? just trying to figure it out..
     
    Last edited: Feb 22, 2019
New Posts