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235 loud knocking?

Discussion in 'The Hokey Ass Message Board' started by hobbyjp, Sep 21, 2010.

  1. hobbyjp
    Joined: Mar 14, 2006
    Posts: 330

    hobbyjp
    Member
    from socal

    Ok so my car breaks down once a week. Eventually it will all be fixed! So I drove about 30 miles on sunday and the car died. it lost spark. It also had a strange noise before it lost power but I thought maybe it was a miss. Towed it home replaced the coil and it fired back up but with a loud knock. I shut it down right away. I'm hopeing I was just paranoid because it was late and the garage echos and it does have some valve noise before the oil gets going. I pulled the side cover and the valve cover everything looks good. with the spark plugs pulled it rotates with no sign of anything making contact. How easy is it to tell if a push rod is bent? I'm gonna try running it without the water pump to see if my noise was there. I know I should drop the pan but I dont want to do that unless I'm ready to pull the bearing and replace the rear seal. Could I make it worse if I try and run it again, I'm sure theres always that chance. I'm also gonna check the compression when I get home.
     
  2. brad chevy
    Joined: Nov 22, 2009
    Posts: 2,627

    brad chevy
    Member

    First off water pumps don"t make loud knocks,you said that you had noise until the oil gets up.sounds like you need a complete rebuild,you crank it up with a loud knock and you might end up with a big hole in the side of the block.
     
  3. you need a piece of hose to use as listening device or stethascope. if the motor is a high mileage unit could be time for a rebuild. need to spend some serious time listening to the motor as it could be bearing gone bad, piston slap..... good luck!
     
  4. hobbyjp
    Joined: Mar 14, 2006
    Posts: 330

    hobbyjp
    Member
    from socal

    Water pumps in the 235 do knock and its well documented fuel pumps have been known to knock also. Its the original motor with 30,000 miles. How hard is it to tell if a push rod is bent on the 235?
     

  5. 29nash
    Joined: Nov 6, 2008
    Posts: 4,544

    29nash
    BANNED
    from colorado

    I thought you said there was a LOUD KNOCKING. If it was the water pump or fuel pump you could have already checked that. ?? What did the oil pressure do, if you know?
     
  6. hobbyjp
    Joined: Mar 14, 2006
    Posts: 330

    hobbyjp
    Member
    from socal

    Well I just did a compression test and number one cylinder is below 50. all other cylinders are 130 nd six is about 110.
     
  7. Snarl
    Joined: Feb 16, 2007
    Posts: 1,639

    Snarl
    Member

    valve train would be more of a tinny clatter than a loud knock.

    with the engine running, if you pull a plug wire one at a time and find that the noise stops, then you probably have a bad rod bearing on that cylinder.

    A stethoscope usually works to tell if other things like the fuel pump are to blame.

    Never heard of a water pump knocking.
     
  8. pcterm2
    Joined: Aug 25, 2009
    Posts: 551

    pcterm2
    Member

    roll your push rods on a piece of flat glass -if theyre bent you will see it
     
  9. hobbyjp
    Joined: Mar 14, 2006
    Posts: 330

    hobbyjp
    Member
    from socal

    The oil pressure was climbing but didnt get all the way up during the compression test. I'm not sure what it was when it was running. So should I crank it back up and start pulling wires or go ahead and pull the pan. The problem appears to be number one cylinder. The valves appear to be moving freely and not sticking.
     
    Last edited: Sep 21, 2010
  10. hotdamn
    Joined: Aug 25, 2006
    Posts: 2,208

    hotdamn
    Member

    trust me if you bend a push rod on a 235 you will know it...

    it sounds like a hit and miss engine but louder...

    for the record guys, if you replece the bolt that holds your coil bracket on be careful
    as the bolt hole goes all the way through and lines up great with a push rod...

    oops.
     
  11. hobbyjp
    Joined: Mar 14, 2006
    Posts: 330

    hobbyjp
    Member
    from socal

    Ok my car has gremlins! I fired it up again and it was knocking and blowing some heavy smoke out the breather. I set the timing and turned down the idle and it started to smooth out. After a few minutes the knock went away. This wasnt the normal valve tick it sounded like the motor was gonna send something threw it. It wasnt an out of time back firing sound either. I know this motor and its sounds well I've had the car for 5 years. Number three cylinder seems it might be getting a little water. the end of the plug has some rust spots and I noticed a small drop of water when I stuck my finger in the hole. but like I said after it ran for about 5 minutes it stopped smoking and and ran like a top with no more hard knock. What gives?
     
  12. CruZer
    Joined: Jan 24, 2003
    Posts: 1,931

    CruZer
    Member

    Sounds to me like you have a lot of carbon build up on the pistons and until the carbon passes out the exhaust it causes a knocking noise in the cylinder. An old trick is to set the engine on fast idle and spray a little water down the carb to loosen the carbon.

    If it's a rod knocking and you want to get some more use out of it before you rebuild,put a can of STP oil treatment in with the oil. That will quiet it down. My wife drove her '63 Nova for three years that way,then we sold the car and the guy who bought it put another 20K on it before the motor finally died. Those 235's are tough.
     
  13. hobbyjp
    Joined: Mar 14, 2006
    Posts: 330

    hobbyjp
    Member
    from socal

    I tested the compression on the cylinders again and number one is up to 100psi still lower than the rest but not the 50 it was before. well I'm still gonna look in the pan and remove the rod bearing and see what I get. then I'll try some of the oil treatment and pour some mystery oil in the carb for the valves.
     
  14. brad chevy
    Joined: Nov 22, 2009
    Posts: 2,627

    brad chevy
    Member

    How long has the car sat without running,you said it was original engine with only 30,000 miles.
     
  15. 6inarow
    Joined: Jan 24, 2007
    Posts: 2,350

    6inarow
    Member

    yep - yank it and go through it
     
  16. hobbyjp
    Joined: Mar 14, 2006
    Posts: 330

    hobbyjp
    Member
    from socal

    Id rather get AAA and run it till it blows. Right now its running good for what ever reason. I like fixing things that are broke not just throwing money at something. I dont have the funds to rebuild a motor. I'll check the bearing clearances tomorrow. the car has only recently been drivin alot though and runs and drives great. it didnt run when I bought it, got it running a week later I dont know how long it sat before but it since then it has just hasnt been down the road due to the body not being finished. I'm trying to fix what ever was causing the knock. If I wanted to just throw money at it I would put a 350 in.
     
  17. Lotek_Racing
    Joined: Sep 6, 2006
    Posts: 690

    Lotek_Racing
    Member

    Just do the simplest stuff first.

    Try cleaning out the carbon with the water trick or some seafoam.

    If that doesn't work, just pull the head and check the cylinders and head, clean up the head while you're in there. If it was just carbon buildup, all you're out is a head gasket set, oil and coolant.

    You'd be pissed if you pulled the motor, tore it down and found nothing wrong but something simple that could be fixed in-car.

    My 261 made a hell of a knocking sound and smoked when it broke a rocker arm.

    Shawn
     
  18. wait until dark then get a qt. of ATF and feed it down the carb at fast idle, it's gonna smoke like a freight train going up a mountain but the end result will be clean valves and you will notice the idle smoother than before. i alway do this to any used motor i install after a compression check first, only a fool installs a used engine without a compression check or worse buys one without checking compression.
     
  19. hobbyjp
    Joined: Mar 14, 2006
    Posts: 330

    hobbyjp
    Member
    from socal

    55 I've spent some time with some rolled stock and fuel line listening I plan to do some more, Hotdamn thanks for describing a bent rod and lotek your on my line of thinking. I do my own work and I like to drive em every chance I get. I've spent more money getting towed than I think I've put into the car. Funny thing is its got shiney paint (by me) and gets driven every week.
     
  20. hobbyjp
    Joined: Mar 14, 2006
    Posts: 330

    hobbyjp
    Member
    from socal

    Well I pulled the rod bearing on number one. Checks it with plastigauge and its under .0045 but it looks to have some wear. How bad would you say these are? I might just wait till the next time I change the oil to replace em. how do I know what size bearings to get?

    [​IMG]
     
    Last edited: Sep 22, 2010
  21. JohnEvans
    Joined: Apr 13, 2008
    Posts: 4,883

    JohnEvans
    Member
    from Phoenix AZ

    Bearing size is usually marked on the back side. Replace NOW not later 'cause ya run it much further knockin you will be replacing the engine.
     
  22. blackrat40
    Joined: Apr 19, 2006
    Posts: 1,167

    blackrat40
    Member Emeritus

    It looks too bad to just replace the bearing unfortunately.
    You need to have a knowledgeable person to measure the wear
    on the crankshaft with a micrometer.
    Sorry to say that your crankshaft needs to come out and be
    reground.
    I used to work for a rebuilding shop and part of my job was to
    take a set of micrometers out to garages that were our customers and "mike" the suspect cranks.
    I'm pretty sure from looking at that bearing that your crank
    needs to be reground or possibly replaced if it is worn too bad.
    The gray dull looking material is called Babbitt material which
    is overlaid on the copper backing of the bearing shell.
    The fact that the copper is showing through means that most
    of the soft babbitt is worn through to the copper backing.
    The worst news is that the worn off metal is being circulated through out your engine by your oil pump and must be cleaned
    out completely or you risk complete destruction of your engine
    and the internal parts.
    Very sorry to have to deliver the bad news. It needs a rebuild.
     
  23. 6inarow
    Joined: Jan 24, 2007
    Posts: 2,350

    6inarow
    Member

    is this a splash or full pressure 235? What year?
     
  24. hobbyjp
    Joined: Mar 14, 2006
    Posts: 330

    hobbyjp
    Member
    from socal

    Its a 54 I dont think its full pressure though
     
  25. 6inarow
    Joined: Jan 24, 2007
    Posts: 2,350

    6inarow
    Member

    54's are all full pressure
     
  26. hobbyjp
    Joined: Mar 14, 2006
    Posts: 330

    hobbyjp
    Member
    from socal

    I really dont want to start dumping a ton of money I dont have into this motor. So if it was running good I cant just cant replace the bad bearings? I'd really like to drive it somemore before the weather changes. Whats the process for removing the crank besides removing all the bearing caps? How do I know when the crank is in the proper position when its reinstalled? I dont see that procedure in the manual.
     
  27. r8odecay
    Joined: Nov 8, 2006
    Posts: 787

    r8odecay
    Member

    Bearing is worn, yes. but how exactly does that translate into low compression in that cylinder?? you have another problem up top as well.
     
  28. hobbyjp
    Joined: Mar 14, 2006
    Posts: 330

    hobbyjp
    Member
    from socal

    Yeah I'm sure there are plenty of things wrong with the motor, but it runs 70 down the road and other then the few wierd noises that lasted about 2 min the engine seems fine. One piece at a time. I'm trying to have my cake and eat it too. I dont have the luxury of rebuilding the motor right now.
     
  29. brad chevy
    Joined: Nov 22, 2009
    Posts: 2,627

    brad chevy
    Member

    Better call AAA now ,you run it 70 much longer like that and you will be walking anyway.
     
  30. 6inarow
    Joined: Jan 24, 2007
    Posts: 2,350

    6inarow
    Member

    AMEN to that.
     

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