Buick LeSabre bad knocking noise coming from the engine.

paddle4paddle4 Member Posts: 11
edited December 2014 in Buick
Have a 2005 Lasabre 3.8. Had a bad knocking noise coming from the engine. Took off the belt and started it up no more noise. Replaced the harmonic balancer still have the noise with the belt on.
Noise goes away if you run the engine at a higher rpm . Car has only 62,000 miles. Not losing any antifreeze or oil. A/c doesn't work. Has plenty of heat. Noise is so loud can't figure out where it is coming from. Can anyone help?
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Answers

  • imidazol97imidazol97 Member Posts: 27,609
    If it doesn't knock with the belt off testing it for that short minute you can run it that way, your choices are limited:

    water pump
    power steering pump
    alternator
    AC compressor pulley unless the compressor is engaged (test by turning HVAC off on the dash)
    idler pulley on the tensioner (pulley and its bearing can be replaced without replacing the tensioner--bolt is reverse threaded)

    Maybe a bad belt? You should be able to visually see a flaw on the grooved side.
    You can rotate each of the devices when you have that belt off and check for wobble, in-and-out play, and a roughness coming as you turn the pulley on each.

    Have you tried a mechanics stethoscope device? Make one using a short broom stick size of wood that you hold against each of the potential items _carefully_ with the engine making the noise and hold the other end to your ear.

    Good luck. Please let me know what you do find. I am curious. Too often the knock is internal and that's bad news.

    2014 Malibu 2LT, 2015 Cruze 2LT,

  • paddle4paddle4 Member Posts: 11
    Pretty sure it's the power steering pump. When I turn the wheels all the way left or right the noise gets louder. There is a slight play in the pulley in and out on the pump. Taking the pump off and putting a new one on. Let you know what happens. Thanks
  • thecardoc3thecardoc3 Member Posts: 5,843
    Does your alternator have a decoupling pulley? Typically the alternator rotor is a heavy component and that means it has a lot of inertia and doesn't like to change speeds. A crankshaft doesn't turn at a steady speed, it actually speeds up and slows down with each cylinders compression and power stroke. The decoupling pulley actually allows the alternator to turn faster than the crankshaft when the crankshaft slows under compression due to the rotor's inertia and then it locks and gets a push when the crankshaft speeds up. When these pulleys wear out they can hammer (knock) pretty loudly.
  • Mr_ShiftrightMr_Shiftright Member Posts: 64,481
    In addition to that, examine each of the belt driven components to make sure nothing is loose in its mounts.
  • paddle4paddle4 Member Posts: 11
    Checked all the belt driven components and the only one that had just a slight play in and out was the power steering pump. The alternator pulley is just the standard pulley. Got the pump off and when I turn the pulley back and forth an inch or so I can feel that there is a little play in it. Parts store had to order a new pump so can't do anymore today. Thanks
  • paddle4paddle4 Member Posts: 11
    Well guys put the new steering pump on and it still makes the same noise. I live in WI and it is cold here 20 degrees . When I first start it up the noise isn't as loud but as it warms up the knocking gets louder. Increase the rpm's and noise stops. Take the belt off no noise. Left with only the water pump and the AC unit. The AC doesn't work but the pulley spins freely and I have plenty of heat. Alternator pulley spins freely and is just a standard pulley. Anyway to test the water pump or AC with out having to take them out? Any suggestions?
  • Mr_ShiftrightMr_Shiftright Member Posts: 64,481
    Well if the AC clutch is not engaged then the compressor isn't spinning--so you have to determine if the clutch is engaged or if only the outer pulley is turning.

    Can you buy or borrow a mechanic's stethoscope? Not very expensive---just a long rod attached to some tubing and simple set of earphones. Naturally doing this with a spinning engine requires a great deal of caution, no loose clothing, good eye protection, etc.
  • paddle4paddle4 Member Posts: 11
    How do you tell if the AC clutch is engaged?
  • Mr_ShiftrightMr_Shiftright Member Posts: 64,481
    Just look at the very front of the pulley---if it's stationary, then it's not engaged.

    Here's a video that shows you:

    https://www.youtube.com/watch?v=KMIHDfnQ9hs

  • paddle4paddle4 Member Posts: 11
    ac clutch is not engaged, only the pulley is turning so nothing inside the compressor is turning right? If that's the case then my water pump must be making the knocking noise. Have plenty of heat and the temp. has been running the same.
  • imidazol97imidazol97 Member Posts: 27,609
    You definitely need to cobble up or borrow a mechanics stethoscope to let you put something against the various parts while you listen at the other end, with the sound conducting through the rod.

    Do the local box stores like Autozone or OReilly have those in their loaner parts?

    The AC compressor pulley has a bearing as well.That pulley could be making noise even though the clutch is not engaged. Also check around the transmission to engine connection--I don't know if it's relevant here but some people have had knocking sounds with a plate that is part of the torque converter connection to the engine.

    As to the water pump, you should have been able to feel something in the pulley and axle for it while the belt was off when you tested each of the accessories. Did you test the idler puller on the tensioner?

    I would stop replacing parts until you can isolate the location. You may need to pay a good mechanic shop with an expert in this for some time for him to listen to the engine with a stethoscope. That might save you in the end.

    2014 Malibu 2LT, 2015 Cruze 2LT,

  • imidazol97imidazol97 Member Posts: 27,609


    $3.99 at harbor freight stores, if you're in an area where they have one.
    harborfreight.com

    http://www.harborfreight.com/mechanics-stethoscope-69913.html

    2014 Malibu 2LT, 2015 Cruze 2LT,

  • Mr_ShiftrightMr_Shiftright Member Posts: 64,481
    A very handy too indeed. I had a similar problem--it really sounded like an engine knock, but what it was was the alternator mount rocking back and forth on a stripped stud. Mr. Stethoscope figured that out quickly, even though I was not happy to be sticking that rod so close to whirling pulleys and belts. Again, no loose clothing or long hair!

    Also i hope and pray that whoever replaced the crank pulley took a good long look at the pulley keyway and the slot on the crankshaft nub.
  • isellhondasisellhondas Member Posts: 20,342
    edited December 2014
    A stethoscope? We used to use a piece of wooden dowel.

    Either way, you REALLY need to be careful when doing this.

    I once saw the aftermath of a long haired VW mechanic getting his hair in the spinning
    generator pulley. I'll skip the description but it wasn't a good thing.
  • imidazol97imidazol97 Member Posts: 27,609
    isellhondas said:

    A stethoscope? We used to use a piece of wooden dowel.

    Either way, you REALLY need to be careful when doing this.

    I once saw the aftermath of a long haired VW mechanic getting his hair in the spinning
    generator pulley. I'll skip the description but it wasn't a good thing.

    Right on. The best clothes for working around the belts and pulleys is a T-shirt--no sleeves, no unbuttoned parts or tails AND a lot of caution. I use only one hand around such things--it's easier to focus to make sure I don't get close. My uncle had lost his full hand in a piece of farm equipment back in the 40s--probably a corn picker. I always was afraid of that iron hook that replaced his hand like something out of a pirate comic book.

    2014 Malibu 2LT, 2015 Cruze 2LT,

  • paddle4paddle4 Member Posts: 11
    I have a mechanic stopping by tom. to see if he can figure it out. Let you all know what he finds.
    Thanks
  • imidazol97imidazol97 Member Posts: 27,609
    paddle4 said:

    I have a mechanic stopping by tom. to see if he can figure it out. Let you all know what he finds.

    I am anxious to know what he finds.

    2014 Malibu 2LT, 2015 Cruze 2LT,

  • paddle4paddle4 Member Posts: 11
    I agree with imidazol97! I am paddle4"s wife, stop buying parts and replacing them until you know what is wrong!!! I got a feeling I just a power steering pump for Christmas, because after this there sure is not going to be much Holiday money!!
  • paddle4paddle4 Member Posts: 11
    Well guys, mechanic came by and got it narrowed down to the back lower side of the engine.
    Said it could be a rod bearing so I dropped the oil pan. Didn't find any metal in the bottom of the pan all the rods are tight from what I could tell. Moved the crank back and forth to see if there was any play in the rods none that I could see. Said it wouldn't be a lifter because the knocking was to low in the engine. May just have to take it to a garage to see if they can figure it out.
    Read that some of these engines 3.8 series 2 develop what they call piston slap. Anyone heard of this or dealt with it. I had changed the oil that's when the knocking got louder and when I drained the oil to take the pan off the oil seemed to me to be pretty dark already since I had only put less than 200 miles on. No gas smell in the oil or milky substance. Any more ideas of what it could be? Thanks
  • thecardoc3thecardoc3 Member Posts: 5,843
    By chance did you check the torque on the convertor bolts?

    This is one of the problems with noises, nothing compares to hearing it first hand and investigating from there. With the location now changed from your original description I wouldn't rule out a broken flexplate. Some of the other thigs i have found through the years are camshaft bearings. These can develop a thrusting of the camshaft behind the timing cover and that causes a pretty good knock if they are too loose. Another potential noise is caused by wear in the balance shaft bearings.
  • paddle4paddle4 Member Posts: 11
    The mechanic did mention that it could be the flexplate. Also didn't check the rod bearings the right way to see if they were bad. So doing that tom. Watched a couple of rod bearing noise videos and they sound just like the knocking I have. Mechanic was also stumped that the knocking wasn't heard with the belt off but was positive that it was coming from the back lower part of the engine which would put it in the area of the flexplate.
  • imidazol97imidazol97 Member Posts: 27,609
    I had mentioned the flexplate but realized after I posted that the noise was not there when the belt was off.

    I had read a few stories in Pontiacs where noises were traced to the plate.

    2014 Malibu 2LT, 2015 Cruze 2LT,

  • Mr_ShiftrightMr_Shiftright Member Posts: 64,481
    edited December 2014
    It can't be a rod bearing---that was off the mark. A rod bearing wouldn't knock at idle unless it was ready to fall out, nor would the noise go away as you revved the engine. Rod bearing knocks are very hard to miss. They are loud and sharp and high up on the block.

    It's possible a main bearing could knock at idle but that is a VERY deep, dull sound. Did anyone try to pry the crankshaft forward and back?

    You can check for a wrist pin noise pretty easily--if you disconnect or short out the spark plug to the suspect cylinder, the noise will double in frequency, from TAP to TAP-TAP, once you disconnect the spark plug.

    Piston slap will generally go away once the engine is warm. It's a cold engine symptom. You can test for piston slap by removing the spark plug and squirting an ounce or two of oil in the cylinder. They re-insert the plug, and if there was piston slap, it will disappear for 30 seconds or so and then return as usual.

    Another thing you can do is remove your oil filter and cut it open and look for metallic debris.

    If there is none, you should probably move onto the flex plate.
  • imidazol97imidazol97 Member Posts: 27,609
    Mr_Shiftright said:

    If there is none, you should probably move onto the flex plate.

    I saw mention of an inspection opening for the flex plate. Said it's a plastic cover. Remove to be able to examine flex plate. I'm going to check my 03 FSM to see if there's an inspection opening.

    After you've already replaced PS pump, I'd really hate to see the flex plate be a wrong diagnosis and have you R&R on it.

    2014 Malibu 2LT, 2015 Cruze 2LT,

  • paddle4paddle4 Member Posts: 11
    I have the plastic cover on the flex plate removed so I'll turn it and see what it looks like. Have to work the next couple of days so won't be able to work on it much. Thanks for all the help everyone. If it is a rod bearing will the rod or where the bearing is move easily?
  • Mr_ShiftrightMr_Shiftright Member Posts: 64,481
    edited December 2014
    I don't think it's a rod bearing from your description. In any event, you might saw the oil filter in half and look for bearing material. A rod bearing would give you a very sharp metallic knock as soon as you blip the throttle. You are describing a noise that occurs under no load, not under load. Bearings knock worse as the engine runs, since the force of combustion is more pronounced.

    this suggests to me that the source of the noise is related to vibration at rest rather than stress.
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