Help me ease my mind.......Rod Knock???

Engines, Exhaust and Fuel Systems

  1. rcmaniac791

    rcmaniac791 Well-Known Member

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    Well, here it goes:

    The car (1984 chrysler fifth avenue, stock 318, stock drivetrain, just hit 80,000 miles) has been running great until about a month ago, when I accidentally put mobil semi-synthetic 10w-30 in the car during an oil change. (they need to label the bottles better). When I started the car to drive it afterwards, I noticed a very mild knocking sound, kinda sounded like rod knock, could have been the fuel pump, not sure. I didn't really worry about it. I should also say that the noise is only audible when at idle, mostly at idle in gear.

    For the month that I had the semi-synthetic in the car, I also noticed that after sitting for more than an hour, the oil pressure light would take about 4 seconds to turn off when the engine was started, but when the car was driving (I put 800 miles on that oil) the oil pressure light was always off. I fixed the start-up oil pressure this last weekend when I did another oil change back to the mobil super conventional 10w-30 that I have been running for the last 6 years without problems. I ran the car for a good amount of time right after the change and I did not hear any noise. The car sounded normal. Oil pressure was now back to normal. I also did not see any aluminum glitter in the oil that I drained out.

    Well, today the noise is back. Still faint, and still only audible when the engine is warm and idling in gear. Today, I removed all the accessories and the fuel pump and ran the engine for a short period of time, and the noise did not change. I also pulled each spark plug wire one by one and not a single one changed the noise. The car is running and driving completely normal, no oil consumption, no smoke, no blow-by, nothing. Just a very faint knocking noise at idle.

    I should also mention that the car has been meticulously maintained and it's had oil changed religiously every 3,000 miles. The knock seems to be coming from the front of the engine, which leads me to think timing chain, but I'm not sure. The volume of the knock is not super consistent, it's just there. Also, when brake-standing the car, the engine sounds completely normal.

    Anyways, Thanks for reading all that. I hope that my fears are nothing and I'm just over-reacting to something silly. Let my know what you guys thing.

    -Jon
     
    Last edited: Apr 23, 2019
  2. Duke5A

    Duke5A Well-Known Member

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    Rod knocks are very distinct and get faster with RPM whether under load or just free revving. Is it possible to get video of the noise with you running the throttle by hand while under the hood?

    I honestly don't think this has anything to do with running a synthetic blend oil. You need to get an oil gauge installed too.
     
  3. volare 77

    volare 77 Well-Known Member

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    flex plate cracked or loose tc bolts is my bet. take a hose to try and narrow down where the sound is coming from.
     
  4. rcmaniac791

    rcmaniac791 Well-Known Member

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    I bet you're right. I had the trans rebuilt a year ago and have put about 4,000 miles on it. they replaced the converter so i bet something came loose. Anyways, I found 2 youtube videos that sound exactly like how my car sounds:






    Here's a quick video from earlier today. I start out in gear, then shift to park, then a few revs. I should also mention that when I went under the car with the phone that I noticed the noise louder under the car.

     
  5. 80mirada

    80mirada Well-Known Member

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    Sounds like the flexplate to convertor bolts are loose. You can take the inspection plate off and tighten them, make sure the plate isn't damaged.
     
  6. rcmaniac791

    rcmaniac791 Well-Known Member

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    Ok. I'm super relieved to hear that that's more than likely the issue and not a bottom-end noise. I'll try to get under the car and inspect in the next couple of days.
     
  7. BudW

    BudW Moderator Staff Member

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    Unless the body is cracked, (Dodge) mechanical fuel pumps rarely make noise.
    A noise that increases sharply upon a quick snap of the throttle is worrisome.
    A steadier noise is still a problem, but nowhere as worrisome.

    The things that come to mind are:
    Loose timing chain,
    Bent pushrod/broken rocker arm,
    Crankshaft to flexplate bolts loose,
    Flexplate to torque converter bolts loose,
    Cracked flexplate,
    Cracked torque converter (usually associated with transmission fluid loss in many cases).

    A cracked flexplate is not easy to see – for the cracks occur either close to the crank bolts or close to converter bolts.
    If you remove the inspection plate and find the four converter bolts are tight, I would first take a can of spray paint and paint one of the four flexplate corners getting a bit of paint on the converter at same time (as a quick marker). Then remove the 4 converter bolts and push converter towards the transmission (it should move back 1/4 to 3/8”.
    Grab ahold of each corner of the flexplate and wiggle it (this will require rotating crankshaft to do). If cracked (or loose crank bolt(s)) you will know when you wiggle that corner.
    Sometimes it helps to turn the flexplate to install one converter bolt a small bit to aid on rotating the crankshaft – but it will be faster just to get a 1¼” socket and ratchet (or breaker bar) to turn the balancer crank bolt.

    Just make sure the paint marking match up before reinstalling the converter bolts (to aid reassembly). The flexplate will only attach to crankshaft in 1 direction and same applies to flexplate to converter.


    If you suspect a loose timing chain, remove the air cleaner and distributor cap (push the cap to the side). Use a 1¼” socket and ratchet (or breaker bar) to turn the balancer crank bolt one direction a short bit. Now turn the crankshaft the other direction. The distributor rotor should immediately turn. If it doesn’t immediately turn right away, then you have a loose timing chain. If a timing chain is loose enough to touch the timing cover and if you have a plastic/aluminum timing gear – then it will also be loose enough to jump time.

    The all metal (steel) double roller chains are louder (not a knock noise, just nosier in general) and the chains can get loose (over a ton of miles) but seldom will ever jump time.
    All Chryslers made from ‘70ish and newer uses the single roller chain with plastic/aluminum gear, except for HP, police or taxi. Unless you have had your timing chain replaced, you have a 99.9% chance of having the aluminum/plastic gear setup. Those plastic teeth wear out (and crumble) over time – which can make a few different noises, one of which is chain hitting timing cover.

    318 Plastic TC.jpg
    This is a single roller chain setup that uses the plastic/aluminum gear (the silent gear set). Most replacements will be an all metal design. The plastic is quieter, but its lifespan is, um, pretty short.

    318 DR TC.jpg
    An aftermarket double roller setup. The main difference between single and double roller is chain is like two narrow chains side to side (made into one).
    There might be a difference between the all metal single and double roller design, maybe/possibly. The plastic single roller gear set shouldn’t be used on anything but on Furds or Chebys, period. Technically, they were bad/defective when installed on the assembly line, but they were cheaper and quieter (which I can agree they are quieter . . . and are REAL CHEAP!).

    Still not sure what the single or double roller chain difference is?
    Look at the cam gear teeth and, if you can, the chain has a runner on both sides and in middle.

    This is some pictures I found on internet. The white plastic has turned orange/brown from the heat. I’m very surprised there are no missing teeth!
    iu2PR13KN8.jpg
    I can see the Right side (of picture) the chain is tight. The Left side (of picture) is saggy loose - enough so to condemn the chain.
    iuNTFZ8CXK.jpg

    I have nothing bad to say about the all metal single roller design. The plastic design should be used for art class or photography purposes – only. Most customers don’t notice the all metal design being nosier, but I can, and a few customers can notice the noise.

    This design of timing chain is a whole lot louder if you are into that kind of thing).
    iuPV4ERKBE.jpg

    Smiles to ya,
    BudW
    318 DR TC Smiles.jpg
     
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  8. rcmaniac791

    rcmaniac791 Well-Known Member

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    This is great to hear. Anytime that I go anywhere near the throttle, the noise goes away. You can probably hear that in the video that I posted above.

    As far as the timing chain goes..............I will probably do a timing set sooner or later, and I'd like to change to a roller cam setup and a double roller timing chain while I'm in there, but that is for another thread. As of now, I need to try to fix this noise.
     
  9. BudW

    BudW Moderator Staff Member

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    I can't play the videos, currently (so not listened to).
     
  10. rcmaniac791

    rcmaniac791 Well-Known Member

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    I talked to the full time mechanic at the research farm that I work at, who has a vast history working on all brands of vehicles, mostly domestic, and after he listened to the noise for about 5 or so minutes he was leaning towards a cracked flexplate. Something new that has developed is when decelerating, I can hear a squeaking noise coming from somewhere under the car. It's inconsistent, but only happens when coasting off the gas or using the brakes. It's not high pitched like brake squeal, but a bit more like a squeaky hinge tone. Not sure if it's related to the flexplate or not, but it seems to be. This squeak happens on rough roads and smooth roads all the same.

    Since I'll be graduating from Virginia Tech in less than 4 weeks, I really don't have time to fool with this currently, so I'm going to park the car and use another vehicle for the time being. I don't want to cause any more damage by driving it. Also, my transmission and TQ/Flexplate is still under warranty at the transmission shop that rebuilt the trans for me. I'll end up calling them to have it looked at once school is behind me.

    Thank you everyone for your help!
     
  11. AJ/FormS

    AJ/FormS Well-Known Member

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    I'm leaning towards crank end-play, with flex-plate a close second.
    Rod noise is steady, not intermittent.
    But it's pretty loud,lol. End play you see on the damper as it shuttles back and forth in time with the knock.
     
  12. M_Body_Coupe

    M_Body_Coupe Well-Known Member

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    I had a flexplate to converter bolt back out on me once...very quickly too, in fact the minute I crawled under the car and took the inspection cover off I could see the bolt heads (ARP hardware, so all black, easy to tell marks) were in fact rubbing/hitting a part of the dustshield.

    However, in my case, the noise was a pingy sounding thing, meaning it was not a dull noise. I had initially thought one of my anti-pump up lifters either collapsed or worse yet the retaining clip let go (I ran the lifters with zero-pumpup, as per the instructions for these types of setups).
     
    Last edited: Apr 27, 2019
  13. volare 77

    volare 77 Well-Known Member

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    loose bolts hitting the cover surely has a tinny sound. the broken flex plate sounds more like a rod knock. ask me how i know.
     
  14. rcmaniac791

    rcmaniac791 Well-Known Member

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    I watched the damper while I heard the knock, and I didn't see it move even in the slightest. I looked at it with a flashlight and used the timing cover as a focal point.

    Makes sense since I confused the noise with rod knock to begin with. Once I have the time to tear into it and get it solved I'll update this thread on what the problem and solution is.
     
  15. Oldiron440

    Oldiron440 Well-Known Member

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    I've seen a couple of Ford v10s take out flex plates and a Chevy sb or two.
     
  16. AJ/FormS

    AJ/FormS Well-Known Member

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    Yeah, that's not from inside the oilpan, so end play is out.
     
  17. rcmaniac791

    rcmaniac791 Well-Known Member

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    Ok everyone, if you're still interested, here's the verdict.

    I took it to one of two shops that I trust with the car, and they inspected and listened for 3 days. they did not hear the noise coming from the bell housing, rather they did hear it coming from the oil pan. So my fear is true......rod knock. Not sure where to go from here, but I'll probably start shopping for a new engine. HEMI anyone?
     
  18. volare 77

    volare 77 Well-Known Member

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    I would have bet anyone $100 that my car had a rod knock. I had a oil pressure line leaking inside the car on a long ride home one night many years ago. I was down to about a 1 1/2 quarts oil when I heard the noise. I added oil and I even used a piece of hose to isolate the noise and I was sure the rod was knocking. When I pulled the engine out and pulled the pan the bearings were still good. Huh? I checked the flex plate and it was cracked around the converter bolt hole. Lesson learned. I also had a drive line vibration from it also.
     
  19. Oldiron440

    Oldiron440 Well-Known Member

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    There's only one way you will know for sure, start pulling parts before something breaks.
     
  20. XfbodyX

    XfbodyX Well-Known Member

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    One good thrash around the neighborhood watching your oil pressure gauge would show one way or another. Ive had rod bearings go south and never make a sound but when 60 psi cruising turns into 40psi in 30 miles.

    Do you have a OP gauge or just a light? Does the light flicker on when hot stopping at a stop light?

    A cracked piston skirt can sound just like a rod bearing, I drove 60k miles on a cracked skirt and it only broke the piston further due to more foolishness on my part.

    Really not a hard problem to solve when you get the time just bear down and pull the trans and look close at things and if you find nothing, pull the pan. If the trans is good id look at it as maybe a good thing, a 1984 motor with 80k miles...... if its a bearing, pull it, freshen it up and your good for a long long time.

    The anxiety of some things can be worse the the fix.