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Thread: Strange noise, only under load...

  1. #21
    Senior Member Jonathan's Avatar
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    Quote Originally Posted by DMC-81 View Post
    I bought a gear oil pump at Advance Auto Parts ( you can probably find them at a Canadian equivalent) and it really makes the filling much easier. I made sure it would fit both quart and gallon bottles.
    Here's a link:

    https://shop.advanceautoparts.com/p/...E&gclsrc=aw.ds
    Quote Originally Posted by Bitsyncmaster View Post
    I had not problem just sticking it in a few inches. I'm talking about the hose so no wise cracks.
    Thanks for the tip. (Eeeek!, lol, aren't I punny!) I found something similar to that gear oil pump locally and it should work just fine.

    Quote Originally Posted by DMCMW Dave View Post
    Replace the differential. it is not really practical to replace just the gears. This is not as bad as it sounds since used ones are pretty readily available, this is the only failure. People sometimes replace an entire faulty automatic trans due to clutch or hub failure, but the differential (a completely separate part) is still in fine condition and available for this sort of repair.

    The damage is that you've worn the face (case) hardening off the surface of the hypoid gears, so they don't mesh properly any more and now make noise. Damage is done, and other than the noise there really isn't any harm in continuing to drive it like that for a long time.

    It really is a gear whine, not a rumble or flutter. Sorry - sounds/feels are hard to put into typed words.
    Once I get the gear oil refilled and other inspections done while it's in the air, I'll take it for a drive and record the audio (or video plus audio if my dashcam will pick up the sound well enough). I'll post that here so it's not so ambiguous as to what the sound is. Agreed on sounds "sounding" different when typed from one guy to another.

    Thanks for the help and advice so far. Really appreciate it!
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  2. #22
    Senior Member Jonathan's Avatar
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    Ok, got the rear differential fluid refilled. Took about 1.4 litres before it was starting to slowly drip out the bottom edge of the fill port.

    Took the car for a ride and thought it might have done the trick, but alas, not so lucky. It was doing the noise again, maybe even more so than before.

    Here's the audio I took from a 15 minute drive. I edited this down to about 1 and a half minutes. This was when I closed my window, so just cabin noise. I think you''ll be able to make out the vibration sound I speak of. Again, only happens when actively pressing the gas and only happens when the car is in motion, i.e. doesn't make any noise when parked and the engine is running.

    (I had my phone sitting on the middle armrest right in front of the coin tray while it was recording the audio)

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  3. #23
    DMC Midwest - 815.459.6439 DMCMW Dave's Avatar
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    Differential noise is a higher-pitched whine. What kind of tires do you have on the car, i.e. brand/size/miles?
    Dave S
    DMC Midwest - retired but helping
    dswingle@DeLorean.com

  4. #24
    Senior Member DMC5180's Avatar
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    That actually does sound like a vibrating heat shield. Like the one attached to the crossover pipe. Its not gear whine.
    DENNIS

    VIN 5180, Frame 3652, STAGE I, DM-eng Solid State Solutions (RPM Rly, Dm.Lt.Mod., Fan Fail Mod. , FAN Rly, HS.Rly) , HID sealed beam style headlights, SPAX user since 2009, Eibach springs, Mid-State Club Adj. Rear LCA's, DPNW poly-sway bar kit, DMCEU LCA Stabilizer link kit, DMCMW Illuminated door sills, Aussie Illuminated SS Shifter plate, GENUINE MOMO EVO Steering wheel, DELOREANA Extended View Side Mirrors w/ Heaters, DELOREANA LED Door Lights.

  5. #25
    Not a DeLorean Guru
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    Cat heat shield? Heat shield on the cross-over pipe? Check those.
    -Mike
    1981 DeLorean, heads/cams/exhaust, EFI
    1999 Corvette, heads/cam/exhaust, 440 BHP
    2005 Elise, stock
    2016 Chevy Cruze

  6. #26
    Senior Member Jonathan's Avatar
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    Quote Originally Posted by DMCMW Dave View Post
    Differential noise is a higher-pitched whine. What kind of tires do you have on the car, i.e. brand/size/miles?
    Tires are Dunlop GT Qualifier (on all four). Standard DeLorean sizes. Dates codes are from late 2006. Been on the car the entire time I've owned it (Fall 2007). About 12,500 miles that I have driven on them and not likely much more than that since they were new (probably bought by place that was selling the car then).

    What noise ideas come to mind with respect to the tires?

    Quote Originally Posted by DMC5180 View Post
    That actually does sound like a vibrating heat shield. Like the one attached to the crossover pipe. Its not gear whine.
    Quote Originally Posted by opethmike View Post
    Cat heat shield? Heat shield on the cross-over pipe? Check those.
    Glad to hear the consensus isn't gear whine. When I listen to that audio myself (on the computer and not while driving), it almost sounds like one of those idiotic fast and furious attempts and the guy's exhaust is rattling up against something. I'm leaning towards the crossover pipe heatshield too and will check it in the morning. Wanted to let the engine get cold tonight before reaching in and around there making sure things are secure.
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  7. #27
    DMC Midwest - 815.459.6439 DMCMW Dave's Avatar
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    I asked about tires because some tires (especially the older blockier treads, and Goodyears) tend to get noisy with age. But that wouldn't change with acceleration/deceleration, only road speed.

    Heat shield is, on paper, hard to fix "properly" and a common rusty-car problem. Luckily it's easy to fix "improperly" with a couple of well-placed hose clamps.

    The heat shield is attached the crossover pipe in two pieces with several bolts that are, at this point, welded into bungs on the crossover pipe. You'd have to remove the pipe for access (it is held to the manifolds and converter with a few more guaranteed to break rusty bolts/studs). Rust isn't always an issue, but on your particular car, and most northern climate cars, it will be.

    I couldn't tell much from the audio file, but it occurs to me that you may be hearing the very early beginnings of exhaust manifold gasket failure. In the begging they are only noisy on acceleration, but won't be noisy revving the engine with no load. It will get worse over time. In that case, at some point you'll have the crossover off the car. This is commonly misdiagnosed as noisy valve rockers BTW.
    Dave S
    DMC Midwest - retired but helping
    dswingle@DeLorean.com

  8. #28
    Senior Member DMC-81's Avatar
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    Quote Originally Posted by DMCMW Dave View Post
    I asked about tires because some tires (especially the older blockier treads, and Goodyears) tend to get noisy with age. But that wouldn't change with acceleration/deceleration, only road speed.

    Heat shield is, on paper, hard to fix "properly" and a common rusty-car problem. Luckily it's easy to fix "improperly" with a couple of well-placed hose clamps.

    The heat shield is attached the crossover pipe in two pieces with several bolts that are, at this point, welded into bungs on the crossover pipe. You'd have to remove the pipe for access (it is held to the manifolds and converter with a few more guaranteed to break rusty bolts/studs). Rust isn't always an issue, but on your particular car, and most northern climate cars, it will be.

    I couldn't tell much from the audio file, but it occurs to me that you may be hearing the very early beginnings of exhaust manifold gasket failure. In the begging they are only noisy on acceleration, but won't be noisy revving the engine with no load. It will get worse over time. In that case, at some point you'll have the crossover off the car. This is commonly misdiagnosed as noisy valve rockers BTW.
    I agree with Dave. As you are checking the crossover pipe, here's a picture of it out of the car and taken apart to give a visual of what you are checking for. I found that the 4 bolts got more rusty than the rest of the pipe. I think if you wiggle the shields a bit on the car, and you are able to move them, that will point to one or more failed/degraded bolts.

    image.jpeg

    When I restored this pipe, I had to use heat, wax, and rust penetrant to gradually coax the bolts out, and that is on a Southern car.

    I also agree on the possible sound of failed exhaust gaskets. Mine made a fluttering sound, and got worse over time. When I got the manifolds off, I found 3 of 6 ports were leaking. I saw black soot around the leaky gaskets, and/or a rusty/disintegrated gasket.

    image.jpeg

    image.jpeg

    image.jpg
    Dana

    Delorean status: CECF 2017 Platinum Award winner. Still tinkering...

    Pictures and comments of my restoration journey are in the albums section on my profile.

    .

  9. #29
    Senior Member Jonathan's Avatar
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    I found the source of the noise.

    It was in fact the crossover pipe heatshield on top. And specifically, it was the passenger side half that had one of those two bolts sheared off at the head. Thanks for the suggestions and pictures. The only thing remaining was a tiny bit of the threaded portion, but enough to keep the washer in place. Sort of. The washer wasn't tightened down onto anything, but couldn't just fall off because a bit of the broken bolt had stopped it from coming out on its own. It was plenty loose enough to rattle though... every time you hit the gas.

    I got the washer out of there and put a hose clamp on for the time being. That is not a nice area to gain access to from above, so once I get some time to get at it from underneath properly, I'll put a couple hose clamps on and make sure they're good and tight and well centred. In the meantime, it stopped the vibration noise. I went out for about a 30 mile drive and the car drove real nice.

    I'd say it was a big relief to get it sorted out, but I wasn't really all that thrilled about it when I finally tracked it down. I probably just muttered asshole to the car as I shut the light off in the garage and went inside.
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  10. #30
    DMC Midwest - 815.459.6439 DMCMW Dave's Avatar
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    Quote Originally Posted by DMC-81 View Post
    That's a really good picture of what to look for when the exhaust starts getting noisy. You'll see black soot marks like this on the bad ones, and you'll often see the gasket starting to fall out, indicated by the unused holes no longer lining up.
    Dave S
    DMC Midwest - retired but helping
    dswingle@DeLorean.com

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