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Thread: rumble strip sound

  1. #1

    Question rumble strip sound

    So every now and then I get this sudden loss of power associated with a sound like I'm driving over a rumble strip.

    It only happens when the car is moving and the ac is on. So I've isolated it to the AC system. I'm just not sure what part of the AC system. anyone have this problem or any idea what it might be?

  2. #2
    Stow It! GM_Guy's Avatar
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    If its grumbling with the a/c on, the only moving part in the system is the compressor.

    Alex.

  3. #3
    The Brown Blob 87gtVIC's Avatar
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    What year car?


    A member on here experiences that occasionally and believes it may be torque converter shutter.

    Not the identical scenario you have but he gave and I felt the rumble strip feeling.
    ~David~

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    I've also seen ignition issues cause something similar to this. Could just be time for a good ol tune up. And yea, post the year of the car.
    These are highly engineered precision vehicles, the first step in diagnosing the problem is to strike the suspected offending part sharply and repeatedly with a blunt object, then re-test.

  5. #5

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    Have you observed this in park, while under the hood ? AC clutch going out, bad bearing in the pulley ? Hell your tensioner might be going south.
    God is a comedian playing to an audience too afraid to laugh - Voltaire

    2001 HPP P74 All KYB (Bilstein next) upgraded intake and exhaust
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  6. #6
    No mean-spiritedness here. IPreferDIY's Avatar
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    A better description of driving conditions would help. The torque converter locks up in limited conditions, so if it's happening while the torque converter is not locked up, that would presumably rule out torque converter shudder. Curiously, the OP describes a rumble strip "sound" rather than a rumble strip "feel", and the stuff I've read suggested one would get the latter from torque converter shudder.

    I don't know much about A/C stuff, but as I understand it, the A/C compressor cycles on and off repeatedly when it's being used. If the sound always happens when the A/C cycles on, that would seem to suggest some kind of compressor issue, as if the compressor is having a hard time rotating when the clutch first engages. If the sound only happens when the A/C cycles on while the torque converter is locked up, or when the torque converter locks up when the A/C is already cycled on, that could suggest a curious bit of torque converter shudder related to the load of the A/C compressor.

    2000 Grand Marquis LS HPP, a hand-me-down in 2008 with 128,000 km; 175,000 km as of July 2014
    mods: air filter box "tuba" (in place of the "trumpet"), headlight relay harness, J-mod (around 186,350 km), 70mm throttle body, NKL4 PCM (from a 2000 CVPI, nothing great there apart from highway cruising), KYB Gas-A-Just shocks (after >202,000 km on originals)

  7. #7
    I'm an air-conditioned gypsy gadget73's Avatar
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    it doesn't cycle that fast. The system cuts out around 25 psi and back in around 45. It takes a couple seconds for that to happen. The shudder I've felt is a whole lot more like a rumble strip. AC cycling is a surge every second or so as the clutch kicks in and out.

    86 Lincoln Town Car (Galactica).
    5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

    91 Lincoln Mark VII LSC SE, triple black (Timewarp) - poly front bushings, KYB struts and shocks, Holley SystemMax1 lower intake, SilverFox AOD valve body,

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  8. #8

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    Sorry folks... a bit more detail.

    It is a 2003 Grand Marquis. The noise does occasionally happen upon first startup but that is the only time it happens when not driving. I cannot replicate the sound from beneath the hood by manually opening and closing the throttle. I have tried a couple of time to have one of my kids start the car with the AC on while I was under the hood but it never seems to do it when I'm under there.

    Speed and or RPM doesn't seem to affect whether or not it happens but does seem to affect the intensity of the power loss/speed scrub/ drag and tone(faster/higher sounds more like rumble strips and slower like...slower deeper rumble strips I guess.)

    There is some sensation that can be felt but it is more of a sound. When it happens on startup it seems to be coming from under the passenger side of the dash if I had to try to pinpoint the noise from the drivers seat.

    Without the AC on it never happens at all and everything functions like a brand new car.

    I haven't thought to check with different intensities of ac high vs low because it only worked on high until about a week ago when I fixed the resistor.

  9. #9
    I post a lot... knucklehead0202's Avatar
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    Another possibility is that your balancer is going away. My '98 would shudder and make a belt-squeal sound whenever the a/c compressor kicked on. I watched underhood while this was happening and saw the balancer spin on the hub. Just throwing that out there. If you do indeed need a balancer, buy the 4.6 underdrive pulley kit from summit. Costs the same as just a balancer and comes with a fancy SFI balancer, as well as underdrive pullies.

  10. #10
    Beater gonna beat sly's Avatar
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    check the belt tension. I have an issue occasionally with my expedition that when the AC compressor engages, the belt tensioner bucks pretty hard keeping the tension on the belt. If the tensioner is getting weak, it could bounce more than that and may sound like a rumble strip. Mine sounds like a once and done speed bump.

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  11. #11

    Angry

    Quote Originally Posted by sly View Post
    check the belt tension. I have an issue occasionally with my expedition that when the AC compressor engages, the belt tensioner bucks pretty hard keeping the tension on the belt. If the tensioner is getting weak, it could bounce more than that and may sound like a rumble strip. Mine sounds like a once and done speed bump.

    So in doing this I found the source of the noise though sadly not the cause. I went out and turned on the ac and opened the hood then fired it up and ran around to the front. nothing for a few seconds then rattle goes the tensioner. So I thought great bad tensioner I'll go get that handled done and done. I went to the pick and pull and grabbed one from a 2011 crown vic figuring that one that much newer than mine is more likely still good. No avail still having the same problem. Though I'll admit it is possible that the one I bought is equally bad. Assuming for now that the tensioner rattle is a symptom of the problem and not the problem itself what do you guys think it may be?

    Consider the Following:
    -only happens when AC is on
    -noise caused by vibrating belt tensioner
    -has now happened in park and more frequently while driving
    -when it happens while driving it scrubs speed and acceleration.

  12. #12
    I'm an air-conditioned gypsy gadget73's Avatar
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    my knowledge of the modern cars is lacking but didn't they convert to one of those stupid clutched over-running pullies for the alternator at some point?

    Also did you check the balancer like was mentioned earlier?

    86 Lincoln Town Car (Galactica).
    5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

    91 Lincoln Mark VII LSC SE, triple black (Timewarp) - poly front bushings, KYB struts and shocks, Holley SystemMax1 lower intake, SilverFox AOD valve body,

    1984 Lincoln Continental TurboDiesel - rolls coal

    Quote Originally Posted by phayzer5 View Post
    I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

  13. #13
    No mean-spiritedness here. IPreferDIY's Avatar
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    Something like a tensioner is going to be mileage-dependent rather than age-dependent. Someone with a 2011 might very well have driven twice as many miles as someone with a 2003. What's the mileage on your 2003? Do you feel any restriction or slop in the tensioner pulleys? (BTW, RockAuto sometimes has them on clearance for cheap enough to buy a spare.) When was the belt last replaced? [Edit: Did you check all the other pulleys while you had the belt off?]

    It looks like the alternator clutch pulleys were only for 04+ CVPIs:

    https://www.crownvic.net/ubbthreads/...Number=2851602
    Last edited by IPreferDIY; 09-11-2019 at 08:29 PM.

    2000 Grand Marquis LS HPP, a hand-me-down in 2008 with 128,000 km; 175,000 km as of July 2014
    mods: air filter box "tuba" (in place of the "trumpet"), headlight relay harness, J-mod (around 186,350 km), 70mm throttle body, NKL4 PCM (from a 2000 CVPI, nothing great there apart from highway cruising), KYB Gas-A-Just shocks (after >202,000 km on originals)

  14. #14
    Beater gonna beat sly's Avatar
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    If everything else is good on the car... you could also use the "crank up the radio" fix. It could just be the sudden shock loading of the clutch engaging on the AC compressor and bounces the tensioner on the belt. There may not be a full fix for that. Like I said... the one on my Expedition does it on first kick but not after that.

    Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
    rides: 88 MGM (SOLD), 93 Vic, 2000 Crown Vic, 2003 Expedition
    Quote Originally Posted by gadget73
    ... and it should all work like magic and unicorns and stuff.
    Quote Originally Posted by dmccaig
    Overhead, some poor bastards are flying in airplanes.

  15. #15
    Fastest Box In South Jersey 86VickyLX's Avatar
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    Try to get a sound clip of it. I'm curious if it's the timing chain tensioners/guide being the problem.
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