Knock knock

Discussion in 'Prius c Technical Discussion' started by Max Taiwan, Mar 24, 2019.

  1. Max Taiwan

    Max Taiwan Member

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    I guess this has been covered a load of time but can't seem to find a fix for it. So here is another!
    Same issue as everyone knock knock when cold which will go away after the engine warms up, until Knock again going up steep hill and stronger vibration felt when flooring the gas om the free way aka high way aka interstate.
    Car is 2013 with just over 43,000km. Dr prius app shows good battery life. Everything on the car is stock with original parts such as spark plugs ignition coils and fuel pump. I'm going to stick a K&N air filter in soon.
    I've noticed something odd with the car when you open the driver door in the moring. The fuel pump runs really long compared to other cars I've owned. Other car fuel pump stop before I could even jump in but this prius C will keep running until I close the door and then some.
    I'm thinking maybe the knocks are linked to this symptom?
     
  2. Max Taiwan

    Max Taiwan Member

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    I timed the fuel pump run time was approximately 10sec. My other cars were under 5sec.
     
  3. Max Taiwan

    Max Taiwan Member

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    I'm slowly thinking its a engine mount or transmission mount problem. Going over rough bumps i get a knock. Also going up bumpy hills too.
     
  4. John in Vermont

    John in Vermont New Member

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    The pump you hear when you get in the car is a vacuum pump charging the brake system, it is normal.
     
  5. Max Taiwan

    Max Taiwan Member

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    Great John thanks for the reply. How about the knock, still trying to figure it out.
     
  6. Max Taiwan

    Max Taiwan Member

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    Guys how do i check the engine mount structural integrity? My guess is that one for now. The reason i eliminated fuel pump, injectors and plugs is I'm having food fuel economy. And this noise only happens on bumpy roads while accelerating like up ac ramp or merging onto freeway. When its a smooth road i don't get any knocking noise.
     
  7. CoolPrius

    CoolPrius Active Member

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    Is the knock in the front or back? Does it happen at idle or only when moving?
     
  8. Max Taiwan

    Max Taiwan Member

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    Knock in the front, only when moving.
     
  9. mjoo

    mjoo Senior Member

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    Who's there?
     
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  10. Max Taiwan

    Max Taiwan Member

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    Hi John,
    Is it normal to keep hearing that pump for the brakes regularly when you drive and use the breaks?
    It comes on for 2 sec when ever i come to a stop or use the brakes during driving. Sometimes not but mostly it does come on when i drive.
     
  11. Max Taiwan

    Max Taiwan Member

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    I think I've located the noise. My strut tower and the body of the car there is a gap( don't know if that's normal) or its time to get a new ones fitted or to tight it down. So when i wobble the car there is play in the strut and body. When i accelerate the weight of the car falls on the rear wheels so any bumps on the road will let the strut top bounce back and forth hitting the body causing the knock.
    Is it a easy fix? Do people also have gap between the strut top and the body?
    On my old Ford Ka my mechanic took off the strut top and trimmed it a little making it fit tightly to the body to eliminate the noise. I'm wondering if i should do the same here or I just need to tighten something down or put some o-rings in between the space...
     
  12. Max Taiwan

    Max Taiwan Member

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    So here is a photographic view of my situation. I have a gap from my top support to the base on the body. World the problem be fixed if i screw down the nut? I thought those nuts were fit tight, in this case meaning my lower seat has flattened from age? Or can i put orings between the top mount and the body to take up the slack?
     

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  13. Max Taiwan

    Max Taiwan Member

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    Is it normal to be a gap here on a prius C? 2013
     

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  14. Royston.K

    Royston.K Junior Member

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    [​IMG]

    Not on mine. I guess you found your culprit.
     
  15. Max Taiwan

    Max Taiwan Member

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    It seems the gap shouldn't be there. My is still making some noise, but I can live with it.
    It stays silent most of the time. Just when accelerating slowly up a hill it will sound when it goes over a bump.
    But regular driving and with speed above a specific threshold, I guess the stress between parts just stops it from having that free play in between.
    Anyways I rest my case on this one. What i should have done is gone for a brand new set may it OEM or aftermarket and get them to trouble shoot it for me.
     
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