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Thread: Over a Bump...Knock under passenger side seat

  1. #1

    Over a Bump...Knock under passenger side seat

    My car, a 72T Targa, has developed a strange knocking sound under the passenger side seat/door sill area when hitting a bump in the road. Thinking it was perished sway bar mounts, I've replaced the rear bushings...but the knock is still there. It's an occasional event...so it's hard to replicate.

    Could it be the front sway bar or suspension mounts? I've also replaced tie rod ends and sway bar drop links.

    Any ideas would be helpful...Have to get on it as Winter is knocking on the door up here in New England. Want to address it before the car is put away and kept clear of the Salt Monster.

    Thanks

  2. #2
    Senior Member
    Join Date
    Aug 2016
    Location
    NE Ohio
    Posts
    280
    Taking a wild guess but do you have an oil cooler in the front right wheel well? If you do, you could have an oil line bracket that is loose or missing.

  3. #3
    Yes, I do...never thought of that...I'll take a look at that. The knock is non-metallic, so it would make sense if a rubber line was bouncing around under there.

    Many thanks

  4. #4
    The closest suspension component near the door sill/seat is the rear spring plate arm that connects to the torsion bar via a large rubber bushing, and since those components 'move' when hitting bumps, perhaps the rubber bushing is failing.

  5. #5
    Thanks...I'll take a look at the rear suspension bushings as well. My guess is that it's something straight forward. I'll report back with what I find.

  6. #6
    Thanks again for the recommendations...Here's what I've found:

    The front oil cooler lines are super secure, with mounts every 12 inches or less. There was also another line, the car has operational AC, that goes to the front condenser. That too was secured in the same fashion as the oil cooler lines.

    So that leaves the rear suspension/swing arm bushings...the knock only happened once a drive around I did this morning and this time it sounded like it was coming from under the right hand rear jump seat. I'll get it up on a lift to check further.

  7. #7
    The swing arm bushing I mentioned is indeed directly below the 'jump' seat . Also, the perished bushing is likely not going to be visible until the swing arm is pulled away from the torsion rod/torsion tube. Not usually a fun repair.

  8. #8
    Senior Member
    Join Date
    Dec 2008
    Location
    Black Mountain, NC
    Posts
    539
    Another easy check is with the car on the ground as driven, look at the torsion bar cover is the is the spring plate hub that mounts to the torsion bar centered in the hole in the cover or is it closer to the top of the hole? Yes, is a sure sign bushings need to be put on the planned maintenance list. If you look close with a light you may see shiny metal where they have been contacting during these bumps. as the bushings deteriorate the car settles down to the spring plate. on a lift it may look normal as it is not loaded.

    Regards

  9. #9
    Had the car on a lift this morning...Checked transmission mounts...they're in good shape. Looked at the swing arm and bushings, didn't notice anything. But will take a look through the torsion bar cover...and signs of metal to metal wear on the spring plate. Thanks

  10. #10
    Senior Member
    Join Date
    Dec 2008
    Location
    Black Mountain, NC
    Posts
    539
    You can see what I was talking about without removing the torsion bar removal cover. main thing to look for is the mount centered in the cover hole or precariously close to the top of the hole in the T Bar cover when loaded.

    Regards

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