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My car rattles when I accelerate

Hi. I have a 2000 VW Jetta that I got used in 2004 from the dealership. It currently has around 95,000 miles on it and is a standard/manual transmission.



Months ago I noticed that if I had the window down, I could hear kind of a clunky rattling when I accelerated. Recently, over the past week, It seems to have gotten a little louder and I can hear it even when the windows are up. The sound goes away when I'm coasting and It seems to not be so pronounced when I'm on the interstate and in 5th gear, but I can still hear it when I need to accelerate again (in 5th gear).



Can anyone tell me what this could be and how much it could end up costing?



Thanks any help anyone can give me.

Comments

  • edited May 2008
    Is the Check Engine light on?

    Tester
  • edited May 2008
    Heat shield
  • edited May 2008
    No, the check engine light is not on.
  • edited May 2008
    Would I need a new one or does it just need to be tightened?
  • edited May 2008
    These are more likely to rattle from being broken or having mount points corrode - but the only way to tell is to look.

    If you need a new one you can probably find one in decent shape at a salvage yard.
  • edited May 2008
    You can sometimes stop a heat shield from rattling by putting a band clamp around the cat. It looks like a big hose clamp.
  • edited May 2008
    Your problem may also be a pre-ignition rattle. Most P.I. rattles are related to an EGR system fault. In theory an EGR fault should set the CEL off; in practice it may not.

    With the vehicle sitting stationary and in neutral try revving the engine slowly with the window down. If you have a heat shield rattle this bad then you should be able to hear a rattle or buzz at some point in the RPM range.
    If not, then my gambling money is on a P.I. rattle probably due to an EGR problem.
  • edited May 2008
    I took your advice and revved my car in neutral. I revved it pretty high and I think I heard a couple minute "clunk" sounds, so I'm going to guess that it probably is the heat shield. I'm assuming the heat shield would not set off the CEL, as it's just plating(?), so that would make sense in this case.
  • edited May 2008
    A heat shield will not set off the CEL. The heat shield is not plating; it's a sheet metal cover that is manufactured to fit around certain parts of the exhaust pipe, converters, etc.
    The heat shield will not normally clunk; it's more of a rattle or a buzz.
    A loose heat shield can often be repaired by simply tacking it with a welder or inserting a few sheet metal screws in the right locations. A decent muffler shop should be able to look the exhaust over and solve the problem.
    While not always 100% foolproof, one can also go to the rear of the car and hit the tailpipe on the side pretty hard. This can often make a heat shield rattle if there is a problem. (Careful to avoid getting cut though)

    A preignition rattle will resemble something like a marble in a muffled coffee can. It may not be present when the engine is cold. It may be worse when the engine is warmed up completely and under a heavy load (passing someone, going uphill, etc.)
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