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Tow or Drive - Engine Knock

We have a 2000 Saturn SL2 (120,000 miles). Last night we drove to L.A. and back (from San Diego) , so about 250 miles round trip. For the last 45 miles or so we had the radio on quite loud. At some point in that 30-45 miles the engine developed a very loud knocking noise - like rocks being spun in a tumbler - which we noticed when we got off the free-way and turned down the radio. This noise did not effect the way the car handled as I did not notice anything when the radio was up. We have been listening to a lot of sounds and I am concerned it could be a Rod Knock - it sounds a lot like this () from inside the car, outside it was more of a constant pinging/thunking noise - less gravel sound.

So my quandary is this, our mechanic is not open Sundays so I cannot ask him, but when we take it to him tomorrow, do we drive it or tow it? If the rod is starting to go I do not want to inadvertently do more damage by driving it. The mechanic is 8-10 miles away. We can get their either on the freeway or through surface streets.
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Comments

  • Oh - and we checked the oil, we were not low on oil. We are due for a change soon but not overdue. Also, in the few weeks leading up to this I had noticed the engine hesitating when accelerating. It seemed to have to work harder to get to and maintain 50-65 mph
  • edited October 2011
    I Take It That You Don't Have Tow Coverage On Your Insurance Policy. Since, You Seem Uncertain About What's Causing The Knocking Then Towing It Would Be Advised.

    We can only hope you are hearing "spark knock" or pre-ignition and not some bearing related sound. The fact that the oil is not very low is promising. The fact that the engine began hesitating a few weeks ago supports this, too.

    Due for a change soon ? How long has that oil been in your engine ?
    Any vibration ?
    Did The "Check Engine" light illuminate ?

    Why not tow it and if it's not a major problem then paying the bill won't be so bad. If it's a major problem then a little more money won't even be noticed.

    CSA
  • A rod knock is unlikely to be compared to rocks being spun in a tumbler. If the noise occurs when attempting to accelerate but lessens and disappears when cruising the term "ping" might be appropriate. Have you possibly pumped some diesel into the car by mistake? Has the engine temperature been above average?
  • See, now the diesel question is the first thing I asked my husband, but he swears he did not do that. Also, don't they make the nozzles in such a way that you can't do that? The engine Temp has been fine - sitting at about halfway between cool and hot same as it has since we got the car 4 years ago.

    Also, we had about 600 miles left on the little sticker they put up in the car when they change the oil. It has been about 2 months since the last oil change. No check engine light, no vibration, no smells, no other signs of problem other than the sound.

    I suppose the wise course of action is to tow it... It is just rather costly in time and money. My partner and I are both Graduate Students living on TA stipends - so the entire situation is a little nerve-wracking financially. I do see the wisdom in the common sense answer though, sometimes you just need someone to say it to you.
  • Oh - and it was loud at idle. the noise increased with acceleration, as in it was more frequent/less time in between taps.
  • Drive it....If the engine has serious problems, the car is totaled anyway,,,You can't hurt it any more than it already is...
  • There are so many possible causes for "can full of gravel" noise, and many could leave you on the side of the road in a desperate effort to get a wrecker and at the same time get home. It would most likely be best to get a wrecker. It may be the timing belt tensioner and it would be best to avoid driving until the belt jumps time.
  • Saturn engines actually use a timing chain rather than a timing belt. They are based heavily on the Quad Four engine design, which also used a timing chain. With a noise like that, I would highly recommend having the car towed to a repair shop. This noise very well could be a timing chain on its way out (this is not uncommon on these engines), and while replacing the timing chain will not be cheap, it will be cheaper than replacing the timing chain, valves, and any other incidentals should the chain fail completely. This is an interference engine, meaning lots of damage if the valve timing goes out of sync.
  • So Far . . . 3 Tow It & 1 Drive It.

    Please let us know what the problem is with the vehicle.
    Good luck,
    CSA
  • It could be a collapsed lifter.
    Not a big problem if corrected promptly.
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