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940 n/a sedan, 236k miles, I've owned it about 8 years and performed all maintenance myself. I'm running Amsoil lubricants everywhere a lubricant is called for. About 2 weeks ago while driving to work I suddenly heard this awful sound from under the hood, kind of like a nasty belt squeal or a scraping noise between two pieces of metal. The noise came and went, sometimes abruptly and sometimes fading in and out. The noise also got louder or quieter and sounded like it was going faster or slower with the revolutions of the engine.
The noise only happened once in my driveway, and it sounded an awful lot like it was coming from the area of the intake, although noises like that can be tricky to pinpoint. Mostly the noise was present while driving and not everyday, although towards the end of last week it was everyday; only once or twice did it happen on a cold start when I was at work. There is also a very high pitched squeal and I'm thinking that the two are associated. The high pitched squeal also sounds like a belt, but I'm wondering if it could also be metal to metal.
And this annoying squeal/scraping is very loud. I can roll down the windows while driving through the parking garage at work and it's quite loud.
Let me preface it by saying that the p/s pump was making noise like maybe the bearing was crapping out (or something else). I thought perhaps the pump was on its last leg. First I sucked the fluid out and replaced it with Amsoil. The p/s pump sounded better for a couple weeks and then got noisy again. I put a rebuilt Beck Arnley p/s pump on and new accessory belts over the weekend. The annoying noise went away. I drive 50 miles a day and yesterday out of the blue the noise came back. Today the noise came and went while driving home from work (25 miles), most of the time it started when sitting at a traffic light and went away after I got up to 30 mph or so. But it didn't come back every time I stopped at a traffic light. It's totally random.
The a/c compressor is less than a year old; the alternator is fairly new; rebuilt p/s pump installed last weekend; p/s drive belt is fairly new and in good shape, or at least it appears to be; new drive belts on the alternator and a/c compressor; harmonic balancer is fairly new. All these things failed or were on their way out when replaced.
The only things left in my mind that can make this type of noise would be the camshaft; crankshaft; water pump; p/s pump drive belt; idler pulley on timing belt; tensioner on timing belt. I don't know what else it could come from.
The noise only happened in my driveway once, and I thought it seemed to be coming from the top of the engine because it was more noticeable there. I used the stethoscope method on the alternator, water pump, a/c compressor, p/s pump and valve cover but did not believe this noise was coming from any of those areas.
I'm puzzled! But I'm also wondering if I have cause to be concerned or if this is just something annoying. Anyone have any thoughts or similar experiences? I love this car and would hate for anything bad/major to happen to the engine.
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