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4.9 engine thump continued


4pursells

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As suggested the other day I removed serpentine belt to help determine if the main bearing is at fault. Upon removal, it seemed that the thumping, banging was more pronounced. This noise only happens for instance, when the car is in park and I give it a little gas or when accelerating from a stop. ( When standing over the engine, hand placed on top, you can really hear and feel the bang). Otherwise, the engine sounds great. Isn`t the main bearing thump supposed to disappear when the belt is loosened or removed. Could I have a serious problem?

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What kind of oil, or more importantly what oil weight, are you using? If you are in a location where it gets warm, using a 10W-40 sometimes takes care of this. I had the opportunity to experience a 4.9. It had a slight bearing thump, which was evident under nearly exact circumstances you describe. It was pushed up to 10W-40 (valvoline maxlife) for the summer months. It worked great at reducing the noise. There may be other ways to deal with this, but I understand it is harmless. It may just annoy you, as it does. Also, I was told oils high in molybdenum help with the noise. I haven't found any that stand out for that, but if you don't mind spending $2.74 for an additive, the local walmart should carry red bottles of valvoline MaxLife engine protectant oil additive. That product is loaded with Moly, ZDDP and other additives. I tried it in a 94 Corsica with the piston slap issue. I was very impressed at the noise reduction (almost gone). GM Engine Oil Supplement MAY contain high amounts of Moly, but I am not sure. Maybe someone else knows for certain. If so, that could also be a viable option for your engine thump. I think the only drawback to using a lot of those additves, ZDDP in particular, is that it may POSSIBLY (not certain) get trapped in the filter element. At any rate, those options have worked great for me. Maybe you can check some more resources and fine a product that helps you with your concern. Good luck with it! The 92 STS is a really neat car!!

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