QuestionQUESTION: I have a 1986 Ford Bronco with the 302 v8 engine.When i rev the egine to about 2500rpm or higher and suddenly let off the gas there is a repeating clunking noise coming out of the exhaust until it returns to idle. The truck still drives great and runs fine and only makes the noise in park or neutral with sudden release of the gas. It sounds kinds of rough and i was wondering if you had any ideas?
Thanks
what it could be.
ANSWER: Check all of you engine and transmission mounts. Also, check to make sure the entire exhaust system is properly fastened.
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QUESTION: Yes everything is pretty tight, The engine noise is clearly coming from inside the engine itself. and the higher you rev and let off the gas the more vicious the clunking noise is. The noise is non existent when revving high while keeping your foot on the gas. It only appears when it you let off the gas.
ANSWER: Unfortunately it sounds like you are about to spin a connecting rod bearing then.
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QUESTION: What are the usual symptoms of a spun connecting rod bearing?
Thanks
AnswerI need to rescind my previous statement. Please follow these instructions unless the noise is really loud. Go to you parts store and buy the following. Two one quart bottles of marvels mystery oil, a bottle of greased lightning oil treatment, one house brand oil filter, 5 quarts of house brand oil, a Mobil one oil filter, and finally five quarts of 5w30 standard synthetic oil. Not the EP flavor of Mobil. As far as the greased lightning goes, what you really are looking for is Dupont Teflon/PTFE. Start by draining the 1 quart out of you're current oil level. Add one of the Marval mystery oils to the oil. Only let it run for 5 minutes max. Drain the oil and change the oil replacing the filter with the house brand filter and oil. Run the engine for 15 minutes this time. Repeat step one. Now for the magic touch. Add the Teflon, which is about as thick as molasses to the dry engine with the Mobil one oil filter installed. Chase it with the 5w30 to the proper level. Take great care with these instructions because it will quieten down anything short of a bent push rod, which you don't have. Worse case scenario you need to replace a rocker arm. If you have to break out the stethoscope to the valve covers. Take the valve covers off and inspect the rocker arms for defects if the Teflon treatment doesn't help. I will go ahead and tell you the obvious, if it sounds like something is coming out of the engine "loud", Teflon won't touch it. Give it a shot, it can't hurt. BTW, I do this at every oil change, for the record. I keep a solid pony.
