Knocking Noise Under 98 STS


LVC Member
Oct 17, 2005
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When I put the car in park and turn the ignition off, I here a knocking noise under the car. It sounds like someone is knocking on the pipes underneath. What the hell is this noise? I read that the 98 STS had problems with not only oil consumption, but also that it had problems with Carbon buildup. What the F**K!!!!!!!!!:mad: If anyone has has problems with this and can get back to me with some information, the help is more than welcome.


What type of knocking noise are you talking about, like the car is still running?

The bets thing that I ever did for my Eldorado was the transmission fluid treatment into the intake.

What you do is hold the idle at about 2000 rpm's and slowly drizzle about 1/2 quart of transmission fluid into the intake. You follow this with about 1 cup of clean water, very slowly drizzled into the intake. It will smoke like hell, and it will try to stall, that is why you do it very slowly. It will make more smoke than you have ever seen, so you may piss off the neighbors. My Eldorado ran like new after this treatment. Also do not allow anyone to stand behind the car as you are doing this as the pieces of carbon are sometimes a little on the large side. This is the same basic procedure as teh seafoam treatment that is done on the Lincoln's, except that you use transmission fluid. Seafoam will also work.
Its probably just your manifold cooling down.And yes,the Northstar consumes oil,they do not burn it.The oil consumption is totally normal.The Northstar was designed to consumer oil to lubricate the piston rings or something like that.Putting in two extra quarts during oil changes is a price your pay for the sheer balls to the wall power of the Northstar!Do a WOT once in a while,or a Wide Open Throttle.Get on the highway and get your beast up to about 55,then floor it to about 85,let off the gas and let it slow down to 55 again,then open her back up to about 85.Do this about 4 times.This burns off the carbon buildup and is neccesary.It will not hurt your engine.
Thanks guys. I'll try the treatment. I usually beast my Caddi an the highway anyway. But I think I'll try the treatment and see what happens. I'll keep you posted on what happens. I was told earlier today that it might be a buildup of carbon. The help was greatly appreciated.


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