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Knocking noise at idle


backtobasics

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Hi everyone,

I couldn't find a topic that was exactly suited to my problem so here goes.

I am getting a knocking noise at idle... cold and warm. When you rev it up or drive it it starts to speed up but then immediately disappears. I raised it up and had someone rev it up while I was under the car and it seems to be coming from the area right around the manifold...maybe a little higher above it. I am at a loss so any advice would be appreciated. I have 92k miles on it and this noise started out just a little quieter than it is now. Only for about 2 weeks. It does it with AC on or off...no difference.

Thanks in advance.

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What kind of oil are you using? Type and viscosity

This sounds like a lifter leaking down maybe, since it goes away when you rev it up....

I would try changing the oil and using some type of upper engine flush like marvel mystery oil to clean the lifters and see what happens.

Oil tends to thin out badly in high temps, where are you located and what are your outside temps?

When was the oil changed last? How are your coolant temps?

Pre-1995 - DTC codes OBD1  >>

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No weird temp fluctuations. Always just below halfway on the temp. gauge. I live in Michigan and use 10w40 Valvoline and a K&N filter about every 4 months (not even 3k miles usually). It was doing it from idle and I could also hear it up to about 15 mph with the windows down not too long ago. It is pretty loud too. I will try the upper eng. lube...thanks!

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Put the drive lug from a 1/2" breaker bar in the square hole on the belt tensioner and use it as a lever to release just enough belt tension so that the belt slips. If the noise goes away, then it is one of the bearings on the belt. Most likely the idler or tensioner pulley bearing. If it doesn't, then obviously it is elsewhere.

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Hi everyone,

I couldn't find a topic that was exactly suited to my problem so here goes.

I am getting a knocking noise at idle... cold and warm. When you rev it up or drive it it starts to speed up but then immediately disappears. I raised it up and had someone rev it up while I was under the car and it seems to be coming from the area right around the manifold...maybe a little higher above it. I am at a loss so any advice would be appreciated. I have 92k miles on it and this noise started out just a little quieter than it is now. Only for about 2 weeks. It does it with AC on or off...no difference.

Thanks in advance.

Hi backtobasics. What year/make/model/engine is this car? Need that information first.

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  • 11 months later...

I too have an 2000 SLS, just bought last week. A real cream puff with 98K.

1st day after I picked it up , I heard the same noise as described above.

Please let me know what you found, I plan on ripping into it this weekend.

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