Knocking noise at idle

10

Asked by Sep 12, 2012 at 11:50 PM about the 1996 Chevrolet S-10 2 Dr LS Extended Cab SB

Question type: Maintenance & Repair

So i have a 96 chevy s10 with a little under 100k miles, and 2.2 engine.  At low idles it was getting a
knocking noise at random intervals.  A little research led me to believe it was due to premature wear
of the timing chain, which i have replaced.  Now, I a very similar noise has returned.  It only so far is
happening at idle after freeway speeds, like at the end of the off ramp.  The noise dissipates and then
disappears with a little speed or higher rpm.  Could this still be the timing chain?  Was I on the wrong
track to begin with and it never was the timing chain?  The quality of the noise is a little different,
slightly more consistent and predictable than before so...any advice?  Thank you,

10 Answers

10,235

What is the oil pressure? oil level? and when was the last oil change?

1 of 1 people found this helpful.
18,515

Agree with Michael. After a highway trip oil pressure tends to be lowest, maybe you need a new oil pump. Make sure the oil level is correct and changes are current.

10

I took it for a drive up and down the freeway and around town and took some notes on the oil pressure. The oil was changed with 10/30 Chevron oil a few weeks ago and is at the full mark. As for pressures, from the dashboard gauge: Cold start: 65 and ranged while cold from about 40-80. No noise. Once warm, it was ranging from about 50 to 75 on the highway, and idled down to about 25 or 20 and the noise would be slightly audible. For whatever reason, it was not so bad today as a couple days ago. It was around 30 at idle when I would not hear. So there definitely seems to be a correlation between oil pressure and the noise. Thanks for your help Michael and Andrew. Do you think this information points to oil pump issues? What do you think I should look at next?

1 of 1 people found this helpful.
10,235

I would not trust the dash gauge for oil pressure. If you have a mechanical gauge that you can hook up to the engine directly, i would use that. Your oil pressure should be around 60 when cold and 30 when warm. 20 is quite low and would start the top end of oil. I would drop the oil pan and make sure the oil pickup tube is not clogged. At a 100k miles, I do not see it being a bad pump, but it is possible. Sitting up that much does leave behind quite a bit of sludge though, which is why I say to check the pick up tube.

2 of 2 people found this helpful.
10

I don't have a mechanical gauge, but I will look into that. I did a little research about the oil pump, and it looks like dropping the oil pan is quite an ordeal on this truck. Chilton and another reference say to pull the motor, some other forums have said to pull the transmission and prop the motor up on one side. This is a big job for a check. Any other recommendations for tests I can do before getting crazy with the oil pan? Thanks again.

10,235

Not really. I have a mechanical gauge I screw into the engine (hooks up where the oil sending unit does) that I use to check oil pressure when I am concerned. And I agree, removing the pan is some work, but it will need to be done if your oil pressure is not correct.

I had the same problem. I waited too long to change the cam-chain tensioner and the chain ate it up. The new tensioner came with a press-in plug for the oil galley above the tensioner. The new plug has a small hole in it to squirt oil on the tensioner. Problem is, when the oil gets hot, the pressure falls way off. Some of that clattering is from collapsed lifters. Also, I suspect the metal filings from the old tensioner wore the oil pump out . If all of this sounds familiar to you, you have some major decisions to make. New pump, new oil galley plug, or new truck.

10

I've had the same problem with my '88 S15 ever since it came out of the shop after getting the entire clutch assembly replaced. I requested to have my spark plugs changed, they replaced 1 and left the other 5 in because they said they looked fine. I live in the arctic circle where the temperature for the last few weeks has been 40 below (C). I'm getting my oil changed in the morning and I'll check to see if the knocking persists after the change. I believe they said that they're gonna put in 0W-40 oil in.

70

I have a 89s10 whith the 4.3 engine when i start it up it idles fine but after a bit it idles down and makes a hissing/squiting noise then it idles fine again and the repets the noise when it idles down is coming from the left side of the engine

1 of 1 people found this helpful.
10

Your oil pump creates flow not pressure. What creates pressure is the resistance of flow between the main and cam bearings. There is suppose to be a lite film of oil between the main and cam bearings which mean that the cam and cam bearings, and main bearings are not suppose to touch. When you run it low on oil it causes the film of oil to decrease between bearings. This creates wear in the bearings because there is no film of oil or very little. Then when you fill the oil back to specs it has already created damage. So the gap that was between the cam and main bearings are larger the normal which allows less resistance. Meaning oil pressure is low. Hope this helps

1 of 1 people found this helpful.

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