Car knocks/pings when cold

[comet605]

Hey people,
My 1997 lumina 3.1 knocks/pings when COLD its a constant knock . It seems to go away when the gauge temp goes to around 40% .
The problem seems to almost go away when i use 93 octane gas but is still there . My check engine and low coolant light is on but the coolant tank is full . The car has 147,653 miles on it. Any tips?

[jeffcoslacker]

Is this something new you noticed, or it's always been there?

3.1's all sound like a can of rocks at cold start...there's usually a light, wet-sounding ticking that's the roller lifters, some racket from the timing cover if higher mileage, and a hollow rhythmic knock, that's the famous Chevy piston skirt slap. All are to be expected at your mileage...

When I get scared is when noises get WORSE as they warm up, that means the oil is not "floating" parts effectively when it warms and thins out, because parts are worn excessively...

So it's hard to say without hearing, but I suspect it's normal...unless it started suddenly...

If you are talking about noise at idle, octane should have no bearing on it. 93 octane is a waste in that car, it won't do a thing for it. It has a knock sensor that will retard the timing if it hears pinging way before you'd ever hear it...

ONE exception, the knock sensor could be failing...that may be what the CEL is trying to tell you...but I'd be surprised...

What weight oil do you use?...if your still running on 5w30 at that mileage you are going to hear a lot more noise out of it for a longer time as it warms up...10w30 all year is fine now...

[comet605]

Yes the sound has gotten a bit louder over the last 2 weeks.
I use 5w30 , ill switch over next oil change ; but for now is using 5w30 okay ? or is it damaging something from being to thin? I suppose it does sound like a can of rocks tumbling , tomorrow ill try to get a audio recording and post it here. Oh and the temp here is around 94 F ( in Florida) don't know if that info helps ...

-thanks for helping

[jeffcoslacker]

You know...I'm ashamed to say because I should know...nut is the coolant level sensor in yours in the reservoir or the radiator? I have the same year and motor, but I've never looked, because it's never given any trouble.

The only reason I bring this up is because a scenario with a very bad outcome comes to mind since you say it's gotten worse recently, and you have those lights on...if the level in the radiator, not the reservoir, is actually low, there's a chance you are leaking coolant internally and it's getting in the oil. It's never a good thing, but if it still has the red extended life antifreeze in it, that stuff is very destructive if it gets in the oil. If that were the case, and you kept driving it, you'd ruin the bottom end pretty quick.

If I were you, I'd check the level in the radiator after the car has sat all night, make sure it's full, and make sure the oil isn't milky....if that all checks out then you should be OK...and if the sensor is in the reservoir sometimes they get mucked up from oil contamination and stay on...

So I'd rule this out first...it's unlikely but not unheard of, and the consequences are too severe to ignore the possibility. Then if it seems good I'd go to 10w30, and see how it sounds then.

[comet605]

I cant find any wires leading to the coolant tank , sooo... does that mean the sensor is in the radiator? Or i just have poor vision? Tomorrow when my car is cool the sun is out ill check the radiator .

[comet605]

Well the car doesn't start anymore , i had to have it towed to pep boys . This happened when i was at a restaurant the engine turns but nothing happens , although it seems to turn slowly so maybe its just the starter? Ill know soon enough..