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'95 seville sts
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Discussion Starter #1
I have a 95 seville sts with 87000 miles on it. I went in today for an oil, lube, and filter at the dealer and now every once in a while it sounds like the engine is knocking. Why would this all of a sudden start happening and what should I do?
 

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2005 STS4 1SG: GM Acc Lights, Corsa, Platnium Grille, Volant
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15,987 Posts
low oil? check it? wost case senerio they may have started it without enough oil and damaged the motor via a rod or something. the dealer did the change take it back to them and have them look it over.
 

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94 ETC,97 STS
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3,531 Posts
Since you have only owned it a short time you probably don't know the history on it. It may have had heavier oil to mask a knock and now it got a light oil.

At 87K it shouldn't have bad bearings but ???
 

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'95 seville sts
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Discussion Starter #4
I think I may have figured it out. They used 5w-30 oil and it we have recently gotten a warm spell in Ohio. It has been around 50 and sometimes 55 degrees. The manual recomends 10w-30 for normal driving and 5w-30 for cold weather. Could this be my problem?
 

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94 ETC,97 STS
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Could be. It shouldn't knock with 5w though. I use it in my wife's Taurus in AZ. 110+ summers and no knock.

You can do some experimenting though. Try an oil thickener, STP or whatever brand, see what happens to the knock. If it goes away good, but it's a bad sign that there is a knock.
 

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'95 White Diamond Eldorado Biarritz
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When is the knock is occurring....While driving? Accelerating? Decelerating? Does the knock only occur at start up, when the engine is cold?...If so that is the classic cold carbon knock/rap and can usually be eliminated with some WOT's....The first thing you need to do is pinpoint when the knock occurs.
 

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'03 STS w/Nav, '93 SLS
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Same thing happended with my 94 seville that I bought with 68k miles . Had it 3 months and was sounding fine until after the 1st oil change I started hearing a tapping at low RPM and then a rap at high RPM. Turned out to be a sloppy wrist pin. Replaced one piston with rings, wrist pin, conn rod & rod bearings and everything was fine after that. Cost me about $2200 to R&R the engne and replace the parts though. Ouch.
The Dealer wanted $5k to do the same work.
 

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'95 seville sts
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36 Posts
Discussion Starter #8
The knocking is intermitent and I only notice it when I am outside of the car and its idling. I opened the hood today and it sounds like the knock is coming from the top, back part of the engine. Maybe it sounds more like a tap? I did the WOT thing and I don't always "baby" the northstar. This is the first car I have ever bought and I think this dissapoints me more because I was so excited about it. By the way, what exactly causes a knock?
 

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'95 White Diamond Eldorado Biarritz
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184 Posts
fartman said:
The knocking is intermitent and I only notice it when I am outside of the car and its idling. I opened the hood today and it sounds like the knock is coming from the top, back part of the engine. Maybe it sounds more like a tap? I did the WOT thing and I don't always "baby" the northstar. This is the first car I have ever bought and I think this dissapoints me more because I was so excited about it. By the way, what exactly causes a knock?

Be carefull WOT-ing the engine untill you have determined the root cause of the knock..Carbon deposits CAN cause the engine to knock, however im sure there are other problems that can reasult in a knock...Hopefully someone else can chime in...Are you positive the knock is coming from inside the engine?...Hopefully it's something simple...I've never heard of an intermitent knock before.
 

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'95 seville sts
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Discussion Starter #10
I listened from outside the car today and it seems to dissapear at higher rpm's(almost anything higher than idle). I also tried to accelarate under a load, with the brakes on, and I didn't notice it then. Thanks for the replies, I am happy to be learning.
 

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'87 Jeep, '10 Thruxton, '00 Duc 748, '01 748R (853cc)
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If it doesn't change pitch, tone, or frequency with RPM, than it's not a rod knock. The factory service manual specifies this type of knock as a timing component. I've got a similar noise, and it seems to be coming form behind the front cover around the intermediate shaft. It's possible that you could have a loose tensioner causing the chain to slap a little, or maybe a damaged tooth on a gear. The manual isn't really specific as to what it could be, they just mention timing. If it was a rod knock, it would get louder and faster as you revved the engine. If the regular engine noise easily overtakes the knock off idle aorund 1200-1500rpm, than it's not the bottom end. Get a Mechanics stethoscope and stick it down near the front cover and around the back of the intake to see if that's where it's coming from. If it is, than it's probably a timing component like the manual says. Mine has made that noise for the last 35k miles or so, and has skipped a beat. I was the dealer yesterday and they were moving a 2003 STS aroudn the lot, and it was making the same noise. My friend's, mother's DTS makes a similar noise. These engines are rather noisy compaired to simlar designs. It's just the nature of the beast. I wouldn't be too concerned about it, until it's starts becoming noticable either inside the car, or under lgith-heavy accereration. That's when you knwo you've really got a problem. By the time it's that loud thoguh, the engine is usually on it's last leg.
 

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'95 seville sts
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Discussion Starter #12
Just got back from the mechanic and he says it's a lifter. My warranty only lasts another 800 miles so I am calling them now. I hope they don't try to screw me, because that would be a pretty expensive fix, am I right?
 

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'95 seville sts
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Discussion Starter #13
If my warranty will not cover this and I leave it go, is it possible that it will damage the engine, or is it just a minor annoyance type thing? My mechanic recomended using synthetic oil, so I will try that, in the heavier weight too.
 
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