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4.6l N* knocks in cold weather, but quiets after operating temp is reached.

7K views 36 replies 13 participants last post by  Submariner409 
#1 ·
I just bought a 2000 Deville, interior and exterior is immaculate. It had 104,000 miles when i bought it. A week later the temp dropped and I heard a knocking sound from the engine compartment. After the engine reached operating temp the sound faded. Now that i heard the noise i cant help but notice it. I am very familiar with ford engines, but this is my first Northstar. I took the car to Midas and had an oil change done. The car took 8 quarts of Shell 30w, after this i drove the car to Texas. The car drove good but i heard the sound in the mornings. The car has been good it only used 80 dollars of gas on a 1300 mile trip and still left half a gas tank. Please guys any advice will be appreciated.
 
#3 ·
Yeah that ^^^^^ and your car uses 5W-30 oil, either dino or synthetic, whatever floats your boat, as Ranger said, 7.5 quarts MAX.

Go up to the Cadillac Technical Archive in the black bar ^^^ and read the whole thing, particularly "Occasional full throttle is good for your engine".

Quite a few engine changes at the start of the 2000 year.......do some homework in here and in Deville/Seville. Read up on how to pull your own Diagnostic Trouble Codes from the car's onboard system: you don't need an aftermarket scanner - too generic and miss some codes. Look on the sticker under the spare tire cover and enter all the 3-character codes into www.cadillacfaq.com/rpo/index.php to find out what's in your car. Look at the driver's door stickers to find out the build date and tire size/speed rating.

If you get antsy to check the transmission fluid, it must be done with the engine hot running in P.....the transmission is a dry sump unit and will show NO oil on the dipstick with the engine off.

Welcome Aboard !!!
 
#7 · (Edited)
Well guys I did some hard accelerations in the past day. Aside from enjoying some WOT, I did get to hear sound last a little less during cold start up. My oil change is due already, and I would like some suggestions on what brand and weight. Also is Marvels mystery oil any good? I tried Lucas but it didn't do much a difference, please advise.
 
#8 ·
The owners manual recommends 5W30. I still use 10W30. Marvel Mystery oil has a purpose, but not much any more with todays oils. It's basically a penetrating oil as I recall and will thin down you oil. It was very useful years ago for freeing up sticky lifters, but that rarely happens with todays oils. Forget it.

There is a decarbonizing procedure where you put Techron (I think) in the cylinders and let it soak for a few hours. Then suck it out, change the oil, take it out and run it, then change the oil again. Since it is improving, maybe you just need to beat on her a little more.
 
#9 ·
Yeah do a few more WOT and she will purr like a kitten. You can use seafoam if you wanna clear it up faster and experience the joy of the cloud of white smoke that will pour out your exhaust!! I took the oppurtunity yesterday to let my baby stretch her legs and opened her up to 110mph on the highway!! Before you guys start ranting about how dangerous it is, we had some great weather with no traffic on a nice 5 lane stretch of highway. The only thing I was indangering was my wallet if the man were to catch me!! :burn:
 
#10 ·
110 sounds like fun but how about just staying in 3rd gear? or even 2nd. that will rev the motor and keep your speed down. its like the joke where the guy got pulled over by a cop and said his alternator was dying so he had to drive fast to keep the motor spinning so the headlights would work. try 2nd gear. duh.
 
#12 ·
As far as I'm concerned I think a certain amount of knock is pretty normal for these engines in the cold.

I can assure you I don't have carbon buildup and my car knocks a little in the cold weather until she's warmed up.
 
#13 ·
Well, i cant say that myne does it. (never really payed attention tho) Ill listen out for it today. Although, i do alot of WOT's. lol Everyday. I never see carbon fly out of the tips. Even in 1 taking off from a dead stop. Its probly because i dont allow carbon build up. Heavy foot FTW! N* FTMFW!!!

:thumbsup:
 
#16 ·
Just ramrodding the car doesn't do it. The WOT is a specific procedure of which the letdown or engine braking is important, as Ranger mentioned.

Mine knocks until the car is thoroughly up to temp and has been driven for a bit.

The soot you see every time you floor it isn't carbon.; That's oil that pools and gets sucked in during hi RPM.
 
#19 ·
A little birdy on this site once told me that. Yes, he says oil can pool in the intake, especially if there's a small leak. The guess was that most people who think they're blowing carbon out are usually sucking this pooled oil in and burning it.

I'm not sure myself but that's what I'm told.
 
#22 ·
*SHRUG* I suppose you're right. Who knows at this point. We've heard so many things from so many people.
 
#24 ·
As far as I know the entire exhaust is stainless and has been for years. I think it used to be an option, maybe in the late 70's and early 80's but I'm pretty sure after that era, they're 100% stainless.

I know my Brougham is because I just replaced the muffler and cat. at 200,000 miles. Neither was rotted on the outside but obviously things don't last for ever.
 
#26 ·
My 2002 OEM system is all stainless, but the spot weld process destroys the protective oxide layer and causes rust spots. Take a look at the joint welds for starters..........my CORSA is mirror-bright after 2.25 years.
 
#27 ·
Sub; did you weld or clamp your Corsa?
 
#28 ·
Clamped.......The whole thing was anti-seized and torqued according to the Torco clamp specs and has not moved or shifted one iota. When we did the install I marked all the joints with black Magic Marker and none show any movement. Luckily my neighbor, Charlie the Transmission Man, has 3 frame hoists so I have unlimited access to easy inspection/work lifts. I did use 4 small s/s hose clamps to center the system by restricting muffler hanger rod side-to-side movement in the rubber hanger cookies.
 
#29 ·
Guys,

I have not been able to quiet down this car. It still makes the sound and I don't think more WOT's will help any. I have done my homework and think the GM TEC will help. This i my last resort i can't seem to find this at any part store. Any leads will help.
 
#31 ·
Ranger,


To tell you the truth I didn't run this Caddy hard I was afraid of breaking something. You know the temp here is getting colder every day and it seems to be lasting longer. It takes about 15 minutes to reach full temp @ 32 degrees. And i hear this sound all fifteen minutes. Also is this something Cadillac is aware of. For example if I take them the car would they say the car has excessive carbon build up. I mean for all I know this car might have never been run hard. It 100.000 miles and its a 2000 model. Im the 2nd owner. Please advise.
 
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