Help! Just bought 2001 Seville STS at a good price. Was owned by elderly lady for first eight years. Decent Carfax however the last owner (for a year) neglected the car. The air filter was black. Anyway, the car is still in decent shape as everything works on it. The seller said the car needed a new AC compressor and water pump. The engine starts right up but sounds like a couple of marbles rattling around in a tin can. Most noticeable at idle and with or without AC on. Any ideas what the rattling is?:cookoo:
Marbles in a tin can!
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Do an oil and filter change with whatever name brand of 5W-30 oil you like and a WIX 51522 filter. Get a WIX air filter.
Go up to the Cadillac Technical Archive in the black bar ^^^ and read it all, especially the article titled "Occasional full throttle operation is good for your engine". For the procedure, especially the first few times, use 91 - 93 octane. You will be amazed at the amount of crap that comes out of the tailpipes when you start......Do NOT under any circumstances start pouring magic potions, foams, and snake oil "cleaners" in the oil or gas. Google "chevron techron" and "top tier gasoline".
If this is a "little old lady" car, you have a common Northstar problem called "Cold Carbon Rap".
Use a stethoscope with long tube to listen to the water pump tensioner pulley - the water pump drive is on the driver's end of the front intake camshaft. Also, listen to the main serpentine drive belt tensioner pulley and the idler pulley.
Take the VIN to your Cadillac dealer and have them pull the GM VIS printout - all warranty, recall, and some GM service work performed on that car. Enter the codes on the sticker under the spare tire cover into www.cadillacfaq.com/rpo/index.php to find out what's in your particular car.
Go up to the Cadillac Technical Archive in the black bar ^^^ and read it all, especially the article titled "Occasional full throttle operation is good for your engine". For the procedure, especially the first few times, use 91 - 93 octane. You will be amazed at the amount of crap that comes out of the tailpipes when you start......Do NOT under any circumstances start pouring magic potions, foams, and snake oil "cleaners" in the oil or gas. Google "chevron techron" and "top tier gasoline".
If this is a "little old lady" car, you have a common Northstar problem called "Cold Carbon Rap".
Use a stethoscope with long tube to listen to the water pump tensioner pulley - the water pump drive is on the driver's end of the front intake camshaft. Also, listen to the main serpentine drive belt tensioner pulley and the idler pulley.
Take the VIN to your Cadillac dealer and have them pull the GM VIS printout - all warranty, recall, and some GM service work performed on that car. Enter the codes on the sticker under the spare tire cover into www.cadillacfaq.com/rpo/index.php to find out what's in your particular car.
Thanks, submariner409! I filled up with Shell VPower 93 octane in the tank immediately (works great in my Vette). Oops, too late...I also put in several ounces of Techron cleaner as I have used this product before on other cars with noticeably good results. I also had to add about a quart of 50/50 Dexcool when I got it as the coolant was low. The car has 92k miles with no signs of anything leaking anywhere. I'll follow your advice and look up the cars GM service history.
Techron is fine. Like sub said give it a good dose of WOT and she should purr like a kitten!
.................not a darn thing wrong with TECHRON.......it's about the only additive that actually does something beneficial. The rest are pure hype.
2003 Cadillac Seville STS 73k Miles, '90 Chevy 1500 Reg Cab
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I will add to it that if you haven't changed(not flushed) the coolant yet go ahead and do it. Its extremely easy in these cars, mix 50/50 with DexCool labeled coolant and distilled water. Repeat every roughly 2 years, some recommendations say good for 5 years but with the ease, marginal cost and known issues with HG's(even though yours is a post '00 model) IMO its foolish to test it. And +1 to the above comments, take it out and enjoy it...WOT!
04 Deville, 11 DTS Premium, 00 Deville (sold), 02 Deville (sold)
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2,690 Posts
I'm remembering a procedure (maybe from the Guru a long time ago) that was for blowing out the carbon and getting the piston rings to rotate.
- Put transmission in 2nd gear go WOT to 70 mph
- let car coast back down to 20-30 mph (no braking, allow the engine to slow her down)
- repeat this 3-4 times
- Put transmission in 2nd gear go WOT to 70 mph
- let car coast back down to 20-30 mph (no braking, allow the engine to slow her down)
- repeat this 3-4 times
I have not had the opportunity to take the STS out for a good run as I've got to change the oil this weekend before doing any real driving. Your statement that the rattling sound should go away after a minute or it's not cold carbon rap has me concerned. My STS rattles for as long as I have it running, albeit in neutral at low rpms. That said, if the rattling is not CCR, what else could it be? I was told by previous owner he thought the car needed a new water pump and AC compressor. The temp gauge stays at 12 o'clock mark when the car is fully warmed up. I've never heard a water pump or AC compressor make a loud rattling sound like this ... Any further ideas? Thanks:hmm:
04 Deville, 11 DTS Premium, 00 Deville (sold), 02 Deville (sold)
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2,690 Posts
If you don't think it's CCR I would take Sub's advice on the stethoscope to try to isolate the noise.
Thanks for the info, Ranger. I did the old long screwdriver as stethascope trick and after listening to various parts of the engine, it seems that the rattling sound is coming from the front area of the engine on the driver's side, near the throttle body. The passenger side part of the engine is quiet and seems normal as does the back of the engine (the back being against the firewall. Sorry, I'm not used to front drive cars). I took the car out for a mild 20 mile jaunt tonight and it ran well. The rattling cannot be heard in the cabin area, either in idle or under speed. When I pulled into the driveway and got out, I could hear the rattling come and go every 4-5 seconds. No leaks, no overheating but no AC either ( will have to get that looked into). I'll try the WOT trick this weekend; I just hope I don't blow the thing up!:bomb:
Sounds like the tensioner pulley for the water pump drive is the culprit. That's down under the cover at the driver's end of the front intake camshaft - the black plastic pulley there runs a 3-rib belt/tensioner/wp pulley.
Remember that the Northstar is a sidewinder (transverse mounted) so the "rear" of the engine is towards the drivers side. Like Sub said, that's where the water pump is. If you don't have a stethoscope, follow his advice and use a length of hose. It is MUCH better than a screwdriver.
Thanks for all the good information. I plan on working on the car this holiday weekend. You have all given me enough info to make some reasonable assumptions about my cars' problem so I should be able to pinpoint the fix. BTW, I did not realize the Caddy had a sealed coolant system and I added some coolant because I thought the tank looked low. It's now about 1.5 inches below the top, no leaks anywhere I can find and no evidence of overheating. I'm going to put in a new water pump & thermostat with appropriate gaskets, replace any bad parts associated with the water pump operation i.e. tensioner pulley, drain the coolant and refill, change the oil & filter and (if the rattling is gone) GO CRUISING! 
Remember that the water pump requires a special socket: the entire unit - pulley, seals, bearings, impeller - is a unitized capsule which unlocks by turning clockwise (remember the tang orientation and amount of engagement) and installs by turning counterclockwise to lock. When I say "turn" I mean with force - some of these puppies are a bear to remove. You'll need the special socket with a retainer strap to hold it properly, or a strong assistant to help keep the socket engaged.
The coolant level is indicated by a rather indistinct arrow molded into the side of the surge tank. About halfway up in the tank, COLD, is the proper level. Too much coolant and it tends to blow out the cap relief as it expands. The Northstar has a large coolant capacity so there's considerable expansion and contraction during heating and cooling.
BEFORE you remove the water pump, do a quick check: remove the surge tank cap and have someone start the car. (There's a 3/8" line which runs from near the thermostat housing to the nipple at the surge tank top side. That's a purge line which constantly passes air bubbles (if any) from the main system to the surge tank, preventing pump cavitation.) Does coolant squirt into the surge tank ? If not, while you have the system open, remove and clean the purge line and the nipple/bolt at the water pump area. That nipple tends to clog easily, defeating the purge system.
The coolant level is indicated by a rather indistinct arrow molded into the side of the surge tank. About halfway up in the tank, COLD, is the proper level. Too much coolant and it tends to blow out the cap relief as it expands. The Northstar has a large coolant capacity so there's considerable expansion and contraction during heating and cooling.
BEFORE you remove the water pump, do a quick check: remove the surge tank cap and have someone start the car. (There's a 3/8" line which runs from near the thermostat housing to the nipple at the surge tank top side. That's a purge line which constantly passes air bubbles (if any) from the main system to the surge tank, preventing pump cavitation.) Does coolant squirt into the surge tank ? If not, while you have the system open, remove and clean the purge line and the nipple/bolt at the water pump area. That nipple tends to clog easily, defeating the purge system.
Did the cavitation plate separate from the impeller or were the bearings shot ?
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