: Engine Cold/Knock/Tick Noise (Replace Pistons)



HaroldC
01-13-05, 06:45 PM
My 2003 DeVille w/34000 miles has a ticking sound upon cold start which lessons as engine warms. The dealer has ordered new pistons to be installed under warranty. He gave me a copy of a technical bulletin and explained that carbon collected on top of the pistons. He said the new pistons are crowned and have a teflon coating. He said they have replaced the pistons on several cadillacs.
Has any one had this same experience and how did it work out after replacement?
Has any one asked for a new motor and if so how much did you have to pay?
Any information on this subject would be helpfull.

HaroldC

BeelzeBob
01-14-05, 01:35 AM
My 2003 DeVille w/34000 miles has a ticking sound upon cold start which lessons as engine warms. The dealer has ordered new pistons to be installed under warranty. He gave me a copy of a technical bulletin and explained that carbon collected on top of the pistons. He said the new pistons are crowned and have a teflon coating. He said they have replaced the pistons on several cadillacs.
Has any one had this same experience and how did it work out after replacement?
Has any one asked for a new motor and if so how much did you have to pay?
Any information on this subject would be helpfull.

HaroldC


There is a ton of previous info on this in the archives as it has been beat to death (several times) in the past. Go to the forum search feature in the tool bar above and type "cold carbon rap" into the drop down box and search. Read my posts on the various threads.

My advice is to save yourself the grief of tearing the motor down to it's elemental parts. There is fundamentally nothing wrong with the motor. There is nothing magic with the new pistons. They have a slightly tighter fit (with the graphite coating on the skirt-not teflon) and a more aggressive and higher tension ring pack for more oil control. The pistons are not crowned but actually relieved around the top of the ring land so as to provide more clearance for carbon to build up and not touch the cylinder head. Carbon will build up just like it did before...it does on all pistons. Just that the new pistons have more room for it.

Quite driving the car like an old woman and it will quite ticking in the morning and the oil consumption will improve. Give it an occasional dose of wide open throttle (WOT) and it will be much happier. Several WOT accels up thru the lower gears and/or some WOT passing like maneuvers on the interstate where safe will clean the carbon out of the chambers, seat the rings to the ring lands of the pistons and exercise the rings to keep the mobil and free of carbon buildup. That is all it needs. The Northstar is a high performance engine and it was designed to be run hard and at high RPM and it actually needs that to keep the carbon cleaned out of it. Try several WOT blasts and I guarantee the noise in the morning will go away and stay away as long as you exercise it regularily.

You can do this very easily and safely without any hooligan like antics by getting on the expressway and putting the trans gear selector in 2. Floor it until the car reaches about 70 and then let it coast with your foot off the throttle down to 55. Floor it again up to 80 and let it coast back down again. If you look in the mirror you'll see clouds of carbon and particulates that were trapped in the exhaust escaping. Keep doing this maneuver 12 times or so. Do this occasionally for several weeks. This will free up the rings, make sure the rings are seated to the piston ring lands on the sides of the lands and will clean the carbon out of the chambers. The engine is absolutely well within it's limits to do this for hundreds of hours...it is designed and built to do far far more than this in terms of performance.

Why do you want a new motor?? The one you have is fine. You don't even want your's torn down and rebuilt with new pistons so that you can then sort out all the problems caused by such a teardown. Forget it. The shop is possibly trying to "sell" this as they get lots of warranty $$$$$$ for the piston job and it keeps their techs busy on slow days. Forget it, in my opinion.

If you read enough posts on this and www.caddyinfo.com you will find many many testimonials from people who have taken this advice, done the WOT activity with the engine and found it to do exactly what I describe. The Northstar is a high performance engine built to make a lot of power and be run hard....we never realized designing it that we would have so much trouble getting people to hold the throttle down enough to at least keep the carbon out of it much less break in the piston ring lands adequately....!!!

an01sts
01-14-05, 10:34 PM
If I can add to this, I bought my car new. I'm not saying that I pussed it all the time; I'd let it stretch, but it wasn't even close to fairly agressive, let alone abusive.



At about 30k, (I posted a similar statement, making the same claim. It's around somewhere so you see that I'm not making this number up to coordinate with your mileage.) the engine as lots noiser than I cared for. Also, moderate acceleration created lots of smoke, which I associate with the typical 1 quar of oil @ 1k. I hesitated at much more than light throttle acceleration because the smoke screen was most embarrasing. Finally, I said the hell with the smoke, and started running some wot because it seemed to eat up just any vehicle on the street.

Anyway, after a while the smoke cleared up, and it took a little more than bbob mentiones. I don't remember how long it took for the smoke to clear, but it cleared up. At 67.2k, the engine runs better now that it has ever ran, and it's quieter now than it has ever been. On hard acceleration, the car doesn't even dust, a normal operating condition of engines upon hard acceleration. I don't know how to stress that you need to run the car like it's a race car.

Why the dealer wants to do the repair: If they can get the work, they'll do it. Trust me: you're not bothering them, making them want to hide when warranty work come in. Everyone at the dealership loves cash jobs because those jobs are the luxury money for the little extras in life. Warranty work, however, is the dealerships bread and butter money, so they take all the warranty work they can get. If they can get away with it, they'll run jobs that should be customer pay through warranty. The thing is that the factory is watching them like a hawk.

What can happen is that, sometimes, the hawk and pidgeon can team up it they can both profit. Some dealers have "inside connections" with the factory. It would be unfair to say that there may be an exchange of gradituites, but there is a money exchange between the dealer and factory on warrenty work. Anytime there is a money exchange, and the money doesn't belong to either part in the swap, the possibility of private trasactions exist.

You don't ever want ANYTHING taken apart on your car if it isn't absolutly nessessary, especailly the engine. Coming from one of the top rated Cadillac technicians, it's isn't a case of shoddy work. (Well, then again, yes it is.) The point is that even the best quality craftsman can only do so much to make it as close as it was when it was assembled at the factory. When they biuld a car, no car builders, they don't take into consideration the need for repairs. (Lexus with its zero tolerance in body construction sounds slick. However it can be a major problem for human beings who have to reconstruct collision damage. You know, even the best of the best needs 1/64"th's play. That aint asking for a lot!)

As bbob says, the last thing you want to have done to your car is rip it open. You have plenty of room on your warrenty. Go out, run the dogshit out of it. Either it will clear up, not change a thing, or it will blow up. It will clear up, and if the other choices come into play, you can have the engine torn open. If it blows up--which it won't--tell 'em, "It just died. So what do you have to loose? After all, you're anxious for them to tear it up; have a legitimate reason for them to tear it up.