: What's this noise....



VinnyT
01-30-06, 09:01 PM
1998 Deville:

If i'm driving 30-40 mph and throttle it 3/4 way down, I hear a horrible 'rapping' noise. I'm guessing spark knock.? It's not a bearing or valve(I don't think). Could that noise be from carbon build-up in the heads? It's fine under normal acceleration. It sounds like someone shaking a can of spray paint VERY fast. Any help is appreciated. V.

BTW, this sound is when engine is at normal temp.

eldorado1
01-30-06, 09:05 PM
What happens at wide open throttle? Does it get worse, or better?

VinnyT
01-30-06, 09:08 PM
Better

eldorado1
01-30-06, 09:15 PM
It's probably carbon then. Have you been exercising it enough?

VinnyT
01-30-06, 09:17 PM
:hide: Umm, no. I was going to get some GM Top-end cleaner (Aerosol) and do that this weekend. I was driving home tonite when I heard it. I was doing 52 mph, then I nailed it. It sounded good, however it was too dark to see if any smoke came out.

eldorado1
01-30-06, 09:20 PM
Tsk tsk tsk. :nono:

That's 3 lashes, and 3 WOT's. :lildevil:

VinnyT
01-30-06, 09:23 PM
Thanks Eldorado for your help!!

eldorado1
01-30-06, 09:26 PM
No problem. If you end up going the top engine cleaner route, pull a spark plug before and after. You'll be amazed at the difference!

peteski
01-31-06, 12:09 AM
Hey, it might also be a loose exhaust or rattling catalyctic converter. They might resonate or rattle at a specific engine speed or load.

Can you hear the noise when the car is sitting parked and you gun the engine?

Peteski

jadcock
01-31-06, 10:30 AM
I bet it's spark knock. My '97 would knock a little bit, usually only at 3/4 throttle or more. Most noticeable on sharp and quick throttle digs. Running premium fuel minimized it, but it was still there, sometimes. It didn't sound like the common "clink clink clink" of an engine "ping", but rather "tick-tick-tick" real fast.

After running some Gumout fuel system cleaner through it (something I swore I'd never do) and after only visiting name brand gas stations since, I haven't heard this noise any more. I would definitely try the GM Top Engine Cleaner. Sometimes there is buildup that WOT cannot clean out like a good solvent can. How many miles are on your engine? Are your plugs and wires in good condition?

mtflight
01-31-06, 11:46 AM
Guys, what kind of contact do the headgaskets endure with the solvent during say a Top Engine Cleaner cleaning?

My concern is that these solvents will dissolve more than carbon--can anyone offer me peace of mind here?

I do have a warranty, so maybe I should try it now, rather than after the warranty expires :-)

I too have heard the "spraycan shaking" sound during what I thought may have been a bad batch of gas.

Lately with the gas prices, I've been babying the throttle.

eldorado1
01-31-06, 12:01 PM
My concern is that these solvents will dissolve more than carbon--can anyone offer me peace of mind here?


That's ridiculous. Just like kerosine won't dissolve or attack aluminum, GM's top engine cleaner won't dissolve or attack anything it could contact in the engine... well, besides carbon.

The "fire rings", the steel(?) head gasket inserts that actually seal the combustion chamber won't be affected.

Just follow the directions in the tech tips, let it sit overnight, and change the oil the next day after you blow everything out. Sometimes crap can accumulate/get lodged in the spark plug gap, so if it starts missing then you may need to change your plugs as well.

Now that I'm more comfortable with how the northstar intake is layed out, I can recommend to others that it's "safe" to use the TEC in a can, vs the aerosol. I think it might be cheaper, or you might get more for the money. Just pour it in slowly to the PVC nipple on the intake. It'll puddle in the bottom of the intake. When you raise the RPM up, the engine will pull it in.

mtflight
01-31-06, 05:56 PM
That's ridiculous. Just like kerosine won't dissolve or attack aluminum, GM's top engine cleaner won't dissolve or attack anything it could contact in the engine... well, besides carbon.

The "fire rings", the steel(?) head gasket inserts that actually seal the combustion chamber won't be affected.

Just follow the directions in the tech tips, let it sit overnight, and change the oil the next day after you blow everything out. Sometimes crap can accumulate/get lodged in the spark plug gap, so if it starts missing then you may need to change your plugs as well.

Now that I'm more comfortable with how the northstar intake is layed out, I can recommend to others that it's "safe" to use the TEC in a can, vs the aerosol. I think it might be cheaper, or you might get more for the money. Just pour it in slowly to the PVC nipple on the intake. It'll puddle in the bottom of the intake. When you raise the RPM up, the engine will pull it in.

That's good to know. Since the headgaskets are comprised of various layers--steel and polymers and what not, I was concerned about the polymer/rubber part--not the steel or aluminum obviously.

What made my concern peak, was that I read in a can of engine cleaner (not TOP) that it is not recommended for higher mileage engines. The method advised on that can, was to dump the contents in the crankcase, idle for a few seconds, then change the oil--so it is probably not the same context.

mtflight
01-31-06, 06:00 PM
Just follow the directions in the tech tips, let it sit overnight, and change the oil the next day after you blow everything out. Sometimes crap can accumulate/get lodged in the spark plug gap, so if it starts missing then you may need to change your plugs as well.

I just replaced my plugs, so would I take them out and put in the old ones (they're in decent shape), prior to the cleaning?

eldorado1
01-31-06, 06:16 PM
What made my concern peak, was that I read in a can of engine cleaner (not TOP) that it is not recommended for higher mileage engines. The method advised on that can, was to dump the contents in the crankcase, idle for a few seconds, then change the oil--so it is probably not the same context.

Those are different. That doesn't do anything to carbon in the combustion chamber, it works on the sludge in the oiling system. It's basically kerosine, and can cause chunks of sludge to "break off", and block ports, clog things, etc on higher mileage engines.


I just replaced my plugs, so would I take them out and put in the old ones (they're in decent shape), prior to the cleaning?
For insurance, it probably wouldn't be a bad idea. Myself? I'm lazy, so I would probably chance it.

mtflight
01-31-06, 06:27 PM
Those are different. That doesn't do anything to carbon in the combustion chamber, it works on the sludge in the oiling system. It's basically kerosine, and can cause chunks of sludge to "break off", and block ports, clog things, etc on higher mileage engines.

Thanks, eldorado1 :thumbsup:

Do you think the above procedure (dumping it in the crankcase) would be beneficial at all? Or is the N* unlikely to develop sludge. We're talking 98 L37 with 86K miles.

eldorado1
01-31-06, 07:06 PM
If you use synthetic, you will never have sludge. I've seen the insides of engines with 120,000+ miles, and they look *spotless*.

On the other end of the spectrum, I took apart a 350 that had regular dino oil, and it looked like it had never been changed. There was literally 1/4-1/2" of sludge buildup on the rockers and ... <shudder> ugh... terrible. Looked something like this:

http://www.renault4.co.uk/technical/mini-oil-sludge.jpg

mtflight
01-31-06, 07:26 PM
Wow. I wonder how the same part of a N* looks when one uses dyno and goes by the oil life monitor? (me).

What has been your experience?

eldorado1
01-31-06, 08:05 PM
Wow. I wonder how the same part of a N* looks when one uses dyno and goes by the oil life monitor? (me).

What has been your experience?

I don't know... Performance engines need performance oil. I stick to, and recommend synthetic. Isn't synthetic factory fill on the northstar?

Yeah, it's expensive. 7 quarts will cost you an arm. If you go with the dinosaur oil, I'd change it every 3000mi for insurance. Unlike synthetic, it breaks down at temperatures normally experienced in an engine.

STS al UK
01-31-06, 08:38 PM
Who mentioned gas prices??? If you worry about that you should think about getting a jap econobox instead, I am learning that the northstar is a very expensive motor to look after but I aint gonna be put off.
You wanna try the gas prices in ENGLAND :cookoo: ... we paying the equivilent of aproximately $8.00 per gallon (:ripped: ) but my STS still gets a regular WOTing lol.
I'm ADDICTED to the rush...:spin:

mtflight
01-31-06, 09:27 PM
I don't know... Performance engines need performance oil. I stick to, and recommend synthetic. Isn't synthetic factory fill on the northstar?

Yeah, it's expensive. 7 quarts will cost you an arm. If you go with the dinosaur oil, I'd change it every 3000mi for insurance. Unlike synthetic, it breaks down at temperatures normally experienced in an engine.

Dyno oil is factory fill on the N*. Good ole Bob mentioned that while synthetic is indeed more heat resistant, that would be at temperatures the N* would not normally see.

Synthetic would obviously not harm anything, but it may find leaks.

He said the reason the 'vette comes factory-filled with Mobil 1, was that they foresaw Joe Bicep possibly taking it to the track.

He was banned from the Bobistheoilguy [who pushed Amsoil] forum, because he showed them enough facts that questioned their logic (for instance that in normal temperatures it's the oil additives depleting and not oil breakdown, that is important--and that synthetics' additive package wears out just as fast) .

Bottom line: dyno oil and stick to OLM, was the message.

Now I know that some engines are prone to sludge, like some VWs, Chryslers and Fords--who have gone as far as extending the factory warranty when it comes to the engine only (sludge related). I haven't heard of that problem with the N* (yet?).

eldorado1
01-31-06, 10:19 PM
Well, I don't want to turn this into a synthetic vs conventional debate (I think there's already another thread for that..)

From what I understand, conventional oil by it's own nature is comprised of many different oil molecules. These molecules have different flash points. On top of that, you have to deal with contaminants natural to them by the refining process.

Synthetic oil is manufactured from methane or LNG, and once processed, has a uniform flash point. It's "one oil", not an amalgam of different oils.



Because a synthetic oilís molecules are much more consistent in size and shape, they are better able to withstand extreme engine temperatures. By contrast, the unstable molecules in conventional oil can easily vaporize or oxidize in extreme heat. Mobil 1 synthetic is said to be capable of protecting engines "at well over 400 degrees F"; in the real world, most racers have no problem running synthetics up to 290 degrees F under prolonged use, but they get really jumpy when a conventional exceeds 270 degrees F.
Because a synthetic oil is chemically produced, there are no contaminants in the oil. By contrast, conventional oils contain small amounts of sulfur, wax, and asphaltic material that can promote detonation as well as varnish and sludge buildup.
from http://www.carcraft.com/techarticles/15378/

It's up to everyone to make their own informed decisions. If you don't do any towing, racing, or forget to change your oil for 20,000 miles, regular oil is probably fine.

Tommy Deville
02-01-06, 03:16 AM
Wot + Fast = Ticket :-(

VinnyT
02-01-06, 02:07 PM
All I know is:

73000 mile N* + Gm TEC = lots of smoke!!

I went ahead with the TEC and it has produce a lot of smoke. Good thing. How long will it smoke for? I want to take it on the road, but I'm afraid it will cause too much smoke. Engine seems to run smoother. I think I'll need to do another can of it however. Should I have to worry about cleaning the plugs? They're only 3 months old. The wires are 1 month old. Thanks!