: Moving Tapping Noise/Knocking Noises



oldsauroraman1
05-11-07, 08:38 AM
Ok, I just had a different 4.0 Engine installed in my 1998 Aurora. This one is out of a 1999 with 58 grand on it. Runs great, idles smooth. One "problem." I have this tapping sometimes knocking noise from the engine. It seems to come from everywhere in the engine. The supplier of the engine told the tech who installed it that it sounded like carbon and to do a treatement of water in it to clear out the carbon. This has been done twice and the noise/knocking went away both times for 50 or so miles then comes back. Which indicates to me that we have carbon on the intake valves that keeps breaking off and getting into the cylinders. This engine sat on a shelf for over a year. I have used seafoam in the last 3 tanks of gas (Premium V-Power Shell). I have driven this engine almost 2,500 miles and still have this problem. Is this normal and would a GM Top Engine Cleaner treatment help? The warranty on this engine expires in 45 days so I am getting a bit concerned about it. The engine has not used any oil so far. Has good oil pressure, 20 in drive while stopped. 60+ at 60 mph. I am really happy with it otherwise. Is this noise normal in a N* ? Your input would be most appreciated!

Ranger
05-11-07, 10:51 AM
See the posts by AJxtcman.
http://www.cadillacforums.com/forums/northstar-performance-technical-discussion/106267-question-exhasut-smoke-chemical-agent-repair.html

oldsauroraman1
05-11-07, 04:51 PM
Thank you!

oldsauroraman1
05-11-07, 09:01 PM
Does anyone know if this would be a bearing or wristpin? The noise comes and goes. ???

Ranger
05-11-07, 09:24 PM
The carbon is not on the valves but on the head or the piston. Do a search for "cold carbon rap".

oldsauroraman1
05-14-07, 09:55 PM
OK Ranger. Thank you. We followed the instructions for the GM Top Engine Cleaner late this afternoon. We will start it up in the morning and hopefully it will have done its job. Thank you!

oldsauroraman1
05-14-07, 10:35 PM
Used these directions:

http://www.cadillacforums.com/forums/cadillac-tech-tips/51792-cleaning-your-engine-evil-carbon.html

oldsauroraman1
05-17-07, 12:51 PM
ARRRRGGH! It came back. After driving over 100 miles. I put it in 2nd and drove it up to 60 mph and slowed down - the tapping is gone. Evidently there is STILL MORE CARBON! Where is it all coming from? Does it take much of it to cause the ticking?

Ranger
05-17-07, 01:41 PM
Per our old Guru (GM powertrain engineer), there is a "squish area" in the chamber that has a pretty tight clearance. Once carbon builds on it, the piston contacts it at TDC causing it to rock on the wrist pin and the skirt to slap the cylinder wall. Several WOT treatments usually take care of it.

oldsauroraman1
05-17-07, 11:23 PM
OK thank you so much for the reply Ranger. So after doing the GM Top Engine Treatment, where is the carbon coming from? WOT, I have done a few of those in the past week. More? I don't want to do any damage to this engine. Thank you for your replies.

Ranger
05-17-07, 11:33 PM
If you are seeing black smoke (carbon) in the rear view mirror when doing a WOT, it is coming from the combustion chamber and you need to do a few more.

oldsauroraman1
05-22-07, 05:57 PM
Have not seen any. Did some WOT today. Still getting the tapping - sometimes. Usually if I do the throttle up to 60 in 2nd gear and let it slow back down to 30 it clears it up and I don't hear the tapping for a while. The TEC did the best as I went 125+ miles without the noise. Taking it for a 500 mile trip Thursday on the interstate, maybe that will help???

Ranger
05-22-07, 08:17 PM
Sure sounds like carbon build up on the heads.

oldsauroraman1
05-29-07, 09:33 PM
Sure sounds like carbon build up on the heads.

Thank you for the information. I drove to NJ and back the other day, around a 450 mile trip. And surprise, the noise is still there. What do you recommend for me to clean the carbon out on those heads? The GM garage already did two "water treatments" on it. :stirpot: The noise went away for a bit and then came back. And it wasted the front 02 sensor, just replaced that tonight. I did the GM Top Engine Clean and that lasted a good 150 miles. Is it possible that I am getting this carbon from the intake? I greatly appreciate your and others input. :worship:

Ranger
05-29-07, 10:58 PM
What do you recommend for me to clean the carbon out on those heads?
More WOT treatments.

oldsauroraman1
05-30-07, 10:18 PM
More WOT treatments.

Yikes. Having been raised not to "Beat a car" that kinda scares me to do so much. Won't that trash my transmission or blow a head gasket? Would it be OK to do another GM TEC on it? Or say, run seafoam in it? Thank you!

Ranger
05-30-07, 10:35 PM
I doubt Seafaom or GM TEC would hurt if you want to give it another try. Being new, you may have seen references to the "Guru". He is a GM powertrain engineer who used to post here and is highly respected. He said the Northstar is a high performance engine and needs to be aired out. he always told us to "Drive 'em like we stole 'em". When the Northstar was being tested at the factory, it was run at WOT for 300 hrs. (12.5 days) straight. He said the trans is very strong and built to handle the Northstar power. We hear of very few trans problems here. Did you read the Tech Tips at the top left of this page? They are from the Guru.

oldsauroraman1
05-30-07, 10:36 PM
We also had two "treatments" of water poured in gradually to "Crack" the carbon off. Should that be done again?

oldsauroraman1
05-30-07, 10:50 PM
I doubt Seafaom or GM TEC would hurt if you want to give it another try. Being new, you may have seen references to the "Guru". He is a GM powertrain engineer who used to post here and is highly respected. He said the Northstar is a high performance engine and needs to be aired out. he always told us to "Drive 'em like we stole 'em". When the Northstar was being tested at the factory, it was run at WOT for 300 hrs. (12.5 days) straight. He said the trans is very strong and built to handle the Northstar power. We hear of very few trans problems here. Did you read the Tech Tips at the top left of this page? They are from the Guru.

WOW! OK, thank you. I will look at those. Thank you!

unruley247
06-02-07, 07:47 AM
Yikes. Having been raised not to "Beat a car" that kinda scares me to do so much. Won't that trash my transmission or blow a head gasket? Would it be OK to do another GM TEC on it? Or say, run seafoam in it? Thank you!
I have 285,000 miles on my N* and I still drive her like am running from the law. Only one problem not enough highway!! :devilheh:

oldsauroraman1
06-02-07, 11:50 AM
Took it out the highway the other night running in 2nd gear from 70 down to 30 for a 6-7 mile stretch. Been quiet since. Also, before I took it out I gave it the "Valvoline Intake Treatment" which required me letting the PCV line suck the 13oz. can in over a period of 20 minutes. We will see.

oldsauroraman1
06-08-07, 10:05 PM
Weird! Still comes back. Even now when the engine is not up completely to running temperature. Gonna do a Top Engine Cleaner treatment in another thousand or so.