The Good The Bad and the Posted May 8, 2010 Report Share Posted May 8, 2010 My first topic, I just received another present from GM, an engine knock. It sounds like its from the upper part (valvetrain)of the engine. It just happened, so I haven't investegated it to much yet. Luckely ??? it started when I was only a block from home, so it only ran for 30 sec./1min. or so. It didn't happen gradually, but instantly. I was at the end of a 30 min. drive (highway)and had WOT 'd it before the knock accured, but that was a few mins. before the knock accured. I don't think it's piston slap or bearing noise. Has anybody had a knock in a Northstar that isn't piston slap? If so, is it hopefully something simple "lol" like a collapsed lifter,broken link on a chain(if possible)etc. I love these cars, but with Head gasket problems,power steering failures,oil leaks ( which I've all had with two Caddy's )I'd like one problem that I could repair myself besides brakes,bulbs,batterys,and bugs. Link to comment Share on other sites More sharing options...
Cadillac Jim Posted May 8, 2010 Report Share Posted May 8, 2010 Carbon rap is not uncommon, particularly with cars that are mainly driven around town and those that are driven mostly on short trips where much of the time the engine isn't fully warmed up. If you run regular gas instead of premium that can make a carbon rap more likely. If you did a WOT some may have loosened and a piece may have stuck in the squish area. If so, it will decrease quickly, going away with a hot engine, in a couple of days. -- Click Here for CaddyInfo page on "How To" Read Your OBD Codes-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data -- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC Yes, I was Jims_97_ETC before I changed cars. Link to comment Share on other sites More sharing options...
Ranger Posted May 9, 2010 Report Share Posted May 9, 2010 Carbon rap is also known as cold carbon rap because it shows up at start up and usually goes away after 30 -60 seconds. Anything dislodged would have made noise immediately and quickly been discharged out the exhaust valve. If this developed after a :30 min. drive, I doubt that it is carbon rap. I have heard of a few engines developing an upper end lifter noise. I think it was a bad cam, but can't swear to it. Get a stethoscope and listen to the cam covers. If the noise (usually a tick more than a knock) is coming from there, then you will probably have to pull the cam covers (not an easy task). Link to comment Share on other sites More sharing options...
BodybyFisher Posted May 9, 2010 Report Share Posted May 9, 2010 First post huh? We have seen Northstars blow a rod through the engine idling at a gas pump We have seen Northstars knock and blow a rod during a WOT We have seen them go 300K miles Fill us in How many miles on this car How many owners How was the oil pressure? Which car the 98 or 97 How has the car been maintained Did it have a case half leak? How high was the RPM when you did the WOT? redline? This is not a gift from GM, this is part an parcel of owning an old vehicle, you will need repairs on any older vehicle of the same sophistocation If you are at all mechanically inclined these engines can be worked on Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
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