BodybyFisher Posted April 28, 2006 Report Share Posted April 28, 2006 If I am correct you have the sprag noise from the transmission. Mine did that. Take note that if when that noise happens the car moves ever so slightly. Do it with the hood up and the car in park on a flat surface and raise the idle to 1500 to 1800. You may observe the car move slightly. If the car moves its related to the sprag. See this (and so a search under 'sprag') http://caddyinfo.ipbhost.com/index.php?sho...c=2104&hl=sprag 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...
adallak Posted April 28, 2006 Report Share Posted April 28, 2006 If I am correct you have the sprag noise from the transmission. Mine did that. Take note that if when that noise happens the car moves ever so slightly. Do it with the hood up and the car in park on a flat surface and raise the idle to 1500 to 1800. You may observe the car move slightly. If the car moves its related to the sprag. See this (and so a search under 'sprag') http://caddyinfo.ipbhost.com/index.php?sho...c=2104&hl=sprag Thanks Mike. I'll look at it. But it happens ONLY when engine is hot. Could be the tranny...But could it be just valve noise or something in the engine? Pistons at certain temperature? Edit: your symptoms were different. There is no knock or any noise when in P or N, only in D. I can rev the engine to 3000-3500 in P or N and nothing will happen. The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
epricedright Posted April 28, 2006 Author Report Share Posted April 28, 2006 Adallak, Do you have the #1 main bearing knock as well? Do all the 4.9's have it or am I just lucky? Link to comment Share on other sites More sharing options...
BodybyFisher Posted April 28, 2006 Report Share Posted April 28, 2006 I couldn't remember if mine only occurred when it was hot. If you are sure its not the #1 main bearing knock... mine only occurred when it was HOT... What made me think your knock was the sprag was because it only happened in P and N, it won't happen in D... (god forbit)...LOL 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...
adallak Posted April 28, 2006 Report Share Posted April 28, 2006 Adallak, Do you have the #1 main bearing knock as well? Do all the 4.9's have it or am I just lucky? I have some knock at cold start for a minute or so. It could be #1. I am pretty sure it is not #1 when engine is hot. I hope it is something piston related. Mystery unsolved .lol The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
epricedright Posted April 28, 2006 Author Report Share Posted April 28, 2006 Adallak, Do you have the #1 main bearing knock as well? Do all the 4.9's have it or am I just lucky? I have some knock at cold start for a minute or so. It could be #1. I am pretty sure it is not #1 when engine is hot. I hope it is something piston related. Mystery unsolved .lol You might want to do the #1 test I referred to above when it's hot and see if it goes away. I get the noise only when the engine is hot as well. Very rearely when it's cold. I really notice it going up my driveway slowly, w/ the engine under load. I've noticed the noise is more pronounced when my oil is old and has less viscosity. Link to comment Share on other sites More sharing options...
BodybyFisher Posted April 28, 2006 Report Share Posted April 28, 2006 My 4.9 had it. It was more pronounced: 1) with synthetic oil 2) when engine was hot and really really hot (August driving) 3) old oil, an oil change always seemed to make it better 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...
Ranger Posted April 28, 2006 Report Share Posted April 28, 2006 Adallak, Do you have the #1 main bearing knock as well? Do all the 4.9's have it or am I just lucky? My '92 never had it in 125,000 miles. Link to comment Share on other sites More sharing options...
adallak Posted April 28, 2006 Report Share Posted April 28, 2006 Gents, Thanks for all the replies. Last year I tested it when hot by removing the serp. belt (did not have a helper at the time). Knock was still there, and the coolant boiled over. lol I'll test it tomorrow again. I am going to change oil (as usual Rotella 15-40), thermostat (switch from 195 to 180) to run it a little bit cooler... and that's it. Not really much I can do about it. The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
adallak Posted May 2, 2006 Report Share Posted May 2, 2006 An update: it is not the main bearing. It is something else. Cannot get rid of that knock. lol BTW, here is the tool I have made to adjust ISC motor's plunger. The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
BodybyFisher Posted May 2, 2006 Report Share Posted May 2, 2006 Cheap enough tool Don't be surprised if Craftsman patents it and charges $5.00 for it, 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...
adallak Posted May 2, 2006 Report Share Posted May 2, 2006 Cheap enough tool Don't be surprised if Craftsman patents it and charges $5.00 for it, Do not be fooled by cheap imitations! The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
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