Starflare5 Posted December 19, 2011 Report Share Posted December 19, 2011 Hey guys, I have a 1989 Oldsmobile Cutlass Supreme SL with the 3.1L engine and automatic. Recently, the engine has developed a piston slap or rod knocking noise only when the engine is warm. I have no check engine light, and, no other issues seem to be arrising from it, just the noise. I have also changed the oil and put in an engine/oil treatment, and the noise still remains. Does anyone have any clue what could be the cause of this? Please let me know. Thank you, Starflare5. Quote Link to comment Share on other sites More sharing options...
AL Posted December 19, 2011 Report Share Posted December 19, 2011 Try and get a video if you can Quote Link to comment Share on other sites More sharing options...
Jprice90 Posted December 21, 2011 Report Share Posted December 21, 2011 how many miles? could be a rod, need a video Quote Link to comment Share on other sites More sharing options...
Mel87 Posted December 21, 2011 Report Share Posted December 21, 2011 Have you changed fuel grades in the car? That would lead to a ping, leading to a knock. Not sure about it if it's warm though. Quote Link to comment Share on other sites More sharing options...
virtuetovice Posted December 21, 2011 Report Share Posted December 21, 2011 What is the oil pressure reading? Quote Link to comment Share on other sites More sharing options...
xtremerevolution Posted December 21, 2011 Report Share Posted December 21, 2011 (edited) No such thing as a rod knock only when warm. When you spin a bearing, you know you spun a bearing. It will sound like bones are crunching in your engine bay. I'd be looking for problems in the upper valve train. Depending on how loud it is, it can be anything from a stuck lifter to a broken valve spring. Edited December 21, 2011 by xtremerevolution Quote Link to comment Share on other sites More sharing options...
Schurkey Posted December 21, 2011 Report Share Posted December 21, 2011 No such thing as a rod knock only when warm. Pretty much...but the knock can be worse when hot, as the oil is thinner and provides less "cushion". Similarly, piston slap only when hot is pretty unusual, too. Typically worse when cold, because the pistons aren't expanded from heat. I'd be looking for problems in the upper valve train. Depending on how loud it is, it can be anything from a stuck lifter to a broken valve spring. Worthwhile. Quote Link to comment Share on other sites More sharing options...
jerseyharold Posted December 24, 2011 Report Share Posted December 24, 2011 My '98 Lumina has had a knock like that for the past 50,000 miles. In my case, it's most noticeable if you take your foot off the gas at around 60 MPH. My friend is a GM tech and said live with it. He's been right so far. I did some reading on the subject and cam bearings were mentioned in some articles. Quote Link to comment Share on other sites More sharing options...
tornado_735 Posted December 24, 2011 Report Share Posted December 24, 2011 Could also be the cat innards rattling...that's been mistaken for rod knock before. Quote Link to comment Share on other sites More sharing options...
Addicted to eaton Posted December 25, 2011 Report Share Posted December 25, 2011 I had a knock you could not hear for bout 4-5 min and it was a spun bearing. it sounded like hell when the oil warmed up. Quote Link to comment Share on other sites More sharing options...
xtremerevolution Posted December 25, 2011 Report Share Posted December 25, 2011 I had a knock you could not hear for bout 4-5 min and it was a spun bearing. it sounded like hell when the oil warmed up. By that point, you should be able to see the shavings in the oil, lol. Sent from my HTC Awesome using Tapatalk Quote Link to comment Share on other sites More sharing options...
Starflare5 Posted December 28, 2011 Author Report Share Posted December 28, 2011 Here's the video guys... I hope this helps and hope that some of you can help me. Thank you, Starflare5. Quote Link to comment Share on other sites More sharing options...
BXX Posted December 28, 2011 Report Share Posted December 28, 2011 Your lifter/s is/are fubar. That's not supposed to sound like that:lol: Quote Link to comment Share on other sites More sharing options...
Starflare5 Posted December 28, 2011 Author Report Share Posted December 28, 2011 Your lifter/s is/are fubar. That's not supposed to sound like that:lol: Could that actually cause the sound to be louder in the underside of the engine? Quote Link to comment Share on other sites More sharing options...
xtremerevolution Posted December 28, 2011 Report Share Posted December 28, 2011 Could that actually cause the sound to be louder in the underside of the engine? The lifter is underneath the lower intake manifold, but above the cam. You can't get it out without removing the lower intake manifold. I'll have a listen when I get a chance, but you can generally tell when its a valvetrain issue and not a bottom end issue. Quote Link to comment Share on other sites More sharing options...
Jprice90 Posted January 2, 2012 Report Share Posted January 2, 2012 definitely sounds like a lifter or something like that..you would know if it was a rod Quote Link to comment Share on other sites More sharing options...
Starflare5 Posted January 8, 2012 Author Report Share Posted January 8, 2012 definitely sounds like a lifter or something like that..you would know if it was a rod Ok thanks. I'll look into getting it replaced right away. Quote Link to comment Share on other sites More sharing options...
xtremerevolution Posted January 9, 2012 Report Share Posted January 9, 2012 Ok thanks. I'll look into getting it replaced right away. Its not quite that simple. Replacing a lifter requires removal of the lower intake manifold, which requires replacement of the lower intake manifold gaskets as well, and by the time you're done, you still won't be 100% sure its the lifter and not the valve spring. If you're taking it in, they'll be able to figure it out for you, but if you're doing this job yourself, don't expect it to be a 1-2 hour deal. Quote Link to comment Share on other sites More sharing options...
Rick Posted January 11, 2012 Report Share Posted January 11, 2012 Its not quite that simple. Replacing a lifter requires removal of the lower intake manifold, which requires replacement of the lower intake manifold gaskets as well, and by the time you're done, you still won't be 100% sure its the lifter and not the valve spring. If you're taking it in, they'll be able to figure it out for you, but if you're doing this job yourself, don't expect it to be a 1-2 hour deal. Leave a solid 6-8hours if I were you just incase any mistake. Had to remove the lower intake manifold(first time) and it took a good 6 or 7 hours to remove and re-assemble. Granted, we were repairing a oil leak in the oil pump which may of taken longer to try to form a new gasket/fit the o-ring around. Which may be leaking again already, but it seems like im leaking somewhere else now. We also got delayed a solid hour or two when the o-ring shot into the engine bay and had to use another we had, and when we missed a connection in the re-assemble and had to disassemble again. I would just make sure you have a nice full day if you're doing it outside. That, and the LQ1 in the cutty vert was a bitch compared to the 3100 I had before. Quote Link to comment Share on other sites More sharing options...
Starflare5 Posted January 12, 2012 Author Report Share Posted January 12, 2012 (edited) I believe I'm going to take it to a local shop here if I can find one inexpensive enough, otherwise, I will look into doing it myself with my trusty Haynes manual. By the way, thank you all soo much for your input. You all have been wonderful. Edited February 25, 2012 by Starflare5 spell check Quote Link to comment Share on other sites More sharing options...
Starflare5 Posted February 25, 2012 Author Report Share Posted February 25, 2012 (edited) I found out that the cheapest a shop said that they'll do it is $400 dollars.... looks like I might be taking apart the engine sometime in the summer. Edited February 25, 2012 by Starflare5 Quote Link to comment Share on other sites More sharing options...
Starflare5 Posted March 6, 2012 Author Report Share Posted March 6, 2012 Well, unfortunately, after getting it thuroughly checked out, it turns out that actually was a rod. Before I lost the car to an engine failure, I bought a 1991 Buick Regal Custom. Pictures later. I've got my work cut out for me, but, it's in a whole better shape than my CS was body wise and mechanically. So far, the only mechanical issue appears to be the cat converter. So, I still stayed with the W-body platform, but, now, have some new work cut out for me. Quote Link to comment Share on other sites More sharing options...
xtremerevolution Posted March 6, 2012 Report Share Posted March 6, 2012 Well, unfortunately, after getting it thuroughly checked out, it turns out that actually was a rod. Before I lost the car to an engine failure, I bought a 1991 Buick Regal Custom. Pictures later. I've got my work cut out for me, but, it's in a whole better shape than my CS was body wise and mechanically. So far, the only mechanical issue appears to be the cat converter. So, I still stayed with the W-body platform, but, now, have some new work cut out for me. 3.1 or 3.8L? Quote Link to comment Share on other sites More sharing options...
Starflare5 Posted March 7, 2012 Author Report Share Posted March 7, 2012 3.1 or 3.8L? 3.1 Quote Link to comment Share on other sites More sharing options...
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