tornado_735 Posted June 6, 2009 Report Share Posted June 6, 2009 I noticed I have piston slap when the engine is cold. I initially thought the valves were just noisy, but then I remember that I had an Alero with a 3400 that just sounded like the top end was coming apart when it was cold. I did a little research, and found that it was piston slap. I'm not all that worried about it. I haven't lost a drop of oil in 3500 miles, and it goes away fairly quickly. But there was not really a clear cut answer in any of the other posts about what can be done to quiet it down and stave off any potential damage. I was thinking thicker oil, maybe 15w40 or maybe even 20w50. I don't see what 20w50 would hurt, seeing as how it has almost 170k. Plus I was just curious... Were the first generation 2.8's and 3.1's prone to piston slap? I never recall actively noticing it in my CS or Lumina. This is newest w-body I have ever owned, and didn't know the gen 2 3100's fell victim to it. Anyway... Thanks all, Aaron Quote Link to comment Share on other sites More sharing options...
pitzel Posted June 6, 2009 Report Share Posted June 6, 2009 Yeah, the first gens had a minor case of it... Its my view on these engines that you really should go to oils like 0W-30, instead of the thicker (at cold temperature) oils, just to make sure everything flows and lubricates as quickly as possible after startup. Quote Link to comment Share on other sites More sharing options...
GP1138 Posted June 6, 2009 Report Share Posted June 6, 2009 I get piston slap on my 3.4L all the time... Quote Link to comment Share on other sites More sharing options...
w-bodys_are_the_best Posted June 7, 2009 Report Share Posted June 7, 2009 My 96 3100 Cutlass had it really bad, it also never used a drop of oil. The 94 never had it, and I have yet to hear a 3.1 with piston slap. My 3.4 knocked like a diesel , but no piston slap there either. Quote Link to comment Share on other sites More sharing options...
Crazy K Posted June 7, 2009 Report Share Posted June 7, 2009 are you using a low quality oil filter like a FRAM, which does not have a good oil drain back valve and therefore created dry starts???? Quote Link to comment Share on other sites More sharing options...
89GP_SE Posted June 7, 2009 Report Share Posted June 7, 2009 piston slap is caused by collapsed pistions. First thing in the morning its loud because the pistons have shrunk back smaller than stock, and when they get warm, roughly ten minutes afterwards, its warm, this pistons have expanded to the cylinder walls. No oil in the world will fix the knocking/slapping, just live with it. Edit: my 3.1 has really bad piston slap for roughly ten minutes first start. Every 3.1 I have owned has had piston slap (3 out of 3) Quote Link to comment Share on other sites More sharing options...
tornado_735 Posted June 7, 2009 Author Report Share Posted June 7, 2009 are you using a low quality oil filter like a FRAM, which does not have a good oil drain back valve and therefore created dry starts???? LOL Let's not get into the oil filter fights Crazy Yes, I do use fram, and I have used nothing but Fram since I started doing my own oil changes. I have never had a problem with them. I do not, however, use the regular fram filter. I use the one made for high mileage vehicles, along with Maxlife. I use the same filter and maxlife in my GP and my XJ, and the same filter and Kendall in the Land Rover. I will do as GPSE said, and live with it. I listened to it today when I was leaving work, and it's more of just a chatter that goes away within a minute. Literally, I started it up, listened to it for 5-10 seconds, pulled out of the parking lot and up to the red light, and it was gone. Quote Link to comment Share on other sites More sharing options...
w-bodys_are_the_best Posted June 7, 2009 Report Share Posted June 7, 2009 piston slap is caused by collapsed pistions. First thing in the morning its loud because the pistons have shrunk back smaller than stock, and when they get warm, roughly ten minutes afterwards, its warm, this pistons have expanded to the cylinder walls. No oil in the world will fix the knocking/slapping, just live with it. Edit: my 3.1 has really bad piston slap for roughly ten minutes first start. Every 3.1 I have owned has had piston slap (3 out of 3) I think you're talking about collapsed lifters, the pistons can't collapse. 3.1's and 3100's can also be noisy from collapsed lifters at startup, but piston slap is alot different. collapsed lifters make a ticking noise rather than a knocking sound as piston slap does. Piston slap sounds like a bad main bearing or rod bearing knock. My 96 CS would sound like it was knocking when first started. It didn't matter if you let it warm up for 5 minutes or 30 minutes, it would still have the knocking sound until you drove it (puting the engine under load) for 10-15 minutes. Piston slap is the secondary (sideways or perpendicular) movement of a piston against the side of a cylinder bore where the primary movement of a piston is intended to be parallel (up and down) to the cylinder bore. In the case of the famous GM piston slap engine defect, the piston design with hypereutectic (high silicon content aluminum alloy) pistons, reduced or eliminated piston skirts (to reduce reciprocating mass), and a higher ring pack to reduce unburned fuel mixture on the sides of the piston crown have made piston to cylinder bore fit much more critical. The amount of tolerance (variation or margin) in allowable clearance between the piston and cylinder bore to prevent audible piston slap has been reduced by a factor of at least 50%. Consistently hitting the narrower margin for piston to cylinder bore tolerance has not happened for GM during mass production. Thus, some engines have no audible piston slap and some have piston slap on only one or two cylinders. Quote Link to comment Share on other sites More sharing options...
89GP_SE Posted June 7, 2009 Report Share Posted June 7, 2009 Collapsed piston A Piston whose Skirt diameter has been reduced due to heat and the forces imposed upon it during service in the engine. Quote Link to comment Share on other sites More sharing options...
w-bodys_are_the_best Posted June 7, 2009 Report Share Posted June 7, 2009 Gotcha Quote Link to comment Share on other sites More sharing options...
89GP_SE Posted June 7, 2009 Report Share Posted June 7, 2009 not quite the same definition for a collapsed lifter LOL. But yet, Most GM motors with alluminum pistons have pistion slap. When I was talking My Auto Service Tech course, we rebuilt a 6.0L out of a GMC 1500 and all the pistons were collapsed. Quote Link to comment Share on other sites More sharing options...
tornado_735 Posted June 7, 2009 Author Report Share Posted June 7, 2009 not quite the same definition for a collapsed lifter LOL. But yet, Most GM motors with alluminum pistons have pistion slap. When I was talking My Auto Service Tech course, we rebuilt a 6.0L out of a GMC 1500 and all the pistons were collapsed. Anybody got a picture of a collapsed piston? Hell I could probably find one on google... Quote Link to comment Share on other sites More sharing options...
98montels Posted June 9, 2009 Report Share Posted June 9, 2009 My 3100 has had what I believe is piston slap for about 3-4 years now. It won't go away until you drive the car as others said. Person I work with has a 3400 in a 03 Prix at 65K it sounded like my 3100 at 90K. Quote Link to comment Share on other sites More sharing options...
Addicted To Boost Posted June 9, 2009 Report Share Posted June 9, 2009 None of the 2.8s or 3.1s I've owned have had piston slap, and 3 out of 4 have had 225,000 or more miles on them. My TGP had some sticky lifters, creating a quiet knock, but I replaced them last spring and the engine is very quiet now. Quote Link to comment Share on other sites More sharing options...
Regal_GS_1989 Posted June 9, 2009 Report Share Posted June 9, 2009 My Mom's Lumina is terrible when you first start it. It sounds more like a duramax then our duramax does. It doesn't burn a drop of oil and still gets the same fuel mileage so we just live with it. Quote Link to comment Share on other sites More sharing options...
5speedz34 Posted June 9, 2009 Report Share Posted June 9, 2009 None of the early 60* I've had have had piston slap. It's my understanding that it was when the 3x00 came out that they changed the piston design allowing for the slap. Quote Link to comment Share on other sites More sharing options...
tornado_735 Posted June 10, 2009 Author Report Share Posted June 10, 2009 I heard it was a fail-safe if the engine overheated. I can't remember the reason, but I think it had to do with how much the piston expanded. Quote Link to comment Share on other sites More sharing options...
1990lumina Posted June 10, 2009 Report Share Posted June 10, 2009 My '90 Lumina's 3.1 sounds like a 6.5L TD, especially when it's really cold. It always has and it always will lol..has ran the same in the four years I've owned it. Quote Link to comment Share on other sites More sharing options...
Schurkey Posted June 15, 2009 Report Share Posted June 15, 2009 Most GM motors with alluminum pistons have pistion slap. Can you name a GM engine that DOESN'T have aluminum pistons? The main issue with piston slap on modern engines is due to the dramatically reduced skirt area; older engines had pistons with much larger skirts that did a better job of cushioning the piston movement side-to-side in the bore as the connecting rod changed thrust angles. As for 3.4 DOHC engines, don't forget that the early ones--up to some time in '94 or '95--have a known issue with oil pressure fluctuations that cause the valves in the hydraulic lifter to be blown off the seats creating valve train noise especially when cold. GM provided a service procedure and a parts kit; the kit is no longer available but the service instructions exist. It would not be impossible to fabricate or otherwise source the parts needed. Quote Link to comment Share on other sites More sharing options...
tornado_735 Posted July 23, 2009 Author Report Share Posted July 23, 2009 Well, I tried switching to thicker oil (Kendall Conventional 20w50 diluted with a quart of Marvel Mystery Oil). Didn't do a thing. In fact, while it seems quieter on the freeway, it's noisier at startup. And I tried a different filter too, an STP filter. I'm going to watch this thing like a hawk, seeing as how I really am out of my comfort zone with the oil and filter. Hell, I checked the oil twice yesterday, Quote Link to comment Share on other sites More sharing options...
88Regal Limited Posted July 24, 2009 Report Share Posted July 24, 2009 mine has the occasional knock when it's cold out (below 40*F or so) and has a slightly worse one below freezing. Never had a problem with it though. The only oil it uses is from leaks, with over 150,000 miles! Quote Link to comment Share on other sites More sharing options...
tornado_735 Posted July 25, 2009 Author Report Share Posted July 25, 2009 mine has the occasional knock when it's cold out (below 40*F or so) and has a slightly worse one below freezing. Never had a problem with it though. The only oil it uses is from leaks, with over 150,000 miles! Yeah, I noticed my power steering pump groans really loud when it's freezing out. 167K miles, 6300 miles on my last oil change and I didn't have to put a drop of oil in it. Surprised the hell out of me. Quote Link to comment Share on other sites More sharing options...
douellette Posted July 25, 2009 Report Share Posted July 25, 2009 not quite the same definition for a collapsed lifter LOL. But yet, Most GM motors with alluminum pistons have pistion slap. When I was talking My Auto Service Tech course, we rebuilt a 6.0L out of a GMC 1500 and all the pistons were collapsed. Anybody got a picture of a collapsed piston? Hell I could probably find one on google... you wouldnt be able to see the difference between a regular piston and a collapsed one, its that little of a change but just enough so it can rock back and forth in the cylinder bore. Quote Link to comment Share on other sites More sharing options...
IRONDOG442 Posted July 25, 2009 Report Share Posted July 25, 2009 The ONLY engines that DOnt get it are Shortstars !! Corrected!! Quote Link to comment Share on other sites More sharing options...
Schurkey Posted July 25, 2009 Report Share Posted July 25, 2009 Well, I tried switching to thicker oil (Kendall Conventional 20w50 diluted with a quart of Marvel Mystery Oil). Didn't do a thing. As has been said, oil isn't likely to affect a piston slap noise. There just isn't enough of it between piston and cylinder wall for it to make a difference. you wouldnt be able to see the difference between a regular piston and a collapsed one, its that little of a change but just enough so it can rock back and forth in the cylinder bore. Yup, just a few thousandths makes all the difference. Takes precision measuring equipment to detect the difference in some cases. Others are obvious--part of the skirt has broken off. HOWEVER, the newer piston designs (low-friction, for "improved fuel economy") are PARTICULARLY susceptible to piston slap because of the dramatically smaller skirt area compared to traditional pistons. Piston slap is pretty common on newer GM engines; there's entire web sites devoted to complaining about it. http://www.pistonslap.com The ONLY engines that DOnt get it are Northstars !! The website linked to above would disagree with your statement. Northstars are included in the list of engines with piston slap complaints. Again, this has more to do with the design of the pistons and their fitment into the bore, than with some magic inherent problem with the overall engine design. ANY engine can have piston slap if the conditions are right--and ANY engine can have piston slap FIXED by assuring the pistons and bore are designed and assembled properly. The problem is the cost to change pistons; and to renew the bore surface if needed. Off-topic: Yeah, I noticed my power steering pump groans really loud when it's freezing out. GM makes a "Cold Climate" power steering fluid; it fixed the cold whine in my Trailblazer. If I were to do it again, though, I'd at least try a quality aftermarket fluid at $4 per quart instead of the Genuine GM stuff at $15+. Quote Link to comment Share on other sites More sharing options...
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