Piston Slap
- Thread starter rogerj
- Start date
I'm a new member. Hello to all of you ! I just bought a 2000 GMC Sierra pickup, longbed , standard cab, with the 5.3 liter engine. I bought it from a new car dealer, where it had been traded in. The truck has been kept in beautiful, nearly showroom condition, and has 119,000 miles on it. However, it also has a piston slap when it's cold started in the morning, but only lasts 30 to 40 seconds in this summer weather. It sounds like a diesel engine rap. After that, the engine is quiet. Oil pressure builds to 45 lb. within 2 seconds, on the gauge. I was surprised to hear the noise the first morning after I drove the truck home from the dealer. Then I realized that both times I test drove the truck, the dealer knew I was coming, so he warmed the truck up both times prior to my arrival. (Lesson learned- always take them by surprise. ) Even so, I'm happy with the truck . That piston slap issue has been much discussed , and the bottom line seems to be that GM says it's mostly a nuisance noise, and that any piston slap noise that goes away within 2 minutes of a cold start is " acceptable". But, many owners say it's an obvious defect and should have been the subject of a recall. I plan to keep my truck , and hope the piston slap doesn't cause serious wear issues or oil burning. I'm switching the engine to Mobil 1 10W-40 full synthetic, which Mobil says was designed for engines with over 75,000 miles. And I'm using an oil filter with an anti-drainback valve to help build faster oil pressure. Possibly, the lubricating properties of the synthetic oil will help keep the piston slap from getting worse. I also have that pesky bad gas gauge problem, but that's another thread.
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i also have the same problem. my 07 gmc sierra has a piston clap. it prevents me from doing auto start. and also is very annoying when i gas it, it sounds faster and louder. i use royal purple synthetic oil 10w-40 to see if it would fix it but its hasn't. please someone help. its throwing out a code, TPS sensor.
Rowdy- Provide us with a little more information . How many miles on your truck ? How long have you had the piston noise, and does it get quieter after the engine warms up ? It might be a rod bearing . What is auto start, and why would a piston noise prevent it from working ? The TPS is the Throttle Position Sensor, and should not be a factor in your engine noise. If the TPS code indicates a defective sensor, you should be able to measure the changing voltage output as the throttle moves, and determine whether it's bad. The TPS shouldn't cost too much, and if in doubt, buy a new one. I don't know what other faulty components might show up as a TPS code, so consult a shop manual. I just bought a set of factory shop manuals for my 2000 Sierra from Helm publishing. They were $135 , and consist of 4 volumes totaling 6,000 pages ! ( with very poor indexes). I'll do some reading in my shop manual, and see what else would trigger a TPS fault code. Remember also that dirty connectors in the wiring often cause problems, so buy some electronics spray cleaner and start separating engine compartment connectors and cleaning them.
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This has really stumped me, if only one cyclinder has this noise, what's happening to the other seven?
I have lost gas millage sence I have had the 100,000 mile tune up and one problem has developed. the change oil light came on and stayed on,
I was close to a GMC dealer, problem solved, mechanic assured it was only a little carbon from cleaning of injecting tube. Yea sure! Light came back on when brought back. When we lifted the hood and removed the oil cap it sounded like there was preasure built up inside. Then the change oil light went out. I haven't had a problem sence accept the poston slap. The change oil light works fine and I have reset it more then once. (5 seconds 3 pumps). Looks like it will be after summer till I get another chance to hear it again,
Lucky Me.
ROGERJ
I have lost gas millage sence I have had the 100,000 mile tune up and one problem has developed. the change oil light came on and stayed on,
I was close to a GMC dealer, problem solved, mechanic assured it was only a little carbon from cleaning of injecting tube. Yea sure! Light came back on when brought back. When we lifted the hood and removed the oil cap it sounded like there was preasure built up inside. Then the change oil light went out. I haven't had a problem sence accept the poston slap. The change oil light works fine and I have reset it more then once. (5 seconds 3 pumps). Looks like it will be after summer till I get another chance to hear it again,
Lucky Me.
ROGERJ
This has really stumped me, if only one cyclinder has this noise, what's happening to the other seven?
I have lost gas millage sence I have had the 100,000 mile tune up and one problem has developed. the change oil light came on and stayed on,
I was close to a GMC dealer, problem solved, mechanic assured it was only a little carbon from cleaning of injecting tube. Yea sure! Light came back on when brought back. When we lifted the hood and removed the oil cap it sounded like there was preasure built up inside. Then the change oil light went out. I haven't had a problem sence accept the poston slap. The change oil light works fine and I have reset it more then once. (5 seconds 3 pumps). Looks like it will be after summer till I get another chance to hear it again,
Lucky Me.
ROGERJ
I have lost gas millage sence I have had the 100,000 mile tune up and one problem has developed. the change oil light came on and stayed on,
I was close to a GMC dealer, problem solved, mechanic assured it was only a little carbon from cleaning of injecting tube. Yea sure! Light came back on when brought back. When we lifted the hood and removed the oil cap it sounded like there was preasure built up inside. Then the change oil light went out. I haven't had a problem sence accept the poston slap. The change oil light works fine and I have reset it more then once. (5 seconds 3 pumps). Looks like it will be after summer till I get another chance to hear it again,
Lucky Me.
ROGERJ
I don't know about the change oil light issue. However, the piston slap problem often involves only one or two pistons. There's a variety of information on the web about this issue, including mentions of special coatings on some pistons but not others, and carbon buildup on the pistons above the ring lands. However, the bulk of the information indicates that GM stopped individually fitting pistons to cylinders to ensure proper clearance. Instead, they apparently decided that their quality control was good enough that every piston would fit every cylinder without confiirming the clearance.
Hence, if you happened to combine a slightly undersized piston with a slightly oversized bore, you have too much clearance, and get piston slap. The problem was apparently made worse by a switch to short skirt pistons, which encourage piston rock. According to the factory manual, a similar noise can be made by excessive wrist pin clearance too. Usually, the noisy piston is identified by disconnecting the spark plug wire to that cylinder, which lowers the combustion chamber pressure and temporarily stops the piston slap. In my humble opinion, if the noise disappears after the engine is hot, then you can live with the issue. If the noise never goes away, then engine damage is probably occuring . Apparently, the symptoms will include excessive oil consumption in that cylinder, unusual carbon buildup in that cylinder, and unusual piston and cylinder wear. I also suspect that the wrist pin and connecting rod bearing may suffer an early demise from the shock loading.
However, GM apparently extended the warranty on some of these engines with piston slap to 100,000 miles, as a show of confidence that the problem can be lived with.
Hence, if you happened to combine a slightly undersized piston with a slightly oversized bore, you have too much clearance, and get piston slap. The problem was apparently made worse by a switch to short skirt pistons, which encourage piston rock. According to the factory manual, a similar noise can be made by excessive wrist pin clearance too. Usually, the noisy piston is identified by disconnecting the spark plug wire to that cylinder, which lowers the combustion chamber pressure and temporarily stops the piston slap. In my humble opinion, if the noise disappears after the engine is hot, then you can live with the issue. If the noise never goes away, then engine damage is probably occuring . Apparently, the symptoms will include excessive oil consumption in that cylinder, unusual carbon buildup in that cylinder, and unusual piston and cylinder wear. I also suspect that the wrist pin and connecting rod bearing may suffer an early demise from the shock loading.
However, GM apparently extended the warranty on some of these engines with piston slap to 100,000 miles, as a show of confidence that the problem can be lived with.
While the piston to cylinder clearance was reportedly an issue, it seems odd to me. Many of us have had engines that went 200,000 miles or more, and never developed piston slap. The cylinders in those high mileage engines had plenty of wear , and the clearances get large indeed. But still, no piston slap. It seems to me that the clearance issue is secondary to a piston design defect in the engines with piston slap. I've read about the shorter piston skirt design, reportedly done to reduce piston drag and improve fuel economy. Piston design is a complex thing, and new designs are constantly coming out, but in my 63 years, I've never before owned a vehicle with obvious piston slap noise. I think GM dropped the ball badly on this issue. ( Is there, by any chance, a tiny little script on those pistons that says " Made in China" ?)
happy 2011
New member
i know some of you are going to jump on me for this but
well i think you all are over reacting a little bit here. 9 9 percent of pistons made today are coated. Yes some pistons will make a noise when cold (even new ones) this is done becaues when the piston heats up it Expandes to to seal the cylinder with the rings. This makes longer engine life belive it or not.
Plus you think GM piston noise is bad you should hear fords -sounds like a diseal - subaru - sounds like a it's going to blow any min. And yes toyota as well can't even get away with no piston noise.
Nothing happens becaues of the noise and it does not take away from engine life at all. It's just you were taught that engine noise was bad Not always true.
well i think you all are over reacting a little bit here. 9 9 percent of pistons made today are coated. Yes some pistons will make a noise when cold (even new ones) this is done becaues when the piston heats up it Expandes to to seal the cylinder with the rings. This makes longer engine life belive it or not.
Plus you think GM piston noise is bad you should hear fords -sounds like a diseal - subaru - sounds like a it's going to blow any min. And yes toyota as well can't even get away with no piston noise.
Nothing happens becaues of the noise and it does not take away from engine life at all. It's just you were taught that engine noise was bad Not always true.
It's interesting that some other vehicles have noises that sound like piston slap. I don't doubt your word. And, it may be true that the issue does not necessarily mean major engine failure. However, this piston slap issue has cost GM a lot of money in buybacks and extended warranties, as well as lawsuits. At the very least, it's bad business to sell engines that make noises that customers will interpret as defects. Also, apparently, some engines have the noise, and some don't. Some pistons in a given engine are noisy, and some are not. That means variability from cylinder to cylinder, and engine to engine. Such variability is not a normal condition, and certainly is bad publicity for GM. It also makes it difficult to sell your vehicle if the engine makes knocking noises . It's hard to believe that GM intended for all of these problems to exist, especially considering that financial disaster was knocking on their door when the problem engines were built.
The real dilemma is, It began after 111,000 miles of perfact motoring, and I knew every noise sence the truck was new. Over night it happened, no warning, It's like driving with a squeeky wheel? do ya drive with the squeek? What are my alternatives? GM made it, what would be their repair?
We fix their problems! Can GM fix mine?
We fix their problems! Can GM fix mine?
20,000 miles
I got my 2001 GMC Z71 brand new. At 20,000 miles one morning I started it up and I thought it was gonna blow. It was so bad it sounded like a diesel engine. I was pissed I just paid $35,000 for this truck and the engine sounds like this after I get just 20,000 miles on it. I took it back like 3 times they just kept telling me it was totally normal to just drive it. Well I got 168,000 on it now and truck is still as good as new and it still knocks like hell on startup. I just keep it service and driving it with no problems. The only thing I've done to this truck is changed the front right bearing hub assembly and thats it. Its been a awsome truck but I still hate the knock on startup.
My truck does use around a quart of oil between 3,000 miles oil changes now but I expect this is normal for 168,000 miles. I've used Valvoline since 1st oil change then went to Valvoline maxlife at 75,000 miles. Just a FYI
I got my 2001 GMC Z71 brand new. At 20,000 miles one morning I started it up and I thought it was gonna blow. It was so bad it sounded like a diesel engine. I was pissed I just paid $35,000 for this truck and the engine sounds like this after I get just 20,000 miles on it. I took it back like 3 times they just kept telling me it was totally normal to just drive it. Well I got 168,000 on it now and truck is still as good as new and it still knocks like hell on startup. I just keep it service and driving it with no problems. The only thing I've done to this truck is changed the front right bearing hub assembly and thats it. Its been a awsome truck but I still hate the knock on startup.
My truck does use around a quart of oil between 3,000 miles oil changes now but I expect this is normal for 168,000 miles. I've used Valvoline since 1st oil change then went to Valvoline maxlife at 75,000 miles. Just a FYI
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my 07 GMC Sierra has 89k miles on it and its been making the piston slap since 65k miles. this noise is crazy annoying and when i gas its louder and faster, it usually starts doing it when the truck is not moving. this comes and goes its not slaping all day long. but its really concerns me that it might crack the block or wear the engine life . i do have the engine light on and it throws the TPS senor code. it doesnt seem like that is the problem but its prevents me from auto start my truck. i need some serious help on what may be causing the problem.
Carbon buildup in the engine can cause anywhere from a ticking sound similar to a lifter to a rather loud knocking noise similar to a main bearing knock. The piston hits the carbon accumulation in the combustion chamber and makes the sound, which is often misdiagnosed as piston slap. Because the carbon swells up upon engine cool down, the noise will be more prevalent on start-up following prolonged downtime.
This is usually the result of lower quality lower detergent gasoline being used over many miles.
If an engine had piston slap is would occur from day 1 and not come on after many thousands of miles. Often top end cleaners will help clean out the engine but you have to be careful using them to prevent engine damage. There is one popular product many use but the name slips me. Sea Foam is the cleaner, many claim it eliminates the noise if only not for just a short time because people go back to buying the lower cost and lower detergent fuels instead of the Top Tier. Google top tier gasoline
This is usually the result of lower quality lower detergent gasoline being used over many miles.
If an engine had piston slap is would occur from day 1 and not come on after many thousands of miles. Often top end cleaners will help clean out the engine but you have to be careful using them to prevent engine damage. There is one popular product many use but the name slips me. Sea Foam is the cleaner, many claim it eliminates the noise if only not for just a short time because people go back to buying the lower cost and lower detergent fuels instead of the Top Tier. Google top tier gasoline
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I've seen an engine ( my 1989 Chevy 350) that had excessive carbon buildup on top of a piston, and the valves were hitting the carbon . Cylinders that burn oil will tend to get the most carbon buildup . Cadillac Northstar engines have had a related problem with carbon buildup. GM blames people who drive too conservatively, and never blow out the carbon with some full throttle blasts. GM has a " top cylinder cleaner" solvent that is poured down the intake while the engine is running as a fix. Some people use a very small trickle of water poured into a running engine for the same purpose. I guess I'm showing my age, since in my younger days carbon buildup was never, never a problem !
GMC Customer Service
New member
Hi Rowdy_GMC. It’s been a few days since you posted… do you have any updates for us on the noise you were experiencing? Have you had a chance to take it to the dealer or look at the vehicle yourself?
Thanks,
Laura
GMC Customer Service
Thanks,
Laura
GMC Customer Service
Well the piston slap has left number two cylinder, only to return next winter! I'll be writing again around November to let you know if it returns. In the mean time only the best gas and oil will be for this 2001 GMC, and maybe the problem will go away just as it came. Happy Motoring
RuffNeck_Canuck
New member
Piston slap is common
GM used to sleeve their pistons in the early 2000's, not sure exactly which years and when they stopped. In the pervious years mentioned the teflon sleeve was like a longer tail on the piston. The piston's in the newer trucks are still sleeved, however not with the tail method, there is teflon built into the piston in the area where wear would most likely occur. but the piston's are shorter without the tail and therefore the slap occurs till the engine heats up the the pistons and rings expand enough that they run smooth. I know this because I have seen both styles, I asked a GM certified mechanic about it, even he can't figure out why they changed. But it is common on the newer GM's, guess it's something we're gonna have to life with.
GM used to sleeve their pistons in the early 2000's, not sure exactly which years and when they stopped. In the pervious years mentioned the teflon sleeve was like a longer tail on the piston. The piston's in the newer trucks are still sleeved, however not with the tail method, there is teflon built into the piston in the area where wear would most likely occur. but the piston's are shorter without the tail and therefore the slap occurs till the engine heats up the the pistons and rings expand enough that they run smooth. I know this because I have seen both styles, I asked a GM certified mechanic about it, even he can't figure out why they changed. But it is common on the newer GM's, guess it's something we're gonna have to life with.
Yea I think all of this is BS! GM should stand up to their products and fix there design. You know how embarrassing it is to start up a new truck and it sounds like a rod is knocking in it and you can here it all over the parking lot? Well it sucks cause I been dealing with it for the last 148,000 miles.
I also thing they should fix everyone's gas gauge that's faulty on 9 out of 10 trucks they make. But its not there problem cause its a wear item. Well I guess a new design would be good since there all shit. The last 3 new trucks I bought have been GM and I like there trucks but this is ridiculous. Just my opinion.
I also thing they should fix everyone's gas gauge that's faulty on 9 out of 10 trucks they make. But its not there problem cause its a wear item. Well I guess a new design would be good since there all shit. The last 3 new trucks I bought have been GM and I like there trucks but this is ridiculous. Just my opinion.