@vipermech I still have the engine, perhaps if they wait long enough I'll get myself some measuring tools and get a REAL look at it. I agree that a small crack would not have made that much of a difference but I appreciate you taking the time to respond and offer REAL theories about this problem. Your input is greatly appreciated.

@dougfoor I appreciate that but when there are enough questions about something like this I like to address them this way rather than typing the same thing over and over. Thanks for your comment.

@benjaminsec Hello Sweden! I do plan to make a video on turbos as well as superchargers at some point but I need to get my hands on some first. Till then you might want to check out my friend ProjectCarTV as he does lots of videos on turbos as well as their installation. Thanks for your comment.

@somenutjob I agree that the jury is still out on this one that's why I still have the engine as I hope to tear it down again and do some more measuring to see what is really going on. Thanks for the comment.

@vipermech Interesting direction but not practical, if the valve wasn't sealing when I put compressed air into it it would not have held air at all and I would have heard it coming out the exhaust or the intake. In fact when I did the test it was a way of finding out if the problem was in the head or in the block. When I removed the head I did not see any broken valve springs either. Thanks for your comment.

@chillincruisin You do them at 90º increments because you still have to set the oil control rings as well which you also stagger, even though they don't control compression it's still good practice.

@neoholland Yea, that sounds like a great idea, the next time I get the chance for something like that I'll make a video. Thanks for your suggestion.

@TheKeyboardKowboy You need it in for doing the compression test but if you want to do a quick leak down without a gauge you need to take the schrader valve out. It was in when I did the compression test but out when I ran straight air into the cylinder.

@vipermech Yea that's been mentioned but I'll admit that the gap might have been a little bigger but my other feeler gauge was in my box as I use it for valve adjustments so I would say it's probably closer to .017 or .018. I don't have the tools to measure it properly to be honest. If not ring gap then what would explain the stains on the cylinder wall where it appeared the compression was going. Don't' worry I won't make another video on this I'm done.

@MoneyMarcMes Keep in mind that you are also setting up the oil control ring gaps and by the time you get to the bottom ring after going 90º on the rest it will line up with the top ring. The basic idea is to stagger the rings so that they don't line up the way these seem to have done.

@Anacinc It has and to be honest it's my favorite theory so far. Thanks for the great comment.

@for2utube The oil control rings were frozen but the compression rings were not, they did however appear to be lined up when the came out of the block. Thanks for the input, that service bulletin sounds interesting but I wasn't able to use the link. There was every indication in my mind that this engine failure was the result of poor maintenance or better yet, no maintenance.

Eric, I have had Tahoes most of my adult life and I have to say, I have learned more about a Tahoe from watching your videos than I've ever come across in my entire life-time of owning Tahoes. Awesome job for sure! I've owned a 1998, 2007, and presently a 2008 LTZ (4x4) 5.3L Vortec that runs as if it only had 10K miles on it. It actually has 156k miles, K&N Cold Air Intake installed, High speed tires, Diablo High Performance package - along with plugs and wires to match and soon to have Borla exhaust. Question - granted I don't race my Tahoe but it is nice to have that speed when you want it (especially during private security contracts). I am stringent about changing the oil every 3-5k miles and ensuring that all fluids/lubricants and tire pressures are maintained at their best at all times. If I continue to maintain that maintenance philosophy will adding the Turbo cause failures. Meaning, if I add a Turbo Charger will it cause the motor (Crank-shaft, Block, Water pump, Rods, Pistons, Rings, Exhaust Gaskets, transmission, differential gears, electronics...etc...) to fail frequently or will it just enhance the capability and speed of my Tahoe? Thanks again for the insight.

Eric, You the man. Keep up the GOOD WORK. All of us gearheads appreciate your videos. Thanks

@tinydx95t2 I appreciate that but to be honest I don't know everything and never claimed to. Fact is that some viewers have brought up some pretty good points. As for master tech that's really just a piece of paper, I know plenty of mechanics that never took any tests that know a lot more than me. The key is to sort the crap from the good stuff. Thanks for your comment.

@MikesFitnessGoals yea, have fun with that. Thanks for YOUR comment.

@cam9522 I might take it in to have a compression test done to see if the problem might be related to excessive blow by, if it is you might still be able to get your engine replaced before your out of warranty.

@bustfer07 The 700 codes are transmission related and I think yours is for a torque converter clutch. As for the diagnosis I would recommend checking the service manual as I'm not familiar with the testing for that particular car.

@Cristo12344 I don't have any experience with the kits your talking about so I really couldn't say. Thing is that alcohol will eat the rubber seals in the fuel system eventually as they were not designed to run on alcohol.

@BigHouseOfBooty Believe it or not that's pretty much it. Coolant changes are also important but #1 thing you can do for your engine is to change the oil regularly with the correct weight and viscosity.

@Camaro17k I didn't find any coolant in the engine, not mixed with oil that is.

@christo930 In total it took about 2.5 days to do. The customer supplied the engine.

@geekdad2000 That is an intelligent theory, in fact I hope to get my hands on some measuring tools and see what kind of shape the cylinder and piston are in that just may confirm it. Thanks for the comment.

Could have been a loose gas cap causing blinker fluid to leak onto the cadillac converter .

@motorhead45102 Cool, I'll check that out if I get the time. Thanks for the comment.

@gratefuldead42022 That's probably the most credible thing I've heard so far and don't worry I won't be revisiting this but I think I would have seen that in Part 4. I like your train of thought however. Thanks for your comment.

Just for the sake of Eric lets drop it. This guy is one of the most thorough online mechanics I've seen and plus the first dissection was pretty dang in-depth for a 11 minute video.

@gratefuldead42022 Hold on there mister, watch the leak down test video as I did a power balance test AND I did not feel it necessary to test the injector on a cylinder with 0 compression. Remember I took the tester off and ran straight shop air into the cylinder at 125psi because I didn't feel the tool was working correctly. Try again.

@Warkhan I hope not but thanks for the comment.

Hey Eric, the ring gap should be about .004 for every 1inch in cylinder bore size in a non-boosted application. Since the 5.3l is a 3.78in bore the ring gap should be just over .015 minimum for expansion when the engine is hot. The specs on the old rings show right around where they should be even with the mileage on them. Awesome video series btw. Thanks and keep them coming.

@trinidee247 Cool, I was hoping for someone to weigh in with some similar experience. To be honest this is the first time I've seen something like this. Thanks very much for your comment.

Eric I am and old fashion guy when it comes to engine maintenance. I do mostly city driving so in winter I change oil more often. I change it in summer often also. Any sign of a problem I take care of it immediately before it gets worse. I have a car for last 54 years and each car I bought lasted me more then 170 thousand on engine not excluding brakes, mufflers, and external parts like waterpumps ect.

@Anacinc I'm sure they would look similar but the only way to really tell would be to measure everything properly I'm afraid as you really can't see thousandths of an inch of wear on something, it's much better to take a measurement.

@tatersalad189 I would hardly call the noise from the oil cap a 'slight hiss, I have done leak downs before and did it on more than one cylinder in the leak down video, the other cylinder tested only had a slight hiss coming from the oil cap at 60% leakage. Even if that was the case it still would not explain the 100% leakage on #6 cylinder or the discoloration on the cylinder wall but would explain the compression test readings.

@tatersalad189 I really appreciate your comment, thank you.

@Drew99GT That has actually been addressed in the comments below by a few people and I believe that to be the most plausible theory till I'm able to get in there and do some real measurements.

@ProjectCarTV It was and then it started snowing again today. It's not socal that's for sure.

I like your vids buddy keep em rolling....but, I too had this exact problem and it was a warped cylinder head as mentioned below. same symptoms, same visible marks.

The rings lining up will cause a dead hole.I had it happen on a 350 Chevy circle track race car engine,my ring end gap was setup at .016.After a leakdown test showed leakage into the crankcase,I disassembled the engine and the only problem I found was the two compression ring end gaps lined up.I reassembled the engine with the same parts and it ran like a champ.

@EricTheCarGuy True dat!!! Rule #1 is I do oil changes every three months even when the oil is only slightly dark and my mechanic says I don't need to change it yet, I still have it done. Rule #2, I check my truck with my scan tool every month to detect any codes if any that may come up. If so,I fix the problem and change sensors out as they fail occasionally. Rule #3 Replace your EGR valve immediately if the code comes up EGR not opening and clean the passages out. Marc

@scott192 I'm pretty sure that would have showed up during the leak down and there would have been evidence of that on the head or block but I didn't see it.

@SgtMcCools1 Yea, re-watch the video as I addressed that.

@chicks123 Nope, big valves are intake valves, you want to get as much air and fuel into the cylinder as possible in order to make the most power.

Still, you put this one to rest, good job. I always want to know the why behind the failure. Glad you took the time to explain it.

EricTheCarGuy Great series Eric, thanks for the effort. I'm kind of surprised the customer didn't get a blinking check engine light conveying that raw fuel was entering the catalyst. (Had the blinking C.E.L when one of my coil packs on my '04 Avalanche 5.3 became intermittent.Could even hear the "Thup thup thup" like a '80s Country Squire with a bad plug wire in the exhaust sound). I guess it was burning enough to not show up raw in the eyes of the ECM. I heard about the piston slapping issue on these engines that SkilledEddie mentioned. Really interesting about that piston gap, and am surprised it doesn't happen more often.

@westin1985 I beg to differ, see the 'Leak Down Test' video for how this was diagnosed as no head gasket failure was present according to the testing.

@RealCadde I don't mind the people that disagree with me many of them make some good points I just ask for a give and take instead of a 'he said she said' kind of thing. I actually enjoy the dialog in those instances.

@vipermech OK but follow me for a second, how would the valve close if it was hanging open when I applied the air? I would think the air would just come right out. Remember I put straight shop air into it because the leak down was crap. In addition the valves looked closed in this video and I did not see any broken springs. Still going back to the discoloration on the cylinder wall as to me this was the smoking gun, I think the miss would have acted different if it was a valve issue.

@spelunkerd It will probably be rebuilt and resold. As for the core it's just that, think of it like a deposit when you buy the engine if you don't return it you don't get your deposit back. I didn't buy the engine so I don't know what it was.

@chillincruisin My Element, the Integra was a second car anyway and I got more that what I paid for it.

@4G63PWR That would make for a fun video for sure, much lighter and easier to handle too. Good luck.

@chicks123 Big valves are always the intakes. Good question.

@KyRock1968 I'm going to admit that I don't know the answer to either of those questions, you might want to look through the comments below because a couple of GM techs responded, you might want to ask them those questions because unfortunately I don't know.

@MultiAngelsfan Hate to say it but it sounds like you might need a heater core especially if when you put it on defrost you get a film on the inside of the windshield. Good luck.

I had a 454 which had been rebuilt by a speed shop. The shop had put new valve guides in, which were too tight. A valve stuck open on break-in and water was weeping into the combustion chamber pass the valve guide. I took the one head back and they had to re-do it.

@tatersalad189 I'm still not convinced that if a valve was hanging open that it would show excessive blow by at the bottom end during the leak down, it was 100% and had 0 compression during the compression test. In addition how do you explain the discoloration in the cylinder wall with that theory?

@Datwhit Thanks for the info. So are you saying that the gap is in spec? I realize that I really didn't check it correctly as I didn't level the rings in the bore but it seemed like a big gap to me.

@geekdad2000 I don't think the valves are recessed because if the were they would not seat. With 2 knock sensors i am having a hard time with detonation, todays knock sensor are super sensitive. With the cooling properties of Ethanol the engine having coolant, no head gasket problem I don't think that cylinder got hot enough to have pre-ignition.

@michaelovitch Yea, watch the Leak Down Test video as it is this very engine.

it is evident that Eric have right, piston ring position cause this discoloration and problems, i have the same opinion...

@gratefuldead42022 If not that then how else do you explain the discoloration at the top of the cylinder?

@21mejia25 I remember that one. It's actually still sitting on my floor.

i understand for the rings lining up causing lose in compression but this wouldn't cause the oil and coolant to mix so there must of been a gap in the head gasket on one side or the other.

@vipermech I've read through these comments and find your theory interesting but how would that explain the 100% leakage at the bottom end with the leak down not even hooked up and the discoloration on the cylinder wall? Not trying to be confrontational just curious what your take on that is.

Hey Eric the reason cylinder #6 doesn't have compression is because that engine have cylinder on demand maybe one or both of the lifters is collapse or stuck in open position inside the engine

@EricTheCarGuy That leak down test would seem to only work with catastrophic failure of the headgasket. The leak down tester showed 15psi when calibrated to 0 air flow. So the leakdown testing pressures are not that much. Also you was not able to have any cylinder pressure due to ring failure. If you could have had higher cylinder pressures with the leak down tester (60 to 140psi) you might have seen the head gasket leak. Some headgasket leaks are small and heat sensitive.

@ProjectCarTV It sounds expensive and fast and a little dangerous, I like that.

@EricTheCarGuy I totally understand it now, very interesting, I forgot about the oil control rings. Thanks for the reply. Marc

Thanks for the video, I had concerns about purchasing the new body Tahoe. Since I seen this video, I will make my purchase. So basically, it is safe to say, as long as I maintain the engine, there should not be any issues. Thanks

@petergriffintubin I agree but I was mostly hoping to put to bed the head gasket theory that kept coming up more than anything.

I don't know about that year of 5.3, but some models with the cylinder deactivation suffered from oil consumption and compression issues. There's a TSB on it. My 2009 Suburban got bit with it and I change my oil on schedule. It's a known problem and most are out of warranty by the time the problem comes around. GM's solution is to ask the owner to trade it in on another GM product.

I haven't watched all the videos so i don't know how he diagnosed this problem but in my opinion "if" the rings gaps actually did align causing loss of compression it was a result of the initial problem and not the initial problem. There was lots of coolant in the engine oil. There's only a couple problems that can cause that and piston ring failure is not one of them. Was a combustion leak test performed when diagnosing the problem? A cylinder leakage test is not always conclusive.

@tatersalad189 The bit of reading i've done said the lifters are being blead to prevent the valves from opening at different times. They don't hold the valves open to bleed off compression. I'm going to research this some more.

Good work eric i am going through the exact same thing right with my 2003 yukon XL with a 5.3. It is throwing a p0305 i am hearing some noises in the bottom end at around 2500 rpm and the car idles like shit. I have done a power balance test by unplugging the coil packs, and the car runs the same on cylinder 5. I also preasurized the fuel pump and pulsed the injector with the power probe and it pules fine, i also tested compression and preasure was at 180 psi. I am stumped lol idk what to do!!!

@EricTheCarGuy We didn't get an accurate leak down with the gauge. We did hear slight air with shop air pressure applied coming from the crankcase. That might be just normal blowby. The actual compression loss might have come from a broken spring but the leak down would not show it because its forcing the valves closed. I know in my head what i'm trying to say, sometimes it doesn't come out so people understand lol. I know this one is out the door. Just something to think about,

Erick you are Exactly Right and the Reason I know this is I have seen it Before , You can see it on top of the Piston and at the Top of the Cylinder Wall. I have seen this 2 times before and I thought I was Crazy and now I see it again in your Engine I got the Clean Piston top on both engines and on one of them I got The Browning at the Top of the Cylinder but not in the Other. I believe you are Correct in your Assessment because that is what I determined also.

Always knew tolerences were close in engines. Im going to take your advice and start doing some engine work. Great video.

@MAzDA6780 I think your right, should have thought of that.

old video no I know but, Think you will find it was a porous piston, I rebuilt one engine 3 times before I discovered it was porous piston, only found it after id replaced rings and liner (old style engine) but still hardly any compression. I got so frustrated I swopped out piston 4 with 2, 2 being the one at fault low and behold 2 was testing good but 4 now was low on compression. Replaced piston all problems solved. I remember the piston looking clean like the one in your engine I suspected that it had been washed with unbent fuel.

Piston rings do spin on the piston while running. I have seen this problem on some 4.3s. Sometimes carbon can cause them not to spin correctly. Sometimes GM top engine cleaner can correct this. There is a excellent very old school chrysler training video on here that covers this subject very well. If you want the link give me a holler back.

I have had this issue two times in my motor issues and again I think u are spot on as looking at replay of vid you see it clear as day that the rings r too close. cant ignore this and anyway no other evidence would cause the systems

I've seen piston ring gap alignment in aircraft engines, cylinder bore look similar too.

@hobieslug45 I could buy a crack in the block or piston as the possible cause as well but nothing to do with the head.

looks to me like it lost a portion of the intake valve seat. In the shots of the cyl head you see a shiny spot on the right of the intake valve. It didn't become shiny from incomplete combustion. Something caused that, after all, aluminum heads are known to lose valve seats from time to time due to different expansion rates.

I am curious what would happen if they cut the rings at 45 degree angles in opposite directions on each ring. It would in theory eliminate any chance of gap alignment.

I know this is very old, and I'm not doubting anything, but I wanted to share some experiences as it was interesting. I have actually been part of Dyno testing to determine if ring stacking will affect compression, and we found two interesting facts. When lined up and assembled, we could see no difference in compression between cylinders with lined up rings and those staggered 90 degrees. What was even more interesting is that when disassembled after test, the rings had significantly moved. Those that were lined up no longer were, and some that were staggered were close to lined up. Given the carbon in this engine, if any rings were stuck, that could cause compression loss as well. A last rule of thumb is that ring Gap of 0.004 per inch of bore is about where you want to be for a street engine, as the ring heats, the Gap will close. If this is a 5.3, 0.015" Gap cold is pretty good.

Hello, Eric here is my 2 cents on this. I agree with you about the rings lining up causing the cylinder leakage. That engine was severely overheated which caused the compression rings to anneal and soften and collapse thus causing the rings to rotate ... my 2 cents .... Keith

@JTheGuitarPlayer With almost no compression I really can't see how it could produce any power really.

I'm wondering if it has a broken valve spring. During the leak down test both valves are closed. The pressure from the air in the cylinder during the test might have closed the valve completely. But doing a compression test the valve is opening and closing without pressure in the cylinder from shop air. If a spring is broken it will cause no compression on a compression test but might give different results on a leak down. Just a thaught.

@Michiganborn1969 I think Civic engine series unless something really cool comes up this Thursday.

So, what happens to the core when you send it back? Does it get melted down and recycled into metal for rebar etc? Or, is the core re-machined and turned back into a rebuilt engine? How much do you get for sending a core like that back to the scrap yard?

@dandim23 That's the plan unless something really cool comes up Thursday at the shop.

By the way i also tested the coil and i have spark, i even swapped out coil pack 7 and placed it on coil pack 5 with the same results. Idk but tomorrow i plan on passing a propane torch over the intake plenum to check for leaks near cylinder 5. The truck accelerates smooth but it does not idle okay. What should i do next?

I have one question. When you pushed that piston out of its bore, the ring gaps were about 180 degrees from the site of discoloration. Doesn't that in itself disprove the aligned ring gap theory?

looked lke there was a little bit of brown residue at the top of the cylender on the head as you said burnin oil

I firmly believe that the bore is out of round. that Brown film/Oil and gas mix that was left at the top of the cylinder was a low spot in the cylinder bore allowing the compression to pass by.

looks like a slow coolant leak in the head gasket. When you don't change coolant often it becomes acidic and bad things happen. The same with motor oil, when you don't change it often, the acidity destroys the seals and metal in your engine.

Hi from Scotland. Enjoyed your vids went on to 2007 Chevy series nice to see someone showing the unknown hidden and unexpected problems you came across, Only comment and its not directly aimed at the line up of rings, On a forum this came up about ring lining up some said the rings rotate when in use and some pistons have pins/stops built in stopping ring rotation. But what the hell engine replaced customer happy and liked the measuring of ring gap 1 way of various I use to measure cylinders.

Sounds maybe basic but did you check or find any blowby before the others tests?

Hey eric...thanks for all videos by the way..very helpful..I saw the heater core video u have but my problem is that when I turn heater on it smells like antifreez..I drive a 00 f150..what can u say to help?