Anyone have any sense for whether the 6.2 failures occur only at highway speeds? Most (if not all) of the stories I've read about have occurred on the highway, presumably at or over 65 mph. I haven't read about a failure occurring in town/in stop-and-go traffic.
Seems to be a number of failure modes.
I posted a YouTube link earlier in the thread of a Cadillac Escalade that failed at the dealer with 4 miles on the engine. Broken connecting rod. This was clearly a wrist pin that walked sideways and jammed the piston in the cylinder. The rod bearing was fine. So this was clearly not an oiling problem.
Most of the highway failures IMHO and based my research have been bearing failures of some sort. Maybe we are only hearing about engines failing on the highway because is can be rather dangerous depending on the situation. Maybe any pre-failures where the engine is noisy are taken to shops before the engine siezes. Maybe there are engines siezing when in town or while idling that nobody is really speaking out about? But given the loading the 6.2l can put on rod bearings due to the high torque at lower RPM's I can see a lot of failures on the highway.
I think most of the bearing failures are oil related:
1. Lack of oil, oil consumption causing the oil level to drop and the low oil light does not come on until the oil is 2+ quarts low. If you own a 6.2l you NEED to check the oil at every other fill up. The stupid dipstick also will not have oil showing if the engine is 1 quart low. You should fill the crankcase up to the dipstick shows oil to the TOP of the hash marks, even slightly above is fine. I run 9 qts in my engine at oil change with filter, the engine really needs somewhere between 8.5-8.75 qts at oil change even though documents indicate 8.0 qts with filter.
2. 6.2 has a 2 stage oil pump, I question the pressure/volume available during high loads at highway speeds with 0W20 engine oil. The 5.3l has the same basic oil pump, but not the ECM 2 stage presure control. I have it from a few sources that the 5.3l runs close to 60 PSI at highway cruise, my 6.2l runs at 45-46 PSI at about 75 MPH/1600 RPM as measured with an advanced scan tool that interogates the oil pressure transducer. This pretty much matched the area the oil pressure gauge as shown on the dash, but with no numbers other than 0 and 120 it is hard to tell based on how far to the left of the center mark!
3. Fuel contamination in the oil either by itself and or oil that is contamined with fuel but it 1-2 quarts low on a regular basis.
4. Higher mileage failures are more likely due to long term exposure to fuel contaminated oil, low oil levels, long OCI's, causing bearing damage due to the 3 above issues and/or LSPI bearing damage.
5. So far I have seen 3 typical failures, but it would nice to have a wider sampling of failures.
A. Front main bearing failure often coupled with #1 and #2 rod bearing failures. These tend to be early failures, often under 10,000 miles, but not always. IMHO clearly oil starvation, oil quality issues. The accessory drive belts may load the crank snout a bit and without enough oil/oil pressure/oil volume, lower viscosity oil due to fuel contamination, this area is the dead last path on the engine oil flow. Maybe the talk about oversize lifter bores factors into this, I could see how it could and would, but we do not have a good idea of how many engines and what timeframe this could have been an issue, sure there was a bulletin or a number of bulletins because they kept extending the window for oversize lifter bores. And are these engine cores being returned and if the lifter bores are oversized, what is being done to address these before the same engine block is rebuilt and sent out? Are they scrapping these engine block or sleveing the lifter bores?
2. Thrust bearing failures. Not sure if this is just the thrust portion of the center bearing or the entire center bearing is failing. Possibly agrevated by towing? But again, oil condition, lack of oil or oil contamination are the first obvious concerns.
3. Other rod bearing failures, most likely oil, lack of oil or oil contamination are the first obvious concerns. Could also be due to piston clearance issues, piston pin walking causing bearing to crank interferance leading to premature bearing failure? LSPI? Could be possible quality issues with bearings, but I would expect to see a much larger amount of failures if this is 100% a bearing quality problems.
4. Not sure I have seen too many main bearing issues other than the #1 and the thrust bearing. Maybe they are out there and I just have not seen them.
5. It almost seems that the DFM lifter issue is scarce now. Maybe with all the premature bearing failures, the lifters have not had a chance to get the hours and miles on them to fail? Maybe they have made improvements with the lifters?
I still think the number of reported cases that have been reported to the NHTSA are low in compared to the number of overall failures. If someone has a failure, even if it is not at highway speeds, please report to the NHTSA so they have a better idea of the number of failures.
Drive defensively and make sure you have a way to the shoulder if you experience a failure. I hate when I get boxed in traffic or have a construction area where there are limited or no shoulders these days! I have actually altered by driving style to expect and deal with a siezed engine while on the highway these days. Not a fun way to drive and to have this nagging in the back of your mind. But as I say, it is what it is. I just do not need the wife and family in the car if there is a catastrohic failure! If that happens a Toyota minivan will be in my future.
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