a co-worker bought a 4.8L-powered '09 Silverado with 120k on the odo from a local used car lot. as-is, no warranty. ten days later, it rattles for a minute then quits running. starter engages but does not crank the engine.
he has it towed to dealer. dealer says "it's not the starter. internal engine failure." and they can't say more until they tear it down. dealer also said that the engine in the truck is not the original engine. dealer noted that the oil level is high (but did not say how high). so it's on hold for a while as we try to gather some info.
i'd like for it to be something simple like a torque converter bolt backing out and jamming between the flex plate and the block. i have no doubt that the engine replacement was done by podunk joe's E36 M3-stain garage, so i wouldn't be surprised to see something like this.
question: does the 4.8L have a known failure mode that would stop the engine from turning? oil pumps, timing chains, piston breakage, etc?
miatame
HalfDork
11/21/11 3:27 p.m.
Ouch...that's surprising. At least 4.8L are cheap and this shouldn't be a nightmare to get back on the road. Hopefully it is something easy to fix though. Can't help sorry.
A coworker today showed me the Hot Rod magazine issue where a higher mileage 4.8 is cleaned up (somewhat) and using a lot of factory parts and head work and turbos, kicked out 1,200 HP at the crank.
I'd start looking for another motor now and track down a yard that will sell you one with a bit of warranty.
I have heard in the 5.3 after 07 the pistons like to ventilate things around them. So maybe something similar? Or it is hydrolocked from fuel.
Now what i have seen with my own two eyes are the lifter retainers are cracking with mileage and allows the lifter to rotate and jams the cam in place. Doesn't provide enough shock to break the chain, just jams everything up.
Yup-a Junkyard replacement with sub 50k is sub $500.
a 3 year old truck that has shelled 2 motors now?
damn- that thing must have seen some abuse..
4.8'S Are not common to grenade. In fact, they have been the most durable of the vortec line of LSx engines. I've seen dozens over 250k miles. Many have the CSK (Cold Start Knock) issue when cold, but almost all that have had them have done it for 200k miles+. i'D say something is wrong there.
Bobzilla wrote:
4.8'S Are not common to grenade. In fact, they have been the most durable of the vortec line of LSx engines. I've seen dozens over 250k miles. Many have the CSK (Cold Start Knock) issue when cold, but almost all that have had them have done it for 200k miles+. i'D say something is wrong there.
And the CSK thing is just that they used some sort of alloy in the pistons that expands a lot when it heats up. So they had to make the pistons so they were a bit undersized when cold, and they rattle around until they come up to operating temperature.
I have 227K on my 99 4.8 GMC Z71
I switched from Mobil 1 to Royal Purple-the "cold rattle" isn't as noticable, sometimes not existant
Mine is particular about gas-would often ping on 87 so I've run 92-93 octane since I bought it used about 5+ years ago.
4x4 ext cab I average 15 mpg back and forth to work, cat back exhaust and cold air intake but with off road tires.
I'd also check the A/C Compressor. My sons Impala-it started to rattle and then locked up-the engine would not crank. Try to remove the surpentine belt and see if it starts.
