I just bought a 99 Sierra with a 5.3, unknown mileage but odo went blank at around 190K a year or so ago I was told. I was told the truck broke the starter (off the bellhousing?) while driving down the road. was towed home, had starter replaced to find that one of the rear cylinders was full of coolant. he said he replaced headgaskets and exhaust gaskets and necessary gaskets as well. the truck has about 100 miles on rebuild and seems to run fine. sometimes the starter does sound odd when cranking though. Ive had these trucks and personally never heard of the 5.3 blowing a headgasket. unless it was ran out of coolant and was completely overheated how common is this? Should I get rid of the truck due to risk of this happening again? thanks for any help... I know these motors are super tough, trans not so much.

 

I knkw some starters need shims to get them to work properly.. if it wasnt properly installed/shimmed then that could be the weird noise occasionally.. if the truck seems to run fine and dosent use alot of oil or coolant then i would run it.. when engines begine to smoke, knock, use oilor coolant then thats when i get alittle weary lol

 

I cant tell that its using oil or coolant yet but it does run a little rich because the connector to the ECTS is screwed up so the truck always thinks that it is cold so it dumps extra fuel? I was mainly just wondering exactly how someone manages to blow a 5.3 since its something you never hear of happening lol

 

if its running rich on the start up maybe the starter is having trouble because its cranking longer to fire the engine.

 

its not taking longer, just while its cranking for that short time the starter has a somewhat higher pitched noise that I figure maybe because its aftermarket? havent had time to even see what kind it is or how its installed.

 

I'm not 100% sure, but some of the early NBS trucks might have used different head gaskets that were more likely to blow than the new MLS ones.

Also, I have 220k on my stock 4L60E so don't believe everything you hear about them being junk.

 

Do you have Castech heads on that 99 5.3? Post a vid of your starter noise if you can.

 

You likely hit the nail on the head for the coolant issue. There have been quite a few of the Gen-1 Avalanches that had Castech heads fail.

 

How about when the starter blew maybe it took some teeth off the flywheel and sometimes it catches those spots

 

couple of things to check, either:

-cracked head as already stated, those castechs were crap
-or, pull the starter and check to see if it was shimmed

better yet, search the castech thread to see the make/model and years for a possible bad batch and drop to the starter. that should give you an idea