Greetings:
I have a 2000 GMC Sierra 1500 with the 4.8 V8 with 204K miles.
Background (long - sorry): I bought the truck at 184K miles in 2011. I didn't get a service history but the engine ran fine and the oil looked OK. It has had regular oil changes since I got it. It is a limited use vehicle now so it only gets an oil change about one a year as it is lucky to get 3000 miles put on it in that time. About a year ago, I started to get noisy lifters so I added a pint of MMO about 500 miles before the next oil change. The lifters got somewhat better but were still intermittently noisy. Oil pressure seemed normal based on the gauge reading. When I pulled the oil plug after 500 miles, nothing came out at first so I pushed a screwdriver in and several chunks of soft, almost black sludge came out before the oil started flowing. Inside the filter I could see an inch or so of sludge at the bottom of the center tube.
I thought that the MMO may have done some cleaning and caused the sludge to show up in the pan and filter so I didn't give it much thought. I refilled the engine with SuperTech Full Synthetic 10W30 and used my usual AC PF61 non-ecore filter. After about 2500 miles the lifter noise came back so this time I added some Rislone concentrate and planned to change it in 500 miles. The Rislone really helped the lifter noise.
This week, 500 miles had passed since I added the Rislone (about 3000 miles total on this oil) so I changed the oil. I made sure the engine was hot when I pulled the plug. Clumps of sludge came out again and this time the filter was completely filled with sludge! The oil had a reddish tint to it - could that be from the Rislone or something else? The sludge is very dark brown (almost black) and is soft. Could this be sludge loosened up from the Rislone - or is this likely to be coolant contamination? I had always thought that these "LS" engines were pretty immune to internal coolant leaks as they have a dry intake. Some have reported cracked heads on these but that was listed as starting in 2001 in a GM service bulletin that I saw online.
The PCV valve is working and I don't have the typical light brown "chocolate milk" on the inside of the oil cap that a blown headgasket or cracked head might cause. The engine has been "using" coolant over the past year but I chalked this up to a small leak that I can smell when the engine is hot but haven't been able to track down.
Does this sound like an internal coolant leak? Thanks for any advice.
Andrew S.
I have a 2000 GMC Sierra 1500 with the 4.8 V8 with 204K miles.
Background (long - sorry): I bought the truck at 184K miles in 2011. I didn't get a service history but the engine ran fine and the oil looked OK. It has had regular oil changes since I got it. It is a limited use vehicle now so it only gets an oil change about one a year as it is lucky to get 3000 miles put on it in that time. About a year ago, I started to get noisy lifters so I added a pint of MMO about 500 miles before the next oil change. The lifters got somewhat better but were still intermittently noisy. Oil pressure seemed normal based on the gauge reading. When I pulled the oil plug after 500 miles, nothing came out at first so I pushed a screwdriver in and several chunks of soft, almost black sludge came out before the oil started flowing. Inside the filter I could see an inch or so of sludge at the bottom of the center tube.
I thought that the MMO may have done some cleaning and caused the sludge to show up in the pan and filter so I didn't give it much thought. I refilled the engine with SuperTech Full Synthetic 10W30 and used my usual AC PF61 non-ecore filter. After about 2500 miles the lifter noise came back so this time I added some Rislone concentrate and planned to change it in 500 miles. The Rislone really helped the lifter noise.
This week, 500 miles had passed since I added the Rislone (about 3000 miles total on this oil) so I changed the oil. I made sure the engine was hot when I pulled the plug. Clumps of sludge came out again and this time the filter was completely filled with sludge! The oil had a reddish tint to it - could that be from the Rislone or something else? The sludge is very dark brown (almost black) and is soft. Could this be sludge loosened up from the Rislone - or is this likely to be coolant contamination? I had always thought that these "LS" engines were pretty immune to internal coolant leaks as they have a dry intake. Some have reported cracked heads on these but that was listed as starting in 2001 in a GM service bulletin that I saw online.
The PCV valve is working and I don't have the typical light brown "chocolate milk" on the inside of the oil cap that a blown headgasket or cracked head might cause. The engine has been "using" coolant over the past year but I chalked this up to a small leak that I can smell when the engine is hot but haven't been able to track down.
Does this sound like an internal coolant leak? Thanks for any advice.
Andrew S.
