Tonyrodz
Resident Resident
Does the high mileage oil have extra detergents in it? What's different about it?
What did you do to your NBS GMT800 Tahoe/Yukon Today?
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clandr1
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Here's a pretty succinct summary I found online. This could all be snake oil for all I know, but it's worked for me so I'm sold on it, even if it is nothing more than a placebo.
What makes high-mileage engine oils different?
High-mileage oils have ingredients to take care of older engines, like conditioners, seal swells, antioxidants, detergents and wear or friction additives. Typically they use a viscosity modifier that is durable and won’t lose viscosity very easily. These oils need to stay thicker longer to protect engine parts.
Here is a longer description from the Mobil 1 site:
PdsDetailsPage
Mobil 1™ High Mileage oils are advanced full synthetic motor oils designed to help extend the engine life of vehicles with over 75,000 miles and to protect for up to 10,000 miles between oil changes*.
www.mobil.com
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NoReverseYukon
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$336 !!!
Uh, no.
iamdub
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Got my oil pan dropped today and that sumbitch is FULL of sludge! Boy am I pissed. I COMPLETELY cleaned this pan out when I replaced the gasket and pickup tube in 2017. Since then I have changed the oil every 5,000 miles with Amsoil XL series oil and either a Mobil1 filter or a Wix XP filter. I'll admit though, the last 2 oil changes I used Mobil1 oil and then Walmart Supertech Full Synthetic for the last oil change. (about 3 months ago). In the bottom of the pan there is a THICK mud like sludge, and on the baffle, there is some hard caked up sludge that is flaking off in chunks kind of like rust. It also has a slight metallic color to it. Can anyone with more insight than me explain WTF is going on here?
How does the rest of the engine look? Same sludge caked on the inside of the block, on the crank, end caps, etc? Once you pull that timing cover, you'll know if it's the engine or if it's the quality oil you're using doing its job. I'm betting/hoping it's just sludge that's been dissolved off the innards by the detergents in the oil. Do this mill have a persistent coolant loss?
ScottyBoy
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Got the timing cover off and yes, there is a layer of sludge on everything. Not NEARLY as bad as the sludge in the oil pan, but it's definitely a thin layer there.
And yes, I did have a coolant leak. The water pump gaskets were leaking. I kept putting it off because it was such a small leak. I would have to add no more than a quart of coolant about every 3-4k miles. It was such a small leak it took me MONTHS to find it. No coolant actually dripped onto the ground.
Another thing I'm wondering about is slack in the timing chain. I have a good bit of slack in the chain (or at least I would consider it to be excessive slack). I can move the chain over with my finger almost 3/4 of an inch.
How many miles did you say that engine has on it? The NBS don’t have a tensioner on the timing chain so they do have slack. I put a new one on mine at 150k when I did the cam and I wanna say the original had probably 1/2” of deflection. New ones have about 1/4” IIRC. If you’re really high mileage it might be normal. Hopefully others will chime in, I’m going off an old mans memory which has been known to be faulty lol.
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ScottyBoy
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I'm at 160k miles. And yes it has just over 1/2" of side to side deflection, probably closer to 3/4".
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Hows the sprockets ??
( I changed them also)
( I changed them also)
Have a look at this video of a new install. They run loose, Google it. https://www.performancetrucks.net/f...ons-158/holy-loose-timing-chain-video-508377/
ScottyBoy
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Sprockets appear fine, other than having a film of sludge on them.
And that video is about how loose mine is. If that's normal then that makes me feel a lot better.
Something else I've been thinking about.......I had a small coolant leak at the water pump, but the timing cover was also leaking. I'm wondering if coolant has been contaminating the oil and causing premature wear and sludge. It definitely wasn't enough to cause "milkshake", but it does due to the condition of the gaskets, it's highly likely that some coolant has been getting into my oil by running down and dripping in thru the timing cover gasket. I do remember a few year ago some trace amounts of coolant showed up on a used oil analysis test, but the following test showed even less so I ignored it and didn't get it tested again after that.
iamdub
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No way was there enough coolant or was your timing cover leaking badly enough to let that much coolant into the system to do anything. The coolant leaking was such a small amount that it just evaporated off the surface of the hot engine block.
I meant internally when I asked about coolant loss, as with a failed head gasket or cracked head or block. A couple years ago, my brother made a fast righthand turn in his '05 Sierra and lost oil pressure. I found that he had the Castech 706 head failure. It was then that he revealed that he's been having to add coolant fairly regularly, but never saw nor smelled it nor did he have a milkshake. He also said his average oil pressures have been lower and lower over the past few months. The driver side cylinder head was cracked around a head bolt and allowing coolant to mix with the oil. It was just enough to not be noticed since the water steamed off and went out with the PCV and exhaust, but the rest of the coolant's chemicals mixed with the oil and made sludge. It was darker and much thicker than what's in your timing chain slack pics. Anyway, when he made that fast turn, a hard flake of sludge, presumably from the bottom of the sump, broke free and stuck to the screen of the pickup tube, blocking the flow.
Everything inside of the block was coated in thick, sticky sludge. I scrubbed the block by hand with plastic-bristled brushes, degreaser and brake parts cleaner. Replaced all lifters, push rods, rockers, the timing set, both heads, got a high-volume oil pump (but used the lower pressure relief spring), all new gaskets, etc. It's been running strong ever since and the oil pressure exceeds 70psi at redline.
I guess my point is for comparison. Your sludge is light and thin compared to what he had. This is why I really think yours had worse sludge from whatever past issue that has been remedied, and the detergents in the oil you're using are still breaking it down. You're slowly cleaning out the entire inside of the engine. You could manually do it if you wanted, or continue as you have been. Eventually, it'll all be dissolved and drained through normal oil changes.
Tonyrodz
Resident Resident
Even out of the oil pan itself? I think that's part of what's happening in my van--05 4,8. I occasionally had to add coolant to my overflow bottle. Probably had to 1/2 fill the overflow bottle every other month. Pretty sure one or both of my 862 heads has a crack. I read somewhere online that the 862's are somewhat prone to cracks, not as common as the Castech heads. Since I added some Blue Devil to my radiator about 1 yr ago, my coolant level has been rock steady. I still keep my oci at 2500 miles and it always comes out black. I thought it was because I have to floor it alot just to move, but now I'm not so sure that's the only reason. BTW--my chain also had alot of slack in it. At the time it had under 150k on it. Still has the original chain in it.
iamdub
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Yeah, if it stays thinned out enough. Although, the pan would be the last to clean itself since the sump is where all the stuff settles and solidifies. Unless you guys wanna drop the pan ever so often to scrub it out...
Personally, if I had the pan off, I'd try to clean as much out of the block and off the rotating assembly as I could. It would really suck doing this underneath the engine with all the goop dripping down on you, but would be worth it. I'm a fan of the Super Tech degreaser and brake parts cleaner from Walmart cuz it's cheap and effective. Wear your PPE! Might as well pop off the rocker covers and scrub the insides of the heads, too. Between the block, rotating assembly, heads and timing chain area, there's really not much else where sludge would need to be cleaned from. Continue using good oil and it'll be clean much faster. Hell, you'd probably be safe to use a chemical flush at that point since there shouldn't be enough sludge to break free and clog up the system. But, slowly dissolving it away with the detergents in the oil is the safest bet.
blueinkd
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Wow. My intake valley and valve covers were super clean when i was working on upper intake back in March. Both me and my friend were shocked at how clean it was. Mind u I have only had the truck for 3-4 years now. Had like 180k miles when I got it in a trade. Needed major TLC but engine ran right
I figured it was a good indication of good maintenance
I figured it was a good indication of good maintenance
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iamdub
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Good maintenance is the key!
Here's mine when I cracked it open at 200K:
Growing up doesn't have to suck
Man DUb, that thing looks stellar... Cam swap and gaskets with oil pump, DOD delete and slap back in... I would not hesitate to run a motor looking that good in cylinders for another 200k... Ya know, the only gasket that was leaking was the oil pan gasket had a small weep. Someone had been in...
www.tahoeyukonforum.com
latvius
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Changed the windshield fluid reservoir and replaced both motors for the heck of it.
Two days ago, I finally did the Cabin Air Filter retrofit kit from Dorman. I had purchased it a long while back, but hadn’t gotten to it yet. I also bought a “hot knife”, thinking this would make the job a lot easier, and cleaner… that knife lasted all of about 5 minutes… the “chrome” part that holds the blade is actually brass, with a chrome plate on it.. POS started flexing, so I tightened it, and took my time… but even doing that, the damn thing broke right away. I even tried to drill it out, as it comes with a spare, but when I went to remove the broken threads, the whole assembly broke, and dropped into the iron sleeve. Lesson learned.. if you want a hot knife, you’ll have to spend the $100+ to get a real one… so moved to the dremel plastic blade, and the good ol’ utility knife. I’ve gotta say, for as simple as this little project should be, it was a royal PITA in my opinion. Glad it’s done, but not anything near as clean as I was aiming for. And yes, I did get the one screw that’s impossible to get out / back in, in place where it belongs..
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