2012 Yukon xl 4x4 eating antifreeze?

lifeisamystery · Aug 8, 2024

Let me start off with the fact that she runs perfectly. She's got the 5.3, no hiccups, no codes, no rough idle, live stream on the scanner shows no reds, etc. I have a generic scanner, but it's able to do almost everything a dealer scanner can do.

She's got 275k miles on her and she purrs like a kitten with all the get up and go of a good beastie

THAT BEING SAID

After our 2500 mile cross country trip hauling 7 people, all their crap and a 4klb trailer (all out we weighed just over 11k lbs, yes I know, well over her limit, but we didn't have much of a choice, so we took it easy and kept a close watch on her and her fluids, etc.) she has started going through about a qt of 5w30 full synthetic every month, and about a gallon of coolant over 3 months. Oil looks good, she could use an oil change, but there are no particulates, and it's not milky at all. Using dexos coolant, no leaks of any kind, anywhere in or under the rig. No oil buildup of any kind anywhere in the bay or under the rig, and trust me, I'm skinny, I've crawled all over her and checked. The other thing she's started to do is rev up and down at stop lights. Nothing extreme, she goes back and forth from 600-1200, but that's only at an idle, doesn't matter if I'm in drive or neutral.

SO, my question is this: Should I be concerned about the disappearing fluids, or is this simply the symptom of an a high mileage motor? Normally I wouldn't be concerned about the oil consumption in an older rig, but the addition of the disappearing coolant has me wondering. I've driven and kept up on high mileage vehicles all my life, and the coolant thing is a new one on me with no apparent leaks. I don't have access to a pressure tester, so unfortunately I can't help there.

Any help, advice or experience is greatly appreciated

donjetman · Aug 8, 2024

Send an oil sample to a lab and have it analyzed.

Fless · Aug 8, 2024

If it's burning the coolant, your cats -- the precious metal ones -- will run out of their nine lives sooner than later.

lifeisamystery · Aug 8, 2024

Fless said:
If it's burning the coolant, your cats -- the precious metal ones -- will run out of their nine lives sooner than later.

I did smell cat a few times, but that was months ago and it hasn't happened since. What would happen if the cat found a new home?

j91z28d1 · Aug 8, 2024

do as said above, send oil sample.

these things do have a history of posts around here of hard to find coolent leaks, they can seep so slowly it drys before you see it. usually it's the plastic T's by the fire wall or the radiator end tanks, you can't really see it till you pull to replace. if it's original, it's passed do anyways.

the fluctuating idle is concerning. normally I'd say vac leak, but don't know I've heard of one of these without a cam with rolling idle. hopefully it's not a crack somewhere it shouldn't be. that oil sample will tell you a lot.

do you have afm active? do you have a catch can? all of these benefit from a 30$ catch can.

lifeisamystery · Aug 8, 2024

j91z28d1 said:
do as said above, send oil sample.

these things do have a history of posts around here of hard to find coolent leaks, they can seep so slowly it drys before you see it. usually it's the plastic T's by the fire wall or the radiator end tanks, you can't really see it till you pull to replace. if it's original, it's passed do anyways.

the fluctuating idle is concerning. normally I'd say vac leak, but don't know I've heard of one of these without a cam with rolling idle. hopefully it's not a crack somewhere it shouldn't be. that oil sample will tell you a lot.

do you have afm active? do you have a catch can? all of these benefit from a 30$ catch can.

I don't currently park over a catch can, but it's something I'll do for a while to see what I find. I park over white gravel, have for months with no discoloration of any kind. As for the afm, I may be mistaken, but I don't believe mine has it. It's got the 6 speed tranny as well. It may be that the previous owner has the afm deleted, because there is absolutely no change whatsoever at cruising speed and no indication of any kind that it's switching down to 4 cyl mode. I'll see about the oil sample though.

j91z28d1 · Aug 8, 2024

lifeisamystery said:
I don't currently park over a catch can, but it's something I'll do for a while to see what I find. I park over white gravel, have for months with no discoloration of any kind. As for the afm, I may be mistaken, but I don't believe mine has it. It's got the 6 speed tranny as well. It may be that the previous owner has the afm deleted, because there is absolutely no change whatsoever at cruising speed and no indication of any kind that it's switching down to 4 cyl mode. I'll see about the oil sample though.

a catch can is a small can that mount between the valve cover oil source and the intake vacuum. the air flows over a mesh inside, the oil sticks to it and drains down into the bottom to remove. there's a bunch of threads about it on here. it works, I consider my engine to be pretty tight and it still collects more than expected and that's all oil not being dumped into the intake ports. it might help with your oil usage. it's said as they burn the pvc system oil for years the piston rings develop build up and don't seal as well, using even more oil from the other side.

I never remember what got afm and what didn't. if it was activate I was going to say around here most believe it can contribute to your oil usage too. good that you don't see it say 4cyl mode on the dash.

swathdiver · Aug 9, 2024

lifeisamystery said:
Any help, advice or experience is greatly appreciated

Inspect all of the spark plugs. If she was turning over 3,000 rpms a lot on that trip, she'll go through a bit of oil. Check out all the cooling system tanks and lines and look for small leaks.

Geotrash · Aug 9, 2024

lifeisamystery said:
Let me start off with the fact that she runs perfectly. She's got the 5.3, no hiccups, no codes, no rough idle, live stream on the scanner shows no reds, etc. I have a generic scanner, but it's able to do almost everything a dealer scanner can do.

She's got 275k miles on her and she purrs like a kitten with all the get up and go of a good beastie

THAT BEING SAID

After our 2500 mile cross country trip hauling 7 people, all their crap and a 4klb trailer (all out we weighed just over 11k lbs, yes I know, well over her limit, but we didn't have much of a choice, so we took it easy and kept a close watch on her and her fluids, etc.) she has started going through about a qt of 5w30 full synthetic every month, and about a gallon of coolant over 3 months. Oil looks good, she could use an oil change, but there are no particulates, and it's not milky at all. Using dexos coolant, no leaks of any kind, anywhere in or under the rig. No oil buildup of any kind anywhere in the bay or under the rig, and trust me, I'm skinny, I've crawled all over her and checked. The other thing she's started to do is rev up and down at stop lights. Nothing extreme, she goes back and forth from 600-1200, but that's only at an idle, doesn't matter if I'm in drive or neutral.

SO, my question is this: Should I be concerned about the disappearing fluids, or is this simply the symptom of an a high mileage motor? Normally I wouldn't be concerned about the oil consumption in an older rig, but the addition of the disappearing coolant has me wondering. I've driven and kept up on high mileage vehicles all my life, and the coolant thing is a new one on me with no apparent leaks. I don't have access to a pressure tester, so unfortunately I can't help there.

Any help, advice or experience is greatly appreciated

At 12 years old and 275K, she's due for new coolant tees at the firewall heater hose connections. They often start to signal they're failing by cracking slightly and seeping coolant. You can run your fingers under them when the engine is cold and check for coolant residue. Either way, it's past due if they haven't been done already, and if they fail, you're on the side of the road with an overheated engine after all of the coolant got pumped onto the highway over about 10 seconds.

You'll need these to do the job:

More Information for DORMAN 626553

More Information for DORMAN 800413

More Information for DORMAN 800414

Plus some heater hose, appropriate spring clamps, and coolant. Early versions of the Dorman brand tees had a poor reputation, but I've found more recent versions to hold up just fine. The Dorman brand hose I linked has a metal wye in it, so it's preferred over the factory part.

I would also be looking at the radiator end tanks. With that mileage, the radiator is also likely due and probably seeping through micro cracks. And if you have the coolant tees out, you might as well replace the radiator, water pump, thermostat and hoses, too. Chances are this will solve all of your coolant loss problems, unless it's a head gasket, which isn't common on these. I consider these items normal maintenance on these trucks, so I did them proactively on both of my Yukon XL's.

the blur · Aug 28, 2024

I just went through this on my 6.2L motor. monthly top off of coolant. It's a radiator. Finally got bad enough to find it.

2012 Yukon xl 4x4 eating antifreeze?

lifeisamystery

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