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Coolant loss, overheating. Can't figure out where its going ? 2012 1500 4.8L

Gn2

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Gn2 New Member

Gn2

Posted
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Hi, I have a high mileage 2012 Sierra 1500 with the 4.8L. Its a 2 wheel drive extended cab. I have been experiencing coolant loss, and overheating when the coolant level gets low. Its the weirdest thing, I can't for the life of me figure out what's happening to the coolant. There's no white smoke, it starts and runs great, no coolant smell anywhere, no puddles, drips, nothing. 

I watched the level in the coolant tank for a couple of weeks and it didn't change, then I went on a 20 minute highway run and lost about 2 jugs worth. Its mostly fine, then does something like this. 
I'd like to take it on a longer trip, but need to get this fixed before I trust it.

 

I've had a mechanic look at it, they can't find anything either. I don't want to go changing stuff willy nilly, if anyone has any suggestions please let me know. 

Brian715 Enthusiast

Brian715

Posted
Posted

I had a lumina do this to me. Exactly the same. Would be fine and then spit everything out at random. Decked heads and put it back together fixed it. 

 

Gn2 New Member

Gn2

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Posted

Thanks for all the replies, but I have to say, its pretty depressing to think that the most likely reason for symptoms like this is such a huge cost to repair, and apparently extremely common in GM trucks.

swathdiver Senior Enthusiast

swathdiver

Posted
Posted
10 hours ago, Gn2 said:

Thanks for all the replies, but I have to say, its pretty depressing to think that the most likely reason for symptoms like this is such a huge cost to repair, and apparently extremely common in GM trucks.

No, it's not common compared to how many are sold, it's just common here, where people come for help.  Compared with other makes, the engines are not expensive to repair or replace either.

  • 4 weeks later...
2003 Chevy Silverado Enthusiast

2003 Chevy Silverado

Posted
Posted

I had a 2004 Silverado and I had the same problem. Ended up having both heads cracked. Coolant would be allowed in and it was come out from the exhaust which gave me my answer where the coolant disappeared to. Luckily my brother is a diesel mechanic so he did the repairs for me but it was costly. I hope it works out. Good luck.

Gn2 New Member

Gn2

Posted
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Following up in case this helps anyone else. It turned out I was very lucky, it was a corroded clamp on a hose underneath(sorry, not sure exactly where, I'm not a mechanic, I was just trying to figure out the problem) that only leaked after the system was pressurized and the temp was high enough. Had all clamps and hoses that were deemed suspect replaced, and the transmission cooling lines done too, since they were apparently in poor condition and at risk to fail at any time. Got away with $520. bill, including all parts. I feel really lucky after hearing about all the horrible other possible causes of disappearing coolant. Thanks to everyone for your replies. 

Now my temp comes up quite a bit more slowly, and doesn't over heat. I don't lose coolant any more either. My mechanic had feared the worst before finding the leak at the clamp, since neither of us could see any sign of it initially. 

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