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2006 sts v
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66 Posts
Discussion Starter #1
Just had the radiator, thermostat and water-pump plus the hoses replaced on the V.

I believe it was too full of coolant as it boiled it out 2 times on me. Now cold, the level is under the "full-cold" mark.

Still concerned about it boiling over....does the radiator have a standard radiator cap? What are the tell-tale signs of bad head gaskets. Thanx for the info.
 

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'06 STS-V, '17 CTS-V
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776 Posts
Never heard of a "too-full" coolant scenario. The pressure should self-regulate through the radiator cap on the reservoir. That being said, it may boil over if it has been overfilled, but then settle in at the full mark. A bad water pump may cause hot spots to develop bc coolant isn't circulating properly, boiling the coolant. A stuck thermostat could be responsible too, as could a corroded radiator or plugged coolant line. Sounds like if it is anything BUT the head gasket, you've eliminated it in the prior service you describe. I'd do a CO test on the reservoir. Run the car, and if the test determines CO, it'll sadly 99% be a head gasket. How many miles?
 

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2006 STS-V and 2007 STS-V The Murdalac
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1,905 Posts
Head gasket problems are pretty rare on the RWD northstar motors. Leaky water pumps are not as rare. Check the water pump.
 

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'06 STS-V, '17 CTS-V
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He just replaced the water pump and t-stat though, Tim. Short of getting a new but "bad" t-stat, which I've both seen and had happen to me multiple times before with other cars, I really don't see how it could be anything else than the head gasket, no?

I'd first try another t-stat (though typically old/used n* lc3 t-stat'swill stick open, forcing the engine to run cooler, perhaps you got a flawed t-stat that due to some manufacturing irregularity is stuck closed) and see if the problem persists. Cheapest, most likely, and easiest first. Then the water pump. Then run it till it smells sweet and/or belches white and/or water is present in the oil and/or co is present in the antifreeze, because you're outta options at that point...
 

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2006 STS-V, 2004 Pontiac GTO, 2008 Pontiac G8 GT, 1999 Chevrolet Suburban LT 4x4
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No radiator cap. Just the overflow tank cap.

It won't "boil-over" if your gauge is in the proper operating range. That is usually at the half mark to the notch just below the half mark.

A sign of a bad head gasket would be;
1) Engine oil would look like a milkshake. This is from oil and coolant mixing.
2) Dexcool in the resevoir that looks dark/muddy. (Dexcool is orange'ish/pink when clean).
3) You would notice leaking under the car after sitting overnight and you would definitely smell the sweet smell (like maple syrup).

N* head gaskets on FWD versions (such as RPO L37's, and some LD8's) were notorious for head gasket issues and/or warpage and requiring re-studding. LC3's (what we have), typically are not. One area that can have issues from leaking outside of head gasket issues (My LD8 did), was freeze plug leaking.
 
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