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Discussion Starter · #1 ·
I have a 3800 series 2 and a couple winters ago it started leaking coolant internally and the car wouldn't run. After doing research I discovered the upper plenum was often the cause, so after spring rolls around and it warmed up I replaced the plenum and car ran fine.... until the following winter when the car did the same thing first time it got cold outside. so after doing more research I discover that the lower intake gaskets can go bad. So after spring rolls around I replaced the lower gaskets and car ran fine... until the next winter when as soon as it got cold internal coolant leak again??? So this past winter I did nothing to fix the issue and let the car sit all winter and as soon as it warmed up topped off the coolant and car runs fine....

So my question is what could possible be causing an internal coolant leak only when its below freezing outside?

I've searched the web for the last couple years and cant find a single post on this. Any help is appreciated.

Thanks in advance!
 

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Everything expands and contracts with temperature. It's hard to say for sure where your leak is without seeing the car myself. Are you saying it's internal because you don't see a puddle on the ground or is it because your oil is milky? If your oil is milky it's either intake or head gaskets. I've never heard of a blown head gasket on an NA car. If your oil isn't milky make sure your heater elbows aren't cracked or leaking. Even new ones are hit or miss.
 

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Discussion Starter · #3 ·
Everything expands and contracts with temperature. It's hard to say for sure where your leak is without seeing the car myself. Are you saying it's internal because you don't see a puddle on the ground or is it because your oil is milky? If your oil is milky it's either intake or head gaskets. I've never heard of a blown head gasket on an NA car. If your oil isn't milky make sure your heater elbows aren't cracked or leaking. Even new ones are hit or miss.
No coolant in oil. Its getting into the combustion system somehow and coming out through exhaust? Elbows have been replaced with aluminum.
 

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No coolant in oil. Its getting into the combustion system somehow and coming out through exhaust? Elbows have been replaced with aluminum.
Coming out the exhaust? Are you sure? Is it puffing a lot of white smoke? White steam is on startup is normal if it's freezing outside. How is your coolant level? Are you frequently topping off?

Be careful with those elbows. A lot of people swear by the aluminums, but they often require some work to get sealed.
 

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Also, how did your intake look? Most of the time, corrosion on the blank spots is totally fine. However, I've seen some pictures going around of people with pitting so bad that it goes all the way through to the plenum. That could could be a cause, but the car would have to be pretty seriously neglected for that to happen.
 

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Discussion Starter · #6 ·
Coolant level is fine I am driving the car right now just fine the problem will be in a couple months when it starts to get cold. Yes white smoke and black soot will be coming out of the exhaust this winter and it will run horrible if at all.
The intake definitely had some wear but nothing horrible like I've seen in pictures.
 

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It's possible that the timing or rear covers can be leaking internally too. That's not a common issue unless they've been replaced in the past. If you're confident in your intake job, then it might be worth looking there.
 

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An intermittent issue is still an issue, and if it's temperature dependent, that just means it's probably just happening slower in the warmer conditions. Coolant going places it shouldn't can turn that engine into a paperweight if you don't address it properly after years of being lucky that hasn't happened yet.

I would suggest blocking the top intake coolant ports where those o-rings go, because that's a terribly sealing spot for a useless function (basically, having coolant keep the TB blade from freezing open if you do a long wide-open run at the North Pole). I think I use 3/8" NPT plugs, and it only gets about 2 threads tapped into there.

Next, I'd consider resealing the water pump and front cover (requires pulling harmonic balancer), along with fresh o-rings on the elbows if you want to measure/shop for those.

Keep looking into it before it gets bad, so you can enjoy the car as long as possible.
 

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Discussion Starter · #14 ·
An intermittent issue is still an issue, and if it's temperature dependent, that just means it's probably just happening slower in the warmer conditions. Coolant going places it shouldn't can turn that engine into a paperweight if you don't address it properly after years of being lucky that hasn't happened yet.

I would suggest blocking the top intake coolant ports where those o-rings go, because that's a terribly sealing spot for a useless function (basically, having coolant keep the TB blade from freezing open if you do a long wide-open run at the North Pole). I think I use 3/8" NPT plugs, and it only gets about 2 threads tapped into there.

Next, I'd consider resealing the water pump and front cover (requires pulling harmonic balancer), along with fresh o-rings on the elbows if you want to measure/shop for those.

Keep looking into it before it gets bad, so you can enjoy the car as long as possible.
Thanks for the response. Could the water pump and front cover cause coolant leaking into the combustion system?
 

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The TB is a step too late, and is a better sealing connection than the 2 o-rings for the 2 holes coming up from the LIM. I just rebuilt a top end for a 3800 Camaro with fresh gaskets that still had leaking from that spot and needed re-addressing. It's a pain.
 
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