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Discussion Starter #1
Hey guys. I have a 2008 CTS here, direct injection. I’ve noticed over the past year my coolant level has gotten low. I will fill it, and it’s low again, repeat. I had to replace the water pump twice, but this time around I have seen no leaks around the pump or anywhere else and oil level appears normal. Where is the coolant going? Could the radiator be failing since I have about 110,000 miles on it and maybe I haven’t noticed any coolant because it’s burning off on the radiator?
 

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2011 CTS Coupe Premium
Orlando - We take orphans
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What I do is to use a coolant tester to pressurize the system to 15 psi. If there is no leak it should hold the pressure, if there is a leak it should be visible particularly with a cool engine in a garage. If the pressure drops but no visible leak check the oil for a milkshake.

In my case the water pump leak was obvious. New pump and it held pressure.
 

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How much coolant is being lost and over what period of time?
 

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Discussion Starter #4
How much coolant is being lost and over what period of time?

Thank you both for the input. I’m losing basically a full reservoir within 2 to 4 weeks. I keep refilling it and it’s empty within weeks. I have kept checking the oil and it has remained the right color and it hasn’t risen in level, so I don’t think it’s the gasket.

Do I need any special tools for a pressure check or should I let a mechanic do it? I guess that’s my next step.
 

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It's possible that you might have a head gasket leak developing. You can see if your exhaust has higher moisture content than normal, or has a "sweet" odor. Also, you can check to see if your coolant has air bubbles in it while the engine is running, though that's not easy to do. As mentioned above, a pressure test could also indicate a head gasket leak if the coolant system will not hold pressure and there are no other signs of leaks. Not all head gasket leaks will contaminate the oil.
 

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2011 CTS Coupe FE3, 2003 Thunderbird, Gone 2013 ATS, 02 Deville
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Thank you both for the input. I’m losing basically a full reservoir within 2 to 4 weeks. I keep refilling it and it’s empty within weeks. I have kept checking the oil and it has remained the right color and it hasn’t risen in level, so I don’t think it’s the gasket.

Do I need any special tools for a pressure check or should I let a mechanic do it? I guess that’s my next step.
Kemp040, please take the car to a mechanic. The leak is very large and it maybe an easy fix like a loose hose clamp or more expansive like a water pump. But get it fixed before you have major engine damage.
 

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Well if you want to play mechanic just go to most any auto parts store and they will lend you a pressure tester for free.
Fill the cooling system with coolant, pump up the pressure to 16 PSI and watch for the coolant leaking.
Note: some water pumps leaks need more PSI because they may only leak when the engine is running and the coolant inside the engine can have a pressure of about 30 PSI plus.
 

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Just a thought but the max fill line on the reservoir is hard to see but should only be about 1/2 full. If filling all the way it is just going out the overflow when expands.
Good point ^^^.
"Full" is where the clear and black halves of the reservoir meet, engine off & cold.
 

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Discussion Starter #13
Just a thought but the max fill line on the reservoir is hard to see but should only be about 1/2 full. If filling all the way it is just going out the overflow when expands.
Thanks, I only fill 1/2 way to that line in the middle. Not coming from overflow. I get the pressure tester from amazon Wednesday so will find out then. Any chance any hoses split under the 15 psi?
 

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Using a pressurized radiator cap can raise the system pressure and thus the coolant boiling point. A typical 1 Bar (14.5psi) pressure cap theoretically raises the boiling point of 50-50 coolant to 253°F, which you would expect to be sufficient to prevent boiling.

So to answer your Q. No, maybe. Your cooling system now has a leak, so it may not be reaching full pressure. It maybe that a hose now has a split in it causing the leak, we do not know. You have 12 year old parts on your car so anything may go wrong, that is why you are going to pressure test it.
 

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Hey guys. I have a 2008 CTS here, direct injection. I’ve noticed over the past year my coolant level has gotten low. I will fill it, and it’s low again, repeat. I had to replace the water pump twice, but this time around I have seen no leaks around the pump or anywhere else and oil level appears normal. Where is the coolant going? Could the radiator be failing since I have about 110,000 miles on it and maybe I haven’t noticed any coolant because it’s burning off on the radiator?
I had a similar problem with another GM product, though not a Cadillac, it may apply. I was losing coolant over a long period of time and not a head gasket issue. It took some time but I finally found it when I stopped the vehicle in the carport and raised the hood. The engine was hot and coolant still under pressure. I smelled anti-freeze and spotted a fine wisp of steam emanating from the connection at the radiator where the transmission coolant hose was connected! The problem was, the coolant tank inside the radiator, where it passed through the radiator wall was leaking - VERY SLIGHTLY! But over time, enough leakage when under pressure, often when stopping the vehicle, a small amount of coolant would escape and over time the level would get low enough to cause heat up. Didn't require any parts, just tightened the connection and fixed it!
 

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I had a similar problem with another GM product, though not a Cadillac, it may apply. I was losing coolant over a long period of time and not a head gasket issue. It took some time but I finally found it when I stopped the vehicle in the carport and raised the hood. The engine was hot and coolant still under pressure. I smelled anti-freeze and spotted a fine wisp of steam emanating from the connection at the radiator where the transmission coolant hose was connected! The problem was, the coolant tank inside the radiator, where it passed through the radiator wall was leaking - VERY SLIGHTLY! But over time, enough leakage when under pressure, often when stopping the vehicle, a small amount of coolant would escape and over time the level would get low enough to cause heat up. Didn't require any parts, just tightened the connection and fixed it!
Hey guys. I have a 2008 CTS here, direct injection. I’ve noticed over the past year my coolant level has gotten low. I will fill it, and it’s low again, repeat. I had to replace the water pump twice, but this time around I have seen no leaks around the pump or anywhere else and oil level appears normal. Where is the coolant going? Could the radiator be failing since I have about 110,000 miles on it and maybe I haven’t noticed any coolant because it’s burning off on the radiator?
I took my car to Cadillac because my alarm kept going off. They fixed it and said "radiator leaking badly, and radiator hoses leaking, estimate $580 to replace. T-fitting at rear of engine leaking coolant, $205 to replace. I didn't do anything yet because it also say's multiple oil leaks. So first I'll find out what's leaking and where.
 

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Discussion Starter #17
Thank you for the continued help. I went ahead and pressure tested the coolant system to 15 psi. Upon doing so, I Noticed a drop in pressure immediately and a small hissing sound coming from the attached picture where I’m pointing. Best I can tell, it’s coming from Somewhere near the of the engine where a hose goes in but I cannot see any coolant. Any ideas?
578082
 

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I had to replace the o-ring seal on the coolant pipe that hose is attached to. Easy job. You can do it. Check out the time spot beginning at 7:09 and slow the movie, or freeze it so you get a good look. Review the entire video which should be all you need to get the job done.

 

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Nice reference, Joseph (y)

So, is all that coolant loss being burnt off/ingested?
 

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Discussion Starter #20
I had to replace the o-ring seal on the coolant pipe that hose is attached to. Easy job. You can do it. Check out the time spot beginning at 7:09 and slow the movie, or freeze it so you get a good look. Review the entire video which should be all you need to get the job done.

Thank you. I watched the video. So you are saying it’s an o ring issue not on the rubber hose itself but where it’s connected to on the engine block? Do I have to take the engine cover off or can I install the new o ring if I just detach the rubber hose?
 
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