Coolant overflow tank

**Nick1234** · 04-15-2019, 08:37 PM

2019 3500 Duramax. Coolant overflow tank is filled to the brim. Is this normal, or did dealer put to much coolant in tank?

**RVRunners** · 04-15-2019, 08:46 PM

Should be a line on the side of the reservoir for max fill when the engine is cold. If you observed the reservoir while the engine was hot this could be a factor.

**Nick1234** · 04-15-2019, 09:23 PM

Originally Posted by RVRunners

Should be a line on the side of the reservoir for max fill when the engine is cold. If you observed the reservoir while the engine was hot this could be a factor.

I have not observed it while the engine is hot. I will do that and see where the level goes. Thanks

**RobM** · 04-16-2019, 08:50 AM

Originally Posted by Nick1234

2019 3500 Duramax. Coolant overflow tank is filled to the brim. Is this normal, or did dealer put to much coolant in tank?

Nick,
I got a "coolant low" message when it looked OK to me. I added about an inch more to bring it up to the arrows, and it is still a bit below the arrows. These new tanks are under pressure, so I did it when cold. That very small diameter hose right at the cap vents to the outside. I'm assuming it somehow will vent overboard if needed, even though the tank itself is under pressure.
Rob M

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**keywestparrothead** · 04-16-2019, 02:29 PM

For us Ford guys, I had a check engine light come on a few weeks back so I break out the code reader and nothing... nothing stored, nothing current, nada. Start checking the obvious stuff and see that my overflow tank is a little low, add some coolant and light goes out! You would think, with all the modern electronics these new trucks have, a simple fluid level monitoring would give you more than a "check engine" light (rant over). All that to say there is some importance to the levels in the overflows :-)

**cfowler55** · 04-16-2019, 02:54 PM

Originally Posted by RobM

Nick,
I got a "coolant low" message when it looked OK to me. I added about an inch more to bring it up to the arrows, and it is still a bit below the arrows. These new tanks are under pressure, so I did it when cold. That very small diameter hose right at the cap vents to the outside. I'm assuming it somehow will vent overboard if needed, even though the tank itself is under pressure.
Rob M

You have an expansion or surge tank , not overflow. And yes , it will push excess coolant by the cap once system pressure reaches the cap limit. I believe you have a 20psi cap. When hot the air space in the top of the tank will be compressed , making the coolant level higher. Fill to the line cold only.

**gengiant** · 04-16-2019, 07:31 PM

Originally Posted by keywestparrothead

For us Ford guys, I had a check engine light come on a few weeks back so I break out the code reader and nothing... nothing stored, nothing current, nada. Start checking the obvious stuff and see that my overflow tank is a little low, add some coolant and light goes out! You would think, with all the modern electronics these new trucks have, a simple fluid level monitoring would give you more than a "check engine" light (rant over). All that to say there is some importance to the levels in the overflows :-)

When I bought my “new to me” 2012 Ford F450 in 2014, I had the “low coolant” code trip. Tank looked full as per the line/mark. Took it to the dealer - they couldn’t figure it out but cleared the code. It came back on a day or two later. So I consulted with a friend of mine who teaches diesel mechanics at the local tech school. He said that sometimes, the system will develop an air bubble/air lock in the line that will keep enough coolant from being in the system. He checked my truck, tapped and shook a bunch of lines and added about a bottle of coolant to the tank. Never had a problem since. Weird. Too much technology for me - and I’m an engineer![emoji1787][emoji56]

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**D2Reid** · 04-16-2019, 08:28 PM

13 Duramax, full to the brim. After having the cooling system flushed I got a check engine light, coolant low. Put more in, good to go. Tank full is good, if you stop when it's hot and you see coolant (not A/c drip) on the ground, bad. Otherwise the ECM will report abnormalities with a check engine light.