QSM11 Coolant expansion tank

[SeaNile]

Curious what the levels are in your tanks? Are they supposed to be empty when cold and not running? Filled 1/2 way when hot and running, etc?

 

[Skybolt]

Curious what the levels are in your tanks? Are they supposed to be empty when cold and not running? Filled 1/2 way when hot and running, etc?

Any expansion tank, when sized properly, will also have marks on them for cold and hot. But if cold very close to empty, like mine are about an inch from the bottom right now. Hot, depends on how much expands out of the heat exchanger, but about half or more is about right.

The thing to look out for is when the cap isn't sealed right or the line to the expansion tank leaks. The the fluid goes into the expansion tank but also when the engine cools off the anti-freeze doesn't get back into the heat exchanger and this will slowly cause the engine to be low on anti-freeze.

So at or around 70° make sure the engine is completely full to the top, no air gap, of anti-freeze. Then run the engine at cruise and mark the high level and get a fell for what is normal. Also look for leaks and then the next day or so after the engine is completely cooled down, re-check the fluid level in the heat exchanger. if there is any noticeable air gap, then there is a leak somewhere.

 

[SeaNile]

Thanks! Was just curious because during the winter I noticed my expansion tanks looked pretty much empty.

 

[Skybolt]

Thanks! Was just curious because during the winter I noticed my expansion tanks looked pretty much empty.

Because the engine room was a lot colder then 70°, the coolant went back into the engine(s).

I am only mentioning 70°, because that is a bench mark "Room Temperature" and a good starting point for liquid to be normalized in. Obviously when your engine room is 100° the levels will be higher in general because of expansion.

 

[ttmott]

Are you talking about the coolant tank atop the engine or the plastic expansion bottle along the stringer?
I keep zero air in the coolant tank and keep around 1/3 full on the expansion bottle when the engine is cold. I don't recall any Hot/Cold lines on the bottle.

 

[SeaNile]

Are you talking about the coolant tank atop the engine or the plastic expansion bottle along the stringer?
I keep zero air in the coolant tank and keep around 1/3 full on the expansion bottle when the engine is cold. I don't recall any Hot/Cold lines on the bottle.

The plastic one along the stringer. I only noticed it this past weekend when I was in the bilge and it was completely empty. Was also fairly cold and well below 70. I'll keep an eye on it when we go out next, which should be on Saturday.

 

[quality time]

I always kept mine filled to the bottom of the logo. Two mechanics said that was a good level.

 

[Woody]

I got tired of guessing, trying to remember exactly what level the expansion tank was at. I did as ttmott suggested. When the engine was cold I made sure the engine/coolant tank were full. I put a black mark on the expansion tank and filled to that level.

I look at the level every time I'm in the bilge but the important checks are always when the engines are fully cooled down, they should be on my line. I compare one engine to the other but those levels move around and sometimes don't seem to make sense when warm. As long as they're on or near my line when cooled down I figure I'm OK.

 

[ttmott]

The plastic one along the stringer. I only noticed it this past weekend when I was in the bilge and it was completely empty. Was also fairly cold and well below 70. I'll keep an eye on it when we go out next, which should be on Saturday.

Unless there is a leak somewhere the coolant expansion bottle being drained is only air in the engine somewhere being purged out. When cold first fill the tank atop the engine then fill to the cold level in the bottle. Eventually, it will all stabilize.