Anti-Freeze Loss

[BCS_ZHP]

My wife is 200 miles away this afternoon, says the low coolant light came on when she cranked it up and then went off when she got to level ground. Coming from dropping off our son at college yesterday, I ran our Denali hard through the mountains of I-85 in SW Virginia, was clocking 80-85 and her ZHP conv was right on my tail so she could get to meet up with her teammates for her state tennis tourney (they won, sectionals in 2 weeks & then nationals, she's serious about that little green fuzzy ball, and thus her vanity plate). We kept that hard driving up for about 2 hours then she headed east while i continued north, and she drove the speed limit after we parted. It's a 2004 with just over 39K miles, all original cooling system, I think it's original coolant too. I know, despite the low miles the age probably warrants a cooling system refresh but I was trying to stretch that to at least 50K miles.

When she arrived home tonight the engine was obviously hot, so dropped the belly pan and looked for signs of leaks -- absolutely none. (I routinely clean the belly pan so I can see if anything is leaking.) After 4 hours it had cooled off enough for me to open the expansion tank and I had to add about a quart. When I bought it with 9K miles 20 months ago I had to add half a quart. So no leaks, oil level is perfect, where is this coolant going??? Is it normal to burn/evaporate a little bit off from a closed cooling system?

[Crestwood1001]

Realistically no, I'd investigate deeper, check all hoses for signs of dried coolant. It could have been a slow leak that just got low enough to pop the light. Did she happens to use the heat in the car on the trip back?

[danewilson77]

Don't overfill it either Bruce.

Sent from Williamsburg, VA USA

[BCS_ZHP]

On the heat, possibly as it was a cool day here. But she drove it all of last winter with heat on and no coolant issues,so I don't think we had a big air pocket somewhere. When i dropped the belly pan, there is no sign of coolant from upper or lower hoses, none from thermostat, none from waterpump either. If I have to do the cooling system refresh I'll go full tilt but I'd much rather know I have to do it now rather than in the cold of winter. I'll continue to monitor this closely.

And why does this kind of stuff pop up when you have absolutely no extra time. The Service Engine Light popped on my 540 this afternoon but she's running perfectly. Going to try to link up with Jon (Au2bahn) tomorrow to get a read on the codes it's throwing.

[danewilson77]

Probably O2 sensor on 540i.

Sent from Williamsburg, VA USA

[echo46]

I don't want to get crazy here about this but any whitish smoke on start up. Very remote chance it could be head gasket?

[BCS_ZHP]

No smoke at start up, or at any time.

[echo46]

I would take another look for small leaks. I just don't think that amount would evaporate. Did you check around the radiator and under expansion tank? Also cheek at the engine block plug for signs of leakage.

[Crestwood1001]

Gotta be leaking somewhere man

[jreyes19]

In my experience i had a leak but i didn't see it so much under the car

the reason was that it would either evaporate from the hot engine , or just dry once the engine cooled
also don't check the floor but the bottom of the bumper under the expansion tank and radiator ( this caught a lot of the leaking fluids, so they never hit the floor)

Let the engine warm up, open the hood and look at it while having some one rev the engine to see where the leak may be coming from

that at least is how i found this (this is a video of the coolant/anti-freeze my car had till I replaced the radiator)


sorry for the blurriness i didn't know how to used the video function of the camera at the time
also all the white you see on the plastic is dried coolant