Coolant leak while parked & No visible leak (1 Viewer)

[lunty100]

Hello,

I have a 2000 LX 470 that seems to loose coolant while parked. I fill up the expansion tank to the full line, then about 8-12 hours later, the level is below the full line by about 1-2cm. I have not driven the car at all in between the fill and when I measure, and don't see any leaks under the vehicle. I also removed the expansion tank and checked for cracks but came up with nothing. I have no history of overheating in the year I have owned the car, the temp gauge is always steady at a mark just below the center on every drive.

I only realized the low coolant issue on a large roadtrip recently, and noticed some residue in the heater tees, so I swapped those out with new tees and hoses. After the change, I have also bled the cooling system by parking up an incline, turning on the heater to full, and letting bubbles escape as I add new coolant. But this coolant loss issue still persists.

I would really appreciate any suggestions, thank you all so much in advance!

 

[UncleJakeNZ]

The expansion tank is designed to allow a variation in coolant level without discharging much coolant onto the ground (as used to happen in 'more' closed systems).

If I'm understanding your post correctly (i.e. you've seen the level change only down to 20mm below full) you most likely have nothing at all to worry about. The levels in an expansion tank find their own happy point and generally stay there once the expansion tank has spat out what it wants to.

If you don't have wet carpets and your engine oil looks good (i.e. isn't emulsified) then don't put any more water into the expansion tank and keep an eye on it over a week or so. If it continues to progressively drop in level below the 10-20mm beneath the full line then you are losing something somewhere..... hopefully not out of an exhaust pipe

 

[jcrun]

My ‘04 does the same thing. If I fill the reservoir it’ll drop down to about 1” below the full line within the first couple days, then it never moves after that. I’d say don’t worry about it.

 

[Ayune]

Expansion tank level is supposed to go up & down. It keeps a constant level inside the radiator as the fluid (and small air) volume expands & contracts with temperature changes.

 

[lunty100]

Thank you so much for all the insights! I will continue monitoring the levels as I drive the car. So when the engine returns to cold can I expect the level to be somewhat the same as what I started with or is this is not a given? If there can be variation, what would you say is the acceptable range?