kelv525

Hey everybody,

I have a 2007 525i. After about every 800 km which is 500 miles, it keeps giving out the low coolant warning. I filled it with about 1 liter or 1.5 liter once a week for the past two weeks. I tried two different BMW dealers and said all the possible leak spots have no leaks. I am going crazy.

Please help.

BimmerFan52

If you are loosing 1.5 liters every 500 miles that is roughly a tenth of an ounce per mile so a relatively slow leak, especially if most of your driving isn't highway (takes longer to drive a mile).

I suggest you pull off your front belly pan so you can see active drips hitting the ground. Look for any white spots on hoses or other parts which suggests coolant drops that have dried.

After pulling the belly pan off drive it until it is fully warmed up and leave it run while you examine the engine bay and under the car for any dripping. You may have to be patient and wait 10-20 minutes until you see dripping.

If you see no drips after 20 minutes, then turn off the engine and continue to examine for leaks, especially near the coolant reservoir tank, the fan behind the radiator and the radiator itself. After the engine is turned off the coolant in the engine block is no longer being circulated and tends to super-heat as block heat is transferred to the stationary coolant. This raises the pressure of the closed coolant system and expanding coolant is pushed out the top of the radiator through the vent tube (under the metal shroud covering the radiator and electric fan) and into the coolant expansion tank. The components in this coolant path (especially the vent tube which is plastic and grows brittle with age) are known points to leak.

Forgot to add the possibility of a leaking head gasket. Remove your oil filler cap and smell the cap to see if it smells like coolant. I don't think you have a dip stick on the 2007, but if you do examine the oil on the stick for a "milky" appearance that would suggest coolant is getting into the oil.

kelv525

I was just in the garage and with a little help of a flashlight I noticed that there was a small pool of I guess coolant on the area under the reservoir. This shows dealers don't know jack about the cars they service. The reservoir seems dry and I do not think it is leaking. Additionally i filled it up with coolant and it still says low coolant. I don't understand. I'll try what you just told me on Monday because tomorrow there are no shops open anyway.I hope its just a hose or something.

Thanks a lot.