E46 coolant loss

[chrisc4290]

2004 318ti with 98000km. Noticed puff of steam from bonnet when waiting at traffic lights. Then water level light came on. Next day when cold had to add about one litre water to header tank. Within a day light came back on and topped up tank again. Idled the engine for 15 mins and switched off. Can hear soft sound similar to water boiling under cylinder head cover, but cannot see water coming from any pipes, radiator or header tank, or sensor under header tank.

Any suggestions please?

[witeshark]

Are there any signs of engine oil in the coolant or the reverse?

[chrisc4290]

Originally Posted by witeshark

Are there any signs of engine oil in the coolant or the reverse?

No, the dipstick is clean and the oil filler cap is also clean - no trace of that usual grey mess you usually see when the oil is contaminated with water.

I can smell the anti-freeze if I sniff close to the head cover. Haven't taken it off yet. Are there any coolant pipes on top of the engine? I thought it was just the camshaft and valve gear inside there.

[witeshark]

That I'm not sure.

[chrisc4290]

I think I fixed it thus:

I started this morning with the engine cold. Then removed the two small black bleed screws from the elbow that connects to the expansion tank and the other above the pipe just in front of the sound cover on top of the engine.

Removed the coolant filler cap. Turn on the ignition but don't start the engine

Turn the heater knob all the way up and put the fan on no 1

Then pour mixed coolant into the expansion tank until coolant runs out of the bleed screw hole (first the expansion tank, then the top bleed screw)

Replace the bleed screw/s and check the coolant level in the expansion tank.

Now start the engine but don't replace the cap yet

Allow the car to idle until normal operating temperature is reached. Observe the bubbles that appear on top of the water just below the level of the expansion tank inlet, close it when the bubbles stop appearing (this took 15 mins)

Allow the motor to cool (3-4 hours) and top up the coolant level again.

Since then, I took it for a drive (20km) and will check tomorrow, but the water level light has not come back on.

[witeshark]

So it may have been a simple matter of eliminating trapped air, I hope so!