Coolant loss

[Mataa]

After about 350km drive, I loose about 150ml of coolant. What should I be looking at? Temperature has always been fine. I changed the expansion tank two years ago. That's when all this started. I'd find a some coolant in the top room of the bottle. The bottle has some kind of rail along its top edge. So coolant would collect there.

A couple of weeks ago I noticed the bleeder pipe was not firmly sealed to the expansion bottle. So I had it fixed.

But I notice I loose about 150ml of coolant when I drove about 400km.

It's an e46 M54.

Sent from my Infinix X606C using Tapatalk

[E39 Newbie]

First, are you getting any white smoke out of the exhaust?

If not, check each hose connection for white residue. If you find noticeable residue, fix that leak.

If you can't find it, buy a radiator pressure test kit and pressurize the system while the car is cold, then check each and every connection. This includes the pipes under the intake.

If you still can't find the leak, buy an exhaust gas in coolant testing kit and check for head gasket issues.

[MarcoZandrini]

What’s the maintenance history on the cooling system? The consensus here and on other bimmer forums is that the cooling system needs to be overhauled every 100k miles/160k kms. The installation of aftermarket cooling system parts is strictly verboten.

[martwauto]

Are you filling the expansion bottle to the very top ?

Mart.

[e464]

Agree with above. Second, have you looked from below when HOT (pressure high) to see if tiny leak around hoses and or temperature sensors.
USE A FLASHLIGHT to focus your eyes on one spot and work from spot to spot.
They will fly off when driving but be seen when hot and no wind present.
I had a minor leak on right hose thermostat which was normally NOT visible. Was old O-RING. Do you measure fluid level FLAT, morning, cold engine. I assume so but not knowing you must state/ask.

[Mataa]

Hi
I may not have been closing the expansion cap right. I made it slightly more tight than usual and coolant is all there even after going 400km plus.