[ventsyv]

My coolant light came on a couple of days ago. I was leaving work, I started the car and the light stayed on. I turned the car off right away, checked the coolant level (the car was cold) and it was bellow the minimum. Actually it seemed that there is no coolant in the expansion tank what so ever.
I added a bottle of water, started the car and the light was off.

I'm about to change my belt pulleys, and I was wondering if there is a way I can diagnose the coolant leak? I replaced the water pump about 6 months ago and everything seemed to be fine. I kept checking the coolant level, but one day i forgot to tighten the cap and the light came on ... I added water then too, So I guess I have to change my coolant also ??

I think I have a very small leak somewhere. I tried looking for any signs but could not find any.

 

[Solidjake]

It's probably your expansion tank. I read that it can leak from the bottom and it dissipates leaving no trace.

 

[fcpeuro]

+1, this seems to be a know issue. You could aways pressurize the tank to know for sure.

 

[ventsyv]

+1, this seems to be a know issue. You could aways pressurize the tank to know for sure.

How do you pressurize the tank?

 

[genuity]

replaced the water pump about 6 months ago and everything seemed to be fine.

Just wondered, what prompted you to change the water pump?

 

[golforcars325i]

You might also want to check the temperature sensor located in your lower radiator hose (standing on the passenger side of the radiator, you can look straight down where the hose connects to the radiator and see it sticking up). The o-ring can become hard after time and the leak is hard to detect since it's at the bottom of the system.

 

[ventsyv]

I was changing the belts, since I was in there I decided to change the pump and coolant as preventive maintenance.
Good idea Golforcars I'll take a look.
By the way, any one on pressurizing the expansion tank?

 

[jeffro3000]

Do you notice any coolant stains on the splash guard under the expansion tank? I had this problem and the leak turned out to be from the thermostat. :dunno:


I did have a leak from the expansion tank about a year earlier though. It was in a big way though. I poured coolant in and it came gushing right back out the side.

 

[ventsyv]

I haven't actually looked. I noticed I'm losing a little bit of coolant a few months back but when I looked I could not see anything. It has to be pretty small leak that evaporates right away otherwise it would've not taken 6 months to go below the minimum.
I've now added almost a liter of water so the coolant concentration is pretty low. I suppose I'll have to replace the coolant again.

 

[ventsyv]

I checked the expansion bottle, no visible cracks. The hoses also look good. They are all soft as they should be. No signs of leakage anywhere. Maybe the radiator is leaking a little and is evaporating.

 

[Solidjake]

Did you check the sensor on the lower radiator hose?

 

[ventsyv]

I looked, but did not see any leakage there. The hose looked fine, it was nice and soft. The part where it was connecting to the radiator was very hard, but I think that's what its supposed to be. It seemed nice and tight ...

 

[bshade1]

I think I may have this problem. Any idea if Autozone or the like carry the o-ring and if so is that what I ask for? Can't be more than a few buck and I refuse to pay labor for something so simple. Thanks. Brian, Tampa,FL.

 

[ventsyv]

The lower radiator hose is 26 bucks on bavauto.com. About the same on getbmwparts.com I could not find O-rings only.

 

[Melquin]

The lower radiator hose is 26 bucks on bavauto.com. About the same on getbmwparts.com I could not find O-rings only.

Supposedly the o-ring it is the same as the air intake sensor one:

see:
http://www.bimmerfest.com/forums/showthread.php?t=409007

 

[smileye46coupe]

I had the same problem last week, the coolant light kept coming on even though i topped it up every morning.it turned out that my expansion tank had 3 pin hole size leaks,which were coming from the seam on the side of the tank. how i noticed it was to start the car and leave it running,one it gets hot and builds up pressure,after 10 - 15 mins i noticed the coolant being forced out the side ofthe tank. Got a new tank from main dealer which cost ***8364;90, which was reasoable even from a main dealer. as it turns out,its apparently a common problem and they have sold quite a few of them. my car is a 2001 coupe.