[Rifta]

As the title states, my 2008 335i says "Coolant Low", but there dont seam to be any leaks. I brought it to my local trusty gas station, since my BMW place is closed on Saturdays, and asked if they could take a look at it since I dont have a garage or a jack stand. They did and they said that they could not find any sort of leak, everything was dry, and the coolant was topped off. Could this just be a coding error or is there possibly something else wrong with my car? Any help is appreciated.

[enrita]

sounds like the sensor is fucked

[TheSpilDog]

Might also be the rear turbo coolant pipe. I had a similar leak. Never saw any evidence of it except for the coolant level slowly dropping over time. The O ring would have to be changed.

[Miller335]

I'd check it yourself and make sure all those things are true, who knows maybe they missed something in trying to get you out the door.

Maybe even get it jacked up and take some of the plastics shields off and really get in there and look.

[xzibit a]

So i have similar issue on my car, once every few months my coolant light comes on and the coolant is at the low level. i cannot find leak anywhere. pressure tested the system @ 20 psi over night and it held perfectly. 2 weeks ago i had a customers 08 335i with a very similar issue. Couldn't find any leaks on his car either.

[ajsalida]

Older BMW's (I'm thinking of my e36 m3) are famous for having bad coolant level sensors in the expansion tank. Of course they are also famous for having mysterious coolant leaks and head gasket leaks.

Obviously if there actually is no coolant loss it is not a leak, it is a sensor. If there is a coolant loss it is a leak. There are kits you can buy that put dye into the coolant and you use UV light to find the leak. Even if it passes an overnight pressure test (cold or hot) there could be a cracked head or head gasket leak that only leaks while running.

Unfortunately our cars HAVE NO DIPSTICK so we can't easily examine oil for water, this drives me crazy. Other common problems in aging bmw cars (again learning from e36) are bad radiator caps (either holds too little or too much pressure) crazy problem I traced down was a cap that would not open under proper pressure and had overfilled coolant. The 3 aftermarket caps I went through did not hold 2 bar pressure and only OEM one worked right. Simple pressure test would not have revealed this.

Also the e36 head & gasket is weird it can crack or leak in a way that lets exhaust gas into the coolant system and over-pressures it, but only while running after getting up to temp. There is another kit for sensing exhaust gas in the coolant. Etc etc. As the N54 ages we'll find out what the weak points are in the cooling system, none of this stuff on the s50 showed up until after 10 years or so.

One thing to check is have any of these cars had coolant system work done? Water pump radiator coolant flush or whatever. Getting all the air out of the system is critical.

[gogunbaba]

I have the same problem, I took everything off and there is no leak in any of the parts. It has to be sensor related...

[ajsalida]

If it is not losing coolant you don't have a leak. If it is you have one. Somewhere.

[Jeff@TopGearSolutions]

Originally Posted by xzibit a

So i have similar issue on my car, once every few months my coolant light comes on and the coolant is at the low level. i cannot find leak anywhere. pressure tested the system @ 20 psi over night and it held perfectly. 2 weeks ago i had a customers 08 335i with a very similar issue. Couldn't find any leaks on his car either.

Do the cars blow a lot of white smoke out the exhaust? Catless?

Originally Posted by TheSpilDog

Might also be the rear turbo coolant pipe. I had a similar leak. Never saw any evidence of it except for the coolant level slowly dropping over time. The O ring would have to be changed.

This makes the most sense since it's hard to see.

[xzibit a]

Originally Posted by Jeff@TopGearSolutions

Do the cars blow a lot of white smoke out the exhaust? Catless?

I have catless downpipes, but the secondaries are still in. No abnormal smoking.


This makes the most sense since it's hard to see.

going to look into this. Its a very small leak so i havent worried about it. Just dealt with it for the past year or so.

[MilehighM3]

some coolant loss is natural for these cars. Just top it off and keep an eye on the level from time to time.

[Tiago@VRSF]

If the coolant is topped off and it's saying the coolant is low, it's a sensor problem.

If the coolant wasn't topped off and it's not leaking, my first guess would be the head gasket.

Most of the time it's a small leak somewhere that's hard to see or reach though, if the motor was ingesting coolant you'd notice quite a bit of excess smoke coming from the exhaust.

[Rifta]

Okay, I have an update if anyone is interested.

A week before I went to the gas station my car said coolant low, like I said in the above post. A few days after it first said that the message turned to "Service Due" instead of just "Coolant Low". I thought it was just the same thing. As I said before, the gas station guys didnt find anything when I took it in. I finally took it to a BMW repair shop and they said my coolant was fine but my brake fluid was low which was what was setting off my "Service Due" message. I guess the coolant low message was just a glitch and showed up for a day or two, but it was really my brake fluid that was low. I now no longer have any error messages after I got my car back from the BMW repair shop with new brake fluid.

[MDORPHN]

Originally Posted by Rifta

Okay, I have an update if anyone is interested.

A week before I went to the gas station my car said coolant low, like I said in the above post. A few days after it first said that the message turned to "Service Due" instead of just "Coolant Low". I thought it was just the same thing. As I said before, the gas station guys didnt find anything when I took it in. I finally took it to a BMW repair shop and they said my coolant was fine but my brake fluid was low which was what was setting off my "Service Due" message. I guess the coolant low message was just a glitch and showed up for a day or two, but it was really my brake fluid that was low. I now no longer have any error messages after I got my car back from the BMW repair shop with new brake fluid.

I hope situation is resolved, but that doesn't make much sense...

Neil

[evoix]

i had the same problem and the dealer told me that the bmw coolant has more alcohol and chemicals that evaporate faster but still confused. BUt if it is in a sealed system where is it going?