2013 135i: Coolant Loss

[JoshInAtlanta]

Hi All - new to the forums. Recently acquired a 2013 135i as a weekend/casual-use car. We bought it with 28,xxx and are still a little shy of the 30k mile mark after a few months.

A couple of weeks ago, after sitting for 6 days, we started it up and the display showed "Low Coolant." Immediately shut it off and since the car was still cold, popped the cap on the tank and it appeared to be completely dry. Went to the dealer and got a bottle of BMW antifreeze the next day, mixed it up and topped it back up. On the first drive, it seemed like the car was leaking a little from the tank area but then it stopped and I assumed maybe I had overfilled. After a week and about 225 miles, the light came back on and the tank is empty again.

It looks like there may be a leak at the tank, possibly where the return line is at the top. I am seeing a little of the white residue in that area of the tank and on the engine cover. It also appears as if it has been wet a time or two in that area. I popped the plastic line off... no visible issues. I checked the cap... no visible issues. I checked the plastic bleeder screw (and o-ring)... no visible issues.

I have ordered a replacement brass bleeder screw but besides that, does anyone have any experience or recommendations on what I can check before I start tossing money at this issue. I have plenty of experience with older BMWs but this is my first newer one... my current 2 are 32 years apart!

Any guidance/advice is much appreciated. Thanks!

[The Wind Breezes]

I had to have the expansion tank replaced around 45k on my 2012. I got the low coolant warning while driving hard once and boom, the tank was done.

Now I don't have any issues but the car does seem to lose coolant really slowly. Maybe out my water pump, which is stock. Who knows.

[juld0zer]

Not rare for the explosion tank to suddenly spring a leak. My car is on its third one in 7yrs

[MightyMouseTech]

Agreed with above. Just order a new tank.

[NorthernDancer]

According to realoem part number is 17 13 7 640 514. Used on all E82 & 88, most E9x, E84 and E89. OE BMW is $118 from Bav Auto but Behr is only $50. I would go for the Behr.

[JoshInAtlanta]

Thanks everyone. I put the new brass screw in this evening - I am going to keep an eye on it and go ahead and order the tank to swap out. No point causing damage over something simple and affordable.

[asiflicious]

When my 335i had this issue, it turned out to be a leaking water pump

[JoshInAtlanta]

Originally Posted by asiflicious

When my 335i had this issue, it turned out to be a leaking water pump

Were you able to see where the leak was coming from? All my coolant loss is coming from the tank - after installing the new bleeder screw it went 40 miles and was low again. I ordered the new tank and it is on the way.

It is definitely dripping and spraying from there somewhere once the car is warm and at speed. Makes a mess all over.

[tock172]

Originally Posted by NorthernDancer

According to realoem part number is 17 13 7 640 514. Used on all E82 & 88, most E9x, E84 and E89. OE BMW is $118 from Bav Auto but Behr is only $50. I would go for the Behr.

Don't bother. This is a well documented issue with the E36 and E46. Behr actually manufactures the tanks for BMW, but the OEM versions (without the Roundel stamped on them) seem to be much more susceptible to developing leaks as opposed to the genuine ones. It's happened to dozens of people over the years. Spend the extra money for the genuine BMW tank and be done with it.

[JoshInAtlanta]

Originally Posted by tock172

Don't bother. This is a well documented issue with the E36 and E46. Behr actually manufactures the tanks for BMW, but the OEM versions (without the Roundel stamped on them) seem to be much more susceptible to developing leaks as opposed to the genuine ones. It's happened to dozens of people over the years. Spend the extra money for the genuine BMW tank and be done with it.

Thanks! I actually went ahead and bought the OE unit from Bav Auto... had a gift certificate so it was less than $19 out of my pocket. No brainer.

[tock172]

Originally Posted by JoshInAtlanta

Thanks! I actually went ahead and bought the OE unit from Bav Auto... had a gift certificate so it was less than $19 out of my pocket. No brainer.

Good deal, I love when things work out like that