[Sean335i]

Guys,

Just driving home, not spirited at all, notice steam coming out from the hood line and pulled into a parking spot and popped the hood. Coolant seems to have sprayed everywhere and its just burning off, no smoke, no overheating, no warning lights, just a surprise. Engine oil temp looked fine as well.

I changed the oil last weekend and topped off the coolant. I just checked coolant level and its almost all gone.

What the heck could have happened?

i havent had any leaks, water pump changed about 6k ago. No other engine issues...

Help!

[Sean335i]

most likely answer thus far is that i overfilled the coolant tank...

[rif75]

I have this issue few weaks ago but in my case it was the water pump that was leaking, since you change yours...Maybe you can try to change the cap of expension tank, it's very cheap, I bought it yesterday for my car 11 €. Chek all the line of coolant, add some coolant et do a purge procedure since you lost a lot of coolant.

[Izero]

not sure if Cobb can turn on the water pump similar to the JB4's "MaxCool Mode" which would run the water pump for you after the car is warmed up and you could then inspect where it might be coming from?

If it "sprayed" all over the engine bay then that would most likely indicate that it's a pressurized part of the system... Or you simply overfilled it while the engine was cold and once the car warmed up the overflow bottle got pressurized enough to pop the lid and splash coolant all over the place... Usually there are "hot" and "cold" lines to fill to.

Usually most common areas for most cars are coolant lines to and from the radiator, the radiator itself, which is usually from the seam between the plastic ends/top/bottom and the metal core itself.

The lines going to and from the heater core are usually a common place as well as the lines coming directly to/from the water pump.

[Sean335i]

Thanks guys. I'll replace the coolant tank lid and go from there. Thankfully she runs well and no other issues. May be a human error of overfilling or the exp tank lid is done.

[Jeff@TopGearSolutions]

Pop the coolant expansion lid and see where the meter reads when the vehicle is cold. A little stick should be floating up with lines that dictate where the level should be if hot or cold, IIRC.

With the hood open, I'd just start the car and let it idle and warm up, see if you can find anything out of the ordinary.

I know one common failure is the coolant line near the charge pipe, driverside. It's very very thin. A quick jab with a screw driver and it's usually done. It's pretty obvious when you hit it though as it makes a mess.

Oh and make sure you hose down the engine bay cause the coolant is corrosive over time.

[zero2sixtyZ]

This happened to me:
Easy check and fix - pull snorkel and check if hose is wet / source of leak.

Coolant Vent Line from upper rad hose to reservoir

http://www.e90post.com/forums/showthread.php?t=935690

RobC fix: http://www.e90post.com/forums/showthread.php?t=870353

I replaced Part #6 in this diagram, but when I pulled it off of Part #1, the plastic nipple snapped, so I had to replace Part #1 as well.

Part Diagram: http://www.realoem.com/bmw/showparts...76&hg=17&fg=30

Then refill and flush: http://blog.bavauto.com/13140/bmw-co...bleeder-screw/

Hope this helps.

[BB_cuda]

2 things.
1) you had the system open for water pump change. Not sure if you did the work or a mechanic. Need to make sure no entrapped air in system
2) pretty sure you can have the system pressure tested to look for leaks.

I'm a decent mechanic but seem to always screw up the entrapped air thing. I paid an Indy to change my engine coolant. He told me he pulled vacuum on my cooling system and then pumped back coolant in system. He showed me his apparatus that has a three way valve that has a vacuum port, an inlet port for new coolant, and lastly a hose going to engine coolant system. Good Luck

[BrianPlum]

Originally Posted by zero2sixtyZ

This happened to me:
Easy check and fix - pull snorkel and check if hose is wet / source of leak.

Coolant Vent Line from upper rad hose to reservoir

http://www.e90post.com/forums/showthread.php?t=935690

RobC fix: http://www.e90post.com/forums/showthread.php?t=870353

I replaced Part #6 in this diagram, but when I pulled it off of Part #1, the plastic nipple snapped, so I had to replace Part #1 as well.

Part Diagram: http://www.realoem.com/bmw/showparts...76&hg=17&fg=30

Then refill and flush: http://blog.bavauto.com/13140/bmw-co...bleeder-screw/

Hope this helps.

Forgive me for commenting on an old thread, but it was tremendously helpful in quickly diagnosing and confirming my coolant leak.

I can't get over how cheap BMW decided to go with this piece of hard plastic venting line above the radiator. The plastic tube cracked open length-wise about an inch long and dumped half a gallon of coolant in 1 minute. I had to be towed home.

I happened to check the coolant level right before the trip and it showed no loss of fluid since 1500 miles ago.

After I removed the plastic tube above the radiator, I decided to experiment with putting it in boiling water for a couple minutes. I took it out and gently squeezed the plastic. It had become soft and brittle and crumbled like cigarette ash.

BTW, the nipple on the hose between the radiator and engine also broke when I was replacing the venting line. That was also made of cheap plastic.

[malgyver]

People commonly replace this hard plastic line with a metal tube and hose clamps. You can use any tube, really, but brake line from an auto parts store is a decent option. I flared both sides of the tube I used, just so there was extra protection from it sliding apart under pressure.