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Old 03-10-2017, 04:48 PM   #1
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Join Date: Mar 2017
Location: Pittsburgh, PA
Posts: 6
My Ride: 2005 BMW 330xi
2004 330xi Coolant Leak Upper Radiator Hose

I've read multiple threads about this, but can't seem to get a clear answer....before anybody tells me to search it on here...

Upper radiator hose that connects to the thermostat side keeps blowing off.

originally the factory clamp which was just a metal ring around it, i thought to be worn, so after 2 times of that slipping off I just replaced it with a metal screw tightening clamp.

I topped off the coolant (did not bleed the system), and drove (this was all on my lunch break) back to work. I decided to leave my car running and keeping a eye on it from inside my store. 10 minutes or so later it was smoking like hell from the hood and the hose on the new clamp side forced itself off once again!

I quickly shut off the ignition, as the temperature was climbing to the red (did not make it all the way about 3/4)...

I have no idea why this keeps blowing off...it's like there is too much pressure and not being able to escape so it blows that hose off.

Please help!

I've only had the car for about 10 days now and it started doing this 3 days ago, otherwise it's been amazing.

Last edited by rlockwich; 03-10-2017 at 04:50 PM.
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Old 03-10-2017, 05:29 PM   #2
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Join Date: Dec 2007
Location: Charlotte, NC
Posts: 1,052
My Ride: 03 325XI Sprt Prem
On the hose, after the metal band is the plastic connection. Within that plastic connection is a thin metal clip. Make sure you are pulling up the metal clip, get the hose fully seated in, then push the metal clip back in. But now since the system was opened, you'll need to bleed the system properly. The air in the system is most likely causing the overheating.

2003 325XI 5-speed ZSP ZPP
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Old 03-10-2017, 09:18 PM   #3
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Join Date: Mar 2017
Location: Pittsburgh, PA
Posts: 6
My Ride: 2005 BMW 330xi
Just finished replacement of the upper radiator hose. Was in a bind, bought it for $25 from AutoZone and did it in the parking lot. They had a incline in their parking lot, had to use Peak 50/50 instead of the wasted 1 gallon of BMW antifreeze it drained out the past day. Went through almost 2 gallons to bleed the air out of the system. Drove it for over 1 hour just now and everything dried up (burned off) and is running fine.

The problem was the hose connecting to the thermostat side had deteriorated from the heat at the plastic connecting to the rubber hose.

FYI for any newbie like myself, not used to BMW parts, unlike traditional vehicles I've owned in the past. The radiator hoses are connected to the plastic parts that mount over their corresponding connectors (e.g. Expansion Tank or Thermostat housing). I'm used to $5 rubber hoses only that slide over these tightening down with just a hose clamp.

If I wasn't doing this reply from my phone is post pics of how bad the plastic underneath the rubber was, there was hardly anything left for the hose to connect to.

Damn just realized...Any parts of plastic probably went down against the thermostat inside the housing. WTF
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