2006 4.4i coolant leak
 

Working on a friend's car. Coolant started to leak, lots of steam from under hood. On teardown, the hose joint under the throttle body just fell apart in my hand as I was working around it. Originally thought it was the valley pan seal, but I bridged the two ports on the cylinder heads and the fitting from the expansion tank. Charged the system up with shop air and found a very slow leak around the pressure cap on the tank. Might have gotten lucky on this one.

Wow. Those hoses are really swollen. If you haven't already, I'd say it's time to change out the rest of the hoses.

When we do our coolant service (roughly every 5-7 years) we replace all of the hoses, water pump, overflow and cap. I'm probably telling you something you already know, but just throwing it out there.

In my experience with BMWs since 1987 (all used), mine and multiple friends, I've never had a coolant hose actually fail.


Once plastic radiators were introduced, failures happened at the connections, usually due to overtighened clamps. Added plastic parts for the quick-connect systems - that's where they fail. Sections of rigid plastic in coolant lines (think bleed line on top of radiator on E60) shatter when you move them once they're aged.


In this case, the 4.4 got new major hoses on the front. Heater hoses left alone. There's a 'y' connector in the upper hose that had another cracked plastic fitting. Nearly 200,000 miles on the OE hoses though.

Totally agree. I too have never had a hose fail, but the composite ends certainly do. Literally had it happen to my daughters friend's car last weekend. Lower radiator hose failed at the connector at the radiator.

What I was getting at was replacing those hoses is cheap insurance against being stranded or a head gasket.

I just bought my first 4.4 e53. I have never owned a BMW V8. Always been a 6 banger guy. Got it cheap but noticed it has the original radiator and hoses. On my list before it goes out of town. As a matter of fact, I had to replace lower radiator hose and overflow hose just to get it home! I'm a little skeptical of the V8. The 6 bangers have been so reliable. We'll see. Fingers crossed!