Originally Posted by rjjarvis
I want to add that Bluebee's posts were incredibly helpful in this process, in particular the little-by-little prying of the hose connector off the fittings. I worked IMMEDIATELY on the disconnection of the lower radiator hose fitting from the metal thermostat housing. I was hoping for the same with the lower connection, but in my 2001 540i6, there wasn't a lot of room to pry with the screwdriver, and there is no metal "ear" to pry against with twisting motion. Plus it is incredibly hard to see down there, even on a sunny day--I recommend additional electric lighting, because even if you do manage to develop a crack to insert a screwdriver into, you won't be able to see it down there. It's just very awkward.
When you apply twisting/prying motion on the lower fitting, you're twisting/prying against the plastic radiator fitting, so you have to use some caution and patience. I found that my hose was on so bleeding tight that I didn't seem to be making much progress: every time I'd exploit a gap down there, and reach for the next biggest screwdriver, the gap would close itself. And then the twisting/prying motion was starting to do damage to the plastic I was prying against. But still nothing would give. And there aren't many angles from which you can twist/pry on the lower hose fitting, due to stuff being in the way. Most of the twisting/prying is going to be from the top, none from the bottom, very difficult from the right side (as you are facing it) and non-existent from the left side. So you lose the potential advantage of being able to pry a little all around the fitting, which would doubtless help if it were possible. If you could get underneath the car, and pry from both the top and bottom, that would probably get the job done faster because of the way the hose fitting is "keyed" into the radiator fitting. But it was cold and damp (and actually snowing) when I did this in my office parking lot and my car is lowered, so it would not have been easy for me to get underneath it.
Things started moving in the right direction for the first time when I pried apart a little, soaked it with PB Blaster, and tapped it with a machinists hammer lightly all around the hose fitting. After a couple of iterations, and continuing both the twisting/prying screwdriver technique outlined by Bluebee, and rocking back and forth a little using a screwdriver stuck down in the hole made available by removing the temp sensor (BTW, if you do this part, you are NOT going to be able to reuse the existing hose), it gradually began to give way.
None of this would have been possible without Bluebee's great instructions and tips, and removal of the fan shroud before attempting the lower hose disconnection.
One last thing: after getting the doggone lower radiator hose off, I STILL could not tell where the water was leaking from it after examining it. I was afraid that would happen, which is why I also bought a new expansion tank just in case (my existing one was 12 years old). I'm not very knowledgeable about radiator hoses but I would bet that if you put 2 bars of pressure and 110 degree celsius coolant into it you'd be able to see some sort of defect open up. But maybe without that pressure it just won't be evident by normal examination. I've made a mental note to myself in the future just to replace suspect hoses, and not fret about being able to pinpoint a leak exactly each time. Once you go to the trouble of taking the thing off, just replace it with a new one, IMHO.