Chaparral2001

So while accelerating onto the highway, I see smoke bellowing out of the rear just as my check coolant light comes on (at least it wasn't blue smoke!). I pulled over and noticed the upper radiator hose came off and was hanging there. Luckily on the N62 the BMW clamp is not adjustable, but since it had popped off, I bought a new clamp, fixed it on and topped off the coolant. After going to BMW to pickup a new hose assembly, I noticed that there are small parts of hard plastic missing from the connector, which means they are somewhere in my cooling system.

Does anyone have any idea where these pieces may end up? Should I flush the system? Will they damage/clog the system anywhere?

Thank you!

2004 545i 6-speed with 115k miles on it..

BimmerFan52

The hose goes over the metal fitting and the clamp is on the outside of both, so I think any broken pieces would have fallen down through the engine to the belly pan before the hose came loose. I wouldn't sweat it.

But if you haven't done any pm on your coolant system before now you are living on borrowed time. It is recommended that the water pump, thermostat, hoses, belts and vent tube all be replaced around 75K miles to prevent the kind of problem you had.

You are lucky you were just getting on the highway and could shut it off immediately. The BMW aluminum engines have nearly zero tolerance for overheating before head gaskets are destroyed. Keep a close eye on your oil for any signs of antifreeze contamination.

Chaparral2001

Thank you BimmerFan, the plastic piece that broke was where that plastic piece meets the rubber hose on the inside, so I'm certain those pieces are in there. If you look at the hose, it's clamped onto the plastic housing that fits onto the aluminum fitting. The clamp is securing the hose onto the housing because there is a small amount of plastic that the rubber hose fits over.

I have replaced a few hoses, but will go back into the history and make sure all other mentioned items have been replaced...thank you!

It did mention engine was hot while I was trying to get to the auto store. I stopped the engine, let it cool down, and then went another couple miles until I got there. This is the second occurance I've seen that warning, but no issues so far. I will double check oil tomorrow.

BimmerFan52

You are right, I was thinking of another one of my cars.

Yes the hose is clamped to the plastic piece and the rubber hose ends well before the plastic fits over the water pump pipe. However, the water pump pipe is fairly horizontal and the plastic part sleeves over the outside of the pipe. I would think water pressure would have been required to move the plastic part into the pipe once the plastic part broke. Was the hose clamp still attached to the pump pipe with the plastic piece just broken, or had it come off the pipe completely? If it was still attached then was the broken plastic from around the pipe, or past where the pipe ends towards the rubber hose? Maybe the serpentine belt beat it up if the hose had come off completely.

I think if you are going to do a flush you would want to pull all of the hoses loose and flush the block, radiator and pump separately, first in the reverse direction of the normal flow of water and then in the normal direction of water flow in case a piece has become lodged.

It can't hurt, but it is a lot of work.

e6t.lab.rat

Hot coolant from engine returns to the radiator via the upper hose so odds are the pieces are in the radiator, and that is not good. However it is possible they may have fallen to the underbody cover and onto the asphault but if they didn't then those pieces are restricting coolant flow through the radiator, and as a result inhibiting coolant flow into the engine and thus possibly causing the hot engine warning you're seeing. I'd recommend you at least r & r your radiator and thermostat, and inspect the water pump and hoses. Good luck