[Another User Name]

Get home with me '08 335xi, smell coolant, open the hood and coolant is squirting all over the engine.

Go to dinner with the wife in her car and when I get home the car is cool, so I take off the air induction hose from behind the upper portion of the grille and see that the hose leaking is a small diameter (8.1mm) hose that runs along the top of the fan shroud.

What burns me is that it joins to heavy duty radiator hoses, one end that goes to the coolant reservoir and the other end to a fitting by the radiator that accepts the upper radiator hose.

Why didn't BMW just run one hose? It looks like there is enough clearance under the air induction component to have simple run a one-piece hose here. Seems like basic engineering...don't put in fittings or unions where a one piece will do.

Anyway, I take of the hose clamps and the straight small diameter hose is reinforced to take coolant pressure and the ends have a pieceof aluminum tube with small ferrel-like rings that are meant to support the hose where the clamp goes.

The hose is so dry-rotted that it came apart when I tried to pull it out of the larger diameter hose on each end.

My question is can I just cut this out and put a slightly longer middle hose in? The rotten small diameter piece had a lot of crud in it, not blocked but this hose looked like an engineering clusterf*ck. BMW managed to put a cheap smaller diameter hose in that was not as durable as the two hoses it connected, while adding two seemingly unnecessary fittings where none seem to be required.

Surprisingly lame engineering, in my humble view. I doubt the local car parts store has this part, and I don't know if I can get the inch or so of rotten hose out of the ends of the larger diameter hose, so may just have to cut about an inch off of the larger diameter hoses.

Any suggestions?

[juld0zer]

I'm guessing you are referring to the crossover pipe that is made of plastic?

You could get some aluminium pipe and make a replacement that will outlast the rest of the plastic bits? The hard part is rolling beads on the ends so the hose doesnt slip off under pressure. You could roam the wrecking yards for suitable candidates?

[Another User Name]

I stopped by my mechanic, who's done work on my American cars for thirty five years, to pick his brain.

I mentioned your aluminum tube idea and showed him the reservoir end of the hose. He had a piece of scrap brake line and a couple of high pressure hose clamps he gave me. Shout out to John May, Proprietor of Branchburg Auto Repair in Branchburg, NJ! Thanks, John!

Believe it or not, the brake line is within 0.05mm in diameter of that cheap piece of crap tube the German geniuses decided was good enough. One end of the tube was already flared, I cut to length and flared the other end, slid on the clamps, pushed the tube in each end and tightened up the clamps John gave me.

Had just enough Beck/Arnley coolant in the garage, topped it off and let it warm up. Keeping an eye on the temp, I saw the thermostat open and headed to a local bypass that no one uses and cranked it up to 120 mph trying to put as much pressure on the system as I could.

Got it back home, no leaks, letting it cool off and I'll double check the coolant level and everything should be good. I love it when a plan comes together.

Thanks for the tube suggestion!

[PichaDis11]

Are you going to replace the plastic screw atop the expansion tank as well? It's next in line...

[BashShah]

Originally Posted by PichaDis11

Are you going to replace the plastic screw atop the expansion tank as well? It's next in line...

1+ on this.
I went to an auto wrecker for something else.
Came back with 5 of these plastic screws from newer BMWs.
3 black and 2 blue.

There are all the same screws and in multiple locations in many BMW suvs.