differential breather hose

[mcerbm]

After seeing that I was losing a splattering of diff oil around the back of my car I removed the boot floor to have a look. There wasn't a breather hose but a cap that was in place on the ford diff breather hose location. It was still in place but must have lifted to allow fluid to escape when pressure built.

How do you route the breather hose, does it just go off horizontal and then routed somewhere so it breathes fluid onto the road and not on the car. Or should there be a cut out on the boot floor to give mpre height to the breather hose. Also is a catch tank necessary?

The car is used almost elusively competitively so it gets a hard life so I'm not worried about touring type issues with catch tanks in the boot.

[Paul Richards]

I know some have fitted a little catch tank, but I don't think this is necessary. I have found success by fitting a long plastic breather pipe like a pigs tail i.e. with a loop in it. No need to alter the boot floor. I cable tied the end of the pipe pointing towards the floor near the wheel arch. 

[dave_h34]

Probably a silly question but does the BMW diff have a breather hose? I couldn't see/feel one on mine.

[Geoff Brown]

BMW Diff does not have a breather.

The lack of a breather pipe was brought up in my lengthy debate about BMW output shaft seals leaking. There are two ways for the internal pressure build up to go.....out through the shaft seals!

 

[A10ROX]

Pipe into boot and add a syringe 

oil heats expands into the pipe syringe opens oil cools shrinks back into diff closing the syringe

not my idea see: Gemzoe Motorsport

[dave_h34]

Thanks Geoff. Despite the fairly continuous weep on mine when the level was checked oil actually came out of the filler hole. A slight overfill perhaps but certainly the weep isn't leading to the loss of a lot of oil.