hydro booster leak

[moshik1958]

hi
my car bmw e23
i have a leak between the hydro booster and the master cylinder
there is an O ring (new 1)
the hydro booster the mc and the regulator are new
i can see that the seal not really can seal the hydrobooste
there is am path on the metal ring on the hydro booster
thx for your help

[Shawn D.]

there is am path on the metal ring on the hydro booster

Could you rephrase this, please?

[moshik1958]

hi
the metal pipe on the booster that hold againts the O ring on the MC its with kind of grooves on it .
i cant understand how the O ring can hold the oil from leaking.
thx

[Federico]

The plastic cup at the end of the booster has an external oring, and also a shaft seal in the center.
Here are some pics: https://www.shiftbmw.com/model/e24/brea ... booster-2/

The shaft seal is metric 9x22x7 if I recall correctly.

[Mike W.]

I'm not really following your description, but by far the most common leak on them is on the booster, there's a large O ring. There might be a O ring between the booster and the master cylinder, but I don't think it's needed, nor would it prevent a leak. On cars with a vacuum booster that O ring between the master and the booster is needed and is critical to hold vacuum, but not on hyrdoboost cars.

Not a difficult repair although you have to remove the booster to do it, just be aware once you remove that screw that holds the cup in place in the booster it's going to want to spring out, it's under a lot of pressure and it will surprise you, so make sure you're pushing down on it hard on a bench or something so parts don't go flying. Like I said, it will surprise you how much pressure it's preloaded with.