Help with master cylinder grommets - incredibly hard to install, splitting

[kombination]

I just found that both of my master grommets split in half above the body of my few-months-new master cylinder, causing all my fluid to dump out. Fortunately this happened in my driveway.

When I installed the reservoir to the grommets as part of replacing the whole MC (Centric replacement for a Lucas MC with the angled outlets), the reservoir pipes/nipples/barbs were incredibly stiff and I had a hell of a time getting them installed into the grommets on my workbench. I thought I was going to break or split the reservoir plastic where the pipes meet the tank. Instead somehow the grommets split almost completely in half right above their holes in the MC body weeks later.

Anyone dealt with this problem successfully? I found a ten year old post of people reporting similar pains in the butt or reporting just "they pop right in". Carefully using a heat gun on the reservoir didn't seem to make a difference when I was last attempting the install - the barbs just did not want to go in all the way. Apparently I got them in deep enough to catch against the rubber but not to actually pop through and hold it properly.

Is there something I can do to soften the grommet rubber instead? Soak them in ATF before installing them? Take the whole MC off and heat that thing up? What is the trick? I'm worried I'm going to end up with the same install problems & resulting failure with the replacement grommets.

DOINK:
Edit update so as not to needlessly bump - the issue ended up being the supplied grommets in the Centric part were 3-4mm too long on the bottom. I never had a chance of getting the barbs to pop through and seat.

The separate replacement grommets I ordered from ECS Tuning were exactly the same save for less rubber on the bottom/MC side. Popped the reservoir in like everyone says it should.

[shogun]

well, as we do not know your VIN and engine type, built year month, p/n of master cylinder, it is difficult to comment what p/n is correct. Use the VIN and check which master cylinder you have and which grommet fits http://bmwfans.info/parts-catalog

[cirrusblau]

Are you referring to the brake master cylinder? I replaced mine a few months ago with a TRW unit that came with new grommets, but since I also had new original BMW grommets, I used those rather than the ones that came with the MC. I remember the TRW grommets to be stiffer than the BMW part. I just lubricated the nipples with brake fluid and pushed it in. You just have to make sure that the reservoir has seated properly against the grommets, particularly the rear nipple.