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Starting at $3.95, AutoBuffy stocks 1 brake master cylinder reservoir grommets from URO. This small rubber seal seats the fluid reservoir onto the master cylinder body, keeping brake fluid contained and pressurized. When it cracks or swells, it allows air into the system and fluid to leak, which directly compromises braking performance and pedal feel.
The most important factor is exact fitment — grommets vary by reservoir port diameter and profile, and an ill-fitting grommet will not seal properly. Material quality also matters because brake fluid is highly corrosive to inferior rubber compounds. Match the grommet to your Porsche 356Sc's master cylinder brand and port configuration first, then choose material grade based on your driving conditions.
| Option | Best for | What you get |
|---|---|---|
| OEM-Equivalent EPDM Rubber | Daily drivers, stock brake systems, longest service life | Factory-spec dimensions, brake fluid-resistant compound, direct drop-in fit with no modification |
| Nitrile (NBR) Rubber | Budget-conscious repairs, older vehicles, mild-climate use | Good fluid resistance at a lower cost, slightly less heat tolerance than EPDM over extended high-temp use |
| Polyurethane | Performance builds, vehicles in extreme heat or heavy braking use | Superior abrasion and heat resistance, firmer material that holds shape longer under pressure cycles |
| Repair Kit (Grommet + O-rings) | Master cylinders showing multiple seal wear points, high-mileage vehicles | Replaces all soft seals at once, prevents repeat leaks from adjacent deteriorated components, better overall value |
Begin by draining the reservoir to minimize spills, then carefully unclip or pull the reservoir straight off the master cylinder — it is held in place by the grommet(s) alone on most applications. Pry the old grommet out of the master cylinder port, clean the port bore of any residue, then press the new grommet in evenly until it sits flush. Reinstall the reservoir with firm, straight downward pressure, refill with fresh brake fluid to the correct level, and inspect for leaks before returning the vehicle to service.