: Brake Reservoir plug

12-04-2008, 02:30 PM
So for as long as I have owned my car (92 525i) it has leaked a very small amount of brake fluid usually every six or seven months it pops up that the brake fluid is low. In three years I have not even added a full bottle's worth so I just let it go as a small leak because I could not find where it was leaking from. Well today I found it, the sensor went off so when I got home I went to add some fluid to it and while trying to unscrew the filler cap the entire reservoir twisted and brake fluid starting pouring out. The rubber plug going from the reservoir to the master cylinder tore and upon looking closer inspection I suspect this was where my problem was to begin with because the rest of the rubber looked very close to tearing. So I am going to replace both plugs, even though only one is actually torn the other looks close. I have two questions, one where is the best place to buy the plugs I know the dealer will have them but they are an hour away and obviously are more expensive. The second question is should I use this opportunity to flush and refill the system with new fluid since I already have lost a good deal of fluid and it is now exposed to the open air? And if yes then has anyone on here done this or know of a good writeup to follow.

Brake reservoir plugs Part #2

Thanks for reading.

bimmer dot info
12-05-2008, 06:50 AM
I got mine from autohausaz.com.

I'd go ahead and bleed the brakes.
When you remove the resivoir be sure to keep a bit of fluid in the master cyl holes (to prevent air ingestion). Replace the plugs and master cyl resivoir and refill. Jack and support the car (much easier than doing one wheel at a time). Find a helper. Have your helper pump up the brakes. Attach a bit of clear tubing to the bleeder screw you are working on. Open the bleeder screw while your helper is pressing on the pedal. The pedal will go to the floor. When it does quicly close the bleeder. Have your helper pump them up again and repeat this untill the fluid is clean and free of air bubles. Repeat at all wheels starting with the one furthest from the master cyl ending with the closest. Remember to add fluid to the resivoir or it will suck in air and make things much harder.

Do not over tighten the bleeder screws. Use new fluid. Keep the fluid off your paint. Test your brakes when you are done before you start moving and before you start moving fast.
If you are left with a spongy pedal (worse than before) bleed it again.