Brake light on dash comes on intermittently - PeachParts Mercedes-Benz Forum

Renntag · #1 02-22-2012, 01:58 PM

Quote:

Originally Posted by ROLLGUY

... If fluid has been added in the interim, then fluid will spill out when the caliper pistons are compressed to renew the linings.

Good point, but air entering the system is more of a risk if the car must be driven a little longer before service. A calculated risk we have all made in the past.

Quote:

Originally Posted by ROLLGUY

... The best thing to do is replace ALL the brake fluid when doing a brake job. The easy way is to suck a majority of the fluid out of the reservoir with a turkey baster (or equivalent tool), add new approved fluid, and then bleed the entire system....

LOL. so in the end, it is still better to add fluid now, then, at the time of brake service, remove the fluid from the reservoir in order to perform a system flush.
This would then negate the overflowing issue.

Perfect. The system flush is very important and the addition of fresh fluid even for the short term in good for the master.

For the newbies reading this it is critical to change out your brake fluid every 2-3 years minimum. Brake fluid is hygroscopic, meaning it absorbs water from the air. This is what destroys your brake system from the inside out. The instructions given by RollGuy above are spot on and should be followed regularly regardless if your brake linings are being replaced. Fresh fluid will keep the system in service for years to come.

Note to all: It is seldom mentioned that in an old master cylinder, there can be a build up outside the normal contact area of internal seals and cylinder walls. When system pressure is lost, or flushing/bleeding is happening, be mindful of staying in the normal travel area. It is common to damage a seal if pedal travel goes to the limit, thus pushing the seal into the "build up" area and damaging the seal. If you find that the master cylinder will no longer make pressure after repeated bleeding attempts, this may be the cause of sudden failure. It is possible to rebuild a master cylinder if replacement cost puts a new one out of reach.

ROLLGUY · #2 02-23-2012, 12:18 AM

Quote:

Originally Posted by Renntag

LOL. so in the end, it is still better to add fluid now, then, at the time of brake service, remove the fluid from the reservoir in order to perform a system flush.

Very true, and it is cheap insurance. However, if the lining and rotors are allowed to get thinner than spec, the caliper pistons will be at full extension or beyond. Having the brake warning light is a good thing, and filling up the reservoir may lead to procrastination in getting the brakes serviced before a major damage would occur. If the reservoir is filled up, be prepared to do the brakes SOON! Don't wait till the red light goes on again (well actually it will be too late by then).