Problem with brakes - PeachParts Mercedes-Benz Forum

digieditny · #1 05-24-2011, 09:59 PM

This might be an obvious problem. I just drove the car to home depot. When I hit the brakes, the car slows down then I felt the brake pedal go down another 2 inches and then I felt grinding.

This only happened on the way to home depot. Did not happen on the way home.

What can this be?

Thanks!

digieditny · #2 05-24-2011, 11:00 PM

Could it be as simple as my brake pads? Sorry! It's got me worried!

vstech · #3 05-24-2011, 11:05 PM

I assume this is on your sig 84 300 wagon.
the part about the pedal dropping has me concerned. totally worn out pads would grind, but they would not cause the pedal to drop UNLESS you were dragging steel pads for quite a while, and caused the caliper to boil the fluid. when you stopped at HD did you smell anything overly hot or boiling?

digieditny · #4 05-24-2011, 11:13 PM

Thanks for the response. Yes my 1984 300 TD. When I first got this car about 8 months ago, the first thing I did was take it to the mechanic and they installed new brakes and rotors. I haven't been dragging steel pads. The brakes haven't really made any noise since today. I didn't smell anything overly hot...

My girlfriend took the car to work today. She said the brakes were normal.

digieditny · #5 05-25-2011, 12:49 AM

From what im reading, it might be my vacuum brake booster, a leaking caliper, or the master cylinder. I dont think its a leaking caliper since the fluid is still full. Are there any tests I can perform to find out whats failing? Ill have all day tomorrow to test things out. Thanks.

leathermang · #6 05-25-2011, 12:54 AM

First try putting new fluid in while bleeding the brakes for any air that might be in there... then report back....

digieditny · #7 05-25-2011, 09:46 AM

Sorry but I'm totally new to all this. Well I don't have a second person to pump the brakes for me today. Anything else I can do?

I've seen some tutorials of making a pressure bleeder. Is this something worth doing?

leathermang · #8 05-25-2011, 10:46 AM

You talked like you had today to really work on it...
so making a pressure bleeder is not effective use of your time in my opinion... FIND A HELPER and train them..
but remember.. the responsibility of not going to far in the pedal travel IS YOURS>>> THE PERSON AT THE BRAKE BLEEDER NIPPLES...
many very short squirts.. just open and close as fast as you can... is the secret to limiting the travel.... I have done it this way more than 40 years without once messing up the seals on the mc by going too far..
new fluid ( just opened bottle so no moisture can have gotten into the ' new can either ) ... assurance that no air is in the system
.. that is the base line from which you need confidence to proceed..
find or hire a helper..

A pressure bleeder has the potential for really helping a one man shop ( like me) ... but one needs to be willing to discard the fluid not used after the job is over ( left in the bleeder ) ... due to air contamination unless one pressurizes with nitrogen or argon or something really dry... most do not have that ability... and it is just fine to just get rid of the fluid so good fluid is used the next time...

leathermang · #9 05-25-2011, 10:51 AM

ok.. I was jumping ahead a little faster than I should have..

On the first time ( perhaps more times ) working on something as important as brakes.... I think you have to have someone experienced to show, guide, or do it while you watch ....
Brakes are too important to be considered ' learning material '... This is not something you can count on a forum or written instructions being able to keep you safe and alive... there are general mechanicing things which are assumed by us and books as to your overall general knowledge.. which, not being compensated for CAN KILL YOU or your FAMILY....
Greg

digieditny · #10 05-25-2011, 11:07 AM

I do have all day but I wasn't aware that I would need a team. This forum has been extremely useful for me. I've done filter changes, tie rods, upper control arms, glow plugs, and shifter bushings all with the help of this forum.

If bleeding brakes are as hard as you say, it's fine. I'll take it to the mechanic. I trust your opinion. You've been bleeding brakes longer than I've been alive.

leathermang · #11 05-25-2011, 11:11 AM

It is not hard per se...
it is only that they are SO important that any mistakes are not acceptable..
There are certain rules which if not followed would put you in harm's way...
not cool for the small amount saved..
but I would encourage you to find someone to mentor you so that this time is the first of your learning experience on them...
But if there are any questions... you just owe it to everyone to lean towards safety side of the equation...

digieditny · #12 05-25-2011, 11:21 AM

Thanks for the advice. I'm just gonna take it to the mechanic. I'll get someone to show me next time when there's nothing wrong so I'm not pressed for time.

leathermang · #13 05-25-2011, 11:40 AM

A very logical and mature choice I believe....

Maxbumpo · #14 05-25-2011, 11:51 AM

My money is on a bad master cylinder.

leathermang · #15 05-25-2011, 11:55 AM

Before taking it in to the shop..
take a file or something and make a little mark where it can not be seen on the MC ... and ask for the return of any bad parts they replace...
which is standard procedure from good shops anyway.... don't tell them yours is marked...