NO BRAKES!!! OH NO! What do I do! - PeachParts Mercedes-Benz Forum

777funk · #1 01-10-2007, 08:45 AM

I just bought a w123 300d turbo 1984 for $750. It's got 180k and runs like a new car. I've done some work to it of course but the engine was solid when I bought it. Just needed some minor things :glow plug relay fixed... etc.

Anyways... I have had the brakes go out completely about a month or two ago. I flushed the brake fluid a few weeks ago and they were much more responsive. I'd barely touch the pedal and they'd engage (like a new car). It seems they're getting weaker and weaker as time goes on. This morning I made a 1 hour drive and I had to push the pedal to the floor to get them to even work. And I mean all the way to the floor. If I pump the brakes it gets a little higher and more pressure (they also work better). But I shouldn't have to do that. What could be wrong???

I love this car but if I can't stop that's a slight problem!!

t walgamuth · #2 01-10-2007, 09:00 AM

it sounds like you have a leak. look for wet spots under the car. it could be at a wheel or in the line running under the car from front to back.

if there are no leaks and the level in the mc is full it would then be a failed master cylinder.

good luck

tom w

777funk · #3 01-10-2007, 09:37 AM

Thanks Tom for the reply! I'll give it a look.
Thanks so much,
Nick S.

TX76513 · #4 01-10-2007, 09:55 AM

If you do not have an obvious leak - have someone apply pressure to brake pedal while you look for any swelling of the rubber brake hoses (especially rear).

Biodiesel300TD · #5 01-10-2007, 12:12 PM

You may have developed a vacuum leak too. Do your door locks work? If they do you probably don't have a vac leak, but if not you might start looking for vac leaks.

dmorrison · #6 01-10-2007, 12:33 PM

No brakes means the pedal goes to the floor and it will not stop. Or the boost is gone and the pedal goes to a point and then has resistance, but you have to push very hard.

If the pedal goes to the floor, then you have a fluid leak.
Check all lines and the rubber lines for swelling. Look for fluid somewhere. If you dont' see any but the fluid level is going down then the master cylinder is leaking into the brake booster.

If the pedal just gets hard and your doing all the work. Then either its the booster of a vacuum problem. If the doors, transmission and shutoff ore normal then its the booster. If the list above is giving you problems then it is a vacuum problem.

Dave

vstech · #7 01-10-2007, 12:51 PM

Quote:

Originally Posted by dmorrison

If the pedal goes to the floor, then you have a fluid leak.
Check all lines and the rubber lines for swelling. Look for fluid somewhere. If you dont' see any but the fluid level is going down then the master sylinder is leaking into the brake booster.

I gotta disagree dave, if the pedal goes to the floor it could also be that the seals in the master cylinder are just allowing fluid/pressure to flow around it. this will not show any leakage, it will not show any fluid loss in the reservoir and the symptoms will be as described. pumping quickly the pedal can sometimes give you full or improved braking. one way to test this, at a stop, with the engine running, put firm pressure on the pedal, if it slowly creeps down, and you are NOT showing any fluid leaks. get a new master cylinder.
John

dmorrison · #8 01-10-2007, 01:32 PM

Quote:

Originally Posted by vstech

I gotta disagree dave, if the pedal goes to the floor it could also be that the seals in the master cylinder are just allowing fluid/pressure to flow around it. this will not show any leakage, it will not show any fluid loss in the reservoir and the symptoms will be as described. pumping quickly the pedal can sometimes give you full or improved braking. one way to test this, at a stop, with the engine running, put firm pressure on the pedal, if it slowly creeps down, and you are NOT showing any fluid leaks. get a new master cylinder.
John

I will NOT disagree with you. The fluid leak into the booster is what happened to my daughters car. Your scenario is another potential problem. It does happen and is indicated by the symptoms you have described.
I would not have disagreed with my post I would have just added to it with your post.
What I was trying to discern with my post is whether the pedal was going all the way to the floor or was it just loosing it's boost.

Dave

PS
Usually if the internal orings are bypassed the fluid is designed to leak out the "leak hole" at the base of the MC. The MC was designed with this to show a leak problem. Could the MC leak internally and not drip out of the leak hole, sure. God could also take away your brakes just because it's your time

vstech · #9 01-10-2007, 01:53 PM

Quote:

Originally Posted by dmorrison

Usually if the internal orings are bypassed the fluid is designed to leak out the "leak hole" at the base of the MC. The MC was designed with this to show a leak problem. Could the MC leak internally and not drip out of the leak hole, sure. God could also take away your brakes just because it's your time

Cool, go MB! I was unaware of this scenario. sorry if my other post was offensive, I only meant to add to the list of possible problems.
those who have read my other posts and future posts will come to realize, I am a slow learner, and sometimes have that stinking foot in mouth disease.
John

patbob · #10 01-10-2007, 04:16 PM

I've not had this happen to me, but have talked to several other people over the years who have.. Sometimes, if a brake rubs and you drive it that way far enough and fast enough, it can generate enough heat to boil the fluid in the slave cylinder down by the wheel. You step on the pedal and it slams to the floor but no brakes. Pump it and you raise the pressure on the fluid enough to recondense it, and then they work. I've known one person who lived with it this way rather than fix it.. definately not my cup 'O tea.

I dunno if MBs can have this happen, but having to pump it up before the brakes work sounds like a symptom. Shoudl be obvious if the brakes on one of the wheels are rubbing.

I remember something about water in the brake fluid being part of this equation (ie. it's what boils?), but I can't recall that far back clearly enough to know for sure (Oops.. dated myslef

)

777funk · #11 01-10-2007, 08:08 PM

Cool, thanks guys... I do see a possible culprit. The rubber grommets that hold the resvoir to the Master Cylinder have fluid on them. It's not a dripping leak (yet) but it's wet looking so I bet air can get in there as well and maybe that's getting into my lines. It's not a vac issue. The pedal's easy to push. And it won't go down if I pump it and hold it so it's not a leak in the line (At least a fast leak).

So... since I bled the lines a couple weeks ago and it was better for a while (worked great). I'm assuming air is getting in there.

... And since I see the wet rubber grommets on the MC/Resvoir connection, I think it may be the problem. I guess I'll try it and see what happens. Also, Dave I like your comment 'may be God's time for you'. Lord, I sure would hope not, but funny! Anyways, thanks guys for your help. Let me know if there are any tips in getting that MC/Resvoir sealed or if someone thinks this is not the correct diagnosis.
Thanks so much!
Nick

777funk · #12 01-20-2007, 11:14 AM

One other question... I've got a master cylinder with 3 brake line outs and one fitting that's larger than a brake line. What's that one for? It's a 300d m.c. but I think it's from an older one. This is a late 70's and my car's a 1984. Can I plug the 4th hole with a bolt and go.
Thanks,
Nick