90% successful on master cylinder change..help - PeachParts Mercedes-Benz Forum

jcd · #1 05-22-2002, 11:04 PM

Swapped out new master cylinder today. Everything went perfect, almost to the point of not spilling a drop of brake fluid. The only problem was, I couldn't get the bleeder valves open on the rear brakes.

Test drive was successful, and I'm going to an Indy Tech to have my valves adjusted Friday. I trust that 1 day of driving will not hurt.

Any advice on breaking loose bleeder valves.

JCD

tcane · #2 05-22-2002, 11:53 PM

Try penetrating oil overnight, then use a soft mallet or a dead blow hammer to strike the bleeder toward the caliper, then use the correct size 6 pt wrench or 6 point socket (not a 12 point, too much slop) to loosen the bleeder. If this fails and the bleeder is stripped, then grab the vise grips and remove them, then replace with new ones. These should be tightened to only 60-80 in. lbs., someone tightened them way too much - common problem. Brake fluid needs to be changed every two years (I do it once a year) because brake fluid absorbs atmospheric moisture leading to rust in the brake system - absorbing moisture is why brake fluid changes color becoming opaque.

Good Luck!
Tom

jcd · #3 05-23-2002, 07:10 AM

I'll try your tips tonite. I survived the drive to work today. It is amazing how much more relaxing your drive into work is when you have brakes.

Except for the bleeder valves, this was a very easy job, and the Haynes Manual is spot on.

I agree with your advice on swapping out brake fluid. Mine looked like _ _ _ _.

JCD

anhydrous7 · #4 05-23-2002, 03:03 PM

JCD,

If the penetrating fluid does not work, I have found heating the bleeders with a torch will loosen up the bleeders and allow you to use the proper size wrench to crack them open. You must be careful, as too much heat can damage parts and also you can potentially boil or even catch the brake fluid on fire.

If you are careful though, it should prevent you from having to replace the bleeders or using a vise-grip or channel locks and destroying the bleeder.

I would recommend flushing the system once you are able to open the bleeders.

Hope this helps.

peterhardie · #5 05-24-2002, 12:23 PM

On most cars that I have repaired I have used a pair of vise-grips (clamp on the flats) to break tough bleeder screws. You just have to be careful, and I have a selection of them, with different clamping faces.

Penetrating oil is good too, the trick is to remember to soak them the day before.

When a vise grip twists the bleeder into oblivion, I take that as a sign that full replacement of caliper/wheel cylinder is in order.

Time to get those brake line wrenches!

Peter

luvmysd · #6 05-24-2002, 05:25 PM

I have had luck to some extent with trying to tighten the bleeder first the try to loosen but be careful that you dont break it. I have also had good luck with a propane torch.

jcd · #7 05-24-2002, 06:45 PM

Just waited 24 hours after dripping on some WD-40. It is amazing what a difference a day makes.

Usually, when I am going to break some bolts loose, I hit them with WD 40 about a week ahead of time to let it soak. This time, because I needed brakes, I broke the rule.

Time and patience are key factors with an old car. I'll be more patient next time.

Thanks for all of the advice.

JCD

#8 05-26-2002, 01:54 AM

Okay, so it isn't exactly text book, but it does work and does give pretty good brakes! Air bubbles are kept to a minimum.

If I can't break the bleeder loose, I loosen the hose and let it drip keeping an eye on the resvoir to make sure it doesnt run empty. You can get a pretty good bleed by bleeding the hose to cylinder method. The only amount of possible air is between the hose fitting and the caliper or cylinder which is not going to make a huge difference. It'll stop! the car. Eventually if any air was in the line it'll work itself out.

Oxy-Cetelene torch is always the better way. It has the most intenze heat - *6,000 deg F - And the brake fluid won't boil or hurt something as long as you direct the heat right.
I've not ever had a problem getting a caliper almost orange and then letting it cool off.

Want to see a brake get orange hot a lot? watch NASCAR, every now and then they show the little mini-cam that shows the brakes. Now you wanna talk about getting brakes Orange hot and that is every turn for how many laps? That is a lot of heat! So, warming a cylinder with a torch isn't going to hurt much. Unless you place the heat directly on the rubber or direct the heat to leaking fluids.
Brake fluid has to get pretty hot before it'll burn - And the Best way to heat it is off the car anyhow.

240 Ed · #9 05-28-2002, 04:37 AM

JCD

Do yourself a favor and buy a can of penetrating oil and use it instead of WD40!

I am glad it all worked out for you, and hope you changed your fluid completely.

good job!

#10 05-28-2002, 12:58 PM

My father knew this chemist who worked for Total Refinery. He asked him to find out the chemical compostition of WD-40. To his amasement, WD-40 is 95% fuel oil! and other ingredients.
Total refinery also made a lubricant that they used solely for themselves that had an extremely small area of penetration. Ratings are done by what is the smallest area a lubricant can penetrate.
It was, I was told the world's smallest area of penetration. Why they didn't market it, I don't know.
But I had the oportunity to try some of this stuff, totally amazing!

Water has a really small area of penetration and WD-40 supposedly is 1/4th that of water. This stuff that Total made had a rating of 1/32.

I am assuming they use water as the base-rating-standard.

CR-2 was a really great penetating lubricant, but EPA people seen how great it works so they said it was unhealthy and so we can't get it anymore.
But it has a different compound now and NAPA carries it. really good stuff, it removes some rust also. (although they don't make that claim)
Oh, before I forget it - ever have rust and want to get rid of it - anywhere? Toilet Bowl cleaner! Tidy Bowl. Squirt it on direct. And then water flush.
Have rust stain in sink or shower head rusted up? or surface rust on your car?, bolt rusted up?, yeah it works great!

I also found out some neat qualties for Brake Cleaning Fluid, that stuff in the spray can. It works great for cleaning your guns! It removes powder and dirty gunky oil from the action and barrel.
But, be pre-warned, it also removes all of the protective coating of oil that protects the metal fom rusting, so you'll want to re-oil right away.
The neat thing is that it cleans so well that it leaves virtually no residue. The active ingredient is, Naptha.
Naptha is great for cleaning any surface of oil. But watch out for those plastics! Melt down can happen!!!
It does some really wierd things to welding helmet clear lenses. Or those eye and face shield protective lenses. Nope, I didn't play around in the shop, liar.

jcd · #11 05-28-2002, 01:24 PM

Not to turn this into a flaming post on penetrating lubricants, but, what do the rest of you guys use.

I did totally replace the brake fluid. Honestly, when I read that it should be changed annually I thought, WHAT THE HECK.

jcd · #12 05-28-2002, 01:25 PM

Hit the wrong button.....continuing post.

But after looking at the condition of the old fluid and seeing how easy it is to change, I'll now do it annually.

JCD

240 Ed · #13 05-29-2002, 12:53 AM

I shall give my standard lecture on brake fluid, for those who may have mercifully missed it! Ha, Ha too late! YOU MUST READ ON...

Brake fluid is hydroscopic (or hygroscopic). Means it LOVES water.
Huh? where does it get water...?

There is a tiny hole in the master cylinder cap which allows atmospheric pressure to equalize when the level drops due to pad wear. Eventually over the year, the fluid becomes diluted with water. This water can cause rust in the system, but a worse fate than that awaits!
(wait for it)

Brake fluid has a certain boiling point. DOT 3 has a lower point than the later DOT 4. (NEVER USE DOT 3) DOT 5.1 has the highest.
DOT 5 is silicone fluid and does not absorb water, and is not included in this discussion.

Okay, here is what happens. Water dilutes the fluid, right? Right.
Unfortunately, water boils at a lower temp than brake fluid, so the boiling point of the brake fluid is now lowered.
Why is this important?
In normal use, you won't notice the difference. Brake feel stays the same. Even if you were to use straight water!
The problem comes with intense use, say coming down a mountain side with sustained brakeing (and pulling an enormous 80 ton yuaght, say). (...how do you spell yatt?)
Your calipers heat up with the attendant friction (normail). But now, because of the comprimised brake fluid, the fluid starts to boil! What happens when the water in the fluid boils?
That's correct, you get STEAM!!! STeam is a gas! gas does NOT work well at all as a hydraulic medium!!!
What happens to your brakes?
NOTHING!
It is known in the trade as "brake fade". (one of several types)
No matter how hard you press on the pedal, you won't get any more brake. You will probably start to speed up as you are going down hill. The press folks call this "...he lost his brakes"

There you have it.
Change your fluid at least once every other year (in dry climates) and if you live in Louisiana or some humid place, once a year.
Pain in the butt, huh.
Your choice, but you are now informed and can now bore other people with said lecture.

#14 05-29-2002, 02:29 AM

Hey 240 Ed.
So why does one get Brake fade with airbrakes? Semi - That brake fad is just plain Hot Hot brakes! so hot they won't do a thing! And then it is either catch on fire and/or find me at the bottom! And hope like hell there ain't no curves! Who's ever seen a 15 % grade with no curves? Yee Haa!
Oh and as for those run offs, they don't stop you! I had always thought they would until one Satuday afternoon coming off the mountain on I-70 West of Denver that last run off that goes right up the side of a mountain, I saw a truck an trailer laying on its' side on top! And all I actually saw were the rear tandems of the trailer! Ohhh Not good! Never forgot that scene! I flew by all the cops doing 65mph (posted speed limit) in a semi (empty of course). ole uncle Jake helping me out all the way down!

Okay, so now down to business - Yacht (I used my Outlook Express spelling) Oh, incidently, the word is spelled: compromise.
Easy way for me to remember that spelling is Com - Promise.

So, changing the Brake Fluid. What I wanna know is, how do I know I have gotten all of the old out and all of the new in?
They are both same color.

I was also told to dry out a brake system, use Alcohol, but again, how does one know if you've bled the entire system???
I have about a half a gallon of alcohol left from driving over the road. Air brake dryer.

Like for instance, say I bleed and want to put in that DOT 5.1 How do I know I have nothing but DOT 5.1 and not some of the older stuff still in the system?

please reply - oh and thanks for the other info

240 Ed · #15 05-30-2002, 03:21 AM

Well, for one thing, the 5.1 stuff from Lucas or Ate has a color to it. Easy.

I spent 10 years doing Donner Pass every day in a highway coach, and yup, even in winter.(scary) There are two runaway ramps going west along with helpful signs for truckers.
i.e. "upgrade ahead, crank up" and "let er drift" (actual language!)

I only saw one truck in a ramp and it definetely worked! It is made out of about one foot deep pea gravel, and when you hit it, you absolutely bury your rig to the axles, no, over your axles! The ramp is probably 300 feet long and it does work. You will need a serious wrecker to get it out!
I have also put out a couple of brake fires before the tires caught, very lucky that...

Brake fade on air brakes: There are two things that happen which have been explained to me.
One; the linings get so hot, they liquify. This is what causes that glazing that ruins your linings.
Two; the linings get hot and cause a gas to form between the drum face and the linings. There was a theory tossed about that if you let off your brakes to cool them, it made things worse because it allowed oxygen to get into the hot lining surface and made things worse. Personally, I don't know about this one and have debated this with other drivers...
In a way, I was fortunate driving a bus because it is lightweight compared to a full rig, however the GMC coach I drove for many years only had two axles total because it was a light bus. (very advanced bus and fun to drive-felt like a 65 Pontiac Bonneville! AND it happened to be made in Pontiac, MI)
The Greyhound MCI-9 reaaallly sucked. Heavy bus (all stainless steel) with a regular axle in back with a "tag" axle with only one tire each side. If you didn't have a "Jake", you could get yourself in trouble real quick and couldn't get out of it. If you tried to ride it down, the suspension was so soft, and they didn't put any sway bars on these models... you would surely tip over. I called them "floppers".
The Eagles that Trailways were super handlers and light. No problems. Well, other than they were poorly built and hard to work on...and a bunch of other stuff.
The thing that made these buses so marvelous was that they used independent suspension on the front axle. Magic.

Oops, loong post.