It started as a brake job - Page 3 - PeachParts Mercedes-Benz Forum

sixto · #31 09-06-2010, 12:29 AM

Since Tom sorted out the fender cladding, I'll jump in.

I guess some folks would use brake fluid that's been sitting in a factory sealed container for 10 years. Most folks wouldn't.

The other side of it is there is enough evidence that replacing brake fluid every one or two years keeps the rest of the brake system healthy. I haven't had to replace an MB caliper or seal in 10 years of MB'ing. I don't let brake fluid go much more than 2 years simply because seeing coffee in the reservoir is such a turnoff. The only advantage of dirty fluid is it's easy to check the level

The FSM and/or owner's manual says to replace the fuel filler cap gasket every so often. I'll bet every 200+K mile MB that graced my driveway had the original gasket

Sixto
87 300D

W124 E300D · #32 09-06-2010, 05:57 AM

All these people talking about dirty brake fluid are also proving my point while attempting to deny it.

If your brake fluid looks like yesterday's coffee then it is contaminated, which means your physical mechanical / hydraulic brake system has issues, to allow that contamination in in the first place.

Yes, if your brake fluid looks like yesterday's coffee, it needs flushing and changing, and THEN you need to go through your physical mechanical / hydraulic brake system components to find out where the contamination got in, and replace / refurb those parts.

Doing anything else is like replacing unevenly worn tires while refusing to acknowledge that there is anything wrong with the tracking... it's only because brake fluid is cheap and tires aren't that there is a disparity, and that means you are a cheap owner, "I'll do it, provided I can do it cheap."

Non serviced brake systems can easily cost you 1 or 2 mile per gallon, every single gallon you burn, it soon adds up.

Nothing is cheaper than GOOD maintenance.

vstech · #33 09-06-2010, 09:31 AM

I'll agree with you on that one. brake fluid will contain all the particulate of the system degradation. it'll also cause degradation when it's absorbed water. the flex lines can degrade over time itself, and cause it's own set of problems. the rubber seals sliding on their bores will wear rubber and steel and aluminum and copper into the fluid.
however.
IF you flush the fluid regularly, you slow down drastically the degradation of the various components. brake fluid in addition to being the hydraulic fluid is a lubricant for the various components of the system, and there is no filter. the only way to remove contaminants from the system is to flush it with new fluid.

4x4_Welder · #34 09-06-2010, 10:42 AM

As I stated before, the darkness of the fluid is rubber particles that are part of normal system wear. And as I and others have said, there does not have to be a failure for moisture to get into the fluid. Even if a flexible rubber diaphragm is used to cover the whole reservoir, it will still absorb moisture through that and around the edges over time. A little tiny bit over a long time will add up.
Then, as that moisture degrades the system, you eventually have the failure you swear must have been what let the moisture in.
I just hope I'm never in front of you trying to make a hard stop.

W124 E300D · #35 09-06-2010, 11:27 AM

Quote:

Originally Posted by 4x4_Welder

As I stated before, the darkness of the fluid is rubber particles that are part of normal system wear. And as I and others have said, there does not have to be a failure for moisture to get into the fluid. Even if a flexible rubber diaphragm is used to cover the whole reservoir, it will still absorb moisture through that and around the edges over time. A little tiny bit over a long time will add up.
Then, as that moisture degrades the system, you eventually have the failure you swear must have been what let the moisture in.
I just hope I'm never in front of you trying to make a hard stop.

I've seen possibly a 3 figure number of used brake fluid analyses, and I have never, ever, seen particulate matter from piston seals in it... not once.

Lumps from flexible hoses, yes.
Metallic particles from steel hoses (often rust), yes.
Metallic particles from piston surface coatings, yes.
Water, yes.
Even found windscreen washer fluid in a couple.

I have never, ever, ever, seen water in brake fluid in a system that was in tip top condition.

I sincerely hope you are in front of me trying to make a hard stop, reaction time being equal, I'll outbrake you nicely, it's the guy behind that worries me... I have a '91 W124 with ABS, good shocks, good tires, good springs, and good balanced brakes.

vstech · #36 09-06-2010, 09:35 PM

Quote:

Originally Posted by W124 E300D

I've seen possibly a 3 figure number of used brake fluid analyses, and I have never, ever, seen particulate matter from piston seals in it... not once.

Lumps from flexible hoses, yes.
Metallic particles from steel hoses (often rust), yes.
Metallic particles from piston surface coatings, yes.
Water, yes.
Even found windscreen washer fluid in a couple.

I have never, ever, ever, seen water in brake fluid in a system that was in tip top condition.

I sincerely hope you are in front of me trying to make a hard stop, reaction time being equal, I'll outbrake you nicely, it's the guy behind that worries me... I have a '91 W124 with ABS, good shocks, good tires, good springs, and good balanced brakes.

do you work for a brake fluid company? I've never heard of anyone submitting brake fluid for analysis...
uh, how are you getting TIP TOP brake fluid to examine that had not been flushed?
how are you determining tip top brake condition without changing parts, and putting fresh fluid in?

W124 E300D · #37 09-07-2010, 06:51 AM

Quote:

Originally Posted by vstech

do you work for a brake fluid company? I've never heard of anyone submitting brake fluid for analysis...
uh, how are you getting TIP TOP brake fluid to examine that had not been flushed?
how are you determining tip top brake condition without changing parts, and putting fresh fluid in?

It was part of an industry test.

Complete strip / analysis / rebuild / do it again.

A very, very well known brake / component company.

Like I said, I personally saw around a 3 figure number of results... unfortunately the tests produced a lot of anomalous data that didn't fit in with expectations, e.g. differences between brand X and brand Y of component Z swamped with things like wheel bearing state, disk state, pad state, road state, atmospheric conditions, suspension conditions, tyre pressures.

Two things stood out across the whole series of tests.

Brake fluid contamination was a precursor/indicators of brake system physical mechanical / hydraulic system wear / neglect.

Rolling resistance due to physical mechanical / hydraulic system wear was way, way, way higher than anyone anticipated... notably only the bikers (one way or another, a biker will push his bike some distance every day) accepted this data without argument.

--------------

Not exactly related, but a friend used to man the test rig at a large facility, big motor driven flywheel attached to the disk under test, tests disk wear, pad wear, braking torque, temperatures (inc fluid) etc... think glowing disks... he reckoned 95% of the people who arranged "meet you for lunch" turned up 15 minutes early in the hopes of watching a test run.

vstech · #38 09-07-2010, 08:34 AM

Quote:

Originally Posted by W124 E300D

It was part of an industry test.

Complete strip / analysis / rebuild / do it again.

A very, very well known brake / component company.

Like I said, I personally saw around a 3 figure number of results... unfortunately the tests produced a lot of anomalous data that didn't fit in with expectations, e.g. differences between brand X and brand Y of component Z swamped with things like wheel bearing state, disk state, pad state, road state, atmospheric conditions, suspension conditions, tyre pressures.

Two things stood out across the whole series of tests.

Brake fluid contamination was a precursor/indicators of brake system physical mechanical / hydraulic system wear / neglect.

Rolling resistance due to physical mechanical / hydraulic system wear was way, way, way higher than anyone anticipated... notably only the bikers (one way or another, a biker will push his bike some distance every day) accepted this data without argument.

so, wouldn't the data also point out that those who neglect the fluid, have more physical and mechanical wear and failure of their brake system? so... flushing regularly the fluid could extend the components? prevent the water build up and the internal rust?

W124 E300D · #39 09-07-2010, 09:40 AM

I get your point, but no, it didn't work out that way.

I have to choose my words carefully, this is "commercial" data...

Brake fluid is not like engine lube oil in that is basically does not circulate at all. There is some mixing, but no circulation.
Point #1 above means that the only way to get an idea of what the brake fluid is like is flush it all out with air, you can't just look in the reservoir, this will give you some idea, but not close enough.
A regular fluid change (30 minute book time) is therefore the cheapest and fastest way to diagnose impending brake system problems.
Regular dealer brake fluid change (and visual examination) is therefore the fastest and cheapest way to generate a brake system component work schedule order / recommendation.
Point #4 was shown to cut down on warranty / recovery / loaner costs, to cut down or eliminate potential legal costs, and to generate additional dealership revenue.

In a sense, you are right, those who neglect things tend to neglect entire systems of things, or all the awkward parts.

In a sense, you are right, flushing contaminated fluid and replacing with clean fluid doesn't do any harm, and reduced ADDITIONAL ongoing damage from contaminants, but it still represents neglect of the CAUSE, and focused on the EFFECT.

Nota Bene, the bulk of the fluid in a brake system is either in the calipers or the reservoir, the lines should contain as small a volume as possible (fluids are not exactly incompressible, a 1/2" hose system will be more spongy)

Nota Bene, most brake fluid boils at >300 ºC, water in an unpressurised (brakes not applied) braking system boils at <125 ºC, so on any decent run where brakes are applied regularly, and PARTICULARLY on worn systems that do not release properly, any water in the caliper is boiled off (same as from engine oil) and can only condense in the reservoir, so you always get a gradient of water contamination.

Bottom line.

If you are a dealer, your goal is maximise revenue and minimise liability.

If you are an owner, your goal is minimise rolling resistance (cost per mile in fuel) and repairs (cost per mile in replacement parts)

Contaminated brake fluid is an indicator to both.

If I get contaminated fluid, I strip and refurb the brake system, and that means every last component... I have never done this and not found problems, out of wear limits, etc, indicated by the contaminated fluid.

Overall I save more money per mile per year with this method.

It's only a ***** the FIRST time on a new (to me) car, and thankfully on the old MB's all these parts are dirt cheap.

New disks are fifty bucks (equivalent) here.
Calipers 150
pads 10
fluid bugger all.

Drive 10,000 miles a year at 10 miles to the litre and burn 1,000 litres of fuel.

Drive 10,000 miles a year at 9.9 miles to the litre (brakes / rolling resistance, really, huge, huge, huge thing, worse than tires at 20psi) and burn 1,010 litres of fuel.

In actual fact less than optimal brake systems represent orders of magnitude more than 1% rolling resistance and therefore operating cost.

As a guide my '91 W124 E300D 603.912 engine 722.415 trans standard 8 hole alloys sweet as a nut tickover is 600 rpm in D, on the flat will pull very gently away and eventually hold at around 15 mph on a dead flat runway near here. All down to correct tyre pressures, good braking system, decent wheel bearings etc.

I have to be more anal than owners of older cars because my car has ABS as standard and the ABS system is more prone to damage and poor operation than a basic brake system from contaminated fluid etc.

vstech · #40 09-07-2010, 11:41 AM

ok, got it, you're anal about brake systems.
I TOTALLY agree, that contaminated fluid should not only be changed, but the entire braking system should be evaluated for damage, and the damaged parts should be changed.
so, you're not saying we should never change our fluid, you are saying that with perfect brake components brake fluid won't contaminate.
ok.
without releasing corporate data, can you recommend a better plan of action than flushing the fluid? do you get it tested? then change what the test indicates?
I'll admit it. I am the type mechanic to change what's worn and flush the fluid. if uneven pad wear, or signs of overheating of the calipers is shown, I'll investigate for damage, and replace what's found, I replace the flex lines, regularly, and keep up with the fluid changes.
inform us.

whunter · #41 09-07-2010, 12:16 PM

Brake:
Brake:

W124 E300D · #42 09-07-2010, 01:12 PM

Quote:

Originally Posted by vstech

ok, got it, you're anal about brake systems.
I TOTALLY agree, that contaminated fluid should not only be changed, but the entire braking system should be evaluated for damage, and the damaged parts should be changed.
so, you're not saying we should never change our fluid, you are saying that with perfect brake components brake fluid won't contaminate.
ok.
without releasing corporate data, can you recommend a better plan of action than flushing the fluid? do you get it tested? then change what the test indicates?
I'll admit it. I am the type mechanic to change what's worn and flush the fluid. if uneven pad wear, or signs of overheating of the calipers is shown, I'll investigate for damage, and replace what's found, I replace the flex lines, regularly, and keep up with the fluid changes.
inform us.

As a biker, I have always been anal about brakes / wheels / tyres / bearings / suspension / steering and fluid leaks... very anal.

I treat brakes like a hydraulic system, it is, but I mean pukka hydraulic systems.

Steel brake hoses are usually "awkward" for access, but provided they aren't badly corroded on the outside flushing them inside is good enough (12v fuel pump, filter on the pickup, some flexible hose and hose clamps and 2 pints of brake fluid in a jar, just let it run through for 5 minutes)
If one or more shows excessive (pitting) corrosion, buy a reel of steel brake hose and and flaring tool etc make up new ones and fit, you need a mate with a car lift, do them ALL. ESPECIALLY the awkward ones.
Calipers removed, stripped, THOROUGHLY cleaned, examined, then service kit or replacement. Always all new bleed nipples and fittings.
Flexi hoses, as the other guy says, unless you know for a fact they are less than 3 years old, change them ALL.
Disks - unless they are exotic, it is almost always cheaper to buy new than to skim... while you're down there check and repack the wheel bearings and check the other joints, track rod ends, etc. DO NOT be tempted to "upgrade" by fitting slotted finish etc if plain finish was standard.
Drums, same deal as disks.
Pads - shoes, fit NEW, fit OEM approved ONLY. NOT cheaper, NOT "performance". Friction material and brake material are matched for optimum performance.
Don't forget the reservoir / servo, the concentrated water tends to accumulate here, so check the master piston / seals etc... on manual merc this means check the clutch master / slave pistons and seals and hoses too...
Reassemble, still with "hydraulic" cleanliness and care, bleed, test, drive.

Job done.

HTH

Skid Row Joe · #43 09-07-2010, 03:15 PM

Great thread!

Excellent pictures!

tlynch · #44 09-07-2010, 09:26 PM

Quote:

Originally Posted by Skid Row Joe

Great thread!

Excellent pictures!

Thanks, Skid Row Joe!

I still have plenty of chores on the list, but stopping safely is always at the top.

BTW, I don't know where you are in Texas, but I hope you are on high ground right now. Hermine is dumping tons of water on and around Austin.

Tom

gsxr · #45 09-08-2010, 11:36 AM

W124 E300D, you sure have some strong opinions for a newbie with <20 posts here. And I'm sure everyone will listen to you rather than dozens of Mercedes engineers. The cost of changing the fluid every 1-3 years is miniscule (under $10 US for most folks) and takes maybe an hour as DIY. You've spent more time trying to explain why it isn't necessary, than it would take us to just do it. And while you've shared lots of reasons why it isn't necessary, you also haven't provided any reason why we shouldn't change the brake fluid every 1-3 years. Hey, if you don't want to, fine. But please don't tell us we should ignore MB's recommended service schedule.

Personal anecdote: A couple times I have flushed brake fluid which was 4-5 years old, and the improvement in pedal feel was SIGNIFICANT. Much firmer. I can't imagine what the pedal would feel like after 10+ years with the same fluid.