rubber brake lines and brake fluid recommentations
 

I'm looking for opinions about proactively replacing the rubber brake lines on Ol' Yeller ('83 300D), a very recent acquisition. I have no idea if they have ever been replaced.

Any thoughts about pro-actively rebuilding/replacing the brake master cylinder?

What is the collective recommendation about brake fluid for a system flush? DOT 3? DOT 4?

Thanks!

- Neil

Replace all rubber-brake-lines by all means--and any other steel brake-lines at the same time that show any corrosion....

But--Use a Power-Bleeder to bleed/change the fluid.

Do NOT use the brake-pedal by pumping to the floor--This will cause the seals in the cylinder to become damaged as they are 'used' to working in only the 1" or so of normal--and worn travel.
--Push the seals past this to unworn cylinder-bore, will cause the seal edges to become damaged and then you'll be replacing the M/C too.....
(Seen this SO many times, on all sorts of makes!)

As the car has Dot 3 in there--little advantage unless all components are replaced to upgrade to dot 4.
--Stick to whats in there--but replace/flush though with fresh....

^^ I have made do with a catch can above the bleeder screw level and pumping the pedal with a limit stop like a piece of wood.

It works - but its about 2 hours compared to the half hour with a pressure system.

I have not read of any specific recommendation concerning Brake Hoses and in fact people say they replaced the Brake Hoses but don't give what make of Hose.

I have what ever the Local Auto Parts stores sell on all of My 4 present Vehicles. 2 that I can remember are Raybestos and Wagner. I have not had any trouble with any of them.

Since around 1968 have owned at least 5 other Vehicles besides the ones previously mentioned and used the local Part Store Brake Hoses with no issues (no internet to shop on; less choices).

Unlike a lot of Parts you buy they do not need to be DOT approved. The Brake Hoses are supposed to be DOT approved and hopefully that means they need to meet some sort of standard no matter where they are made.


If you want Mercedes Hosese I looked these up at a dealers site for My Car:
A 129 428 00 35 Brake Hose Front MSRP $48.50 Internet Price $36.38

A 126 428 03 35 Brake Hose Rear MSRP $48.50 Internet Price $36.38

A 000 428 06 73 Hose Spring Retainer MSRP $1.50 Internet Price $1.13

Pelican has decent Prices on the non-OEM Hoses.

For Brake Bleeding I have a Jar setup and connect My Mighty Vac (Hand Held Vacuum Tester) connected to the Bleed Screw.
You can either keep pumping through the whole proceedure or pump some to get the Fluid moving and go Eat something and let Gravity do the rest.

Thanks for the replies everyone! I use a power bleeder.

Answer
 

Some Facts About Brake Hoses:
#1. The industry standard average safety life of a brake hose is six years. FYI data SAE: J1401, J1703, J1705, J1873, J1406, J1288, J1403, J1833, J1402.
#2. Brake hoses deteriorate from the inside as well as the outside.
#3. Moisture is absorbed into brake fluid systems through brake hoses.
#4. Contaminants in brake fluid act abrasively on the inner wall of brake hoses.
#5. The brake hose reinforcing fabric deteriorates through expansion and moisture.
#6. High operating temperatures contribute to the deterioration of hoses.
#7. Brake hoses swell with age and restrict flow.
#8. Generally all brake hoses on a vehicle deteriorate at the same rate, So all hoses should be replaced if one is found to be faulty!

Brake hose failure mode:

#A. Rupture (burst hose) = age, exercise (too many miles) or impact are the typical cause.

*B. Partial internal collapse = the inner ply becomes damaged/detached acting as a partial restriction and/or one way valve.

#C. Full internal Blockage = the inner ply becomes damaged/detached acting as a plug = brake pedal still feels good but there is no brake application.


http://www.peachparts.com/shopforum/diy-links-parts-category/142411-brake.html

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This can happen to even the most experienced mechanic, "Especially" on a high mileage car.
The old school manual brake pedal "down" - "up" - "down" - "up" bleed method risks over-stroking the master cylinder.

The master cylinder piston seals can get scored if they're pushed into a normally unused - corroded, region of the master cylinder's bore.
If this happens, you'll have little or no brake pedal, and will need a new master cylinder.

I strongly recommend using a pressure bleeder or put a wood block under the pedal to avoid the issue.

My most recent personal experience Over-stroking the master cylinder.
Ford Truck Enthusiasts Forums - View Single Post - 1995 E350 7.3 DI turbo turbo, no power, stalls at normal operating temp

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Brake bleeder recommendation
Brake bleeder recommendation - PeachParts Mercedes ShopForum

Power Bleeder or what?
Power Bleeder or what? - PeachParts Mercedes ShopForum

Brake bleeder - power bleeder Homemade
Brake bleeder - power bleeder Homemade - PeachParts Mercedes ShopForum



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Thanks whunter, thats a good one to keep in the file.

The vacuum bleeder works great....

BTW, all brake fluids are synthetic, so don't fall for that marketing. DOT 4 is better than DOT 3, it has more additives to deal with moisture. DOT 5.1 is even better, and is the best glycol fluid. Should be no concern adding a better glycol at the next flush, which should be every 2 years or so, depending on where you live. I think DOT 5 (silicone) is the best since it doesn't absorb water vapor at all and doesn't need flushing. Plus won't eat your paint. I just removed a cast-iron master cylinder where I had used it since ~1995 and it had no rust at all inside and the fluid was still clear (but blue dye had turned yellow). I removed it to go to a dual MC. Much mis-information out there. You could even mix silicone with glycols with no adverse effects, other than having blobs of glycol that can still cause rust.

Read this link for an anal analysis of brake fluids by an engineer with way too much time on his hands. Probably more telling that he is an American with an old British car, which is almost as bad as owning old German cars. BTW, I am also an engineer.
Selecting Brake Fluid

I installed stainless steel brake lines on both my 190E and 300D. The price was not bad at all at $86 for a complete set. Visually, they are high quality. The steel braid is encased in a plastic coating as opposed to my previous stainless steel lines..

WRXtra

I plan on installing these on the 420SEL when the time comes.

+1 for ss brake lines if you can find them.

Edit: looks like the above link covers a good number of our chassis! Kool

Thanks for everyone's comments.

Our host sells ATE rubber lines that are about 1/3-1/2 the cost of the MB rubber lines. Is there any reason to believe that the MB brake lines are better than ATE? ATE is the OEM for all brake system pieces for Porsches.

I have heard mixed opinions about mixing DOT 3/4 glycol based brake fluid with DOT 5 silicone. If I switched from one to the other, I would replace the MC, rubber lines, rebuild calipers.

I use DOT 5 silicone in a couple of antiques but bleeding them to a solid pedal is a PIA. I also change DOT 5 silicone fluid one every 10 years or so 'just because.'

Thanks!

I think you'd be OK with the ATE brand ones. I believe I've purchased PEX brand lines once or twice, no problems with those units.

I would stick with the DOT3/4 fluid. I've got that in all my cars and no problems, i just flush every 2-3 years as recommended.

FYI, I have seen modern brake hoses deteriorate much faster then "old stock" working on modern cars at the dealer we were replacing rubber hoses at 5-6 years, and the replacment hoses again even sooner. Modern rubber ain't what it used to be, or the enviroment just got alot harsher on rubber brake hoses...this is referring to crack rubber on the hoses so you can see the inner steel braiding, not failures. Never seen a hose burst, just collapse internally so the brake stays stuck on. I leave em alone knowing older hoses last longer then new ones, so long as they are safe to use. Change the fluid often, I remove the calipers and hang em upside down a few minutes with the bleeder and hose removed to drain out the crap settled down inside that bleeding does not remove. Then clean out the bleeders, antiseize the threads etc and make sure to pack some grease in the nipple and add a rubber cap on top once finished, saves the day next time you expect them to function!
If your master cylinder is that old that the orings inside cannot pass a certain point your better off changing it, it is past due! I generally run my pedal through a long travel when bleeding to be sure there is NOT an issue with this, if a line fails and you need to use that travel in an emergency, then what if the orings fail too? (Yes I know the park brake system). Point is, you need to make sure your brakes are good, all aspects. Old cars need maintenace, a master cylinder is not expensive and you may even be able to open it up and clean out inside if your adventurous...
The same applies to clutch hydraulics too.