Brake Line Flushing - Necessary/recommended? and Procedure ?

[ChrisZeiss]

As a novice to maintaining my 1966 230SL, 4 Spd. manual, no AC, Euro version - I'm trying to learn how to do all regular maintenance tasks (exchange all fluids, filters, adjust FI, clutch and brakes, etc.) - so, your advice would help a lot on these questions:

1. Brake line flush - necessary or recommended ? On my newer cars, flushing the brake lines is recommended every two years, but the MB Workshop Manual for the 230SL (from 1966) says brake line venting/flushing is only required after work on the brake system (and they do not list it in the list of regular maintenance works) - is it good or necessary to flush the brake lines (every two years, e.g., even if no lines were opened or work done on the brakes) on the 113s ?

2. Brake flushing procedure - can one fill the main reservoir, then attach a handpumped container to the main reservoir and pressure it up (by hand pumping) - then go and open one by one little vent fittings on each brake and drain/flush out the old fluid ?

3. The MB Manual states to start by venting the main master cylinder , followed by the disc brake line farthest from the master cylinder, then the other disc brake, followed by the drum brake farthest from the cylinder, and finally the second drum brake line. Where and how does one vent the master cylinder ?

Thanks in advance for advice on this simple matter.

Chris Zeiss
Edmonton, Alberta

[wisnia07]

I would flash it anyway, as I did on all my others cars. The brake fluid is collecting moist from air and is turning corrosive. I think that's the main reason why you should change it.
Regarding the procedure I always did it with help of someone. One is pumping the brake pedal, and the other is opening and closing the bleeder screws. As soon as the brake pedal got stiff after a couple of 'pumps', keep pressing it and let the other person open the bleeder screw. The fluid will go out (stick a fuel line on the bleeder screw so you don't splash the fluid around). As the fluid goes out the pedal sinks to the floor - keep it there until the bleeder screw is closed. Then you pump the pedal again until it gets stiff and open the bleeder screw again and so on.
You do it until you see clear fluid going out at every wheel.

Remember to keep the the main reservoir filled with fresh fluid!

There are some youtube videos showing how to do it alone (for example this one https://www.youtube.com/watch?v=ag-Q_lP0dOk) I never did it this way, but it seems fine to me.

I'm not sure about the master cylinder venting, but I assume it will vent itself while you bleed the system at the wheels.

Good luck with the work!

[Jonny B]

I live in a dry climate (Southern California) and am able to drive the car year round. I do a brake flush every two years.

A friend and I have been doing the brake bleed, using a vacuum pump (Hand held) at the bleed point. We start at the back right and work our way around the car (back right, back left, front right, front left).

As stated, be sure to keep topping up the master brake cylinder reservoir.

We have never done any bleeding of the master cylinder.

[wwheeler]

Here is what I use. Makes it almost fun.....sort of. I have the red metal cap like is shown. I think they have a plastic cap for less, but I prefer the metal.

https://www.motiveproducts.com/products/copy-of-0100rp-or-0109rp-european-bleeder-race-pack

[A Dalton]

   

   Hygroscopic

[ChrisZeiss]

Dear Gents -

Thanks for the tips, I will flush the brake lines (every two years) as per your recommendations.

WWheeler - You showed a brake/clutch line flushing system similar to the one I have (but haven't used yet) - it sounds like you attach the pressure container with the 45mm threaded cap onto the main reservoir - and then pump it up to what pressure please ?

Then you go around the wheels - back right first, then back left, then front right and finally front left - and attach the drain hose and bottle and open the vent nozzle until clean hydraulic fluid comes out -

My pressure bottle cap has a hose going down to the bottom and space in the bottom to put ATE brake fluid in - so one pumps fluid into the reservoir while pressuring up - so as not to have to disconnect the cap on the reservoir and refill it every time - does this work alright ?

Thanks again for your expertise and help,

Chris Zeiss
Edmonton, Alberta

[wwheeler]

I do not put fluid into the bottle. Yes, you have to depressurize and remove the cap to put new fluid in when it gets low. But it is better than cleaning the bottle out and having fluid from the cap dripping onto painted surfaces. I use about 10 to 15 PSI and works just fine. Much better than vacuum systems which suck air around the bleeding nipple. Just keep flushing until the old darker fluid disappears and the new fluid appears.   

[jaymanek]

For some reason my pressure bleeder never works on the pagoda.
Not sure why. Its an electric Snap on one that I use on all of my cars.

I use the two man method and I do mine every 2 years.

[UJJ]

I replaced/rebuild all my calipers, brake lines and hoses a few years back. Some bores of the calipers were pitted badly, the heaviest in the rear. I do not know why the rear calipers are more expensive that the front? Perhaps because the demand for them is less.
I switched to silicone based brake fluid and only check/flush my brake fluid every 4 years. Last time I checked it was this spring and it is very clean.
Regards, Urban

[mnahon]

I use brake fluid test strips to decide when to change the fluid.

https://www.summitracing.com/int/search/product-line/phoenix-systems-brakestrip-brake-fluid-test-strips

[ChrisZeiss]

Thanks Urban - for the tip re:synthetic brake fluid and Meyer re: brake fluid test strips - I'm looking into both for use on my Pagodawagon.

Merci bien !

CAZ

[WRe]

Hi,
a pressure bleeder does not work very good on our cars with the late version of brake fluid reservoir with warning sensors because the pressure will squeeze the fluid out of the sensor access. The early brake fluid reservoirs w/o are ok.
Vacuum bleeder are better.
...WRe

[wwheeler]

For the pressure bleeder, I only use 10 to 15 PSI. I have never had that problem and maybe your O-rings on the sensor bodies need to be replaced. I have never used it on an old reservoir with old O-rings, only one with new seals. One note, I did have a problem on the new reproduction reservoir because that molding can have voids near the O-ring seat. I was able to sand the area down enough to resolve the problem. However, original factory reservoirs with new O-rings should be able to handle the small amount of pressure.

[Shvegel]

If your car isn’t a show car Ate makes 2 brake fluids “Super Blue” and “Super Gold”.  They are racing spec fluids that are blue and gold respectively and you switch colors at each change to make sure you get all the old stuff out. 

[wwheeler]

The Blue is NLA because of US DOT regulations. That is as of a few years ago. And yes, because it is blue.

[Shvegel]

Hahaha.  I guess the sealed can in my basement is worth a fortune now.

https://m.ebay.com/itm/ATE-Super-Blue-Racing-Brake-Fluid-DOT-4-1LITRE-BLUE-COLOUR-VERY-RARE/253618302896?epid=1237804770&hash=item3b0cd42fb0:g:q3EAAOSwNyFWe~MD

[wwheeler]

Unbelievable is all I can say. Yes, you should sell now and undercut the competition. I have the blue in my W128 and one day soon will have to flush it out. I just flushed the blue out on the W111 a couple of years ago and now it is gold. Never thought I would ever get sentimental about brake fluid.

[Shvegel]

There is a company by me that makes a variety of dyes. I bet one of their dyes would work. Name escapes me right now but i wil look it up.