brake bleeding what`s wrong here?

[jan lauwers]

Hello folks,

I am working on the front wheels (Caliper), and I was thinking: while I am at it, why not change the brake fluid, since I dont know when that was last done. (PO?)
 
I wanted to empty the system completely, replace the flex lines and refill. My plan was to start with rear right... but that was difficult to access.... (small garage) so I started with rear left... opened the nipple... pumped the pedal... fluid came out. Then I saw that the back end reservoir was empty, BUT the front tank was/is still top full. I opened right front nipple), pumped the pedal, no fluid came out. I unscrewed the flex line, still no fluid coming out.
Now I realize that I have probably done this wrongly, but I still don't understand why I can not get any liquid out of that front reservoir. My questions:

What did I do wrong?
Now that I am here, I should replace the flexes. Are these MB parts, or general purpose, i.e. can I buy them in any automotive shop?
I see that the bottom of the empty reservoir is dirty, so now I am thinking of first flushing the system with methylized spirit. Good idea or not?

I really feel that I have screwed up again!!!
Thanks gentlemen!

Jan

[jameshoward]

There are easier ways of achieving what you seek. A way is to remove the old fluid from the reservoir using a syringe or something and replace it with the new fluid of choice (no doubt having fretted about DOT 3 or 4 or silicone and all the other stuff that people here talk about). Try to find one that's a different colour to the one you're currently using (see below).

Add new fluid to fill res. Keep topped up. Bleed brakes in the usual way starting from the caliper furthest from the res. Would recommend using a bleeder or some sort here. Gunson do one that's v cheap (Eazi-bleed; I have one; I like it). If you have air, you could use a bleeder that sucks the fluid through; v handy. At all times keep the res topped up (second pair of hands/eyes helps). Repeat on all wheels. If doing it the hard way (brake pedal) then it is recommended that you place a block of wood behind the brake pedal to avoid full travel and damaging the master cylinder.

With new fluid in the system, you should be set. Bleed properly and ensure you have a good pedal. (May as well do the clutch also if you have a manual). You'll know you have cleaned out the system of the old stuff when your new, different coloured brake fluid appears in the bottom of your jam jar or coke bottle. (Some links to a home made bleeder on YouTube are on the site; or just look on YouTube).

If you wanted to change the flex hoses (good idea if you don't know how old they are) you should probably do that at the start. It makes no sense bleeding the brakes twice, after all. It's a bit messy, but worth doing. They are available from anywhere, eg ebay always has plenty. Pretty standard. You don't need MB ones.

Would strongly recommend against using anything other than brake fluid in your brake system. (Spirits, for example, boil at a lower temp than brake fluid might and so would change the composition of the fluid introducing a variable where it's probably better not to have one as you speed towards a red light on a rainy evening. Additionally, you could damage the seals. All in all = a bad idea).

Enjoy!

[jan lauwers]

Thanks James, that's very helpful. Still I don't understand why the front reservoir did not empty by pushing the pedal.

Jan

[Benz Dr.]

I have a car in right now that had normal brakes until we changed the brake fluid. Suddenly, I couldn't get any pressure in the system unless the pedal was pumped several times. Brake fluid would come out of the bleeder as usuall and then it would take several more pumps to build up enough pressure to bleed again. Clearly this MC is done.
Owner had no idea when the last fluid change was done and the fluid looked that way too.

 I would be very suspect of your MC and if you have any doubts that it isn't 100%, then you should get a new one.

[Shvegel]

I second what Dan has to say only to add a much rarer occurrence which is the pedal not returning enough to allow brake fluid to enter the master cylinder from the reservoir. Try pulling back on the pedal to make sure it is returning fully.  Also a chance of a clogged bleeder screw.