bobs master cyl project

[bob66542]

thanks alfred of the group for the link to mbparts guy's ebay page, as i was the only bidder for the master cyl, $69.95.quite a good price! i have searched "master cyl" and read the posts, and read my manual, but not yet started hands on. i do have 1 question-in the past when changing a master cyl,they come with plastic fittings and hose so you can bench bleed the cyl- but ive seen no mention of it in the posts- is there a reason to not do this procedure?

65 SL 230 4-sp. purchase 12-08-03

[66andBlue]

Hi Bob,
I am glad you got it, the price just went up to $119.50!
Unfortunately I have no answer to your question. Let's hope that the "master bleeders" among the forum members will have an answer for you soon.

Alfred
1966 blue 230SL automatic

[waqas]

Can you explain what you mean by "bench bleeding"..?  Correct me if I'm wrong, but doesn't one simply install the master cylinder, connect all the lines, fill up the reservoir with fluid, and then bleed all the brake lines as usual?

WAQAS in Austin, Texas

[Shvegel]

Bench bleeding helps particularly if you are not set up to pressure bleed the brakes. Sometimes air can get trapped in the master cylinder and no matter how many time you pump the pedal you can't get the brake fluid to start flowing through the cylinder.

The good reason not to do it is that you are now installing a cylinder that is full of brake fluid which can make a mess out of your paint. I would reccomend getting a suction gun from an auto parts store. It looks like a grease gun but when you pull the handle on the end of the tube you get suction on the hose at the other end. This will enable you to suck the fluid out of your old master cylinder and keep the mess to a minimum.

Also I like to use Ate "Super Blue" brake fluid in my cars. Super blue is essentially a race fluid and probably overkill but when you change the brake fluid again in two years you can use Ate "Super Gold" fluid. You bleed until the blue turns gold and you know you changed all the fluid.

[waqas]

Thanks for the explanation!

Does this mean that without a pressure bleeder, we will most likely need to bench-bleed the master cylinder before installation?

And if we bench-bleed prior to installation, won't we always get a mess when we re-connect the brake lines to the master cylinder? I'm assuming the brake line outlets are plugged with bleeders on the master cylinder during bench bleeding, and that re-installation requires switching from the plugs to the brake lines themselves...

I'm asking because this might be a good reason for me to buy a pressure bleeder... unless there's some way I can stick to the old fashioned way !

WAQAS in Austin, Texas

[graphic66]

Easy homemade bleeder http://www.bmw-m.net/TechProc/bleeder.htm

[bob66542]

"bench bleeding" is when you clamp the m/c in a vice,attach temporary lines to where your brake lines attach, fill the m/c,run flexible lines into the reservoir,making sure the lines are submerged in fluid, then slowly pumping the m/c piston, bleeding the air from the m/c. you can then usually mount the m/c in the car with little or no more bleeding needed.

65 SL 230 4-sp. purchase 12-08-03

[bob66542]

thanks, graphic 66 for the link to the brake bleeder!

65 SL 230 4-sp. purchase 12-08-03

[graphic66]

Your very welcome. I use that bleeder all the time. It is a very handy tool. The same MC cap is on my 230SL as is on my 406 Unimog, and that always can use bleeding, as it is in water plenty. It works great on clutches also.

[bob66542]

final update- the master cyl for mb partsguy was very good- shipped quickly, and he was very helpful and honest. he had told me i might need the res. assy. kit which comes w/ the bolt that attaches the m/c- well i got mine apart, no problem, but the rubber grommet that attaches the rear of res. to the m/c was pretty bad.he told me thats no problem, as that grommet comes w/ the m/c. (he could have easily sold me the kit, and put the grommet in with it) so id have to say id definitly do business with him again.i also built the pressure bleeder and used it. worked pretty good, except it leaked a bit. i bleed the brakes and clutch, so ive got fresh fluid in both now. put about a hundred miles on in the last couple days, everythings working great and no leaks. thanks again to the group for all the excellent advice!

65 SL 230 4-sp. purchase 12-08-03