Brake bleed - not very successful - help!
 

1986 420 SEL w/ABS

I am trying to bleed brakes using a (one person) power bleeder I bought from Griots; started at the RR wheel and very little BF is coming out. I can even take out the entire nipple and still nothing leaks out. The bleeder sucks out a tiny bit of BF and the MC reservoir remains full. Tried the LR wheel and same result. doesn't help if I pump the brakes.

The bleeder seems to be sucking; it will stick to my finger.

Any ideas what might be happening?

Thanks

The reservoir is empty. ;)

MB uses a 2 chamber reservoir (fore and aft/front and rear). Take your brake fluid and fill the reservoir to the tippy top. Then bleed. Make sure you keep it at the top.

As already mentioned, the rear section of the MC reservoir may be empty, and/or you may need to remove or at least loosen the MC cover to allow air to replace any fluid you’re trying to remove.

If you are willing to spend $40 plus on the Griots tool you might want to consider returning it and purchasing a positive pressure type brake bleeder instead. The problem with all vacuum bleeders is you will always be sucking some air past the bleed screw’s threads. If you use a little grease or oil around it to prevent air leaking past you’re pulling the grease or oil into and contaminating the brake fluid. With air leaking past the screw you can’t tell when you’re past any air bubbles that would be in the brake fluid circuit which you might be trying to remove.

I’ve never known anyone to be happy with a vacuum bleeder and never known anyone who ever wanted to change after they used a pressure bleeder!

Pump up the filled reservoir, put the cap in place, open the valve, go and open each bleeder until you’ve got good new bubble free fluid flowing out the hose on the bleeder, tighten the bleeders down, release the pressure on the reservoir, put the MC reservoir cap back in place and your done!

Thanks
 

I have ordered a pressure brake bleeder...

You're doing yourself a nice favor, you'll enjoy it I'm sure! Good luck!

brake bleed
 

brake hoses swell as they get older. could be swelled shut on the rears in addition to the other comments/suggestions. Pressure bleeder will be easier /more effective.

just wondering what type of pressure bleeder you're using? the only one i could find that was decent was some "motive" pressure bleeder. i'm still on the have someone in the car pump the pedal bleeding thing. :)

I use this:

http://store.motiveproducts.com/shared/StoreFront/default.asp?CS=motive&StoreType=BtoC&Count1=960338771&Count2=877479195

Works great, especially that the kids are no longer around to be pressed into service!
;)

Engine Running???
 

Is the engine running??? If not start the engine and it will help you... Jim

In 35 years I've never done any brake bleeding, manually or with a bleeder where the car was running. Not to be a smart ass, but have I been missing something?

I use a phoenix systems reverse bleeder only when I have to, and that's usually only on new master cylinders that need bleeding.

Otherwise, the plain old gravity method works 99% of the time, and by it's very nature doesn't allow air back into the system - and it's gentle. It doesn't force the collected crud at the bottom of your reservoir through the very fine openings of your ABS system at hundreds of PSI where they can get easily lodged. Plus, everytime you pump that pedal and pressurize the system, you turn a few big bubbles into a hundreds of small ones.

Just open up the bleed screws and stand by the reservoir to keep it topped up. You can put tubing on the end of the bleeder screws and run them into cups if you don't want to make a mess (brake fluid eats paint).

Of course, if you're not getting any fluid at all, and your reservoirs are full (and your caps are off), then you may have a collapsed hose, a kink in your hard lines, a "bunged up" caliper, a stuck proportioning valve, clogged MC, clogged ABS controller, etc...

Start The Engine
 

I have not spent my life bleeding brakes but I have found that in similar situations I have started the engine and maybe the booster has helped open up passageways.. I have had about 6 Mercedes Cars the last 10 years that would not bleed and starting the engine did the trick... Doesn't take or waste much time... Jim

Not to be a bummer, but the booster probably just helped you push the pedal down - nothing more.

I have read that the trick to vacuum bleeding is to wrap a little Teflon tape around the threads of the bleeder screw to prevent the air leaks. Haven't tried it yet but I'm going to.

x2 on the Motive. Best tool for the job. Pressure bleeders do a far better job than vacuum bleeders, and are easier to use.

Tip: use a turkey baster or similar to suck all the old fluid out of the reservoir first, then fill the reservoir with clean new fluid, then go about your brake bleeding. The fluid in the reservoir will be more contaminated with moisture than the fluid in the rest of the system. Better to change it for new clean fluid before forcing it all the way through the system.

Precisely. Vacuum booster only provides mechanical assistance with pushing the brake pedal. It has absolutely zero affect on the brake fluid system. Therefore, there is no benefit to leaving the car running while you perform a brake bleed. Don't do it.