bleeding 240d clutch with pressure bleeder - PeachParts Mercedes-Benz Forum

ambush276 · #1 11-25-2015, 11:41 AM

i have read a couple of posts on this forum about how to bleed the clutch (with the right brake bleed) but i was wondering if there is an easier method with a pressure bleeder?

I have a pressure bleeder that connects to the brake fluid reservoir and i was wondering if there is a way to open the slave bleed screw and pump up enough pressure to push the new fluid through the reservoir into the master and slave to push out the old fluid.

Is this possible? (would i have to pump the clutch... or can i literally put pressure with my bleeder, open the slave screw and the old fluid will push out?

Thanks!

Thanks

cooljjay · #2 11-25-2015, 01:09 PM

The clutch, has to be bleed from the bottom up. No way to do it with a pressure bleeder, easiest way to bleed the clutch, is with an old fashion metal oil can and a piece of hose....Fill it with brake fluid, attach hose, depress clutch peddle and bleed....Works great...

ambush276 · #3 11-25-2015, 01:20 PM

where does all the old fluid go?

cooljjay · #4 11-25-2015, 01:42 PM

Back into the brake fluid reservoir. What I did was to remove the hose from the reservoir, drain and put the clutch hose into a small soda bottle...That way I could flush the old fluid with out contaminating the brake reservoir.....That is the issue if you use the right brake to bleed the clutch, you push all that crud into the reservoir...

ambush276 · #5 11-25-2015, 03:41 PM

if i do this, what type of hose do i need to connect the right caliper to the slave cylinder?

is this then a normal procedure to bleed the right brake (or do i need to pump the clutch as well).

cooljjay · #6 11-25-2015, 04:40 PM

This post will help answer that..

Replace clutch slave cylinder and bleed clutch - Mercedes-Benz Forum

This isn't the procedure to bleed the brake system, what you would do, if you did it this way. Is to push the clutch to the floor, open the bleeders and use the brake peddle to slowly force the fluid(dot4) threw the clutch system until the peddle pops back into place...

Again BIG WARNING!! If your brake/hydraulic system, hasn't been flushed/bleed for many moons...You will contaminant the brake fluid, this can/will lead to premature failer of calipers/master cylinder and maybe even braking ability. Their is some nasty gunk that builds up in the cylinders. If you've replaced both slave/master...You have less of a chance of forcing crud into the brake system...

mannys9130 · #7 11-25-2015, 06:13 PM

It is true that you have to bleed from slave to reservoir with an oil can to get all of the air out of the system. However, I think that once all the air is bled, it will be just fine to bleed from top down with a pressure bleeder. The clutch is a hydraulic system, meaning if you put pressure at one end of the system it will be transferred to the other end (the clutch wouldn't work otherwise). If air is in there, yeah it's impossible to pressure bleed. Once it's solid fluid though, just pump up the pressure tank and open the slave bleeder. Old fluid will shoot out followed by new fluid.

Suck out the master cylinder before you begin. Refill with new fluid. Fill your pressure bleeder with fluid. Bleed the right rear, left rear, right front, left front brake calipers on that order, and then the clutch system. You'll have all new fluid.

charmalu · #8 11-25-2015, 07:29 PM

Manny is correct, bleed the brakes first and then the clutch system as he mentions.

Here is a You tube video on bleeding the system with an oil can from the bottom up.

https://www.youtube.com/watch?v=wdf--suwqw0

When I swapped in the 4-spd into my 85 300d, I tried to pressure bleed the clutch from the top down.
Blew a ton of fluid through it, and still had air in the system.
You do have to go up from the bottom as air rises.

Using the R/F Brake Caliper to bleed the system is listed in the MB FSM.

Charlie

sent from my pos computer

ambush276 · #9 11-26-2015, 11:26 AM

in the pictures in the post above with the clamps... Is that clamp clamping the return line?

So i guess my method would be to

1. flush the brakes

2. open the bleeder valve to the slave... let it ooze out.

3. connect the slave bleeder to the front right caliper bleeder

4. remove the return line from the reservoir and put it in a clear container. (plug up the reservoir hole that it leaves).

5. open the bleeder for the right caliper, start pumping and watch the clear container to see if liquid start to flow.

6. when good brake fluid starts to flow out (no excess gunk), then re attach that return line to the reservoir.

my only last question , assuming i am correct with that return line, is what is the diameter for the return line that goes into the reservoir... the 3/16 is the size hose i need for the bleed nipples... but what about the return line?

-- Thanks

mannys9130 · #10 11-26-2015, 11:44 AM

You asked if there was an easier way. I told you there was. If the clutch is totally bled, just pump your bleeder up and open the nipple on the slave.

ambush276 · #11 11-26-2015, 12:45 PM

yes... i could do that instead of the pumping...

but i was still wondering about that return line. I would rather waste a little brake fluid going into a throw away can instead of throwing gunk back into the reservoir.

leathermang · #12 11-26-2015, 12:50 PM

I think Charlie's youtube url shows a good way which avoids that... treating them as different entities... and using clean fluid the proper direction.... you are going to have to attach the master clutch cylinder to something either way... and that puts clean fluid into the system ....

mannys9130 · #13 11-26-2015, 07:40 PM

Ambush, if you have the pressure bleeder I'm thinking of, it looks like a garden sprayer and you attach its cap to the master cylinder. You put brake fluid in the bleeder's tank, pump it up, and it pushes new fluid from the master cylinder reservoir down to all the calipers.

Here's what you do:

Get your bleeder ready to go.
Suck out the old fluid from the master reservoir. Refill with clean fluid. Attach the power bleeder to the master reservoir and pump it up. Open the RR, LR, RF, LF caliper bleeders in that sequence, checking your fluid in the bledder and master frequently. Once you have all the wheels bled with new fluid, go down to the slave cylinder and open its bleeder. Old fluid will come down and out just like the brake caliper, and when you see new fluid come out close the bleeder and you're finished.

The bottom-up method is critical *if there is air in the system* because the air wants to go up and the traditional method tries to push it down. Once you have all the air out of it, it becomes a hydraulic system where the fluid is incompressible and a force applied at the beginning of the column transmits all the way to the end. So, applying pressure at the master cylinder will force the fluid down through the clutch and out the bleeder without pushing a bunch of trash up into the master and contaminating all of your nice new fluid.

If your clutch works, it has no air in it.

ambush276 · #14 11-29-2015, 07:44 PM

will be trying this next weekend. Will report how it goes. Thanks!

mannys9130 · #15 11-29-2015, 07:52 PM

If there is air in the clutch, it won't work and it will feel spongey.

Does your clutch feel like this now? Does it work?

If no, and yes, you have no air.

It is impossible to force air into the system by pressure bleeding it with fluid from the master reservoir.

Your revision WILL POSSIBLY inject air into the system, and you'll be screwed.

Just do like I suggest and you'll see.