240d clutch bleed - Page 3 - PeachParts Mercedes-Benz Forum

vwnate1 · #31 03-01-2019, 11:43 PM

Wow, what a P.I.T.A. .

I can't wait t hear how you eventully fix it .

rwd4evr · #32 03-02-2019, 12:08 AM

Ok. Wait a min. Are you getting fuild dripping squirting or any other action OUT of the bleeder when it is open?

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240dd · #33 03-04-2019, 12:30 AM

Huge shout out to rwd4evr who walked me thru a 5 minute troubleshoot over the phone and I found that my bleeder just wasn't cracked enough...in my case it had to be turned about a half turn from tight. Test drive went good! Taking her to work tomorrow and hoping for a smooth ride...now if someone can help me get the ants out of the car... lol thank you all

rwd4evr · #34 03-04-2019, 10:19 AM

Get an ardvark. I think lions eat ardvarks.

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vwnate1 · #35 03-04-2019, 06:13 PM

So then, it's fixed and working fine now ? .

That's great ! .

tsa · #36 03-09-2019, 01:36 PM

Great to see that 240dd got there in the end, with help from this forum.

I've started the second part of my "clutch job" - after replacing an obviously failing SC in 2017. My symptoms now was a gradually failing pressure to build up, sometimes requiring up to three pushes on the clutch pedal to disengage the engine. Sometimes the pedal just stayed down as well. The MC to be replaced is actually the one pictured on page 1 :-).

I went for a new aftermarket MC, which I could get sent from Germany for one 4th of what my local dealer wanted. TRW is a well known generic parts supplier, probably as good quality as the "FAG" MC pictured in post #7.

The reason for searching, and posting here, is that I cannot get any pressure in the new MC (the pedal returns, though!). Was I foolish enough to believe that the MC is ". . the very upper point of the hydraulic system, so there’s no need in bleeding" - ? Which is claimed here:

Replacing the clutch master cylinder on W201 and other models | OldMerc.net

I was wondering if the rubber hose from the brake MC reservoir to the clutch MC has deteriorated enough to be (partially) blocked, so I unhooked it from the reservoir and connected a big syringe to it, to try and push fluid down with more force than just gravity - but no cigar.

Before I crawl under the car (in the snow) I'm going to crack open the flare nut at the "bottom" of the MC, to see if any fluid leaks out.

tsa · #37 06-07-2019, 05:42 PM

A late update; this job has been pushed down on my to do list too long.

My problem with bleeding the new MC was caused by two separate problems; a) the bleeding nipple on my recently fitted refurbished RF brake caliper didn't fit very well, so most of the brake fluid pushed through the system leaked out past the threads instead of going to the SC. And b), with the push rod fitted to the piston of the MC, the piston must have been held down just enough to more of less block the way up to the reservoir.

With plenty of thread tape on the caliper bleed nipple threads, and the MC piston push-rod off (I ended up taking the MC off its bracket), I was finally able to bleed the system. A bit awkward, since I had no assistant to open & close the caliper nipple for me. Whilst doing the bleeding, I had no idea if it had worked, since I wasn't able to get all the air out of the PVC tubing between the caliper and SC.

Hopefully done for the next 30 years now :-)

vwnate1 · #38 06-07-2019, 05:47 PM

So ;

You now have a rock hard brake pedal with the engine running ? .

rwd4evr · #39 06-07-2019, 07:28 PM

I can't say this enough. Easiest way to bleed your clutch is reverse fluid injection. Get a mighty vac bleeder and use the canister with the tube to the bottom tho force the fluid in through the bleeder. 15-psi or so from REGULATED AIR SOURCE. Close bleeder. Pump pedal a couple times. Repeat. Done.

tsa · #40 06-08-2019, 03:07 AM

Quote:

Originally Posted by vwnate1

So ;

You now have a rock hard brake pedal with the engine running ? .

Good point :-) - yes, rock hard, and with good "servo suck". Before finishing, I bent a loop into the transfer PVC hose so the air stayed at the top.

Only annoying thing now is that when I start the engine, there is a rattly/squeaky noise that lasts for a while before suddenly going away. Could that be a sticking starter solenoid?? Hopefully it will disappear with some use of the car, which has been standing for three months. I should mention that I disconnected a multi-connector block that blocked access to the top of the MC (the one visible at the top of the picture in post 7 earlier in this thread).

Quote:

Originally Posted by rwd4evr

Easiest way to bleed your clutch is reverse fluid injection. Get a mighty vac bleeder and . . . . . Repeat. Done.

I'm sure this is a good approach, but may also be struggling if the MC piston happen to block the return path, which was my working hypothesis for the initial failure. I had to use zip ties on the PVC hose between the caliper and SC to prevent it from being blown off by the built up pressure . . .

tsa · #41 06-08-2019, 04:58 AM

Seems like my replies take a while before showing up.

This post, just to point out that, will hopefully take me one more step towards "inmate" status :-)

rwd4evr · #42 06-11-2019, 01:58 AM

Quote:

Originally Posted by tsa

Good point :-) - yes, rock hard, and with good "servo suck". Before finishing, I bent a loop into the transfer PVC hose so the air stayed at the top.

Only annoying thing now is that when I start the engine, there is a rattly/squeaky noise that lasts for a while before suddenly going away. Could that be a sticking starter solenoid?? Hopefully it will disappear with some use of the car, which has been standing for three months. I should mention that I disconnected a multi-connector block that blocked access to the top of the MC (the one visible at the top of the picture in post 7 earlier in this thread).

I'm sure this is a good approach, but may also be struggling if the MC piston happen to block the return path, which was my working hypothesis for the initial failure. I had to use zip ties on the PVC hose between the caliper and SC to prevent it from being blown off by the built up pressure . . .

The pressure on the slave bleeder will push the master piston back to it's correct resting position unless the pedal is adjusted too far restricting the pistons up travel. If that's the case it will never work right anyway. I would pull the pedal up before any attempt but in reality it should pop it back up with the pressure introduced. It's normal to have to zip tie the line unless it is a very good fit.

tsa · #43 06-11-2019, 03:40 PM

Quote:

Originally Posted by rwd4evr

The pressure on the slave bleeder will push the master piston back to it's correct resting position unless the pedal is adjusted too far restricting the pistons up travel. If that's the case it will never work right anyway. I would pull the pedal up before any attempt but in reality it should pop it back up with the pressure introduced. It's normal to have to zip tie the line unless it is a very good fit.

Yes - this makes sense. The only previous experience I could base my efforts on was when I bled the system after replacing the SC two year-ish ago; the I had no problems with the (same!) PVC line popping off, and leaving the MC in peace with the piston rod in place.

In my second to last bleeding attempt, I made sure the eccentric adjuster allowed the piston to reach its uppermost position, but still I couldn't get fluid back up to the reservoir. Then I was basking in the snow in minus 5-10 centigrades, but apart from making the job less unpleasant I can't see how the bleeding should be easier in + 15.

Anyhow, job done now. Some good news is that the rattly/squeaky noise I mentioned has disappeared. Probably only something in the starter assembly sticking due to lack of use.

Next job - to investigate the play at the steering wheel. All links/rods/joints etc showing wear from the steering box to the wheel spindles have been replaced, so I suspect I might have to get a new or refurbished 'box.

C.Doner · #44 06-11-2019, 04:20 PM

Loop method is still my vote for simplicity. Make a loop in a clear hose connected to the slave cylinder and tie it in a manner so the fluid does not flow out with gravity . Fill the master cylinder and keep topped. Pump until bubbles are gone. See the clear loop to be sure no air comes back in when you return the pedal to the up position before closing the bleeder.
Done . Bleeding should be the same amount of work as jacking up the car. Its a one hour job and works, for me, every time.

rwd4evr · #45 06-11-2019, 04:25 PM

Quote:

Originally Posted by tsa

Yes - this makes sense. The only previous experience I could base my efforts on was when I bled the system after replacing the SC two year-ish ago; the I had no problems with the (same!) PVC line popping off, and leaving the MC in peace with the piston rod in place.

In my second to last bleeding attempt, I made sure the eccentric adjuster allowed the piston to reach its uppermost position, but still I couldn't get fluid back up to the reservoir. Then I was basking in the snow in minus 5-10 centigrades, but apart from making the job less unpleasant I can't see how the bleeding should be easier in + 15.

Anyhow, job done now. Some good news is that the rattly/squeaky noise I mentioned has disappeared. Probably only something in the starter assembly sticking due to lack of use.

Next job - to investigate the play at the steering wheel. All links/rods/joints etc showing wear from the steering box to the wheel spindles have been replaced, so I suspect I might have to get a new or refurbished 'box.

Temperature will have a large effect on the hardness of the PVC allowing it to grip the bleeder and the viscosity of the fluid causing it to create more pressure in the system when freezing cold .

I've never done it but I believe the backlash in the steering gearbox is adjustable for wear to an extent. Also make sure the idler arm mount/pivot bushings are new.

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