240D ('81) clutch pedal down! - PeachParts Mercedes-Benz Forum

sun tortise · #1 12-30-2020, 03:11 PM

Clutch would not disengage but barely made it home and found that the rear brake reservoir was low, and a small leak in L. front brake caliper. So i topped it off, and after much pumping and an overnite rest, clutch seemed to work fine. It seemed that the pedal return and the stiffness of the pedal was a bit weaker than usual.

Let it rest 2 days, and come to find the clutch pedal is ON THE FLOOR!

Some brake fluid under where the transmission joins the engine. But i just replaced the slave cylinder 4 1/2 years ago! Also had a new clutch kit, p.p. etc installed professionally about 4 months ago.

So what gives? Isn't there a spring or something that holds the clutch pedal up even if there is a leak in the slave cylinder?

What to do? I always value the advice i get from my Peach friends!

Frank Reiner · #2 12-30-2020, 04:07 PM

Quote:

Originally Posted by sun tortise

Clutch would not disengage but barely made it home and found that the rear brake reservoir was low, and a small leak in L. front brake caliper. So i topped it off, and after much pumping and an overnite rest, clutch seemed to work fine. It seemed that the pedal return and the stiffness of the pedal was a bit weaker than usual.
Let it rest 2 days, and come to find the clutch pedal is ON THE FLOOR!
Some brake fluid under where the transmission joins the engine. But i just replaced the slave cylinder 4 1/2 years ago! Also had a new clutch kit, p.p. etc installed professionally about 4 months ago.
So what gives? Isn't there a spring or something that holds the clutch pedal up even if there is a leak in the slave cylinder?
What to do? I always value the advice i get from my Peach friends!

There is, in fact, a spring on the clutch pedal. It joins the pedal on the right side of the pedal about five inches above the pedal pad. It is called an "over-center spring", and is adjustable. When the pedal is up, the spring acts to keep the pedal up; as the pedal is progressively depressed the spring force goes to zero, and then with more downward movement, the spring force acts downward to aid in releasing the clutch.
If the over-center spring is broken or missing, a leak in the system would cause the pedal to fall.

sun tortise · #3 12-31-2020, 12:36 AM

Thanks. I will look for that spring if daylight returns. Why would a clutch slave cylinder fail in less than 50,000 miles? I forget what brand it was, but i got it from Pelican.

ykobayashi · #4 01-01-2021, 12:46 PM

After I put 300,000 miles on my 240d the clutch had these issues. It never went to the floor but it had little resistance to the foot.

I fixed it twice replacing a master cylinder, then later on a slave cylinder and finally it refused to engage a few years later and had had little resistance. Turned out to be a broken throwout bearing.

The fact you see fluid under the trans and you had clutch service says to me you’d better look at your slave and the plumbing to it.

sun tortise · #5 01-02-2021, 01:36 PM

The over center spring is working; when i pulled the pedal up manually, i could feel the spring action and it stayed up.

I guess i will need a new slave cylinder, even tho i replaced it 4 yrs ago (Master cylinder never replaced on my watch,about 60 K miles, & shows no sign of leaking)

I notice Pelican has one for about $17, and the next ones are $35 and up. Is it a case of get what you pay for, or are they all about the same?

Thanks!

sun tortise · #6 01-03-2021, 01:58 PM

Pretty sure i need a clutch slave cylinder, and I see that Pelican has a Meteli for $17.25 and several others starting with a Meyle for $35.

Is there really any difference among the various brands?

Thanks.

sun tortise · #7 01-11-2021, 11:40 PM

I ordered the Meteli slave cylinder, $17. Says on the box made in Italy.

So if it gets warm enough to not have fingers stick to the metal, i will try to install it. I will search the site to find out how to install and bleed it. I did it once before, so hoping it will come back to me, but i remember it took some cussing!

Junkman · #8 01-12-2021, 08:27 AM

Rebuilding used to be considered normal procedure for clutch and brakes. Now parts are so cheap that buying new is normal.

I went through a couple of 126 master cylinders then bought one of the more expensive units from Pelican when Roy was here and haven't had a problem since. OE was too expensive for my cheap self.

sun tortise · #9 01-12-2021, 11:56 PM

I replaced that slave cylinder about 4 or 5 years ago, but just had the clutch replaced a few months ago. I read somewhere here on the forum that a new clutch can put more stress on a slave cylinder that is near the end of its wear cycle.

sun tortise · #10 01-18-2021, 02:03 AM

Tomorrow it may go up to 40 F, so i may bite the bullet and try to put the new slave cylinder in.

I read elsewhere about bleeding the slave cyl by running a line from the front right brake caliper bleeder bolt to the slave bleeder bolt.

But that method was disparaged in favor of bench bleeding the cylinder. The brake caliper method would feed old degraded fluid into the new clutch slave cylinder.

So i will try to bench bleed, but just in case, today i flushed the old brake fluid out of that right front brake cylinder, so that if i need a little assistance from that method, @ least the fluid will hopefully be closer to pristine.

sun tortise · #11 01-18-2021, 05:06 PM

Pulled the slave cylinder, and the rod stayed in the bell housing, held by .a rubber thing that seemed extraneous. Got it out, and noticed the rod was backwards from the one on the new slave cylinder, and the gasket/spacer thing with the slots was missing.

I am thinking the guy who did my clutch recently may have taken the slave cyl out and put it back in wrongly. Wondering what to do if i cannot find that spacer, and if that could have caused the slave cylinder to fail after only 7 years.

sun tortise · #12 03-10-2021, 10:58 PM

I ordered the spacer, bench bled the new slave cylinder as best i could, and it was such a PITA to get the bolts started, especially the top one that you can't get at, But by using an extra long bolt on the lower bolthole, i was able to draw it into position, and then get the inaccessible bolt in with the aid of a 1/4 drive springy bendy thing that can screw around corners. Even tho i had bench bled it, it didn't seem to have enough resistance on the pedal, so i tried embellishing the bleed with the 3/16 hose from the front right brake caliper method. I had previously flushed the old fluid out of that brake caliper. This did not seem to help, as most of the fluid dripped out of both ends of the 3/16 hose. So i gave up on that, and just tried it with the seemingly too low pedal. Lo and Behold, it DOES seem to be working. So i am hoping it will stay working. Wondering if the low pedal resistance is a cause for concern that might leave me stranded. Thanks.