Manual 1981 240D


So i took my daughter to school and on my way there i noticed that i was loosing clutch pedal pressure. in less than 3 minutes i could not shift anymore and barely got it into first (little grinding) just to be able to limp back home in 1st. was not a fun drive...

1. So i checked my master brake cylinder, and it is halfway between the lines.
2. The right rear spring, shock, area is all wet looking, and i saw this before. i thought it was fuel that ran down to the rain hose after overfilling it slightly, but that was a few days ago, and the wetness looks fresh. I am now thinking this might be brake fluid, but need to see if i can find any brake lines that could be affected there.
3. *IF* i have a brake fluid leak, does it make sense that i would be loosing my clutch, even though the rest of the braking system is working fine?
4. Can i just try to bleed the slave cylinder (never done that before yay!!) and see if i have a leak somewhere?

I guess i just need help in what to check or address first.

Thanks all

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Grey '91 350SDL 214k Dad's car
Beige '81 240D 4 Speed 254k SOLD
Blue '82 300D 225k SOLD
White '95 E300D 46k SOLD
Blue '87 190D 2.5 Turbo 315k SOLD
Brown '80 240D 4 Speed 716k SOLD
Beige '80 300D N/A 119k SOLD
Blue '85 300D Model 186k T-Boned

Sudden clutch failure is usually related to hydros. Remove the slave cylinder and see whether a slight press on the pedal moves the rod in the slave. Note the word "slight" because you can easily push the piston out of the slave. You could also have an internally failed master cylinder where pushing on the pedal moves the master cylinder piston but the seals leak. Replace or rebuild both if 1 is bad. Rebuilding used to be SOP before cheap import parts. It is not difficult but requires a $10 cylinder hone.

The next thing would be to check for pressure on the arm that moves the clutch.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

The clutch and brakes share the brake reservoir. It's likely from the way you describe the situation that you have a leak in the rear caliper, which means you not only lost your clutch but 1/2 your brakes as well. There are two circuits so that when something like this happens, you still have limp-home braking. First thing to check is that indeed the fluid you see is brake fluid. I don't have a manual but from what I've read on these forums bleeding the clutch is no fun - I'll leave the specifics to others.

By the way, you can drive the car "normally" without a clutch. The key is to match the speed of the engine with the speed of the car for that gear. Accelerate in first, take your foot off the accelerator and simultaneously move the shifter to N, pause briefly while the engine RPMs drop to the speed of second and move the lever to 2. Same for 3 and 4. If you catch it right the gears won't grind at all - let the synchronizers help you find the time to move the lever. If you miss it completely, just rev the engine slightly and have another go. (It's best to practice this a bit before you need it so you're ready.) if you have to stop, you can shut down the engine and restart it in first gear.

Back in college I drove a school bus and lost the clutch with four stops to go. I managed to finish the route and get the bus back to the barn using the above technique. Fortunately the bus had a Granny Gear which was low enough that I could actually start the engine in first gear (granny low) so I could drop off the kids with the engine off and then get it started again. It was a crash box transmission (no synchronizers) so it was a bit more challenging than it would otherwise have been. No damage and no tow and the kids got home on time - everyone was happy.

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Re: #2 above
The wetness may very well be a leaking shock. If so, clutch problem is coincidental, and not linked.

Re: #3
No.

Sorry to disagree but I'd say the leaking is most likely the brake line or caliper. It could be unrelated but not likely imho.

And yes, since the nipple to supply the clutch master is higher than the brake supply point you can lose your clutch and not the brakes if the clutch system is what is leaking. If you have a brake fluid leak and it empties the res you will lose rear brakes and clutch....assuming the rear is the portion supplying the clutch which I believe is true but am not 100% certain....but you'll always lose the clutch before the brakes.

The high nipple is to prevent a clutch leak from causing loss of brakes.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Well the shocks and springs will be replaced soon, and the car leans to the back passenger side anyway. so it could be a shock, but that will be replaced. I am just going to replace all the brake lines, and flush the whole system.

Question... the rubber grommets that seal the brake fluid reservoir to the brake master cylinder, is very brittle and has visible cracks. I cant get one of those shipped to me (or from a mercedes dealer) this weekend. Can i essentially do all the work to fix and bleed the system this weekend and then just replace those grommets later? will i need to rebleed the whole system? I was hoping to just empty the reservoir, swap the grommets, and then reinstall and fill the reservoir.

Will a new brake master cylinder actually have these installed, so i might not have a problem, if i replace both slave and master cylinders?



number 53 in the above image.

__________________

Grey '91 350SDL 214k Dad's car
Beige '81 240D 4 Speed 254k SOLD
Blue '82 300D 225k SOLD
White '95 E300D 46k SOLD
Blue '87 190D 2.5 Turbo 315k SOLD
Brown '80 240D 4 Speed 716k SOLD
Beige '80 300D N/A 119k SOLD
Blue '85 300D Model 186k T-Boned

I believe a new one will have the grommets.

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Re: Loss of brake fluid
If a leak in the brake circuits results in draining the master cylinder reservoir section that also feeds the clutch M/C, the fluid in the clutch hydraulic components will not be lost. The fluid in the clutch M/C will still be moved to the slave cyl. when the pedal is depressed, and will return to the M/C when the pedal is released; the same fluid simply moves back and forth. Absent a leak in the clutch hydraulics, there will not be a loss of fluid, and hence, no replenishment required, and no loss of clutch function.

You make a good argument. I cannot verify one way or the other though from my experience. My question is whether the fluid goes back into the res from the clutch master.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Hmm. I think each release of the pedal pushes the excess fluid back into the brake reservoir... as, the clutch master does not have any storage potential... so... total loss of fluid in the rear reservoir could eventually lose enough clutch fluid to prevent function.

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My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
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FYI - the grommets that came with my brake master cylinder did not give me a lot of confidence in their ability to hold the reservoir securely. I'm not usually one to push for OEM parts or nothing, but for this - I'd suggest getting OEM grommets at least. (Not sure if you can get an OEM MC or not.

update:

Well i got the car on jack stands and took the wheels off. The rear passenger side sure looks like the brake line is broken. I will see if my wife can pump the brakes and if I can confirm the source of the fluid. pic below.





There is no fluid around the master cylinder or under the carpet by the pedals. I hope I can leave the brake M/C alone for now and just do a complete flush. We will see how that goes. The back section of the reservoir is low and that is why my clutch went out. To get the theory correct, with the levels visible, does it make sense that a rear brake line leak will lower the brake fluid, and then only the clutch goes out first? I was expecting a slave clutch failure or leak to lower that reservoir first. see picture.



Also, the brake light had been flashing, and I thought it was due to my emergency brake needing to be adjusted. Now it dawns on me that there are 2 sensors in my reservoir, and I am now thinking that they are level sensors. This means my car was warning me of the imminent brake/clutch system failure but I was ignoring it. Am i correct and stupid??

This is my 999th post

__________________

Grey '91 350SDL 214k Dad's car
Beige '81 240D 4 Speed 254k SOLD
Blue '82 300D 225k SOLD
White '95 E300D 46k SOLD
Blue '87 190D 2.5 Turbo 315k SOLD
Brown '80 240D 4 Speed 716k SOLD
Beige '80 300D N/A 119k SOLD
Blue '85 300D Model 186k T-Boned

With change in temperature, there is change in the volume of the fluid in the clutch hydraulic system (as there is with all fluids). Hence, with an increase of the temperature of the fluid, a small amount is displaced to the reservoir, and with a decrease in temperature, the contraction of the fluid volume draws the same amount back from the reservoir.

And the source of the "excess"? Is there a continuous creation of excess fluid that must be removed from time to time? Do the makers of brake fluid know about this?

From the OP's last post:
"The back section of the reservoir is low and that is why my clutch went out. To get the theory correct, with the levels visible, does it make sense that a rear brake line leak will lower the brake fluid, and then only the clutch goes out first? "

In the accompanying photo, the fluid level is way above the clutch nipple, hence, the supply of fluid is not the culprit. As to brake leaks, see the discussion above.

Had this exact thing happen just after my 4 speed swap.
stuck caliper turned into leaky caliper, drained brake fluid from master cylinder. lost clutch too.

bleeding isn't too bad, I used a pressure bleeder I made for about 10 bucks. bleed from the slave back into the master cylinder.

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1982 300D (w123, "Grey Car")
1982 300D (w123, "Blue Car")
2001 Ford F150 "Clifford" (The Big Red Truck)
1997 Dodge Ram 2500 12V Cummins
1996 Dodge Ram 2500 12V Cummins
Previous Vehicles:
1995 E300D, 1980 300SD, 1992 Buick Century, 2005 Saturn Ion

its actually way below it. there's 2 separate sections.

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1982 300D (w123, "Grey Car")
1982 300D (w123, "Blue Car")
2001 Ford F150 "Clifford" (The Big Red Truck)
1997 Dodge Ram 2500 12V Cummins
1996 Dodge Ram 2500 12V Cummins
Previous Vehicles:
1995 E300D, 1980 300SD, 1992 Buick Century, 2005 Saturn Ion