Fading Clutch Pedal After Extensive Drive = Stranded - PeachParts Mercedes-Benz Forum

Binnkin · #1 12-15-2014, 08:29 PM

Hello! I am in the midst of an attempt of a road trip from Ohio to Florida, and my 82 240d has left me stranded in the middle of nowhere! Ive been driving for a total of about 9 hours today with a few breaks, and the clutch pedal began to fade. I changed the master and slave clutch cylinders just a year ago, and neither of them show a leak. Also, the reservoir appears full. Moreover, Ive let it sit for approximately an hour and now the pressure has magically returned/the car is shiftable. Any ideas who be greatly greatly appreciated!

leathermang · #2 12-15-2014, 10:17 PM

Chances are you have moisture in your fluid...
thus when it gets hot you develop steam... which will compress...
but when it cools.. you get your pressure back...+
So new fluid from a newly opened can...

Lucas · #3 12-15-2014, 10:59 PM

Runner lines collapsed internally? I have this problem and those symptoms.

Not sure about the 123, but mine was 8mm ID. I got auto tranny cooler hose from oreillys. It's a bear to change.

mach4 · #4 12-15-2014, 11:04 PM

Assuming you're following the freeways, you can likely nurse things along and get to a warmer and better location to deal with your issue - that is if you're comfortable with shifting without the clutch. It takes a little finesse but it's definitely doable. Back in college I was driving a school bus for a side job and had a clutch go out near the end of my run. I made the rest of my stops shifting without the clutch. To get started again after stopping to let the kids off, I just restarted the bus with the transmission in first gear (actually it had a granny so that made it pretty doable).

(On one of my cross country trips I made it from San Diego to Phoenix without ever even touching the brakes, so it is possible to go quite a distance without stopping or needing to shift. )

I'd definitely try it, particularly if you're in an area where you'd really prefer not being....and if you think you can drive shifting without the clutch.

Here's some tips

- Stay in the right lane and be ready to wait it out on the shoulder if traffic starts backing up.
- If you do stop, get the engine started and let it warm up a bit before setting out
- From a dead stop, put the car in 1st and hit the starter
- Rolling stops are ok if there's no traffic around.
- When downshifting (e.g 4-3), go to neutral, rev the engine to the speed of the next lower gear or a bit higher and gingerly slide it in gear.
- When upshifting (e.g. 3-4) go to neutral, let the engine drop rpm to the next higher gear and gingerly slide it in gear.
- Pace yourself so you minimize the need for shifting
- Get fuel/food at easy off-easy on truck stops
- Time your transit of big cities during non rush hour times
- Use Google maps to anticipate and avoid accidents, construction and detours

Good luck

leathermang · #5 12-15-2014, 11:25 PM

On these old cars.... and particularly if the wrong trans fluid has been used... the synchronizer may not allow shifting without the clutch...without causing damage.... even with a clutch these are not fast shifter cars... many have to ' take a count' between leaving one gear and putting it in the next....

vstech · #6 12-15-2014, 11:30 PM

Quote:

Originally Posted by leathermang

On these old cars.... and particularly if the wrong trans fluid has been used... the synchronizer may not allow shifting without the clutch...without causing damage.... even with a clutch these are not fast shifter cars... many have to ' take a count' between leaving one gear and putting it in the next....

Actually, clutch less shifting methods are appropriate with this type of transmission damage.

mach4 · #7 12-15-2014, 11:34 PM

Quote:

Originally Posted by leathermang

On these old cars.... and particularly if the wrong trans fluid has been used... the synchronizer may not allow shifting without the clutch...without causing damage.... even with a clutch these are not fast shifter cars... many have to ' take a count' between leaving one gear and putting it in the next....

If you get the speeds correct it will slip right into gear. The synchronizers do nothing in a no-clutch scenario. I should have more explicit about not jamming it into gear - it has to be spot on between the engine speed and the transmission speed. Thanks for pointing that out.

leathermang · #8 12-15-2014, 11:37 PM

Quote:

Originally Posted by mach4

If you get the speeds correct ......

How does one do that ?

Lucas · #9 12-15-2014, 11:39 PM

There's a sweet spot in there. But I wouldn't recommend it.

You can also pump that thing up to gain pressure sometimes. Depending what the problem is.

I'm excited to drive again without thinking about avoiding stopping, looking for cops, slowing down behind everyone and praying for a green light, etc.

Last trip out I was getting mom a fancy coffee for her birthday. Well not just that, we went to the nutcracker also.

I was getting on the freeway, two fingers on the coffee cups in center console area, clutch in, off the coffee, shift, back on coffee, lift clutch pedal with right toe with right heel on gas without touching the brake, and left foot on top of pedal so it doesn't slam up.

I thought Jesus I need to fix this, I've been driving like this too much.

Tangent anyone?

Lucas · #10 12-15-2014, 11:42 PM

Quote:

Originally Posted by leathermang

How does one do that ?

Usually easier downhill. I couldn't get the benz to not grind. So idk. Made it home 5 miles and shifted once. That was all.

leathermang · #11 12-15-2014, 11:43 PM

Quote:

Originally Posted by Lucas

.....Tangent anyone?

No , you did a fine job of that....

Lucas · #12 12-15-2014, 11:47 PM

Quote:

Originally Posted by leathermang

No , you did a fine job of that....

Lol. Hey at least he will have the nutcracker song stuck in his head while broke down.

One thing I'm contemplating with my currently frozen system is cracking the bleeder to get the pressure out. Hopefully the master will lift back up. And I can move it 50 feet to where I can work on it.

Not that it's the same. I'm the least experienced here. The fading isn't like mine, just the cooling part. I was intrigued by the fluid causing this.

You can get a turkey baster at any grocery store to get the reservoir side out. But should be try bleeding and draining to get going? Or will some fresh fluid on top mix and get by.

mach4 · #13 12-16-2014, 12:54 AM

Quote:

Originally Posted by leathermang

How does one do that ?

There is an engine speed that exactly matches the speed of the transmission for any gear such that you can move it in and out of the gear at will as there is no pressure on the gears. In an old-style crash-box transmission, one without synchronizers, you needed to get the speed correct to keep from grinding the gears - push the clutch in, put it in neutral, wait a second or two for the engine to spin down, slide it in gear, let the clutch out. Down shifting is the opposite - push the clutch in, put it in neutral, let the clutch out, rev the engine, put the clutch in, slide it in gear, let the clutch out.

The synchronizers are brass devices that work to put a drag on the clutch end of the transmission to "synchronize" the gears to the correct speed so they will drop right in and do so without grinding the gears. This can happen only when the clutch is in, otherwise you'd be trying to change the speed of the engine to match the transmission. This is also why "double clutching" can save huge amounts of wear and tear on the synchronizers as you're getting the engine very close to the proper speed so the synchronizers do not need to work as hard. This is also why transmissions start grinding gears when the synchronizers get worn out.

Lucas · #14 12-16-2014, 01:11 AM

He won't rest until you post a video of you doing it.

I can shift without the clutch in an 18 wheeler or a Ducati. But couldn't in my benz.

It's hard with a 4 speed. Maybe with a 5 speed. Typical in a 6 speed or more.

But I'm intrigued. I would try again if i didn't care about my car. But this tranny is a sloppy Sally matched for low hp.

mach4 · #15 12-16-2014, 01:20 AM

Quote:

Originally Posted by Lucas

He won't rest until you post a video of you doing it.

I can shift without the clutch in an 18 wheeler or a Ducati. But couldn't in my benz.

It's hard with a 4 speed. Maybe with a 5 speed. Typical in a 6 speed or more.

But I'm intrigued. I would try again if i didn't care about my car. But this tranny is a sloppy Sally matched for low hp.

My comments were/are theoretical as I've never had the opportunity to actually drive a manual MB. If there's something about the Benz 4-speed that makes this difficult/impossible I'm happy to stand corrected. I've done it in the bus referenced above, a Ford, an MG, various VWs, my Corvette and probably a couple others I'm forgetting - just kind of assumed that it would be the same.