300TD wagon manual trans shifting problem- ideas?
 

Hi All,

My manual 4-speed '83 300TD wagon is experiencingshifting issues. It started out just being difficult to get into 1st gear while the engine was running, not so bad with the other gears. I basically had to force it into first, though there's usually no grinding sounds unless I'm trying to get into reverse, in which case there's continuous grinding (of the gears and my teeth).

It has now progressed pretty quickly to difficult to get into most gears and impossible to get into reverse when the engine is cold, improving noticeably after driving for about 30 miles (but still not perfect). There is now obvious "creep" on startup, meaning the clutch is obviously not disengaging completely when the clutch pedal is depressed. I won't be able to drive it all soon (although presently, if I need reverse, I just turn the engine off, put it in reverse, and then restart with the clutch in. Not exactly a long-term solution).

Any ideas on diagnosis would be greatly appreciated. I'd love for it to be a hydraulic problem and not a clutch guts problem, but I have no clue.

thanks,
Randy

It's most likely a problem either in the clutch master or slave cylinder. If pumping the clutch pedal a number of times makes the problem disappear it is almost certainly a problem in one of those components.

Looks like you diagnosed they problem already. Clutch not disengaging properly.

yeah, but....
 

Right-o, but the problem is that I don't know whether that means the clutch mechanism itself is toast (knock-on-wood) or whether the mechanism that disengages the clutch (the hydraulics, in my limited undertstanding of what's going on) is toast (ojala!).

I was kinda hoping someone would see the symptoms and be able to jump in and say "you idiot, that's obviously a slave cylinder problem," but perhaps it's not so simple as all that?

cheers,
r

It is almost certainly a slave or clutch master problem. Have you made sure your brake fluid is full?

generally a worn clutch loses reverse then first. But it could also be one of the hydraulic cylinders. There is a tool you can make to check clutch wear, someone here will chime in with a picture.

edit: see post #3 here

Did you try pumping the clutch to see if the symptoms disappear?

Definitely clutch problem. My bet's on the slave, but check both for leaks and check your fluid level. It's probably one or the other.

Collapsed or leaking hose might be something to look at to.

Thanks for the input folks- The fluid level in the resevoir is good, so nothing as easy as burping the air out of the system, unfortunately. Pumping the pedal doesn't seem to do anything at all to improve things.

So next question- since no 300TD's for the American market had manual transmissions, which master and slave cylinders do I get for my '83 300TD (non-turbo)? Are the 240D master and slave (which are available online) different than those that would be used for the standard in-line 5 cyl. that's in the Beluga?

I'm guessing they're all the same but if pumping the pedal doesn't improve the situation, I don't think that replacing master and slave will resolve the problem. On some slaves, there is an adjustment on the actuating rod. Don't know if MB's have it but I would certainly look because it sounds as if you are not getting enough travel out of that rod. Lengthening the rod should give you more travel and a full release of the clutch.

I know there is a difference when ordering slave, master and release
bearing. I think the older iron boxes use a different part # than the later
all one piece aluminium box.

I know when I ordered my parts when I did the trans swap, it`s listed for
chassis# XXXX for one group, and after chassis# XXXX for the later parts.

Look under your TD and see what type tran you have.

Charlie

when a master starts to go away ( bypassing fluid ) usually what happens is the travel of the slave cylinder becomes liminated -meaning it ( the slave ) does not extend as far as it should, this causes the clutch to act as if you put a block under the clutch pedel and limit the throw --

if you unbolt and with out removing the lines, slide out the clutch master, look behind it you may notice it seems wet even tho your resv is full < bypassing fluid - not every time but most of the time you will find this ( a small fluid loss )

if a slave goes bad it normally will leak fluid out ( 99% of the time ) of the boot causing the same problem but with fluid loss

change them both - fresh fluid in an old slave most times will start leaking soon after a master replacement - jz

First thing I would do is pull the carpet down up under the pedal assembly and feel for wetness on the hard line from the clutch master and if its been leaking for a while there will be brake fluid under the carpet. I'm sure you already know this but I gota ask anyway, the brake master has two chambers and the fluid in the rear one is often very hard to see, which is the one for the clutch, you know this chamber is full?

If it is a problem with hydraulics why doesn't pumping the clutch pedal solve the problem?

if the master cylinder bore is out of round from wear, then the seals do not stop all the fluid ans some escapes past the seal as the pedel is pushed down, the worn spot ( By passes ) and as such the travel needed for the slave to compleatly extend the clutch plate and disengage the disc from the flywheel is not going to happen -- it causes the unit to act as if you only depress the clutch 3/4 of the way -- jz

I realize that. But 3/4 +3/4 push = 1 1/2 push so the slave should operate on two quick pumps.

That does happen sometimes but its a maybe

and it really dont matter the cylinder bore is an alloy and the piston is normally stainless so wear and seal / seal comes into play

on the back stroke it is causing bubbles it pulls air in to itself from the open end BOOT location and its like soapy water so a solid like you think might happen does not because of the introduction of air - jz

Issue Resolved! I fixed my clutch with a dremel.
 

You guys are gonna love this one....

I appreciate any advice, Steve-o, and I never take umbrage when helpful people ask me questions to which I may already know the answer. And it was more careful examination of the "most likely cause" scenario that you were asking about that lead to the solution here.

So my brake fluid resevoir was full to the top, and that was indeed the first thing I checked a week ago. So in prep to really get in there and diagnose the problem, I rechecked the resevoir- still full. But I was bothered by the fact that I couldn't see the fluid level in the clutch resevoir and had to assume it was full without verifying. So expecting to get messy, I cracked the line off the bottom of the clutch resevoir so I could just make sure there was fluid in there, and lo and behold, exactly squat came out of the resevoir and the line was bone dry! Eureka- made me feel stupid, but at least it was going to be an easy fix.

So now you're thinking either "what a dork" or "how was it that the clutch resevoir was dry when the brake resevoir was full? They're connected." Both thoughts that occurred to me immediately, too. So I take a look at the nipple onto which the clutch fluid line attaches, and I'm greeted by... a solid piece of plastic, factory sealed! And then it all comes back to me.....

When I bought the car and was preparing to drive it acorss country, I had to redo pretty much the entire break system, which included replacing the fluid resevoir. Got a new dry one from some boneyard, yanked off the old one, put the new one on, replaced the clutch fluid line on the nipple, then filled with fluid. Hunky-dory, everything works fine.

Until I start having the shifting issues 8 months later, whereupon it occurs to me that the new brake fluid resevoir (which I'd completely forgotten I'd swapped out) almost certainly came off a Benz with an automatic transmission that had no need of clutch fluid. Apparently for some models, Mercedes decided to use the same brake fluid resevoir (i.e., with attached clutch fluid resevoir) for both manual and automatic trans models, but just didn't slice off the end of the plastic clutch fluid nipple for automatics. So assuming that my clutch fluid resevoir was attached to my clutch master cylinder, I've been driving this thing for 8 months with the 8 tablespoons of brake fluid that was left in the line between the resevoir and the master cylinder, and it took those 8 months for the car to develop severe shifting problems.

I sliced off the nipple with a dremel cut-off wheel whereupon the full resevoir began to drain into the line, and voila! the car immediately shifts like I just drove it off the lot. :D Didn't even have to bleed the lines! Just hope I didn't grind anything important off the transmission in the last week....

Thanks for the suggestions, all of you who offered advice- the MS forum rocks.

randy

Wow, thats a new one on me, glad you got it sorted out.

That's one hell of a story. Wonder how many hours and how much $$$ it would have cost had you taken it to the dealership with those symptoms.

There is an important lesson to be learned here. MB designed these hydraulic systems with the clutch feeding off the brake master cylinder reservoir higher than the brake feed so that the clutch would fail before the brakes do should the fluid run out. So, if you are loousing fluid and brakes and still want to drive the car home, we now know we could pinch off the clutch master feed line with a pair of vice grips before it takes a gulp of air, and continue to have a functioning clutch without the necessity of functioning brakes.

yeah, I had the same thought after figuring it out- and it gave me the heebie-jeebies.