I'm Baffled! - PeachParts Mercedes-Benz Forum

#1 02-26-2003, 06:50 PM

Great forum everyone. I have searched all of the old threads for a solution to my problem... put a lot of the suggestions to the test and I still can't seem to get my '80 240D to shift.

Here, in a nutshell is the problem: about a month ago, while driving I lost the ability to shift into any gear ( sloppy clutch, etc.). I was able to limp home by starting the car in first and even shifted into second "on-the-fly" and backed the car into the garage by turning the engine over in reverse. I am a fair mechanic (or so I thought) and approached the issue logically... replaced master cylinder (no fix), replaced the slave (ditto), replaced the shift bushings, and have been struggling to bleed the system thinking that that was why the problem persisted even with an almost entirely new clutch system. Well about 20 minutes ago I thought that I had finally worn down her teutonic stubborness (I finally had a hard clutch pedal with nice resistance), but I was mistaken. Still no shifting. I can still start the car in gear and she goes but I cannot shift into any gear with the engine running.

The only warning I had prior to the failure was a slight grinding when shifting into second gear (it had been doing that for years and by waiting momentarily between depressing the clutch and engaging the shifter I could avoid it).

So my question is, what am I overlooking? could this be a release bearing problem? Is the clutch disk frozen on the splined transmission shaft? Hilfe!

K. E. Houtler

#2 02-26-2003, 07:29 PM

If pressing the clutch does not disengage the transmission, your problem is most definetely with the clutch itself., most likely with the pressure plate.
However, a very remote possibility could be the your transmission input shaft is seized in/with the pilot bearing in the flywheel. Very rare problem, although I have seen it on one of my previous car (a racing 1964 Ginetta)
If you are positive the hydraulic system is in good condition, the next step is to get to the clutch.
Good luck
jackD

#3 02-27-2003, 05:23 AM

If you are CONVINCED that the hydraulic system is properly bled, which can be a challenge sometimes, then it is time to get to the clutch.

On my first 240D, a '77 model, I had one of the diaphragm fingers break off and jam the clutch so it couldn't release. I would be shocked if the input shaft is frozen to the pilot bearing. These enginse have the best pilot bearing I've ever seen. My current 240D had the same pilot bearing for 380,000 miles. I finally replaced it at engine time.

I have in the past replaced a clutch/pressure plate/TO bearing only to find that the problem was hydraulic, so make sure before going to the trouble. A clutch job on these cars is a pain from underneath. The last time I put a clutch in my 240D I pulled the engine and it was easier. I have a walking beam in my shop so I'm better equipped to work above the car than below.

Bleeding a clutch is not as easy as brakes. The best way is to do it bottom up. Figure some way to push fluid through the bleed screw at the slave cylinder. You could fashion something from clear plastic tubing and a large hypodermic syringe or turkey baster.

Best of luck,

#4 02-27-2003, 10:34 PM

larry: I was shocked too when I saw the pilot bearing seized on my Ginetta. I just could not believe this could happen. But like anything impossible, it did happen.
That's why I listed it as a ''very remote possibility''.
Can you imagine the work involved in trying to get the transmission out of the car with a welded pilot bearing/transmission input shaft/crankshaft hole.
jackD

william rogers · #5 02-28-2003, 02:52 AM

I changed both master and slave cylindes on my 74 240 D and had a devil of a time getting the air out possibly a power bleeder like used on brakes would do it, sure would try everthing before pulled engine
and or tranny........
William Rogers......

#6 03-01-2003, 06:29 PM

Thanks guys for taking the time to pass along your thoughts. I will try to bleed the clutch system once again but was wondering if there was a way to tell if all of the air has been bled out? For instance, shouldn't I be unable to depress the clutch pedal if the clutch system is properly bled and the slave is working against a frozen release bearing, pressure plate or clutch plate?

Thanks again for all of the help,

K.E. Houtler

stevebfl · #7 03-01-2003, 07:01 PM

In most cases if you don't have the clutch properly bled then the pedal will stay down. (It won't return).

These cars have no access hole so one can not see what actually happens. Of the various ways that a clutch won't disengage very few of them will show up on the pedal. The throw out bearing rides in and out on the shout of the trans. I have seen them jam due to lack of lubrication. That would be the only way that the pedal would resist movement. The act of depressing the clutch makes a ten inch plate move back a small amount. The disc is then free to move. Any malfunction that causes the movement to be non parrallel will only release one side of the disc. This is the normal problem. The springs in the rpessure plate fail or the disc fails in a way that bunches up the material in a thick spot. It takes very little dragging to accelerate the dics and input of the tranny.

If one wishes to see this effect take the car and place the trans in neutral. let the clutch out, now step on the clutch and pull it into reverse. If done quickly it will grind as the disc takes time to slow down. Now do the same thing and pull it into a forward gear. One should notice that it doesn't grind. The reason is that the syncronizer acts as a brake and stops the still spinning clutch. Go back to reverse and try it a few times you will get a feel for how much drag there is. Try it with the clutch just dragging a bit. With just the slightest drag you won't get reverse and yet you will get a forward gear because of the syncros.

Don't try this on a late model manual trans as they have syncros into reverse and you won't see this you will just burnup syncros.

kip Foss · #8 03-01-2003, 09:41 PM

I am not familiar with your specific clutch but from my years under standard shift cars I will offer this. There should be a lever that goes from the slave cyl. across a ball pivot, into the bell housing and branches into two fingers that go into a collar on the pressure plate. As you push the clutch peddal in the slave cyl. pushes this fork against the pivot which inturn depresses a set of springs on the pressure plate and frees the clutch disk from the flywheel. If one or both of these fingers has broken off you can not depress the springs on the pressure plate. Old US cars had an inspection cover under the bell housing that you could remove and check this. I doubt that MB has one since this would make things too easy. You might be able to remove the slave cyl. and wiggle the fork. There should be vritually no fore and aft movement in the fork.

mplafleur · #9 03-02-2003, 10:39 AM

I am in the same predicament in regards to bleeding the slave and master. I've gotten a little air out of the slave and that's all. Still no real resistance at the clutch pedal.

I bought a power bleeder from http://www.************************ and it is on the way. This one is manually pumped up and cost about $45.