Manual Tranny - Won't go into any gear when cold - PeachParts Mercedes-Benz Forum

mjquillici · #1 02-05-2009, 02:15 AM

On several occasions lately, after starting the car and putting my foot on the clutch, I find that it refuses to go into gear (any gear). I then let my foot off the clutch, and depress it a second time, and it goes right in and operates just fine. Other than that, I'm not having any other problems. The tranny fluid is full and fresh, the brake fluid reservoir is full, and the clutch appears to be disengaging fully. This just started in the last week or so, and only happens when the car is cold (mid to low 30s outside). I really don't know why this would suddenly become a problem, since it's been this cold in the mornings for several weeks. Any ideas?

charmalu · #2 02-05-2009, 03:03 AM

Iam thinking if this just started, and you have full and fresh fluid, then either the Master cylinder or the Slave cylinder may be leaking off some.
Or fluid is by-passing internally when it sits for a while.

Pushing the peddle a couple times pumps it up.

Iam 3 hrs from you,by santa Cruz. we haven`t been all that cold compared to back east. So I don`t think that is an issue.

Charlie

t walgamuth · #3 02-05-2009, 06:06 AM

Yes, thats an indication of a worn clutch master or air in its lines.

Stevo · #4 02-05-2009, 10:08 AM

Pull the carpet down between the pedals and check for brake fluid on the hard line to the master cylinder. It does sound like either master or slave has gone south.

mjquillici · #5 02-05-2009, 04:17 PM

Thats more or less what I was thinking. I don't know how old the fluid is in the system. It could be ancient for all I know.

A few questions:

- Would old fluid potentially cause this type of symptom?
- I know that the brake and the clutch systems share the same fluid, but do they also share the same master cylinder?
- Is there a way to determine whether the problem is with the master cylinder or the slave cylinder?

I will check for leaks when I get home.

Thanks.

Stevo · #6 02-05-2009, 05:46 PM

Quote:

Originally Posted by mjquillici

Thats more or less what I was thinking. I don't know how old the fluid is in the system. It could be ancient for all I know.

A few questions:

- Would old fluid potentially cause this type of symptom?
- I know that the brake and the clutch systems share the same fluid, but do they also share the same master cylinder?
- Is there a way to determine whether the problem is with the master cylinder or the slave cylinder?

I will check for leaks when I get home.

Thanks.

The reservoir above the master cylinder has two chambers. The back one with the hose coming out supplies the clutch master. Its hard to see the level, shake the reservoir a little. Its a common mistake to neglect it since its so hard to see, once you have too bleed the clutch your usually more attentive

mjquillici · #7 02-05-2009, 06:05 PM

Cool. I will check it out. Is it completely isolated from the brake reservoir?

Stevo · #8 02-05-2009, 09:17 PM

[QUOTE=mjquillici;2101367 Is it completely isolated from the brake reservoir?[/QUOTE]

No, The reservoir is actually split into two chambers.

t walgamuth · #9 02-05-2009, 09:28 PM

A bad clutch master can make this symptom and have no external leaks. IMHO its unlikely that old fluid would make this symptom....impossible, I believe, actually.

mjquillici · #10 02-05-2009, 09:38 PM

Got it. So, if the fluid level is at the max fill line on the front part of the reservoir (farthest from firewall), I should have plenty of fluid for both brake and clutch? In other words, can it appear full, but really not be?

Also, how would one go about diagnosing a bad master cylinder from a bad slave cylinder?

Stevo · #11 02-05-2009, 10:31 PM

Quote:

Originally Posted by mjquillici

Got it. So, if the fluid level is at the max fill line on the front part of the reservoir (farthest from firewall), I should have plenty of fluid for both brake and clutch? In other words, can it appear full, but really not be?

Also, how would one go about diagnosing a bad master cylinder from a bad slave cylinder?

There are TWO chambers, in the reservoir both should be full. Look very carefully and make sure the aft chamber has brake fluid in it.

rs899 · #12 02-06-2009, 06:33 AM

Quote:

Also, how would one go about diagnosing a bad master cylinder from a bad slave cylinder?

It is pretty hard to be sure which one is bad, unless one or the other is leaking very badly. And even then, you are probably better off to replace them together.

I have been fighting clutch hydraulics issues since summer. I rebuilt the master cylinder (twice) then replaced it when I figured the kits I had weren't probably the right ones. Then the new M/C worked for 2 weeks (but felt a little softer than the old lashup when it was working properly). Now the pedal is really low so I'm going in there this weekend and replace the slave with a new one. Can you imagine how much time and brake fluid I have wasted in all this?

Rick

Stevo · #13 02-06-2009, 09:51 AM

I, also, dont know how you could tell which is at fault, master or slave. The slave is allot easier and cheaper so I would start there. Unless your down to your last dime buy new ones.

But first make sure you didn't just run out of fluid.

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