Mercedes-Benz Forum banner

1 - 20 of 23 Posts

·
Registered
Joined
·
11 Posts
Discussion Starter #1
Hello everybody,
I'm new of this forum.
As a quick introduction, since I cannot find a section where to present myself, I'm Italian (sorry in advance for my mistakes in ENG) and I'm an enthusiast of Mercedes youtimer.
I own a 124 series 300 CE-24 with several options and among them a 5 speed automatic gear which is giving me lot of headaches. In particular there is a problem between the 4th and 5th gear: one of them is missing and I cannot realize exactly which of the two.
If I try to use in manual way, it upshifts from 3rd to 4th but nothing happens on the upshifting to the 5th. Same, if I run on highway, around 130km/h (around 80 miles/h) and I try to downshift from 5th to 4th, it doesn't work. Said like this may seem an issue on the 5th but I have the doubt since the car can run at 130 km/h (again around 80 miles/h) at around 3000 rpm which should be pretty normal in 5th gear.
The other issue I experiences is that sometimes, actually very seldom, it stop in second gear and won't upshift. If I stop the car and start it again sometimes issue is solved. It is very randomly happening.

Reading here as well on other web sources I tried to check and fix some parts but issue is still there. In particular I tried to change MAS unit but nothing changed. I tried to change the OVP but still the same issues. My mechanic change/repair all wirings and the clutches and clean everything without success.
Of course oil and filter are ok and recently changed.

If anybody has any hint and may reccomend any additional part to check, I'll be very happy to listen.
Thanks a lot in advance.
 

·
Immoderately Caffeinated/ Vintage Moderator
Joined
·
16,362 Posts
Ciao Cioa, will just pop you over to the 124 fellows. They're very nice and helpful.
 

·
Registered
Joined
·
604 Posts
5th gear is missing from what you describe.
It is vacuum controlled but the vacuum is electrically controlled by an electrical valve.
The first thing you should check is the condition of the bellows on the side of the gearbox. See my thread, post 7.
2 vacuum pipes are at the gearbox and one knocks out first gear start if you select W at the shifter and the other is for upshift delay when cold to allow the cats to heat up, usually half a mile.
 

·
Registered
Joined
·
604 Posts
Check also your kickdown switch under the gas pedal to make sure it is not permanently stuck down (on) and forcing a downshift.
 

·
Registered
Joined
·
11 Posts
Discussion Starter #8
Hi, it is from 1989. Yes, 5 speed automatic transmission was an available option at that time.
Cheers
 

·
Registered
Joined
·
11 Posts
Discussion Starter #9
I tought that at early begin. But car run at just 3000 rpm at 130km/h so must be in 5th
Gear was actually disasselbled and the only parts replaced where the frictions and some of wirings. All other parts were found ok. I therefore tend to exclude vacuum issues and I believe more something electric/electronic.
Cheers
 

·
Registered
Joined
·
11 Posts
Discussion Starter #10
My kick down is foulty as well. But this is a very new issue. It was working until few days ago when I still had the gear issues and suddently stop working few days ago. I need to check it as well. Maybe related issues. Is the kick down also commanded by any electonic unit such as MAS or similar?
 

·
Registered
Joined
·
858 Posts
This is just a quick reply as I'm working ...

Check vaccum connection to EZL from inlet manifold - ensure no leaks as they will cause "no 5th gear".

In fact, check ALL vacuum connections and eliminate leaks.

Buy or build a code reader. Read and clear codes then test. Missing 4th gear and no kick-down can be caused by this.

Great car and great gearbox, by the way!!

RayH
 

·
Registered
Joined
·
11 Posts
Discussion Starter #12
This is just a quick reply as I'm working ...

Check vaccum connection to EZL from inlet manifold - ensure no leaks as they will cause "no 5th gear".

In fact, check ALL vacuum connections and eliminate leaks.

Buy or build a code reader. Read and clear codes then test. Missing 4th gear and no kick-down can be caused by this.

Great car and great gearbox, by the way!!

RayH


Thanks a lot, I will check that. If you have a picture of the vaccum pipe I should check would be perfect. Otherwise I will just look for it.
 

·
Registered
Joined
·
858 Posts
Thanks a lot, I will check that. If you have a picture of the vaccum pipe I should check would be perfect. Otherwise I will just look for it.
It is that vacuum pipe, I think. But check both ends - mine was split at the manifold end - the EZL end was OK.

And, of course, check all vacuum connections. These cars are almost 30 years old and rubber connections are likely to suffer.

RayH
 

Attachments

·
Premium Member
Joined
·
6,726 Posts
What year is your car? I am not aware of a 5 speed automatic ever having been an option for a W124.
world market. they got both the 4 speed with the S/E mode switch, and the 5 speed auto in various cars, as well as stick shifts.

its just us USA 124's that are stuck with the 722.4 4 speed slushbox, rigged to start in 2nd until 1993-1995 they actually started in 1st.
 

·
Registered
Joined
·
11 Posts
Discussion Starter #15
Hi,
I checked today the engine compartment and I found a disconnected vacuum pipe. It was just back the headlight, on left side (looking in front the engine compartment), next to the washer pan. I couldn't find where it should be connected.
I tried to look back where it was connected on the other side and it is again back to the washer pan, opposite side, and attached to front right panel.
I took some pictures that I attach for a better understanding
Not sure it is the cause of automatic transmission fault. Btw, do you know whar that pipe command?
I started that engine and I could not feel anything blowing from there...
Cheers
 

Attachments

·
Registered
Joined
·
11 Posts
Discussion Starter #16
Updates...
I have tested the error codes on 16 pins diagnosis. We found several codes and we cleared all of them. I then run the car for few miles and... gearshift working properly!!
After few miles unfortunately turned back to have the same issue. I stopped, clear again the error code and again works well.
The error is on the pin 13 which should be the one for transmission control. The number of flashes is 9. I just need to understand what this code refers to and fix it. Stay tuned 🙂
 

·
Registered
Joined
·
858 Posts
On mine, the error code was triggered by a faulty 4th/5th switch. Replaced the switch, cleared the code, all OK.

All in about 30 minutes.

RayH
 

·
Registered
Joined
·
11 Posts
Discussion Starter #19
Thanks Ryan.
I think I need to go back to identify the foulty under 9 blinks on pin13. Then clean or replace the part and, I hope, everythink should be fine.
I'm trying to check on code books but I couldn't find yet. I'll work on that. I feel to be very close to the solution now.
I need then to understand where the vacuum line (the one mentioned on prior posts) shall be connected. There could be a link between the two issues...
Thanks
 
1 - 20 of 23 Posts
About this Discussion
22 Replies
6 Participants
300 CE-24
Mercedes-Benz Forum
BenzWorld.org forum is one of the largest Mercedes-Benz owner websites offering the most comprehensive collection of Mercedes-Benz information anywhere in the world. The site includes MB Forums, News, Galleries, Publications, Classifieds, Events and much more!
Full Forum Listing
Top