Mercedes-Benz Forum banner

1 - 12 of 12 Posts

·
Registered
1978 240D sedan, blue, 4-cyl, manual (parting) and 1990 300TE 4matic wagon, automatic, with A/C
Joined
·
21 Posts
Discussion Starter #1 (Edited)
I just bought this 1978 240D sedan a few weeks ago. It is old and dumpy but it has a lot of new parts on it, and it drove beautifully while it ran. Then the front brakes seized up. When I changed them, they did look pretty sad to me: rusty and whatnot, so I had no problem getting new ones and feeling that I am improving this old car along the way. Now that I just changed the front calipers, rotors, pads, and brake wear sensors, I have a few problems.

One is: I probably need to bleed the clutch slave cylinder... I had the first little bit of gear grinding going from 2nd back into first, whereas it used to shift marvellously everywhere. And I see that if the brake fluid gets too low in the one chamber (the one that connects to the clutch), then air can get into the clutch master and slave. Is that right??

The other problem, though, is that the car continues to accelerate (sometimes) after I let my foot off the gas...? I have a 4 speed manual transmission and this thing will drive along like an automatic until I put my foot on the brake to slow it down. It ALSO does this when I shift. I let off the gas, I step on the clutch, and the engine SURGES or accelerates...

What is that all about? I am thinking vacuum or?? Also still thinking of air in clutch.

Do you know the worst of it? The previous owner just changed the master cylinder... Then the front brakes seized two weeks into my tenure... Could there be something wrong with this combination of newness (master cylinder, brake calipers on front, new rotors, new pads, new sensors, bled brakes (may need to bleed clutch), and... how can I put this... the general sloppiness of the previous owner (ie. new master cylinder... why was that put in? because the old one bled into the vacuum booster and ruined it? because the truly rotten front brake calipers weren't stopping the car?? maybe someone should have changed the front brake calipers sooner??).

Still, great little car.

But have I done something now that makes it crazy/loco? I love to work on cars, am no mechanic, and it is always the last thing I touch that causes the next problem, know what I mean?

I really need ideas on this. The car has been off the road for over a week or more now, waiting on parts, waiting on other parts, and now I test drove it and, great, it has wonderful braking, and it DOES still shut off with the key, but what's going on with... vacuum? clutch? run-on acceleration?? Thanks.
 

·
Registered
2001 Volvo V40
Joined
·
2,954 Posts
Have a look at the linkage in the engine bay. Disconnect the ball joints and grease them. See if you have all the springs still there. If you move the linkage by hand, it should spring back immediately upon release.

How often do you shift back from 2nd to 1st? Those are difficult shifts when driving even with the clutch in good order. You can bleed the clutch system with the bleed screw on the slave cylinder. Fill the reservoir up to the maximum level.
 

·
Registered
84 300TD, 2004 E320 wagon, 2006 CLS55,
Joined
·
1,051 Posts
Have a look at the linkage in the engine bay. Disconnect the ball joints and grease them. See if you have all the springs still there. If you move the linkage by hand, it should spring back immediately upon release.
..x2..
 

·
Registered
1979 240D 4 spd
Joined
·
320 Posts
bfin - my acceleration was doing the same thing after I did a compression test. Turned out that the C-clamp on the throttle linkage had fallen off at some point so the linkage would shift in the engine bay and get cought up on some metal - hence the constant acceleration. Make sure all that linkage is free of getting snagged.
 

·
Registered
1978 240D sedan, blue, 4-cyl, manual (parting) and 1990 300TE 4matic wagon, automatic, with A/C
Joined
·
21 Posts
Discussion Starter #5
I think you are right

The throttle linkage seems sticky at it's lowest point on the left side of the engine.

And I see no springs? Where are they? What look like? There are the ball cup joints, and there are these flat plastic slightly yellow type bushing connections at a few spots.

I have cleaned and greased ball and cup connections. Don't know solution for plastic bushing type items.

The stickiest spot seems to be that lowest portion of linkage, on left side of engine.

Where is the C clamp someone mentioned? And again, I see no springs...

It is quite a lot colder outside now than when I first had to park it due to brakes. This seems to be part of the difference, but I'd sure like to know about springs.

Thanks for any info!
 

·
Registered
2001 Volvo V40
Joined
·
2,954 Posts
There is a spring at the firewall, low down, and there is usually one on the injection pump (between injection pump and engine).
 

·
Registered
1981 300D with a funny tranny
Joined
·
965 Posts
Or, if you have cruise control. It may be going bananas.
See if the bowden cable is too tight or if you can just unplug it ( i mean the electric plug and the vacuum) make sure that u don't create a leak. Drive it w/out the CC, and see if it makes a difference.
It makes more sense what others are saying about the linkage though, it is normally neglected and not lubricated.
 

·
Registered
1985 300CD Turbo coupe, 2006 E320 CDI sedan
Joined
·
573 Posts
Assuming you have the configuration in the right hand diagram above, locate rod #125 on your car. It's the one that disappears down between the injection pump and the engine block. While you were doing the other work, you may have dropped something down into that crevasse - something that's now jamming that part of the linkage. If you're lucky, all you'll need to fix it is a flashlight and a magnet. IF that doesn't pan out, disconnect rod #85. That will isolate the cruise control servo.

But if your linkage is like the other diagram, I'm afraid I can't help.

//greg//
 

·
Registered
82' Euro 240D 84' 300D 01' SLK320 6 Speed Sport!
Joined
·
315 Posts
My 82' 240D does the exact same thing its like having a little extra horse power between shifts :D

No, but seriously, I am going to take your all's advise in helping the other benzworld member.
 

·
Registered
1978 240D sedan, blue, 4-cyl, manual (parting) and 1990 300TE 4matic wagon, automatic, with A/C
Joined
·
21 Posts
Discussion Starter #11
thank you all

I have the linkage like in photo #2, and it definitely sticks/was sticking/will again... down on the left side of the engine between the injector pump and block. So I don't know what the heck is down there. It is a pretty tight crawl space in between those two. But lubricating everything else I could get to worked well.

People mentioned cruise control. Did these cars have cruise control?? This is a 1978 240D. I don't see any controls to control cruise control inside the vehicle...

Anyhow, it is working alright although I'd still like to be able to see/feel between the engine and pump a lot better... no room there!
 

·
Registered
2013 MINI Copper S Clubman, '84 300CD-weekend car
Joined
·
10,152 Posts
Your car would have the servo unit, a black round item (#32) with a Bowden cable going to the cam cover.

Do you have a combination switch on the steering wheel column? Items #110 and #122 in pic. The latter is the cruise control stalk.
 

Attachments

1 - 12 of 12 Posts
Top