Hi everyone,

I am having trouble getting the brakes to work right on my car, a 1965 200D. It has the disks in the front, and drums in the back. The master cylinder is brand new, the brake booster is a good used item, that has been tested before being put into the car. The front calipers were rebuilt, and the rear cylinders were replaced. All rubber brake lines were replaced. There are no leaks, no loss of brake fluid. What I‘m experiencing is a springy brake pedal, that I have to really press on, all the way to the floor to get it to stop, and it stops slowly at that… The lines are bled, and I get good flow out of the bleed screws. I‘m at a loss. And I pressure bleed the brakes too. Any suggestions from the more learned W110 owners?

Any help would be greatly appreciated!!

Thank you,

Nick.

...now perform a traditional 2-men brake bleeding procedure. Spare no fluid in the procedure,do it right.
If disks and pads are brand new,give them several hundred stops to bed in. The new disks needs the friction pad material stuck on the contact surfaces good.

Did you get the correct master cylinder? If the bore is too big the brakes will never work properly.
Have you adjusted the length of the push rod ?
There should be a return valve on the firewall which regulates how much brake fluid pressure is released from the rear brakes. It may need replacing.
Finally, adjust the rear shoes in the brakes until they lock the drum,then wind them off so you can hear them rubbing slightly when you turn the brake drums.

You said new. Or is it a rebuilt master cylinder. I had a rebuilt master cylinder that did that to some degree but not as bad. It turned out to be the master cylinder sucked.

__________________
84 300D, 82 Volvo 244Gl Diesel

Hello everybody,
I have not yet performed the two-man brake bleeding procedure, I will be doing that within the next couple of days. The brake master cylinder was brand new ATE, and it was the one that was said to fit my car by PelicanParts.

I also do not see a return valve on my firewall… I will also be adjusting the brake shoes in a day or two, too.

Seeing as I don‘t have a check valve at all, how do I replace it? Searches have yielded no results so far… I have found another PeachParts Forum post that shows of it‘s existence and what it looks like, but I can‘t find replacement parts anywhere….

The check valve is integrated in the brake master cylinder (assy 493-499). Since the master cyl is brand new,I'd leave it alone.

There is a proportioning valve under the carriage, #556 .Actually it may not be a valve...may be a simple 3-way splitter,but I am not sure.

Oh, okay, so that is why I do not have one! Thank you! I have not adjusted the pushrod, how does one go about doing that?

The pushrod of the brake booster that engage the master cylinder is held to the brake pedal by a cam (eccentric)bolt.



Per Chilton manual:
"The brake pedаl travel should be 6.08" on all (dual circuit) models. To adjust on all models (except 230SL), turn adjusting bolt (the cam bolt) until the notch on the bolt head points rearwards.This gives maximum travel, and adjystment is made from that point.
NOTE: If If pedal hits brass thread of brake light switch, use shims under switch so that switch button protrudes 0.16" .

The above may be wrong on the total pedal travel ...however you need to make sure that there is some pedal freeplay before master cylinder engagement (by changing the position of the cam bolt).

Thank you vox_incognita, I just adjusted, and there was little play to begin with, it seems. So that wasn‘t my issue, apparently… I was banking on that, because I‘m stumped. Still have to press almost all the way to the floor, and only get light braking fully pressed down.

I am going to adjust the brake shoes again, to make sure I did that right. Incidentally, how much material should be on the brake shoes? Maybe they‘re too far worn? That‘s the only thing I can think of. Or that they‘re still not bled correctly… I used almost the full rear tank compartment of fluid bleeding the rear brakes (each cylinder, refilling between each one to full….)

I don’t like drum brakes. You need to have them adjusted right so the cylinder forces contact quickly.

If you’re 100% sure it isn’t trapped air, then I’d suspect there is a cylinder that is operating too far and not hitting the pad/forcing it against the drum.

__________________
Current Diesels:
1981 240D (73K)
1982 300CD (169k)
1985 190D (169k)
1991 350SD (116k)
1991 350SD (206k)
1991 300D (228k)
2008 ML320 CDI (199k)
1996 Dodge Ram CTD (442k)
1996 Dodge Ram CTD (267k)

Past Diesels:
1983 300D (228K), 1985 300D (233K), 1993 300D 2.5T (338k), 1993 300SD (291k)

I haven't really dug into the rear brakes except for cylinders overhaul and bleeding.
Have a look at these videos to get the idea of the way this type of brake shoe self-adjustment works.
There have been some changes on the pin design for the friction assemblies but the idea remains .



https://www.youtube.com/watch?v=-0ZIN7gG-7U

https://www.youtube.com/watch?v=s20pLwIBNHM

https://www.youtube.com/watch?v=WDRB0Udo-AY

Do the two persons brake bleeding procedure before dealing with the rear brakes.


You can start a new thread in the Vintage subforum .

Make sure you find some literature too. Look for the "Early Model Years" vol.3 that MBUSA issued some years ago...also check for Chilton's manual covering the 60-ies MB's.

Just in case...can you confirm this is the MC (A0014306301):

https://www.pelicanparts.com/More_Info/0014306301.htm?pn=001-430-63-01-M4&bc=c&SVSVSI=2247

Hey,

Yes, that is my master cylinder. The only thing is, my brake assemblies aren‘t the same as those in the videos, because those are self adjusting, and mine are not, I have to adjust them myself with a 19mm wrench or socket. But I will be doing the two-man bleeding procedure before touching any of that anyway. That method is better than pressure bleeding? I was led to believe they would do the same thing, but I would definitely like to know if that is wrong, then I‘ll always do it the right way!!

As always, thank you all for your responses and help!!