No brakes when cold 87'SDL - PeachParts Mercedes-Benz Forum

Mrbiskit · #1 08-06-2008, 11:33 AM

When I first start my car, I have no braking power.

The pedal just sinks to the floor and it feels like the ABS is kicking in. As I drive it or pump the pedal a few times the problem goes away. But when I first start it cold or hot, and I apply the brake after acceleration, the pedal starts to sink to the floor and the brakes grab but it kinda slips and makes that ABS noise.

I can only assume my vacuum booster is bad. This car is new to me, so there are a lot of things I am still learning. What is causing the brakes not to work when the car is initially start. I will be getting a manual this weekend, so any help is appreciated. BH

vstech · #2 08-06-2008, 11:47 AM

nope, booster would keep your foot from doing much of anything. foot would just push against the brick of a pedal.
foot sinking to floor points to master cylinder. check your fluid.

Mrbiskit · #3 08-06-2008, 12:15 PM

Thank you for the info VSTECH. My master cylinder appears to be brand new, its one of things I noticed when I purchased the car and the fluid level seems to be correct. The last owner replaced all the brake lines and rotors except for one, and I was going to finish that yesterday, but I was using a friends car jack and it was only a 2 ton (very small not very stable) and I thought I was going to get hurt using it and the tiny jack stands....

Could the replacement brake line solve the issue if the old one is "bad"?

I seem to get good brake pressure if i pump the pedal a few times and once that happens it pretty much goes away, unless I stop the engine and start it again....then the brake pedal sinks to the floor and here comes the ABS sound....

Thanks again VSTECH!

vstech · #4 08-06-2008, 12:17 PM

no matter how new the MC looks, the seals inside need to be intact for fluid pressure to build. some old seals/fluid and poof. there goes the pedal.
classic MC symptoms. get it changed or rebuilt before you rear end somebody!

Mrbiskit · #5 08-06-2008, 12:21 PM

I am at work right now so I will check it out later when I get home. I appreciate all your help VSTECH. You seem to be pretty confident that it is the master cylinder, I just wanted to narrow it down a little. THANKS!

LUVMBDiesels · #6 08-06-2008, 02:44 PM

Did the PO bench bleed the MC? You might just need to bleed the entire system.

Try that before replacing the MC...

Replace the old brake line then bleed RR, LR, RF, LF.

Diesel911 · #7 08-06-2008, 02:55 PM

As the other member said it sounds as if the Prior Owner did not bleed the system well. Since you are going to replace one of the Brake Lines anyway; you will need to bleed again. Follow the Factory Proceedure and bleed the whole system.

Mrbiskit · #8 08-06-2008, 03:33 PM

I really didn't think about bleeding the entire brake system, I will check out the rotor/brake hose today if I can borrow a friends jack. LuvMB and Diesel911 your help is much appreciated and I will let you know what I discover. Thanks again, BH

Brian Carlton · #9 08-06-2008, 04:13 PM

Quote:

Originally Posted by Mrbiskit

I really didn't think about bleeding the entire brake system, I will check out the rotor/brake hose today if I can borrow a friends jack. LuvMB and Diesel911 your help is much appreciated and I will let you know what I discover. Thanks again, BH

One of the classic errors that folks make with that system is to check the master cylinder reservoir by looking at it from the driver's side of the vehicle.

Due to the design of the reservoir, the view from the driver's side is exclusively the front chamber.........it extends all the way to the back wall of the reservoir.

The only way to see the rear chamber (and to determine if it's empty) is to view it from the passenger side. Of course, you can lean over into the vehicle and look at it from the opposite side if you choose.

Take a look for the level in the rear chamber as instructed and report back with your findings.

Hatterasguy · #10 08-06-2008, 07:16 PM

The rear chamber should fill if you fill it up to the brim.

Sounds like the PO didn't bleed the brakes properly.

Get someone to help you with an old soda bottle and run a ton of DOT 4 through the system.

Mrbiskit · #11 08-07-2008, 08:53 AM

I am parking the car until I can figure out the O bar oil pressure issue, hopefully it is just a sending unit. I plan on working on the car quite a bit this weekend and I will let you guys know how things progress.

Thanks for all the helpful information.

BH