I'm working on my girlfriend's 1984 Mercedes 190e and the brakes are giving me some strange symptoms (at least strange in my experience). Since we bought the car, the brakes have been an issue. When we first got it, I did the pads and rotors since they were tired. The brakes have also been bled, and all the old nasty fluid has been replaced.
So here's the issue. The brake pedal is very very stiff, and only depresses about an inch or less. The car doesn't stop well. It stops like it has manual brakes or a bad brake booster, but the pedal feel doesn't really go along with that. I replaced the booster with one I had laying around, but the brakes are unchanged. Help me GRM, you're my only hope!
Ballooned hose? Internal cut to the hose? Bad master?
Sounds like a bad proportioning valve, maybe plugged. Did it bleed hard? Also check that the calipers are operating correctly.
Bad check valve or clogged vacuum line would give you unboosted brakes. With the engine off press down on the pedal & start the car, The pedal should go down a little as the booster gets vacuum.
carbon
HalfDork
2/22/14 1:57 p.m.
seized caliper or slides?
The check valve and vacuum line are fine, I've checked those. I was thinking the master might be at fault. Though on the two occasions I've had bad masters, there was a complete loss of pedal. This seems to be the opposite of that.
What does it mean to "bleed hard?" What's the best way to check the calipers?
RoughandReady wrote:
...What does it mean to "bleed hard?" What's the best way to check the calipers?
Hard bleeding is when you open the bleeder wide and the peddle still pushes down hard, which could be a crushed line.
Check the calipers by removing the wheels and watching the caliper while some one puts on the brakes.Make sure both pads are clamping. If not then lube the slid pins or floating pad holders so that everything works smoothly. The caliper brackets might also be warped but this is rare.
In reply to pjbgravely:
Hm, I don't know if they bled hard. She was on pedal duty when we did the bleed. Could that also indicate an issue with the master, since it's before of the junction block? If the calipers check out, is there a way to determine if the issue is with the j block or the master?
sounds like swollen hoses to me
RoughandReady wrote:
In reply to pjbgravely:
Hm, I don't know if they bled hard. She was on pedal duty when we did the bleed. Could that also indicate an issue with the master, since it's before of the junction block? If the calipers check out, is there a way to determine if the issue is with the j block or the master?
I really don't know, maybe crack one line going to the valve? Most brake problems are the peddle too soft but I did have a VW van that had the same peddle, (non power of course) because I crimped shut the line going to the rear brakes.
ok, if there's vacuum on the booster hose, i'm betting on a ruptured diaphragm or other leak inside the booster.
In reply to AngryCorvair:
Wouldn't I hear a whistling? I had a bad booster on this old Dodge van I had. Pedal went to the floor and there was like a 30 second delay between standing on the pedal and the van stopping.
Let me clarify a little. The Mercedes stops okay. It's definitely a delayed reaction, though. Emergency stops are pretty sketchy. The pedal feel is what has me stumped.
So frustrating!
Something I remembered that might be important:
Car off, new booster in, master not in: pedal throw normal.
Car off, new booster in, master in: Pedal throw .75".
I remember I pressed on the brake pedal with my hand after bolting the booster in, just to see If there was any improvement.
You have a clogged line somewhere.
In reply to Kenny_McCormic:
Sounds like a nightmare.
