Weak brakes, but good pedal feel.

[Hatterasguy]

Here is the problem the car is a 1982 300SD. My dad registered it Saturday and noticed a brake line was leaking. So he bent up a new peice of tubing and replaced it along with bleeding the brakes and changing the fluid (DOT4). Thanks dad!

Anyway the pedal feels great but the brakes have no bite to them. I am used to the brakes in my SDL and being able to throw a passenger into the dash if I wanted to.

I suspect the brakes are getting tired, would worn discs cause this? My dad didn't really inspect them closely but he said the pads have about 50% left on them. He did say the front discs look tired. I will be putting another set of wheels on it tomarrow and plan on inspecting the brakes. Since this car is shot and I really don't want to spend more then I have to on it I am thinking about just putting on a new set of front rotors. Anyone run into this problem before? I don't want to spend $100 on rotors and not fix the problem.

Does anyone know if Autozone can get rotors for these things cheaper? I'll try Napa as well.

[boneheaddoctor]

Are the pads glazed from a PO who drove around with one foot on the brake?

Rotors should be easy to find local.....

[whunter]

Good feel = good vacuum + good master cylinder =
Brake flex hoses and calipers is where I would start.

Read this thread:
DANG. can't break this caliper retaining bolt.
DANG. can't break this caliper retaining bolt.

[boneheaddoctor]

My W116 has far stronger brakes (higher vacuum asist) than my W123 that takes more effort to stop,,,but the W123 holds vaccum for 30 days I know of..(did it this summer, door locks all opened after sitting 30 days)

The W116 won't do that 4 hours after you park it.

But there are multiple variables that will affect their function.

[MS Fowler]

I'd be at least suspicious of one, or more frozen pistons in the calipers. If they're frozen, the pedal will feel firm ( like a rock) but they won't move to apply pressure to the pads.

[Hatterasguy]

One more thing to add, the car doesn't seem to have any pull. I can let go of the wheel and she stops dead straight.

I will inspect the brakes tomarrow. My thinking is even if the discs are shot the car should still stop well.

Right now I am suspecting either a stuck piston or swollen soft brake lines.

[Brian Carlton]

I tend to agree with your approach. Rotors and pads are likely a waste of money and won't provide any more stopping power, with the possible exception of glazed pads, as BHD mentioned. Pull the pads and take a look.

Additionally, when the pads are out, thoroughly clean the slides with a wire brush and apply a dab of grease.

Take a check of the vacuum. If the pump output is reduced, the vacuum assist is proportionally reduced. The vehicle will still stop in the same distance, but you need more leg to do it.

Take a look at the brake hoses. But, don't replace them out of hand. Have Dad step on the pedal hard, and you feel the hose while he does this. See if you sense any bulging of the hose. If not, don't waste any money on them.

You don't have any frozen pistons in the calipers because the vehicle stops perfectly straight.

Comparing this vehicle to the SDL is an exercise in futility. Accept it for what it is and move on. It will never perform like a new vehicle, and, you don't expect it to.

[t walgamuth]

that operating properly 82 300sd brakes should feel the same as an sdl. everything is essentially the same.

i have driven a 140 car, 300se, and i dont remember anything about the way it brakes that is different than my 350sdl. i was impressed with how quick it was with a little six and a big 140.

did your dad replace a hard line? did he have the proper double flaring tool?

tom w

So the only things I will ad are. Cleaning and greasing the slides is something I have always done with my vehicles. I learned from experience that lithium grease lasts much longer because it doesn't wash out from moisture contact like regular grease can. And if the problem seems to be glazed pad or rotors. Scuff them up with emery cloth or fine sandpaper first. Give them a test drive and see how they feel. If they feel better,but still not up to standards. Then you can have the rotors resurfaced or replaced. And replacing the pads is entirely up to you. Me personaly. At 50% pads left and they don't look like their deteriorating and seperating at all. I scuff off the glaze if there is any and reuse them. Of course any uneaven wear,signs of damage or overheating enough to cause cracking means their no longer safe to use. My two cents,and I hope it helps.

[t walgamuth]

i have the wheels off and find 50% pads i would replace them. usually. and save them for a rainy day. course i have about 12 sets of 50% pads laying about.

tom w

[pawoSD]

My 82SD has a "soft feel" to the pedal and won't lock the wheels with a quick press, but if I push harder/punch it it WILL stop hard, I know this from experience whunter has driven my car and even commented on the "Weird" feeling brakes/pedal They've been the same over the entire 2.5 years/24,000 miles I've had the car, and all new rotors and pads didn't really change the feel a whole lot (little more stopping power, but same feel) Rear rotors and pads are brand new a week ago. Our 83 has neck snapping brake force. Its pedal is weird, you can apply it, and it goes down a little feeling very very light and soft, then all the sudden it will apple some REAL force and stop like no tomorrow, mine is more even. The other day my dad and I were on the way home from autozone.....(buying rust treatment items ) and we had to slam on them because of a moron moving out of his lane where he was sitting and into ours which was clear and had us coming at 40+ mph down....so my dad had to punch the brakes, WHOA, seatbelts locked, we go forward, front tires skittered/squealed, and we had a burned rubber smell for a couple mins after that. It has AMAZING stopping power. Way better than our van, and way more confident. The van feels like it will roll over frontwards if you hit the brakes too hard. The SD just....stops. I've only had to punch mine on two occassions, and they react just like the 83, with a tire squeal and severe braking force....so I think they are both just fine in terms of how well they're working. Mine just feel more gentle/pleasant in general.

[whunter]

Originally Posted by Brian Carlton

You don't have any frozen pistons in the calipers because the vehicle stops perfectly straight.

If both front or both rear are frozen = still stop straight.
If the outer piston of every caliper is frozen = still stops straight.
If all four hoses are 99% bad = will still stop straight.

[Pete Burton]

Hattie, I would not discount the front rotors. I knew my rotors were in need of replacement last year, but I was honestly rather surprised at what a difference it made. The old rotors really had some hard spots in them, and the uneven wear really limited the proper contact. I replaced them with ATE power discs - they have a wavy slot undulating back and forth on the surface. It made a really big difference actually, and a year later it's still great. The ATE's were only like $43 each, and were well worth it. I understand that your SD is a beater, while mine is a 12 month driver, but still, $100 for strong brakes is worth it. Check the surface of the old rotors with a spoon file - if they are hard, I think it's worth it to replace.

[Brian Carlton]

Originally Posted by whunter

If both front or both rear are frozen = still stop straight.
If the outer piston of every caliper is frozen = still stops straight.

.............be realistic Roy........what's the odds??

He never mentioned excessive stopping distances.........only higher pedal forces.

[pawoSD]

Originally Posted by Pete Burton

Hattie, I would not discount the front rotors. I knew my rotors were in need of replacement last year, but I was honestly rather surprised at what a difference it made. The old rotors really had some hard spots in them, and the uneven wear really limited the proper contact. I replaced them with ATE power discs - they have a wavy slot undulating back and forth on the surface. It made a really big difference actually, and a year later it's still great. The ATE's were only like $43 each, and were well worth it. I understand that your SD is a beater, while mine is a 12 month driver, but still, $100 for strong brakes is worth it. Check the surface of the old rotors with a spoon file - if they are hard, I think it's worth it to replace.

I also use the ATE Powerdiscs and I recommend them as well. We put regular Brembo rotors on the front of the 83, and its also fine....new rotors are always good though. The 83 had DEEPly carved out old ones, they sequealed whenever applied. Pads had about 10ish percent left.