1986 560sl possible brake problem - PeachParts Mercedes-Benz Forum

fpilot · #1 05-29-2006, 11:30 PM

Hey there guys. Now I know some about brakes but being a female do not know all the ins and outs of brakes, not as technical as I have read in most of the threads. I say all this because I am not sure how to describe my problem. I am in the Dallas, TX area and have had this car now for 4 months. It seems for the past couple of months when I am going slow in a parking lot and braking, it feels almost like a cable is loose. It does make a noise as well. Kind of like a grinding but too feels like something is not grabbing. The brakes work great otherwise. In fact, they were looked at about 6 weeks ago because they were squeaking really bad and they put a greaser on it to stop the squeaking. It has helped and they told me then the brakes were in good shape. This does not feel like any other brake problem I have had on other cars. Now this is the first MB I have owned. I just know this is not normal and I do not want to have my brakes go out when I need them. This problem is not consistent but really becomes apparent going really slow and then braking. Any ideas?

Thank you all very much.

New proud owner of my dream car!

nhdoc · #2 05-30-2006, 07:37 AM

Does your car have ABS (antilock braking)? My '88 does 560SL and I think your '86 does too. The ABS pump in these cars, when it cycles, will make the brake peddle pulse and make a noise so that may be the problem you describe. You may have a faulty wheel sensor or ABS controller causing the ABS pump to activate when it shouldn't.

fpilot · #3 05-30-2006, 09:02 AM

Thank you for the reply NHDOC. Yes, I do have ABS Brakes. Can this be repaired if it is the pulsing?

Thank you again.

Marla

Richard Wooldridge · #4 05-30-2006, 09:10 AM

Hi there,
It could be that the previous owner installed pads with a high metallic content. The original Mercedes pads have a high organic content and work very well, but "shed" a lot, leaving the wheel rims soon dirty. You might try some new pads from MB to see if the "grinding" disappears.
My '82 has a noise when going very slow and if I step on the brakes I hear a noise, but it is the exhaust pipe hitting the body due to the torque of the engine... probably needs new motor mounts.
Another thing to check is the front wheel bearings. Make sure they are in good shape and adjusted properly.

Congrats on acquiring a great car!

nhdoc · #5 05-30-2006, 10:44 AM

Quote:

Originally Posted by fpilot

Thank you for the reply NHDOC. Yes, I do have ABS Brakes. Can this be repaired if it is the pulsing?

Thank you again.

Marla

Yes, of course it can be repaired...the thing to do is confirm it is the ABS that is causing it. It would feel like the pedal is pulsing up and down slightly and the brakes are not grabbing and you can also hear the noise of the pump cycling if that is it. The same as if you were in a skid and the ABS takes over. If you lived where it is snowy like here you would know exactly what ABS feels like when it kicks in, but in sunny Texas you might have to wait for an ice storm to test it out. You can also try on wet pavement to brake very hard and induce a skid to test it, just make sure nobody is around or behind you when you do!

If your problem fits this description tell the mechanics to check the wheel sensors and clean the rotors too...maybe when they were servicing the brakes recently they left some crud on the rotor near the sensing surfaces. There is a common enough problem with these that several automakers have had to recall their ABS brakes to correct it.

dmorrison · #6 05-30-2006, 01:22 PM

Not sure what you are flying, but if it has any performance to it you should be aware of the antilock systems pulsing when the brakes are releasing. In the 560SL you will feel the pulsing in the pedal as the computer releases the brake pressure to that wheel.
It could be one sensor giving the computer a "lock up" signal so that one wheel is releasing. The ABS light will not come on when the system is "working" as designed. The wires to the wheels are known for breaking and needing to be replaced. But usually the ABS light will come on for this failure.

Another common problem are worped rotors. As you slightly add brakes at low speeds you feel a pulsing in the car that slows it frequency as you get slower and slower. This is a worped rotor that is caused by heating the rotor in a hard brakeing situation and then leaving the pad agains the rotor once stopped at the light or stop sign. You have to replace the rotor in this situation. They can be turned at a shop but the woped rotor will return in about 5000 miles.

Do the brakes feel like the power booster is going bad. This would feel like you lost the application abillity pressure. The brakes would work but you would have to press harder than normal to get the same braking effectiveness. Your booster is the "power boost" supply to the brakes.

Consider taking the car to a independent or dealer you trust. Robert Schnider at ******** is a good guy, Ive known him since 1981. Zims, right next to Park Place Mid Cities is a good shop also. they have worked on my 560SL

Dave

PS What are you flying and were. I fly the MD80 for American at DFW.

fpilot · #7 05-30-2006, 11:20 PM

Thank you all for your replies. Excellent suggestions. I will have the abs brakes looked at as well as the wheel bearings and rotors. It could be any of those things. The noise it makes is not a grinding like when you know you need new pads and it is the metal to metal sound. It sounds like a "dragging" maybe but the scary thing to me is it feels like the brakes are not grabbing and something comes out of sync for a moment. It is a strange feeling. And only sometimes when I brake going very slow...parking lots mostly and even in reverse when I am backing out of my driveway. Hope this is making it more clear. Again, I thank all of you for your help, nhdoc, R. Wooldridge and dmorrison! I will keep you alll posted.

dmorrison - I fly what you would probably consider a toy.

I fly Cherokee Warriors usually and out of ADS. Do have some time in a Caravan though oh and one of my company's jets, the Challenger 604 (hardly call it flying though but did sit left seat)! That is awesome that you fly the MD80. Maybe one day I will get there. Am enjoying selling them for now. How do you like the MD80?

wbain5280 · #8 05-30-2006, 11:49 PM

The dragging noise and loose cable could also be the parking brakes in the top hat section of the rear discs. Have them checked as well.

Then the front discs could have a lip on them and if the pads are 'low' the metal backing plate would contact the lip on the disc.

It would be best to take the car to a competant MB shop, including the dealer, and test drive the car with the tech. Only then can a proper diagnosis be done.

You life depends on the brakes.

fpilot · #9 05-30-2006, 11:58 PM

You are right, my life does depend on the brakes. They do seem to be working very good when I really need them it is the slow braking. But definitely will take into a good shop here in Dallas. Great idea on the loose cable as well. I know the parking brake was worked on before I bought it. Thank you again!

Marla

t walgamuth · #10 05-31-2006, 05:58 AM

when they feel like they arent working right do you have to push harder on the pedal?

it also could be a lack of vacuum or a leaky brake booster (vac operated) if this is the symptom.

tom w

fpilot · #11 05-31-2006, 07:20 AM

t walgamuth - No I have not been pushing harder on the pedal. In fact, I let off the pedal because I do not want to do any damage then I lightly push on the pedal. Good info though and I will certainly keep it in mind. I am thinking I am going to take it to a shop this Friday. Thank you again! I will keep you posted.

dmorrison · #12 05-31-2006, 06:42 PM

Quote:

Originally Posted by fpilot

dmorrison - I fly what you would probably consider a toy.

I fly Cherokee Warriors usually and out of ADS. Do have some time in a Caravan though oh and one of my company's jets, the Challenger 604 (hardly call it flying though but did sit left seat)! That is awesome that you fly the MD80. Maybe one day I will get there. Am enjoying selling them for now. How do you like the MD80?

Used to fly Warriors out of RDU while at NC state. My son used to instruct at American Flyer at ADS. He is now getting his MBA and a MS in Finance at UTD.
The MD 80 is a good Aircraft, 777 would be better but I'm sort of done with the International flying. Flew world wide in the C141 in the Air Force Reserves. And I've had enough of the Jet lag. I do turns to the west coast. Go out and back in the same day. Sleep in my own bed.
I enjoy the MD80, I hope I would with 13,000 hrs in it. Its a VERY familiar "glove" to me.

Fly safe.

Dave

PS The DFW area Mercedes forum group is having a get together on the 9th of June the west end.
Consider comming.