1994 E320 station wagon ABS sensors issues - PeachParts Mercedes-Benz Forum

dmorgan · #1 07-03-2012, 04:44 PM

Hi Everyone:

Just had four new brakes pads replaced on the E320 station wagon. The sensor brakelight came on the dashboard just in time before the damage on the rotor could have been worse. I asked the mechanic to check on the ABS sensors on all fours. The mechanic told me that all four ABS
sensors have to be replace. All told in labor and parts costs for the ABS sensors replacement comes around $1,160. I checked the cost of each of the ABS sensors and comes around $170 each. I tried to find some information on how to install these sensors and came up empty. My question is this: Are the ABS sensors are absolutely necessary to have and is it worth replacing them? What about these Brake Pad Electronic Wear Sensor that cost only $3.00 each? Would that be sufficient to replace instead of the more expensive ABS Sensors? I am confused and need guidance and advice on this issue. Thanks for reading.

jcyuhn · #2 07-03-2012, 04:55 PM

Step 1: Acquire new mechanic, yours is either incompetent or dishonest. Neither is acceptable.

First, this car only has 3 ABS sensors. The rear wheels are controlled together via a single sensor mounted at/near the differential.

Second, if there were a problem with the ABS, you would have a red ABS warning light on the dash. So long as that light comes on before you start the car and goes out after, then the ABS system is fine. If the system has a problem reading any one of the three ABS sensors, then the light will be illuminated and the ABS disabled.

daddi · #3 07-03-2012, 05:37 PM

Quote:

Originally Posted by dmorgan

Hi Everyone:

Just had four new brakes pads replaced on the E320 station wagon. The sensor brakelight came on the dashboard just in time before the damage on the rotor could have been worse. I asked the mechanic to check on the ABS sensors on all fours. The mechanic told me that all four ABS
sensors have to be replace. All told in labor and parts costs for the ABS sensors replacement comes around $1,160. I checked the cost of each of the ABS sensors and comes around $170 each. I tried to find some information on how to install these sensors and came up empty. My question is this: Are the ABS sensors are absolutely necessary to have and is it worth replacing them? What about these Brake Pad Electronic Wear Sensor that cost only $3.00 each? Would that be sufficient to replace instead of the more expensive ABS Sensors? I am confused and need guidance and advice on this issue. Thanks for reading.

You're getting royally screwed.

dmorgan · #4 07-03-2012, 06:47 PM

Just pick up my mercedes and the brakes are solid. I should have asked for the olds pads to see if it really is the problem. The ABS sensors light still on the dashboard after driving. I asked the owner about the ABS sensors whether is it really necessary to have those on. His respose was the only thing the ABS sensors does is to let the driver know that brakes pads are getting low in traction with the rotors and beginning to wear out and needs to replace the brake pads. Right now, he said I really don't need the ABS sensors since the brake pads are new and I drive less than 100 miles a month. Any comments?

daddi · #5 07-03-2012, 07:13 PM

ABS Stands for Antilock Brake System. That means that the tires wont lock up under heavy braking, the ABS sensors are three, one on each front wheel and one on the rear diff pinion. If the system is working as it's supposed too the sensors monitor the wheel speed by a method of small electric current produced by a magnetic field from a small magnetized ring the sensor reads from. If the electric current from one wheel gets too low the computer controlling the system reads it as a wheel locking up and activates a high pressure electric motor inside the ABS valve box. The electric motor maintains maximum braking power while electric valves alternate the brake fluid between the locking wheel and a bypass, as soon as the bypass opens the brake fluid pressure to the wheel drops and allows the wheel to turn for a split second, as soon as the bypass closes the wheel brakes again. If your mechanic does not know this than maybe he should not be fixing something composed of more than one object.

daddi · #6 07-03-2012, 07:23 PM

The most common problems with this system is the over voltage protection relay or rust on the front wheel sensors, i've seen one or two failed front wheel speed sensors. Front wheel speed sensors are all the same for the two wheel drive cars made after 1987, as can the plug for the rear sensor fail it's under the rear seat on the right side next to the central locking pump.

dmorgan · #7 07-03-2012, 07:33 PM

Thanks for the information, daddi. What do I need to do? Check the ABS sensors or replace them or leave the ABS sensors alone? Should I take the Mercedes to a Mercedes Dealership to check out the ABS Sensors? Can you recommend an honest mechanic that is knowledgable? The nearest dealership is in Nashville, Tenn.

Kestas · #8 07-04-2012, 09:53 PM

I'm glad you sorted out the two issues. If the brake pads are new and the brake pad wear warning light is on, then the sensor wiring was probably dressed wrong during installation (either pinched or worn), and is making contact with ground.

dmorgan · #9 07-28-2012, 11:06 AM

Just to follow up on the issue. The new brake pads works fine but the yellow icon on the dashboard still show solid yellow light indicating the brake pad wear sensor is on. I asked some people about that. Some say, like the last messge above, the sensor is making contact with metal. Can the brake pad wear sensor be remove without taking the new brake pads off? The mechanic I spoke to said sometimes. Is it safe to drive the mercedes with the yellow light on even though with new brake pads on all four wheels? I still have not taken the mercedes to the shop at this time because I am getting all kinds of different answers to my issue. I want to make sure to make the right decision before I decide what to do. Any comments/feedback is greatly appreciated.

Kestas · #10 07-29-2012, 01:15 PM

It is possible to remove the wear sensor without removing the pads. Some mechanics may balk at such a tricky procedure, because the sensor can break during removal.

dmorgan · #11 07-29-2012, 03:45 PM

I finally solve the problem with the dashboard yellow light (brake pads wear sensor). I took off the left front tire (driver's side). I saw the caliber and two white wires. One of the wires was EXPOSED showing the copper wiring. I proceed to put on the electrical black tape over the exposed wire. I follow the trail of brake pads wear sensor cable to the inside of the hood facing the left corner (driver's side). The connector was loose to the cable and I hooked it together. I noticed how the sensor snapped on the outer edge of the brake pads. I can see why mechanics don't want to pull out the sensor due to possible breakage on the end tip of the sensor that goes on the outer edge of the brake pad. In any event, after that was done with the taping, I started the car and the yellow light on the dashboard was gone!! Funny though, the brake pad wear sensor was made of solid metal and the ones that I saw for sale are plastic made. I wondered if the plastic made brake pad wear sensor are just as good and long lasting as the metal ones. Just curious on my end. Now I know what to see and look for after hours of researching and reading the forum. Thanks for all those who took the time reading and responding to my issue.