ABS problem at first meters driven.

[Juan B]

Hello everyone.

Yesterday I removed the front ABS sensors of my car, for cleaning. They were not very dirty, but yes a little.

I have not cleaned the teeth of the hub, because I have not known how do it. I thouth in a brake cleaner through the hole of the ABS sensor and with the help of a brush. I don't know if it's a good idea.

The problem is that when I turn on the engine, the ABS light goes out (this is normal), but when the car starts to move, up of about 5 km/h, I hear how the ABS pump is turned on (I can hear a "brrrrrrr" noise) for about two seconds, and two secons later stops for start on again for another two seconds. If you press the brake pedal (when I hear the noise), I notice the vibration in the foot and the brake is poor, until the car is almost stopped. I don't like this, because when you start to drive, the brake does not respond to pressure from the brake pedal.

After I've driven about 50-100 meters, it works fine, until the car is stopped for a few days.

Once, after driving about 5 km, ABS light turned on and it not turn off until the I turned off the engine and turned on again.

I know there are another sensor for the rear wheels, located in the transmission, but not where it is located exactly. Is it easy to remove for cleaning? Does anyone have a picture to see where you are?
I wanted to measure the resistance of the front sensors, but have not found the connectors. I think that the driver side one is near of the fuse box, isn't it?. There are two connectors, one is flat and the other is round. What is the plug of the ABS sensor?
Where is the ABS sensor connector, on the passenger side?

Thanks in advance.

 

[kth286]

I would suggest that the sensor may not have been seated back into it's position correctly and that some grit or the like is preventing it doing so.

I would be inclined to remove it and clean the seating area where the faces meet and refit.

Some of the gunge that was probably losened when you applied spray cleaner has also likely got onto the sensor from the spinning hub. Clean it off the sensor before refitting.

If all is well then I would leave the other sensors alone and not go curing non existent faults.

It is reckond from trade surveys, that 30% of work done by garages is as the result of owners 'messing' with their cars.

 

[219]

I had exactly this problem with my 500SEL about two years ago .

In the end I took the car to a specialist for diagnosis and it turned out that both front wheel sensors had to be replaced ( at a cost of , from memory , something like £120 each , plus labour charges for fitting and diagnosis bringing the total bill to something like £350 ) .

I was told that the flexible wires which run from the body to the wheel become brittle with age and cause the signal from the sensors to be corrupted .

It may be that , in removing the sensors , you have broken the wires which were already very fragile ?

 

[Juan B]

I would suggest that the sensor may not have been seated back into it's position correctly and that some grit or the like is preventing it doing so.

I would be inclined to remove it and clean the seating area where the faces meet and refit.

Some of the gunge that was probably losened when you applied spray cleaner has also likely got onto the sensor from the spinning hub. Clean it off the sensor before refitting.

If all is well then I would leave the other sensors alone and not go curing non existent faults.

It is reckond from trade surveys, that 30% of work done by garages is as the result of owners 'messing' with their cars.

I cleaned very well all the sensor (metal and plastic zone) and I cleaned too, the base where the connector is subjected.

I can revise it, to be safe, but before cleaning the sensors it had the same symptoms.

Juan.

 

[219]

Perhaps one or both of your wires were already broken - that is what was wrong with my car .

I had not removed the sensors ( the fixing bolts were rusty so , after trying the ABS control unit from my other car , which was working fine and made no difference , I took it to the garage ) .

 

[Juan B]

I had exactly this problem with my 500SEL about two years ago .

In the end I took the car to a specialist for diagnosis and it turned out that both front wheel sensors had to be replaced ( at a cost of , from memory , something like £120 each , plus labour charges for fitting and diagnosis bringing the total bill to something like £350 ) .

I was told that the flexible wires which run from the body to the wheel become brittle with age and cause the signal from the sensors to be corrupted .

It may be that , in removing the sensors , you have broken the wires which were already very fragile ?

I think that I'll have to change the two front sensors too.

It may be that the cable is broken, but before cleaning the sensors had the same symptoms, no better or worse.

Curiously, only do so when the car has long been inactive.

 

[Juan B]

Perhaps one or both of your wires were already broken - that is what was wrong with my car .

I had not removed the sensors ( the fixing bolts were rusty so , after trying the ABS control unit from my other car , which was working fine and made no difference , I took it to the garage ) .

Yes, I'm thinking the same too.