I have never worked on a Benz. So before I pull out the repair manual .....I'll pick on you guys.

After making a hard stop my ABS/SRS light lit up. After turning off the car, it did not come on again. The pedal was much softer and lower than before, but the car stopped okay. Now if I make easy stops no problem and no light. Sometimes it flashes on for a moment or if I make a hard stop it comes on until I turn off the car.

I realized time was getting away to inspect it. so I took it to a shop I trust...and the pads are in VERY good condition. However, the rear were not even engaging and apparently haven't been in a long time.
In my little mind I've narrowed it to the ABS relay. I have not had a chance to check vacuum hoses or anything else.
Any advice and how do I replace it, IF that is the problem?

 

Initial thoughts.

If rear pads are not contacting rotors I would first make sure the pads are of the correct type (are the pads part worn or new thickness? New thickness pads may be significant) and then ensure that the pads or caliper pistons are not seized.

Next I would check to see if there is any pressure at the caliper. Whilst pressing the brake pedal I would see if fluid "squirts" out when loosening the bleed nipple on the caliper.
Take care to only allow a little fluid out otherwise you may end up having to bleed the whole brake unnecessarily. Maybe easier to do this check first. No pressure. No need to inspect pads etc.

I assume reservoir fluid level is OK.

I don't believe that it is the ABS modulator since the ABS light resets on ignition off but this is not a definitive outcome. ABS modulators are very expensive. ABDS modulators are very reliable after any assembly gremlins are resolved.

So recapping are the rear calipers free and do yiou have rear line pressure.
Once you know the answer to this we can proceed further.

The supply relay to the ABS could be faulty BUT this would not explain the rear pad non contact issue.
Even with no electrical supply to the ABS system all four brakes should work hydrostatically, i,e, as though no ABS was fitted.
This is to ensure that you have braking should the ABS system fail.

Stuart

 

I can't say much about the pads in the rear but I can comment on the light coming on after a hard stop. Check out the owner's manual... it is supposed to come on after a very hard stop to let you know that the system engaged. I found this out about 1 year into my ownership. On a country road I had a turkey or some sort of large bird run out in front of my car. I stood up on the brakes and was amazed at how agressive the car stopped. The ABS didn't pulse, it just slowed down very rapidly. It was reassuring. Anyway, the BAS/SAR light came on. I was upset thinking that I had jacked something up. After I got home and later restarted the car, it never came back on. I did my research and found out that it was normal for this to happen after a hard start.

Again, I can't comment on your rear brakes but I can tell you that the light coming on under very hard braking is normal. If it comes on more frequently, you are either stopping very hard quite often or something else is afoot. Best of luck to you.[8D]

 

What light comes on.
I think there may be some confusion here.

IMHO under HEAVY braking the ABS should have pulsed.
The warning light most probably indicated that for some reason or other the ABS didn't work but the fault cleared on restart.

BAS also determines that you are in an emergency situation and applies FULL stopping power, since some drivers don't actually push the brake pedal hard enough under such conditions....always wondered why is the case if your life depends on it!

 

I love this place.

 

Isn't it great? The stories are the best. I have already saved some money by following the advice and guidance of others. Have a great Christmas.

 

Hey folks!! This is highly appreciated.
I haven't bled the rear brakes yet, of course I'll start there. The rear brakes appear as if the pads have never engaged. I've checked and no apparent leaks. I fully expected the brake fluid to be low when I raised the hood but it was full as well. With that said I suppose my concern is the low brake pedal and now the ABS/SRS light comes on unless I use moderate to light braking. It does go out after I turn the car off and back on again.
I'm pretty sure the car has been stopping on just the front brakes possibly since the new brakes were installed or a short time there after. (LOL no I didn't do the last brake job)
Prior to the "hard brake" action, the pedal was never low and the car responded easily to any braking situation.
I've experimented on quite a few stops to make sure the car held once brakes were applied to see if I was losing pressure from the booster.Are there any vacuum hoses that are typical of needing replacement.

The one thing that bugs me is the pedal has always been in the proper position with no sign of softness over a year.....and this along with the back brakes not working the two conditions don't match???