w4sim

This has not happened over night or just recently, but my brake pedal has always been quite soft ever since i bought the car about a year and a half ago. The feeling you get is that its quite "spongy" and on a very rare few occasions i thought it wasnt going to stop.

Iv not really driven any other S55's to compare this to but despite the fact that people keep telling me its big and heavy car i know its supposed to stop better than that, especially on 8 pot calipers!!! I think my mums diesel Saab has better braking than this, and im not even kidding.

So the question is, where do i start to essentially "tighten" the brakes?

Iv changed the front discs and pads and it hasnt really made any noticeable difference so im wondering what else i could do? I dont think brake fluid has been changed for a while so thats step 1, but from the experience of another car a very long time ago that didnt really make much of a difference. Is there a part that could be worn or needs replacing/updating/tightening etc etc???

Thanks.

mrbobby

You may have a break down in the fluid performance factor necessitating a fluid change, you may have air in the system or you may have hard front pads. My S55 also was, in my opinion, poor in the stopping department. My Indie suggested going to OE brake pads which he said would provide better braking but on the down side create a lot of brake dust. He was right. The car now stops on a dime but I'm forever cleaning my chrome front rims.

w4sim

The first time i changed the front discs and pads on mine the braking power improved but just a little. Discs were not OEM, pads were Pagid, which i was told were what Mercedes also use as OEM???

Iv had the car for about a year and half now and i havnt changed the brake fluid, im pretty sure it hasnt been changed for a number of years now, so next weekend im looking at changing the brake fluid and hoping for the best. Failing that i will then also change the front discs and pads once again, but parts only from Mercedes this time (expecting this to hurt quite a lot).

Quadcammer

woah, you need to slow down. First of all, rotors are not going to affect your brake feel. Pads might, and there are some options that may be more suited.

That said, your first problem is the lack of brake fluid maintenance. You can try fluids like Endless, Motul, or Castrol SRF. They have reported to produce a more solid brake feel and for all practical purposes eliminate the chance of boiling the fluid on the street.

Next, you can switch to stainless steel braided brake lines. I'm not sure who produces them for the S55, but I'm sure you can have it done. This should again give you a firmer pedal feel and less chance of ballooning a hose.

Back to pads.

If you don't care about dust and some potential noise, you can put in something like HAWK HPS or HPS+ pads. They should have a bit more bite. Absolutely no need to change rotors again.

w4sim

I was looking at the option of braided hose lines, but again i cant find too much for an S55.

As for Pads, the current ones are Textar, produce a fair bit of dust and do a half decent job, but nothing too firm.

I think the first thing in order is a fluid change, followed by just pads and then maybe discs if what your saying is right.

w4sim

Is there any particular difference between DOT 4 and DOT 4 PLUS??? Or is it the same thing?

grane

My wife discovered a similar problem with her CL55.

Turned out the pistons in the left front caliper were sticking. The tech said this threw the entire system off. The caliper was replaced, the fluid was changed with OEM fluid, and the brakes were adjusted. Of course the lines, ABS etc. were also inspected at that time.

Now the thing stops on a dime with plenty of proper brake feel as per the AMG profile.

Before this service the car exhibited the symptoms you described.

BTW we change all our MBs brake fluid every year now, or at least have a hydrometer test performed. If the weather/temp where you are goes through large seasonal swings as ours does this is the plan we would follow. Cheap insurance!

Quadcammer

My understanding is that they can be used interchangeably.

Dot 5 can not though.

alx

4 plus is 4 with a higher boiling point.

However, any modern synthetic 4 far exceeds what 4 plus calls for anyway so as long as you use synthetic 4 it can replace 4 plus.

w4sim

Thanks chaps, will make sure to use the proper fluid incase thats one of the causes of the spongy brakes if the last owner used normal DOT 4.

alx

it is not the dot 4 (most modern dot 4 are better than what dot 4 calls for)... i have in my pile of fluids even a synthetic dot 3 that far exceeds the dot 4 plus properties.

it is however the age of the fluid. as the fluid ages it absorbs water which makes it easier to compress and results in spongy brakes.

btw, if your fluid has never been changed there is a good chance that the brake bleeder valves in the calipers are stuck. presoak with some wd40 before attempting to remove and then remove _only_ with a socket or the socket side of a wrench. do not use an open wrench. if they dont budge- do not force as you will either strip or break off the bleeder valves. break the bleeders and you are in for a silly mess of removing the caliper, drilling through the broken bleeder, retreading and often requiring the use +1 size bleeders.

ask me how i know...

w4sim

I dont wana know how you know . . . . makes me shudder just thinking about it!!!

Iv been looking through the service history of the car and at about 2 years ago the indicator for the "2 year service" is ticked as done. Looking through the rest of the book shows that the "2 year service" should include a brake fluid change amongst other things. Im not 100% convinced that the fluid was changed the last time this happened.

I hope nothing goes wrong but we will try a fluid change on Thursday night. Will also take the time to make sure all the caliper pistons are moving freely and not getting stuck, and what the general wear and tear state is on the discs and pads.

w4sim

It seems to only take 1 litre of fluid, so will just get it from the Merc stealers themselves. Atleast it will be the right stuff.

PillDrive

Goodridge G-Stop 34005 is the braided lines for that car if im not mistaken. I haven't had the chance yet to do them but I will once I have a minute. For the pads I have used Akebono and they bite pretty good.

w4sim

Thanks for that Pill, iv seen this Goodridge kit on ebay, but it seems a different part number to what you have given:- Part number = SME0920-4

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=271166481693&ssPageName=ADME:X:RTQ:GB:1123
Its listed for all W220 S-class's, including the S55 and even the S65 for that matter. Im not 100% convinced that all the hoses across the entire W220 range are the same, especially the big 8 pot calipers like ours. I could be wrong but i just imagine the S55/S65/S600 hoses to be bigger.