Retrofit 500E/400E brake booster & master cylinder?
 

As some of you know, I have installed 500E front & rear brake calipers on our 1988 300TE, along with a C36 engine/tranny/diff.

Unfortunately, at a braking intensive track (ButtonWillow Raceway), both myself and my instructor noticed that we could NOT get the front brakes to invoke ABS/lockup, no matter how hard we pressed and even with the brake cold, warm, or hot. This was using Porterfield brake pads.

We flushed the ENTIRE system with ATE Type 200 brake fluid, cleaned-off the rotors with a 200grit Emery cloth, and sanded down the Porterfield pads. No help. We installed the "yellow-box" Textar pads, still no ABS/lockup. The brake-lines are new MB OEM rubber lines, and the system has no leaks.

Could it be that there is not enough pressure in the stock brake system to get the maximum out of 500E calipers? If so, can I retro-fit the 500E/400E's double-diaphragm brake booster and master-cylinder (yes, I know I'll have to re-route the brake lines)?

Thanks in advance,
:-) neil
1988 360TE AMG
1993 500E

TTT

Anyone know?

:-) neil

Can't speak for the W124 but I do know that it is not needed on the W201, no difference with the 500E brake booster on a W201.

Are you sure there is not another problem? Maybe the ABS unit?

That doesn't make sense. Per the MB EPC CD, the 1992 190E 2.6 uses the following:

005.430.26.01 Master cylinder
004.430.00.30 Brake Booster

While the 500E (and 400E, and R129 SL's) use the following:
004.430.75.01 Master cylinder
004.430.65.30 Brake booster

:-( neil

Neil,

according to the "Tabellenbuch Personenwagen" from April 1991 the brake booster for 190E 2.6 and 500E both are tandem ones with 8"/9" diameter, OEM part numbers are ATE T52/4A/225-210 or Girling LSC 115. They should be identical while the 300TE has a 10" single membran brake booster.

The master cylinder is different, the 190E 2.6 has the same as a 300TE (15/16" and 3/4") but the 500E got a larger master cylinder with 1" / 3/4".

The overall pressure in the brake line is nearly the same for 300TE and 190E 2.6 - but the 500E produces more pressure for the same weight of your foot.

bis denn,
Christian

1989 300TE

FYI, I replaced BOTH the master cylinder and brake booster with the ones for a 500E application.

Brake pedal feel is nice and firm.

:-) neil

FYI:

Stock 124 single-diaphragm 10" booster has a boost factor of 3.85
The 190E 2.6 has a dual diaphragm 8"/9" booster with a factor of 4.50
The 400E/500E has a dual diaphragm 8"/9" booster with a factor of 5.60

Although the 190E and 500E boosters look identical externally, they are different internally, and provide different levels of power assist. The 500E booster on a lighweight sedan provides a little too much assist (pedal effort is too light). But on a heavier car (like Neil's wagon, which weighs almost as much as the 500E) it works fine. I picked up a 190E booster than I plan to install soon, this should correct the pedal feel on my '87 sedan.

Details are in this spreadsheet, look at the "MC & Booster specs" tab:
http://www.w124performance.com/docs/mb/W124/124_brakes.xls

:stuart:

Dave,

Do you know what the booster factor is on an S600 car and do you know if this Booster will fit into a w124 500e?

I am wondering if there is an upgrade booster that would fit the 500e when doing a SA brake upgrade and if how much better the braking could be?

The data is all in my spreadsheet. The W140 booster has a boost factor of 6.85 however this would probably result in the pedal being far too "touchy", resulting the pedal that is either on or off, with poor modulation.

After trying multiple combinations, I ended up using the W201 booster (4.50 factor) with the standard 6-cyl MC on my 300D. The 500E booster+MC was way, way too touchy... the 500E booster with 6-cyl MC was better but still not right. Full details are in a forum thread on MB World.

The Silver Arrow brakes on a 500E work fine with the 500E booster+MC, no upgrades are needed. I have this setup on my '92 and dozens of other people have done the same with zero complaints. You'd likely end up wasting a lot of time and $$$ trying to fix what ain't broken...

:balloon2: