Brake fluid replacement

[mauro12]

Brake fluid replacement

Hello guys , I have to replace the brake fluid and master cylinder but I have a question to ask you.
I’ve read that when you empty the brake fluid reservoir and you open the door , a strage phenomenon occurs , the fuel pump starts to run as there is some connection in the wiring diagram . Correct me if I’m wrong but this function should be in place only for the 280sl because the 230 and 250 do not have the sensor for the low brake fluid .
The reservoir is different and has no wires in it and no floating sensors (230-250)
Am I right or am I missing something ?
Do I have to take some precautions while replacing the fluid ? Thank you

[WRe]

https://www.sl113.org/forums/index.php?topic=20425.msg227490#msg227490

[BobH]

Brake fluid replacement

Hello guys , I have to replace the brake fluid and master cylinder but I have a question to ask you.
I’ve read that when you empty the brake fluid reservoir and you open the door , a strage phenomenon occurs , the fuel pump starts to run as there is some connection in the wiring diagram . Correct me if I’m wrong but this function should be in place only for the 280sl because the 230 and 250 do not have the sensor for the low brake fluid .
The reservoir is different and has no wires in it and no floating sensors (230-250)
Am I right or am I missing something ?
Do I have to take some precautions while replacing the fluid ? Thank you

According to the list of changes, the monitoring of the brake fluid level happened at VIN 2980, July 1967, so some 250's will have this.  If you do have it, surely all you need to do is unplug the two connectors to the reservoir when changing the fluid, or disconnect the battery

[mauro12]

My vin ends with 1533 so it’s an early 250 and doesn’t have the reservoir with sensor .

[mauro12]

Hi , during the replacement of the brake fluid , i have the intention to replace the master cylinder too. Do you think is necessary to buy a new fluid reservoir? i'm asking because i dont want to damage the old reservoir during the separation with the master cylinder . Advices are appreciated . Thank you

[TJMart]

Hi , during the replacement of the brake fluid , i have the intention to replace the master cylinder too. Do you think is necessary to buy a new fluid reservoir? i'm asking because i dont want to damage the old reservoir during the separation with the master cylinder . Advices are appreciated . Thank you

Mauro,

What condition is your reservoir in? If it is yellowed real bad it probably would be a good idea since you are replacing your master cylinder. Mercedes replacement is not like the original one and is a modern looking version. The problem is that it is slanted to one side, when it is installed, which looks pretty bad in my opinion. Don't ask how I know.

Vintage Euro Parts and Authentic Classic Parts here in the States have replicas that are real close to the original. If you choose not to replace yours be very careful to pry it up slowly equally from each end until the reservoir releases from the seals. At a minimum order new seals.

Before you install the new Master cylinder don't forget to bench bleed it before you install it. This will eliminate any air from the Master cylinder. You can then bleed the entire system.

Tony

[mauro12]

Hi , yes my reservoir is old and yellowed but is not leaking . I saw for sale the new white reservoir ( aftermarket) which is quite expensive for the size itself , about 65€. I like the old patina of the original reservoir . Probably I will clean it and buy only a new set of gasket just to put togheter master cylinder and reservoir .

[Jonny B]

Just be careful when handling it. I replaced the master cylinder on my 280 SL, and when I did, I replaced the grommets on the bottom of the reservoir. These are available. The old ones were pretty well shot. It fit together easily.

You are correct the issue with the sensors is only for the later cars as noted in the string here.

Be watchful of the blocked off port on the front of the brake fluid reservoir, it needs to be capped.

As ever, be careful to not get the brake fluid on the paint.

[Pawel66]

I see that the way of connecting brake fluid reservoir to the master cylinder changed at chassis 043 002980. The connecting parts are available at Mercedes dealers. I bought the rubber connectors from Mercedes (for the later, simpler version), A 000 431 09 35, 2pcs, EUR 7 each.

For the earlier version you would need a repair set, A 000 586 01 43, ca EUR 70.

I do not know about the fitting of the earlier set, the later one is just push in solution.

[mauro12]

Unfortunately my vin is prior of 002980 and I always need more expensive parts . I don’t know why but I’ve noticed that generally speaking, earlier versions of 230and 250 have more expensive parts than later 280. I will keep the original reservoir with a good clean and buy a new set of grommets to make a perfect combination with the new master cylinder .

[Pawel66]

You may want to check what you have in the car vs. drawing on SLS pages - maybe somebody replaced the parts with the newer version.

As for rubbers - I would by from Mercedes.

[mauro12]

I have the earlier version . The most expensive master cylinder . The rubbers are available from many websites or from Mercedes . They are made by ate which is the Mercedes supplier. I guess from Mercedes they cost probably the double .

[Pawel66]

There is a set of fittings form Mercedes, not only rubber parts. Also, I have a golden rule: buy rubber from Mercedes.