Another brake bleeding question - C230, ABS?
 

I did the brakes on my 1998 C230 and bled them with the Motive pressure bleeder last fall. The brakes are mushy. I just bled them again this morning and no change. I wasn't sure of how high to go with the Motive so I went to 12 to 15 psi. Do I have to go higher pressure? Also do I have to bleed the ABS unit and how do I do that?


John

No need to bleed the abs system separately, Mercedes recommend you do not go above 29psi when using a pressure bleeder so you can try a higher pressure than you have been using. Always start by bleeding the longest line first (passenger side rear) and finally the shortest line from the master cylinder.
This may sound elementary;but I have seen experienced people do it; do not shake the bottle of brake fluid to mix it before use as all you will do is introduce air into the system.
If your brakes still feel spongy i would think you may have a worn master cylinder or soft flexible brake pipes.
Hope this helps,
Geo.

George - where did that max 29psi info come from? I've never been able to find an actual pressure number recomended by Mercedes before. I have also heard that in the early 90's Mercedes recommended pressure bleeding for ABS systems using AT LEAST 30psi. Never saw that in print either. The "pump the pedal" bleeding method is shown in the Mercedes maintenance manual as acceptable for my '99 and I would think that the psi generated by pumping the pedal would be more than 29psi. Certainly a panic braking while driving would be significantly more than 29psi. BTW, I do use a pressure bleeder and try to use a pressure of 25psi or more.

Len

sokolof,
That figure came from Haynes manual #3511; 1993-2000 C180-C250 ;section 9.2 paragraph 24. Hadn't noticed it myself previously, but it is probably more to do with safe pressure in the reservoir than in the braking system itself which is considerably higher than this.
Geo.

Thre is a bleeder on the ABS pump.
Hook a hose to it when bleedin it b/c it is under pressure.

I did a brake fluid flush recently, and used about 20-25 psi on my power bleeder. I don't believe I got hardly any fluid flow below 15 psi.

I'll have to try again at higher pressure. Thanks.