Hello. This might be pretty lenghthy, please bear with me. I have a 2001 S40 that my daughter drives and she said that her brake pedal did not feel right. Took the car to a european mechanic and they diagnosed the problem to a faulty master cylinder. They replaced it and the pedal felt the same and said the master cylinder was by-passing and they would order another one. They installed the new master cylinder and it performed the same way. They said they would order one direct from Volvo. They installed that one and it did the same thing. They also performed a "power bleed" on the system, they checked all of the sensors and came up with the same results. They mechanic threw the towel in, replace my original master cylinder and said they did not have the test equipment to check out the ABS pump system. Any feed back will be welcomed. Please advise.

Thank you, TJH

 

I have had bad experience with this too, just one though.

Here is some advice to try:

DO NOT ATTEMPT TO BENCH BLEED NEW ONE, INSTALL ON CAR, PUMP BRAKE WITH ASSISTANT FOR A FEW CYCLES, HOLD, JUST LIKE MANUAL BLEEDING, LOOSEN ALL LINES ON MASTER CYLINDER, PEDAL GOES TO FLOOR, TIGHTEN ALL LINES, LET UP ON PEDAL, REPEAT FOR ABOUT 5 TIMES, MAINTAIN FLUID, WATCH FOR AIR. THEN BLEED ALL THE BRAKES WITH NO MACHINES, JUST TWO PEOPLE, STARTING WITH THE FARTHEST, WORKING FORWARD, NO AIR BUBBLES.

 

We had one we just finished today. 2 weeks messing with it master cylinders and thinking brake lines or calipers.
What it finally turned out being is the ABS unit.

When we started bleeding a GEL started coming out of the bleeders. I have seen this alot on S40's. I think the GEL worked into the ABS unit and caused blockage.

After installing the New(used) one today brake pedal as normal.

 

Thank you SVTfocus03 and Tech for commenting on the brake issue. I understand how to bleed brakes, when replacing the ABS unit why bleed the Master Cylinder? Is it to get fluid into the ABS unit before bleeding the brakes? Is there a bleeder on the ABS unit itself? And is there any special thing I need to do to the ABS unit or any part of the brake system? Once again thank you for all your help.

TJH

 

If you have been bleeding alot I would only install the ABS unit and then bleed the system through the calipers and be done. I wanted to make sure I had all the crap out of the system on the one I worked on.

 

Tech, Thanks for responding quickly. It seems my next step is to get an ABS pump and install it. Thank you for all your expertise. Will post when I get something done. Once again Thank you.

TJH

 

Your welcome I hope all is easy from here!

 

Sorry, I have not posted for a while. Before I replaced the abs pump, some mechanic I was talking to said to check all the fuses that apply to the abs/bake system. So I checked ll the fuses and did not find anything wrong. All fuses were good. Took the car for a ride and the pedal felt fine. No mushy pedal, nice and firm. To this day it is working is good. Did not replace abs pump. Maybe I got lucky. Anything happens I will post. Thanks to all for your expertise.

Ted