ABS module/Mstr Cylinder

rman · Post by **rman** » Wed May 25, 2011 5:56 am

Hi all,
Does anybody have any experience with their abs control mod malfunctioning in such a way as to cause the master cylinder not to function properly? This 2000 v70 has been largely sitting for a few months, opened abs mod,re soldered pins, put it back on-No lights on dash for it but waiting to pull codes. When I drove it, peddle would go down without building pressure-had to pump it up to get anything appreciable. . It strikes me as unrelated but hey..a knowledgeable person said these mast cyls rarely fail..My fluid is clean and full with no detectable leaks
Thanks

Post by **jimmy57** » Wed May 25, 2011 8:05 am

It is possible but falls further down the list of suspicions when you mention an 11 year old sitting for a few months.
If the ABS unit were holding a valve open due to a fault you not be able to pump it up.
Try first by bleeding rear circuit at each caliper and see what that does. Low pedal on FWD with the fixed dual piston calipers has been seen a lot.
The failure rate for master cylinders is not high but it goes up drastically at 10 years of age.

Post by **EstVolvo** » Wed May 25, 2011 8:48 am

Why did you re-solder the ABS module - did you have ABS light on or something else?
How were your brakes before the re-soldering?
I have the same car with intermittent no brake override every now and then and no ABS light. I have been thinking of re-soldering ABS module.

Post by **JRL** » Wed May 25, 2011 5:12 pm

Flush the brake fluid and try again

rman · Post by **rman** » Wed May 25, 2011 6:57 pm

Thanks Guys! I will look at bleeding the rear circuit- and that's also the second "flush the system " I've heard.
And Estvolvo- the previous owner had it go into limp mode, dealer pulled codes and said the abs control module was malfunctioning and to replace it..The abs light did come on and something else i think.. at any rate, they cleared the codes and it got driven for another month with no light on. I got the car,and its not been driven really since january to speak of. So, I took off the module, cut it open, examined the pins on the board( under a magnifying glass) saw 3, maybe 4 that had cracked solder joints and reheated them with a solder iron(40 watts). put it back and here we are. Oh, this car has 176,000 plus miles..

Post by **EstVolvo** » Wed May 25, 2011 10:15 pm

It sounds like you lost brakes after re-soldering the ABS module?

rman · Post by **rman** » Thu May 26, 2011 7:36 pm

I'm not altogether sure, it hadn't been driven, then I soldered the abs module, put it in and drove it and no pedal. went out with the abs module unplugged- no dash light, no brakes. going to bleed the secondary/rear circuit and check it saturday

Post by **jblackburn** » Thu May 26, 2011 8:52 pm

Your brake lines may be dry-rotted and slowly leaking if the car's sat for a really long time - give them a good once over when you get around to it this weekend.

rman · Post by **rman** » Sun Jun 12, 2011 11:28 am

Guys, Thanks for the help! As Jimmy57 mentioned, I bled the rear calipers and the pedal came up and held pressure..just went on and did the fronts also while I was at it and it acts as it should now..strange,but.. So,No connection to abs module in the in the symptom department. Abs fine at this time.