02 Volvo xc70 Spongy brake issue .

Autoshaman · Post by **Autoshaman** » 11 Aug 2016, 20:34

Hello , I purchased a Volvo xc70 from auction recently and notice it had a spongy brake pedal . Upon inspection i noticed that the front pads,rotors and calipers were relatively new and that then rears were not so new but functional . I went ahead and replaced the rear pads and bled the brakes and still no change . I decided to replace the master cylinder and also double checked the front caliper anti rattle springs which were installed wrong so i reinstalled them properly and have since run a gallon of dot 4 through the lines and had some improvement but... there still not right . I drove the car activated the abs and the pedal went back to its original wicked spongy state . I bled the brakes again got some improvement but no air came out at all . Doesn't make sense . Also no abs lights are on and the car otherwise runs great . Any advise would be greatly appreciated . I have a snap on solice and have performed all the functions with no avail .

Post by **vtl** » 12 Aug 2016, 05:45

Same problem puzzled me for 3.5 years in my 05 XC70 - whatever I did, including new master cylinder and gallons of brake fluid pushed down at 30+ PSI, the pedal was spongy.

The air is trapped in ABS module and can't be pushed out of it with the bleeder alone. You need DiCE and VIDA to fix the problem. Attach your bleeder (I used Motiv), bleed one wheel (I did right rear). With bleed valve closed, go to Diagnostics->Vehicle Communication->BCM->Activation page and toggle your wheel's ABS valves, it has two of them per wheel, in and out. ABS module will buzz and click for a few seconds. Open bleed valve and you'll see a lot of air escaping. Repeat a few times.

Not sure if it's necessary to do the same for the rest of wheels, I did two wheels only, and the other one did not have any air. My brakes were finally back.

Autoshaman · Post by **Autoshaman** » 12 Aug 2016, 10:19

I can perform this with my Solus pro but i think it crashed ! Thanks Vtl . Any advise on wheel studs that wont come out ? I broke two snap on breaker bars and numerous impact sockets ....

Post by **vtl** » 12 Aug 2016, 10:28

Did you try to rotate clockwise (tighten) as well? That helps to break the fused/cold welded layer. Also the key is not just apply maximum torque in one motion, but do it in steps, pushing and relaxing, pushing and relaxing. Impact wrench may also help to weaken the welded layer.

You can also try ot heat the lug's head with a large soldering iron, but you need a really mighty one, 100 Wt, perhaps.