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Brakes calipers are engaged when not pushing on brake pedal.

Help, Advice, Owners' Discussion and DIY Tutorials on Volvo XC90s. The XC90 proved to be very popular, and very good for Volvo's sales numbers, since its introduction in model year 2003 (North America).
weespoon
Posts: 7
Joined: Fri May 27, 2016 9:02 am
Year and Model: 2003 XC90
Location: Asheville, NC
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weespoon

Brakes calipers are engaged when not pushing on brake pedal.

Post by weespoon » Fri May 27, 2016 9:11 am

Brakes calipers are engaged when not pushing on brake pedal.

Synopsis: Replaced Master Cylinder, Brake Booster, ABS system, pressure bled, brakes appear engaged.

More Detail:
My brake pedal was fading to the floor, and the brake booster was hissing. I replaced the master cylinder and brake booster.
The brake fluid was awful, dark and very gloopy.

Then when I pressure bled the brakes I noticed no fluid made it to the RR brake. I traced this back to the ABS unit. I ordered a used ABS unit, attached in the new ABS system and pressure bled all brakes: LF, RF, LR, RR.

The ABS unit light is on, which I expected, hoping to drive to dealer to get them to do some VADIS magic on it. But the problem is that my brakes are clamping even without foot on pedal.

With no pressure bleeder I bled again same order, sealing the brake nipple when the foot was down on pedal. There appears to still be pressure in the lines, even though I have bled twice same order. I looked for a ballooning flexible line, while braking and do not see one.

I can't drive the car to the dealer with the brakes engaged? Even driving a short distance they heat up. Suggestions of what to try next?
Current:
2005 V50 T5
2003 XC90 T6
2001 V70

Prior:
XC70, V70, 200 series Wagons and Sedans

weespoon
Posts: 7
Joined: Fri May 27, 2016 9:02 am
Year and Model: 2003 XC90
Location: Asheville, NC
Has thanked: 0
Been thanked: 0
United States of America
weespoon

Re: Brakes calipers are engaged when not pushing on brake pedal.

Post by weespoon » Sat May 28, 2016 7:37 am

Worked on it some more, still an issue.

The brakes work at first, pedal nice and high, minimal pressure to stop.
After driving all brakes clamped.
After driving, if I relieve pressure on DF all brakes release.
All of these brakes (with exception of DR) were working correctly prior to main cylinder, booster and abs.

I removed each tire, opened brake bleed nipples, expanded calipers. DF, PF, DR, PR.
All wheels moved freely.

I drove car 2 miles at avg speed of 30 mph with minimal braking.

When done, brakes were hot and all brakes were clamped.

Messages include:
Anti Skid needs service
Brake Assist needs help (this message comes on after braking)
Engine Service Required

I believe the brake assist vacuum switch and pump may not be working.
But I was under the impression that this would simply make cold braking more difficult.
Current:
2005 V50 T5
2003 XC90 T6
2001 V70

Prior:
XC70, V70, 200 series Wagons and Sedans

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