1988 Volvo 740

JAMES4639

MEMBER
1988 VOLVO 740

Brakes problem
1988 Volvo 740 4 cyl Two Wheel Drive Automatic

Brake system is ABS. While driving recently, brakes were working fine with normal pedal until the next stop when pedal went almost to floor and had to use hand brake to help stop. After driving (very carefully) the rest of the way home, brake pedal went to floor at stops until at the last two stops when they worked normally. No brake warning lights came on at any time. With car parked in driveway, the pedal is hard. Fluid reservoir is full. Fluid has not been changed since I got the car about three years ago. Non-Turbo.

Thanks, James

5 Replies

DOCFIXIT

MECHANIC
18,828 POSTS

Hi
When this occured did ABS/brake failure light come on? Suspect a master cylinder fault probably piston seals. Check brake operation at rears and fronts. Start car hold pressure on pedal see if it slowely bleeds off and pedal drops. If so replace master.
Let me know
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Monday, May 18th, 2009 AT 1:49 PM

JAMES4639

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3 POSTS

No, the brake warning light did not come on during the failures. The light does work as it comes on when ignition key is first turned. As per your above suggestions, I held the brake pedal down and it did not bleed down. Tried several times with car running. Also, jacked up driver side of car, spun wheels and had wife apply brakes. Both wheels stopped turning when brake applied. I also felt the rubber going from brake lines to each caliper and they all feel firm. At least when brakes not applied.

Since the car, apparently has two chambers in the master cylinder, is it likely that both failed at the same time? I don't mind changing the master cylinder, but would not like to trust the brakes if the problem was somewhere else.

Any further suggestions?

Thank, James

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Monday, May 18th, 2009 AT 3:26 PM

DOCFIXIT

MECHANIC
18,828 POSTS

No failure light is puzzling if pressure loss then it should have come on. Not likely an ABS problem unless module glitched and released all pressure. To be safe have ABS scanned to see if system functions properly.

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Tuesday, May 19th, 2009 AT 9:16 AM

JAMES4639

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3 POSTS

Thanks for the reply. Is it possible to remove all the electrical components from the ABS modulator and thereby bypass it? I have no way to scan the modulator and afraid to drive the car 20 miles to the Volvo dealer.
Thanks, James

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Tuesday, May 19th, 2009 AT 1:24 PM

DOCFIXIT