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1996 850R intermittent brake pulsation over bumps

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, 850 R, 850 T5-R, 850 T5, 850 GLT
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
1997 - 2000 V70-XC
1997 - 2004 C70

wackenhut
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1996 850R intermittent brake pulsation over bumps

Post by wackenhut » Thu Jun 13, 2019 7:48 am

I have noticed in the last few days that at least one time per driving, the brake pulsates (seems like abs is kicking in) when going over bumps. This has never occurred before. Does anyone have any idea what could be causing this. There are no codes coming up. Any help is much appreciated.

Thank you.

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bmdubya1198
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Re: 1996 850R intermittent brake pulsation over bumps

Post by bmdubya1198 » Thu Jun 13, 2019 8:33 am

My '98 has done that too. How do your brakes perform otherwise? I always associated it with pads that are too hard, and don't seem to grab very well.
Otherwise, it would be a good idea to check your brake fluid to make sure it's at the proper level.
2000 V70R Venetian Red/Charcoal M56 Swapped 195k
2003 S60 2.4T Silver/Black 112k
2007 XC90 V8 AWD Sport Titanium Grey/Black 166k
1991 944 Turbo Dark Green/Beige 173k
1992 245 Base White/Beige 249k
2006 BMW 330i
1999 BMW 528i
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2000 S70 GLT Mystic Silver/Taupe 253k
1993 944 Base Beige/Beige 221k
1998 V70 GLT Black/Beige 199k
1998 S90- Silver/Gray 207k
1995 850 GLT Tropic Green... crushed
2001 S60 2.4T Black/Black 230k
1988 744 Turbo M46 Beige Metallic/Beige 188k

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abscate

Re: 1996 850R intermittent brake pulsation over bumps

Post by abscate » Thu Jun 13, 2019 8:55 am

If the wheels are losing traction on a bump, the traction controls (TRACS or STC) uses ABS to control wheel spin - that might be it.
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wackenhut
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Re: 1996 850R intermittent brake pulsation over bumps

Post by wackenhut » Thu Jun 13, 2019 9:07 am

Just strange that all the sudden this started happening

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Re: 1996 850R intermittent brake pulsation over bumps

Post by WhatAmIDoing » Thu Jun 13, 2019 8:28 pm

It is more likely for your wheels to lock up when braking on a rough surface, because there is more rolling resistance. I know on my last trip through PA, every braking event set off ABS because the roads are nothing but potholes.
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Re: 1996 850R intermittent brake pulsation over bumps

Post by tardcart » Thu Jun 13, 2019 8:35 pm

start by turning tracks off, also may be the insulation is gone on the pump wires and they are arcing.

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Re: 1996 850R intermittent brake pulsation over bumps

Post by wackenhut » Fri Jun 14, 2019 5:37 pm

I just noticed now, that the TRACS OFF Light is permanently illuminated. Does this help any in the diagnosis of the issue?

Thank you

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Re: 1996 850R intermittent brake pulsation over bumps

Post by bmdubya1198 » Fri Jun 14, 2019 8:47 pm

Nothing changes when you hit the TRACS button? That could be indicative of a failing ABS module, or other ABS/TRACS issues. You can't get flash codes on a '96, right? You probably need Vol-FCR or 850-OBD2 on Android to read ABS codes.
2000 V70R Venetian Red/Charcoal M56 Swapped 195k
2003 S60 2.4T Silver/Black 112k
2007 XC90 V8 AWD Sport Titanium Grey/Black 166k
1991 944 Turbo Dark Green/Beige 173k
1992 245 Base White/Beige 249k
2006 BMW 330i
1999 BMW 528i
Sold-
2000 S70 GLT Mystic Silver/Taupe 253k
1993 944 Base Beige/Beige 221k
1998 V70 GLT Black/Beige 199k
1998 S90- Silver/Gray 207k
1995 850 GLT Tropic Green... crushed
2001 S60 2.4T Black/Black 230k
1988 744 Turbo M46 Beige Metallic/Beige 188k

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