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1996 850R intermittent brake pulsation over bumps

Help, Advice and DIY Tutorials on Volvo's P80 platform cars -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, including 850 R, 850 T-5R, 850 T-5, 850 GLT
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
1997 - 2000 V70-XC
1997 - 2004 C70

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wackenhut
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Year and Model: 850R 1996
Location: FLORIDA

1996 850R intermittent brake pulsation over bumps

Post by wackenhut »

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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Post by bmdubya1198 »

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.
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Post by abscate »

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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Year and Model: 850R 1996
Location: FLORIDA

Post by wackenhut »

Just strange that all the sudden this started happening

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WhatAmIDoing
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Post by WhatAmIDoing »

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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tardcart
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Post by tardcart »

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

wackenhut
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Year and Model: 850R 1996
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Post by wackenhut »

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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bmdubya1198
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Post by bmdubya1198 »

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.
00 V70R Venetian Red/Charcoal M56 Swapped 214k
07 XC90 V8 AWD Sport Titanium Grey/Black 220k
92 245 White/Beige 249k
91 944 Turbo 175k
…and a bunch of other stuff
Sold-
03 S60 2.4T
00 S70 GLT
98 V70 GLT
93 944
98 S90
95 850 GLT
01 S60 2.4T
05 S60R M66
08 S40 2.4i
88 744 Turbo M46

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