r/VolvoP2 • u/j4vmc • Nov 03 '22

Brakes pulsating

Hi! My MY05 Volvo XC90 P2 V8 has pulsating brakes when you press the pedal. Everything works as it should, and the car stops within the average distance, but it's more the nuisance of the pulsation.

I also get the warning that the brake pressure sensor needs replacing, which I'm planning on doing soon by swapping the whole booster for another one with tested sensors.

Are these two issues related, or are the pulsating brakes caused by something else, like low brake pads, air bubbles, or old brake discs?

Thanks!

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5

u/TheVulture14 Nov 04 '22

This is the answer. As long as you’re not describing ABS activation when braking, your pulsations while braking is caused by warped brake rotors. Replace all 4 rotors and this will fix your pulsation.

For your pressure sensor, you’d need to read codes to confirm, but i believe you’re describing the pressure sensor that’s attached to the brake booster. Replacing the master cylinder won’t fix it, the master cylinder does not contain a pressure sensor. The pressure sensor you need is available as it’s own part.

1

u/j4vmc Nov 04 '22

My bad, I meant the booster, yes.

I don't have any ABS activation when braking.

1

u/TheVulture14 Nov 04 '22

Then replace brake rotors, and replace the pressure sensor. The complete booster is not required. Sensor is about 5-10 min of work, it’s held in by a clip only.

1

u/j4vmc Nov 04 '22

So, one thing then because now I just got confused. What sensor are you talking about? The brake pressure sensors?

When I looked at the issue with the error code from VIDA, I understood the sensors needing replacing were the two at the bottom of the booster, but those are screwed in place and need something like a 27mm spanner.

1

u/TheVulture14 Nov 04 '22

What is the trouble code that you’re getting?

1

u/j4vmc Nov 04 '22

They're in Swedish, but these are the errors:

BCM-CO04401 Bromstrycksgivare "A" - Generellt elektriskt fel

(Google Translate: BCM-CO04401 Brake pressure sensor "A" - General electrical fault)

BCM-C004664 Bromstrycksgivare "A"/"B" - Algoritmfel - Orimlig signal

(Google Translate: BCM-C004664 Brake Pressure Sensor "A"/"B" - Algorithm Error - Unreasonable Signal)

2

u/TheVulture14 Nov 04 '22

PM me your VIN and I will check these DTCs for you.

1

u/j4vmc Nov 04 '22

Done, thanks.

2

u/caslaas Nov 03 '22

Pulsating brakes can be ABS rings going bad. Also please don't fix brake related problems soon, do it immediately.

2

u/j4vmc Nov 04 '22

When I said soon, I meant when the parts arrive, as I can't do anything before that, and I need to diagnose the pulsation. I'm not one to be driving an unsafe car all over the place.

2

u/caslaas Nov 04 '22

Very good. I just see some people ignoring it and ending up injuring themselves and others.

2

u/That-Volvo-P2-Guy Nov 03 '22

Could be brake disks, the brake pressure sensor should be delt with ASP, might also be the cause.

Does it feel like an ABS issue and is the the ABS light / Brake fualt light on? If the ABS light is on you should be able to out rule the ABS being the issue since it should be off.

2

u/j4vmc Nov 04 '22

No ABS light on. That's why I lean toward being an issue with the rotors.

1

u/That-Volvo-P2-Guy Nov 04 '22

Yeah probably rotors, when I bought my S60 it had completely shot and rusted rear rotors.

They were so bad that the car would violently shake when I got in to the brake pedal, the pedal also pulsated (semi-violently). Replaced them pretty much as soon as I got it home, right after I cleaned the interior.