Brakes: 70: Strong vibrations in the pedal

[Volvo V70 diesel]

Hy everyone,
I had an issue with my ABS System recently. A feeling I was driving over an tree trunk something like that. I get out the front ABS sensor and cleaned them, they were looking good.

The pedal brakes came back to a normal use, no shaking. But again, this afternoon, the feeling described up : a shake in the pedal. I've disconnect the ABS by the switch on the board.

Does it means that I should think about changing the ABS block ?

VV 70

[SteveSarre]

Hi

Not sure what you mean by "driving over a tree trunk". Trunks are pretty big!

Do you get the strong buzz that the ABS makes when it activates? (You can test the ABS by choosing a safe place and braking hard on a slippery surface. You dont have to be going fast).

If it buzzes when a wheel starts to skid, then it is working correctly.

Steve

[Volvo V70 diesel]

Hy,

Something new happened. While I was driving to my sport lesson, I've heard again a sort of vibrating noise like a "zzzzzzzzzzzz" which seemed to come from the motor bay, an locating in the car on the board, around the speaker cover driver side. I had to brake because the car above me, and I realized that the noise was running to the brake pedal and when I braked, it stopped the noise directly and I heard again the sensation one driving over a tree trunk...

Before looking at the ABS could it be the master cylinder rather ?

A friend of mine thinks about the brake booster : I have got a brake booster on my volvo TDI ?

VV 70

[GreenBrick]

This does sound like the ABS is firing at the wrong time especially if taking the power off the unit stops the vibration.
If it is not throwing up any warning lights though I would get the whole system checked before replacing anything expensive.

[Luxobarge]

Corroded or cracked front ABS reluctor rings will cause symptoms like this. It won't throw a fault light as the system just thinks one wheel is skidding, so it reacts in the way it's supposed to.

[Bob 88]

I need to replace the front reluctor rings on my '97 V70.
The OEM part is £42 and aftermarket replacements are available on eBay for less than £10.

Are the aftermarket ones okay?

[Martin Cox]

Bob 88,

I've just fitted a pair of aftermarket ones to the front of my V70 since the originals had corroded away and both had split. Strange to relate but the ABS was still working perfectly but goodness knows how!

Anyway the aftermarket ones went on easily enough after cleaning up the surface of the CV joint where they fit. The ABS has continued to work perfectly since they were fitted.

The originals lasted 21 years so after just a month, it's probably too early to tell if getting the aftermarket ones was a false economy. Unfortunately I can't remember where I got them from but they looked decently made as far as I could tell. Doubtless time will tell!

[Martin Cox]

Volvo V70 Diesel,

I'd be inclined to suspect the soldering on the ABS module. This is a well documented problem and can cause the problems you are experiencing. In my case it was spurious triggering of the ABS when driving over potholes. Resoldering the connectors on the ABS module cured it.

If you are adept with a soldering iron you can do it yourself.

A search on ABS module repair should give some useful results

[mike19691969]

OP Have you got access to VIDA?

I had this very problem last week and it was a simple solution but would have been impossible without Vida and this forum of course.

In short I had the ABS activating constantly when braking below 30mph. Originally I had an ABS sensor fault on FR and I also changed both front Reluctor rings as they where in poor condition. This cleared the fault but the pedal issue was still there and the only way I saw what was going on was to go for a drive with Vida showing the speed reading for each wheel. this showed me that the FR sensor was saying the speed was dropping when it wasn't, which I can only assume the system interpreted as a wheel locking thus activating the ABS.

My problem was rust below the sensor mating surface causing it to move away from the ring.

If I was you I would do the simple stuff before going the solder route, I was about to but good advice on here sorted it for me another way.

P.S. the aftermarket reluctor rings are good enough as I have been running them on other volvos for years

[SteveSarre]

Hi

I have bought some reluctor rings in the past from https://jandrcvjoints.co.uk which were very cheap.

I left them sitting around (in a damp shed) for a while and they rusted. So when fitting some new rings would I think of applying a thin coat of paint or some other protection. Hopefully that wouldn't interfere with the sensors (but if it did it could be a lot of work to strip it off again).

Maybe worth getting rings which already have some sort of corrosion protection.

Steve