Volvo 850 GLT 1995 - ABS Brake Groaning

mikemmb · Post by **mikemmb** » 24 Mar 2007, 13:34

[i][quote="volvo5er"]Its a pretty common issue on 850.

[quote]Pulsing brakes on 850 Series

Some early 850's sometimes suffer from a pulsing brake pedal - most noticeable when driving slowly in city traffic. This is basically a manufacturing defect: not all the plastic sheathing is stripped off the ABS sensor wires at both front wheels. A factory modification kit is available (under warranty) and fitting requires removing the existing wiring to both front wheel sensors, but not changing the actual sensors. Instead, you solder the new wires on to the loom. The connections are made inside the square plastic trunking on the nearside, near the ABS module. The joint must be soldered, as a crimped connection will cause current drop and affect the system's operation.
[/quote][/quote][/i]

Hi thanks, this sounds like the problem I have.

From the quote it seems that it is to do with the plastic sheathing on the sensor wiring?
Is it that the sheathing should have been stripped back more (and is interfering with the sensor operation), or that it was stripped back too much (and is allowing the sensor/wire to short out)??

I am way out of warranty and fear that if I go near a volvo dealer they will try to replace the whole braking system (which must cost more than the car is worth). But apart from this fault the car is as solid as a rock and I would like to fix it myself .......... any help will be much appreciated.

Thanks,
Mike

Post by **MadeInJapan** » 24 Mar 2007, 18:30

Thanks...I wonder what TSB that was....I'll ask the dealer to see if I can get more specific information or a description/pictures of the kit they sell or used to sell.

Baker · Post by **Baker** » 24 Mar 2007, 21:36

mikemmb wrote:Hi,
Is there any way of testing the sensors to see if they are working OK?
Mike

The following is not a substitute for professional advice.

Yes if you have the right test equipment.
1. Jack up the wheel.
2. Disconnect the sensor cable.
3. Connect an oscilloscope to sensor.
4. Spin wheel. You should see a very low voltage sine wave. Less than one volt. The wave decays as wheel slows. No scope? Hook up a hand held voltmeter. Set to alternating current.
5. You should not see any spikes.

Tally Ho

mikemmb · Post by **mikemmb** » 25 Mar 2007, 03:02

[quote="MadeInJapan"]Thanks...I wonder what TSB that was....I'll ask the dealer to see if I can get more specific information or a description/pictures of the kit they sell or used to sell.[/quote]

Hi, would be great if you could get details of the mod.
Please post any info you get.
Thanks,
Mike

mikemmb · Post by **mikemmb** » 29 Mar 2007, 12:38

Hi, just wondering if anyone found anything on the brake sensor mod?
Mike

agoia · Post by **agoia** » 02 Apr 2007, 01:58

GET THIS LOOKED AT!

this happened to me on a rear brake, its squeaked, then it groaned, sometimes stopping after a tap on the brakes sometimes not... and it turned out to be going from sticking caliper to locked caliper grinding the heck out of my rotor, had to replace both to the tune of like $650