Volvo Owners Club Forum - View Single Post - S40 V40 Cars: - Master cylinder or ABS? Spongy and rumble

oliverpervasive · Sep 3rd, 2019, 19:48

So tested master cylinder as per Haynes manual - seems fine (phew can take the new one back as not taken out of box)
Next suspect was servo - seems fine = hold vaccum. Grommit lubed - all looked good.
We disconnected this ( stuck bung in the valve) and drove without assisted brakes - needed lot of force on pedal - we still got the one second rumble as you accelerated off.

It must be something to do with the ABS. Possibly the self test it does.
Took it for a burn on gravel road - wacked on brakes - ABS kicked in fine.

We tried driving with the boot up to see if we could positively ID the rumble as coming from ABS - but too tricky and dangerous.

Im not sure what to try next = possibly wheel sensors giving bad reading?
No error codes coming up.

Sep 3rd, 2019, 19:48	#3
oliverpervasive Member Last Online: Feb 4th, 2021 14:56 Join Date: Jul 2008 Location: london	ABS it is - I think. Not sure on next step. So tested master cylinder as per Haynes manual - seems fine (phew can take the new one back as not taken out of box) Next suspect was servo - seems fine = hold vaccum. Grommit lubed - all looked good. We disconnected this ( stuck bung in the valve) and drove without assisted brakes - needed lot of force on pedal - we still got the one second rumble as you accelerated off. It must be something to do with the ABS. Possibly the self test it does. Took it for a burn on gravel road - wacked on brakes - ABS kicked in fine. We tried driving with the boot up to see if we could positively ID the rumble as coming from ABS - but too tricky and dangerous. Im not sure what to try next = possibly wheel sensors giving bad reading? No error codes coming up.