Member Since: 28 Apr 2015
Location: Doncaster
Posts: 208
I had a similar issue this summer which plagued me for a good 3 months but I was also getting some wheel wobble at speed. Turned out to be a restriction in the abs module I assume caused by forcing the pistons back in the caliper on the n/s front during an earlier disc change. Removed, cleaned and blew out all the ports in the module and it has been fine since.
Pushing back the pistons and clamping off the n/s front caliper proved the theory - no wobble and normal(ish) pedal consistently. If you are going to go clamping off calipers please be very careful, they pull VERY strongly with only one side working
3rd Nov 2023 8:48 pm
seacutter
Member Since: 07 Oct 2021
Location: Lauderdale
Posts: 17
Update; replaced calipers and issue remains
Just a quick update. I’ve now replaced the calipers too. Initially thought it had solved it but on my third drive it returned.
I’m now thinking that I didn’t correctly bleed the system back when I replaced the master cylinder. I.e. I only bled the old fashioned way. Not the purge abs module way (via scan tool) in addition to old school way.
Maybe there is some air trapped in the system that is stopping the pistons from returning after applying brakes.
This is very hard to diagnose too as I just can’t figure out a way to make the issue happen, it seems to just be somewhat random.
19th Nov 2023 8:41 am
seacutter
Member Since: 07 Oct 2021
Location: Lauderdale
Posts: 17
Nc1989 wrote:
I had a similar issue this summer which plagued me for a good 3 months but I was also getting some wheel wobble at speed. Turned out to be a restriction in the abs module I assume caused by forcing the pistons back in the caliper on the n/s front during an earlier disc change. Removed, cleaned and blew out all the ports in the module and it has been fine since.
Pushing back the pistons and clamping off the n/s front caliper proved the theory - no wobble and normal(ish) pedal consistently. If you are going to go clamping off calipers please be very careful, they pull VERY strongly with only one side working
Thanks Nc1989, I'm interested to hear if you had to do the electronic ABS Purge / bleed command procedure following this work, or if just a normal 'old school' bleeding method is ok?
20th Nov 2023 12:17 am
seacutter
Member Since: 07 Oct 2021
Location: Lauderdale
Posts: 17
Update; have ordered new flexi hoses. Doing a full flush with new fluid first though.
22nd Nov 2023 6:32 am
seacutter
Member Since: 07 Oct 2021
Location: Lauderdale
Posts: 17
Admirable wrote:
Have you checked the servo for oil deposits?
loanrangie wrote:
That is usually the case but its possible that you have too much vacuum.
Forgot to update; I checked the Brake Booster again for oil and had none. It certainly does seem to hold a lot of vacuum when I disconnect the pipe and release the pressure though. I'm unsure how much is normal.
New flexible lines for FR/FL going on tomorrow and a full bleed.
28th Nov 2023 9:14 am
seacutter
Member Since: 07 Oct 2021
Location: Lauderdale
Posts: 17
If anyone else has this issue I found I could just disconnect the booster and release the vacuum, this was like a full reset and the brakes back to normal.
New booster went on today and brakes are perfect now.
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