I have had this a couple of times and its always been the servo, on some early servo's the rod that went through to the master cylinder was adjustable so after an adjustment it was fixed.
Also if I was you I would fit a new oil vac pump.
Also check the servo for leaks, I know its a new one but they still fail.
Flack
21st Jun 2021 10:23 am
cfcjim
Member Since: 22 Jun 2010
Location: Munich
Posts: 65
Lumberjackinfrance wrote:
Thanks to everyone for all the effort in replying and the advice.
Check if the clevis pin is moving freely and the servo actuator is not misaligned.
When you let the brake pedal off does it spring back with a decent force? i.e. when you push it down and let your foot slip off the side does it return swiftly?
If not, suspect the servo mechanism. I had one which was damaged but you couldn't tell until it was installed and the pedal was slow to return to its home position.
It was a new TRW unit. The supplier replaced it with no qualms.
21st Jun 2021 11:57 am
Lumberjackinfrance
Member Since: 07 Jun 2021
Location: France
Posts: 8
Ok, many thanks again for all your combined effort and time.
I have read all the suggestions, I watched the you tube video on the brake switch and my brake light switch was installed in the same way.
I inspected the brake pedal, the pivot and the brake pedal return when my foot comes off the pedal.
There appears to be nothing wrong with the alignment of the pivot and the pedal springs back firmly and appears that there is no delay or sticking when my foot comes off the pedal. It 'snaps' back up, or springs back up if you like, it doesn't seem it's returning wrongly in any way.
In terms of play, there is 1mm - 2mm play in the pedal when it is in the off brake position, meaning that you can lift the bottom part of where the foot sits on the brake pedal up by 1 to 2mm, it seems normal, very minor wear maybe, but certainly not loose and it is in alignment.
The part that I am now focusing on is the pedal height and or the brake light switch bracket. The reason I am focusing on this is two fold, firstly I coasted the car to a stop when the brake pressure started to stay higher than normal on the live data display, luckily I live in the very quiet country and very few if any cars drive in my area, so I just coasted to a stop without touching the brake pedal. Once the car stopped I got down and pushed the brake switch bracket closer to the brake pedal and the brake pressure immediately reduced to normal.
I did not move the pedal or pivot or servo rod, only pushed the brake light switch closer to the pedal, the bracket flexed and the switch moved closer, the bracket flexed back when I let go.
This lead me to look at the distance between the switch and the pedal.
This is an image of the distance between the pedal and switch when it is in the normal foot off position.
I felt it was worth a try bringing the switch closer to the pedal, so I adjusted the brake light switch bracket
This is after I adjusted the bracket, so the switch is now depressed a lot more when the pedal is not in use.
I just drove the disco round the farm with a trailer on, and there is no brake drag, but it's early days, I will take it for a longer run this afternoon and check the disk temps and monitor the mpg and report back what I find.
If.... If this solves the problem it could be the new servo doesn't quite come up to the brake pedal enough or it could be a heffa has wedged their boot between the pedal and the bracket and just moved it out of place enough to cause the issue, or it could have been knocked during the servo install.
If it doesn't solve the issue, then I am convinced its a loose wire connection in that area, because the brake fluid pressure build up can be returned to normal by moving the brake light switch, without moving any mechanic part of the pedal, servo or cylinder.
I am not discounting anything that has been suggested at all, I am just working through things logically (and cheaply) before moving to the next possible.
I will return with an update.
Must say, this is a great forum and thanks
Lumber
22nd Jun 2021 12:59 pm
Lumberjackinfrance
Member Since: 07 Jun 2021
Location: France
Posts: 8
Update after adjusting the brake light switch bracket.
This afternoon I drove for 15 miles with a 4 meter bed trailer loaded with blocks and rocks.
There was no brake fluid pressure increase above 'normal' nor did the brake fluid pressure not go down to normal levels after braking.
The MPG has started to increase, it is normally around 30 give or take, with the brake drag issue it has been dropping to 21/23 and now it has started rising, even with the trailer to 25.5 MPG, and looks like it's still rising.
Also my gearbox jolt when slowing into roundabouts has returned, its jolts or clunks from what I guess is second into first at slower speeds, it stopped doing this when the brakes were dragging, it has returned, so to me the disco has returned to normal.
I am not saying the fault is fixed, all I can say at this time is the issue seems to have gone, but it was only a short drive, I will take it for a longer drive without a trailer this week and report back what I find.
Can a bloody brake light switch really cause so much grief????
I can honestly say I have never been so happy to hear and feel a gearbox clunk again
This issue has cost a huge amount of time and effort trying to find the issue, I wonder if I had not tried the foot lifting the brake pedal thing, how would I have found it.
It's a fine line between genius and madness......
I will report back and thank you to all that took the time to offer advice and help.
Sounds like you have found the problem, its all linked to the ABS module so it must have thrown a wobbler..
Flack
22nd Jun 2021 7:07 pm
Lumberjackinfrance
Member Since: 07 Jun 2021
Location: France
Posts: 8
I think the brake switch could be part of the problem, not sure about "all" of the problem.
Before throwing all your money at it, the brake switch is worth a go ... as is the notion of only changing one thing at a time so you know what fixed it ![/quote]
Thanks to everyone for their input, the issue is no fixed.
It was the brake light switch as I documented I adjusted the distance and it's fixed now. Took the disco for a long drive, hills, roundabouts, slow moving tractors to negotiate, fast stretches and all with no issues, MPG is back to 30, and no increased brake fluid pressure or holding the pressure higher after braking.
As to why the distance between the brake pedal and brake light switch changed? No idea, I do not have the old servo so cannot compare length of servo rod to the new RRS one, it could have been knocked out of position while the new servo was being fitted, it could have been knocked by a foot, no idea, my gut feel is the rod on the RRS servo is fractionally different to the old servo, and we are talking mills here.
Anyway the issue is now fixed.
To be clear, I checked the distance between pedal and switch, saw that it was not depressing the switch very far, removed the switch, adjusted the bracket, fitted the switch again as per the youtube video and that's it, it now works.
Thank you to all, great forum
If anyone has any questions regarding the issues I had, I will gladly help out if I can.
Cheers
Lumber
23rd Jun 2021 6:11 pm
craig_bennett
Member Since: 05 Oct 2012
Location: Bristol
Posts: 52
Thanks for the update, I'm having the same problen and have changed everything trying to fix it, including the switch. somone suggested lifting the pedal when its locked on, which did release the pressure. I think a new genuine switch might help allong with an additional return spring on the pedal.craig.
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