Forums34
Topics48,346
Posts813,056
Members9,208
|
Most Online1,046 Aug 24th, 2023
|
|
|
Joined: Oct 2013
Posts: 135
L - Learner Plates On
|
OP
L - Learner Plates On
Joined: Oct 2013
Posts: 135 |
My 94 plus 8 disk brakes start dragging when the car heats up. You can feel it when you come to a stop, it grabs and doesn't roll when the pedal is released. I jacked up the car and confirmed it at the wheels as well.
I thought that it might be too much fluid in the master cylinder so I siphoned some out with no improvement.
Car has headers and dual exhaust fyi.
I am wondering if master cylinder that is located close the the headers could be causing the issue?
Anyone have experience with this type of Thing? It's a first for me. Thanks
2019 M3W 110 Anniversary Black Previous: 2005 Plus 8
|
|
|
|
Joined: Feb 2011
Posts: 1,484
Has a lot to Say!
|
Has a lot to Say!
Joined: Feb 2011
Posts: 1,484 |
Could be thermal expansion of the disc pistons. I might pull the wheels and pull the pads and pistons. Clean the pistons to be sure they aren't rusty or corroded in any way and free to move in and out properly. I have never heard of temp sensitivity with brake fluid.
Cheers,
Mark
1934 SS MX4 1938 Series 1 DHC 1951 Plus 4 2005 Roadster
|
|
|
|
Joined: Jan 2012
Posts: 14,976 Likes: 1
Member of the Inner Circle
|
Member of the Inner Circle
Joined: Jan 2012
Posts: 14,976 Likes: 1 |
Does the brake pedal have enough slack movement. If the pedal is too "tight" the breather hole in the master cylinder might not be able to vent and cause the effect of the brakes staying on.
I made this mistake when I changed my brake master cylinder.
Richard 1976 4/4 4 Seater
|
|
|
|
Joined: Nov 2015
Posts: 52
Just Getting Started
|
Just Getting Started
Joined: Nov 2015
Posts: 52 |
I'll second Richard's advice. This is exactly what happens when the master cylinder cannot fully retract. regards, Phil
|
|
|
|
Joined: Jul 2016
Posts: 19
New to Talk Morgan
|
New to Talk Morgan
Joined: Jul 2016
Posts: 19 |
Are you using silicone brake fluid by any chance? I have had this issue with a TR3 and an Alfa after changing to silicone fluid. In both cases the brakes took a couple of seconds to release fully when hot after coming to a halt and releasing the pedal. They didn't remain hard on though, just sticky. I think there is possibly less lubricity in the silicone fluid and it took longer for the caller pistons to retract. Just a thought but could be barking up the wrong tree.
|
|
|
|
Joined: Jan 2012
Posts: 14,976 Likes: 1
Member of the Inner Circle
|
Member of the Inner Circle
Joined: Jan 2012
Posts: 14,976 Likes: 1 |
The advice from SimonH here was spot on when this happened to me.
Richard 1976 4/4 4 Seater
|
|
|
|
Joined: Dec 2008
Posts: 21,868 Likes: 167
Roadster Guru Member of the Inner Circle
|
Roadster Guru Member of the Inner Circle
Joined: Dec 2008
Posts: 21,868 Likes: 167 |
A sticking servo can also cause momentary drag.
DaveW '05 Red Roadster S1 '16 Yellow (Not the only) Narrow AR GDI Plus 4
|
|
|
|
Joined: Oct 2013
Posts: 135
L - Learner Plates On
|
OP
L - Learner Plates On
Joined: Oct 2013
Posts: 135 |
I felt some play in the linkage with my foot, but have not confirmed if there is adequate play in the right places on the linkage. I will do that.
Also the sticking is not momentary fyi. Thanks
2019 M3W 110 Anniversary Black Previous: 2005 Plus 8
|
|
|
|
Joined: Jan 2012
Posts: 14,976 Likes: 1
Member of the Inner Circle
|
Member of the Inner Circle
Joined: Jan 2012
Posts: 14,976 Likes: 1 |
Simple check would be to back it off a bit and go for a drive (after a few cold and slow checks the pedal still works OK).
Richard 1976 4/4 4 Seater
|
|
|
|
Joined: May 2011
Posts: 4,896
Drive on the Wild Side Part of the Furniture
|
Drive on the Wild Side Part of the Furniture
Joined: May 2011
Posts: 4,896 |
Hi Bluesman, I had a discussion with Peter Mulberry, about the standard brake callipers on my 96 +8 when I had it. I had similar issues start but evident as a judder on light braking that only went when the pedal was pressed hard. Peter said that the issue with these callipers which should be the same as those on your 94 +8 are that they distort after many years and then the pistons can become sticky. In your case it sounds like you have one or two that are holding the piston out after braking. I firstly would check that the disks on each side are running true and in tolerance, there should only be a few thousands of inch of variation. If more the disks could have overheated and distorted. To check true jack car up at front putting on axle stands, make sure it is safe and chock the rear wheels, and in gear. Remove one front wheel at a time and then get a metal object that will stand upright that you can clamp a suitable sharp nail to.Place the pointed end immediately next to the disk at right angles so it just touches the shiny outer edge. Slowly spin the disk and see it wavers a lot from the nail point or rubs it. As already said it should only fluctuate a few thousands. Do each side and each disk, if no perceivable wavering then it is likely its the callipers. If the callipers are the next step, then you can try and take them apart and replace the piston seals, although this does not always work as the actual calliper casing can distort and grab the pistons. There are 2 alternatives, send them of to have reconditioned or bite the bullet and upgrade to new callipers and possibly vented disks at the same time. Which is what I ended up doing in the end. I hope this helps, I would ring Peter at Mulfab first and explain you issues he is very helpful.
Adrian
Buggered Off, to a modern none leaky car, heart's still ticking
|
|
|
|
|