84 280i Brake Pressure
Discussion
Gentlemen,
Took the car for a ride yesterday and on the way home I lost brake pressure unless I pumped the pedal. Once I got home I visually inspected the car and there are no signs of leaks, reservoir is full. No issues with the brakes until now. Going to get under the car for a closer look. Any feedback would be appreciated. MT
Took the car for a ride yesterday and on the way home I lost brake pressure unless I pumped the pedal. Once I got home I visually inspected the car and there are no signs of leaks, reservoir is full. No issues with the brakes until now. Going to get under the car for a closer look. Any feedback would be appreciated. MT
Brake fluid getting hot because rear brakes are rubbing. I bet they are back to normal when let to cool. Solution, free off brakes. Sometimes the drag may not be obvious and it could be that the old brake fluid just needs changing and would cure problem. Could also be a master cylinder problem but unlikely as it only happens on a long run. It sounds heat related.
Tony.TCB.
Tony.TCB.
Not arguing with the above, just adding an idea.
It's also worth checking the master cyl isn't leaking internally (I'm assuming it's not new/recon)
This can happen when seals get worn, the fluid leaks back into reservoir, so no leaks apparent.
Do this whilst car is stood, can be engine on or off.
Press hard on pedal and hold. It should go to a certain point and stop. Check that your foot doesn't slowly sink downwards.
If it does, then you've got wear and will need new seals at least.
Also on Jag based rear setups, whilst you are there, it's worth checking the handbrake mechanism is releasing properly.
It's also worth checking the master cyl isn't leaking internally (I'm assuming it's not new/recon)
This can happen when seals get worn, the fluid leaks back into reservoir, so no leaks apparent.
Do this whilst car is stood, can be engine on or off.
Press hard on pedal and hold. It should go to a certain point and stop. Check that your foot doesn't slowly sink downwards.
If it does, then you've got wear and will need new seals at least.
Also on Jag based rear setups, whilst you are there, it's worth checking the handbrake mechanism is releasing properly.
Brake fluid is hygroscopic so over long periods of time it can absorb water and become less effective...Check for any black residue in the shelves of the master cylinder as this could be the seals failing or if the fluid looks dirty brown then definitely change it...
Have the brakes ever been hard to press?...If so then this could also be a sign of a failing brake servo/Booster...
Have the brakes ever been hard to press?...If so then this could also be a sign of a failing brake servo/Booster...
RCK974X,
The brake pedal performs as you state. I took a closer look at the rear pads and they definitely need replacing. I can see edge cracks. The hand brake does work but it takes a lot of pressure. Clearly could be adding to the problem.
Would appreciate suggestions on pads and rotors
Millard
The brake pedal performs as you state. I took a closer look at the rear pads and they definitely need replacing. I can see edge cracks. The hand brake does work but it takes a lot of pressure. Clearly could be adding to the problem.
Would appreciate suggestions on pads and rotors
Millard
"The brake pedal performs as you state."
Er... you didn't say which way !
OK, if pedal stops and doesn't sink any more, then that's good, no need to worry about master cyl. If it sinks, then it will need looking at.
if hbrake stiff, it could also be dragging on discs.
Rears - when I got mine, rears were sticking AND hbrake didn't work properly and was dragging. I ended up taking the diff out, as it's actually less work than trying to p*ss around in tiny spaces on your back trying to get the calipers out, so I did the rear UJs and one wheel bearing at the same time...
I used standard Jag pads, cleaned everything, put new seals in calipers, and dismantled the hbrake mechanism and had a good go with the wire brush.... one piston was really tough to get out without damage. The hbrake mechanism design is OK, but it's ratchet setup isn't good for muck/grime etc, and tends to stop self adjusting. Also I added some extra springs between the levers to push them apart (it's fairly obvious when you see how it works).
New brake fluid and many goes at bleeding (the pipe layiout doesn't help flush the bubbles) and finally got everything sorted. hbrake a lot lighter after clean and grease....
Er... you didn't say which way !
OK, if pedal stops and doesn't sink any more, then that's good, no need to worry about master cyl. If it sinks, then it will need looking at.
if hbrake stiff, it could also be dragging on discs.
Rears - when I got mine, rears were sticking AND hbrake didn't work properly and was dragging. I ended up taking the diff out, as it's actually less work than trying to p*ss around in tiny spaces on your back trying to get the calipers out, so I did the rear UJs and one wheel bearing at the same time...
I used standard Jag pads, cleaned everything, put new seals in calipers, and dismantled the hbrake mechanism and had a good go with the wire brush.... one piston was really tough to get out without damage. The hbrake mechanism design is OK, but it's ratchet setup isn't good for muck/grime etc, and tends to stop self adjusting. Also I added some extra springs between the levers to push them apart (it's fairly obvious when you see how it works).
New brake fluid and many goes at bleeding (the pipe layiout doesn't help flush the bubbles) and finally got everything sorted. hbrake a lot lighter after clean and grease....
Edited by RCK974X on Sunday 12th June 00:39
I had a sticking rear caliper(s) and after a short run there was smoke pouring out from the rear. Since I had previously had the MC rebuilt by Apple Hydraulics, I just changed out the rear calipers ($60 each at O'Reiley's) and changed out the fluid. Really pretty simple.
In your case I'd look to the MC as suggested. I wouldn't fool with rebuild kits. I'd get an exchange or have yours rebuilt. Bill at Dominion should have a replacement. Grady
In your case I'd look to the MC as suggested. I wouldn't fool with rebuild kits. I'd get an exchange or have yours rebuilt. Bill at Dominion should have a replacement. Grady
Hi, a little off topic although "Wesleys" brakes did have a similar problem and was a result of a binding rear brake caliper. Andy I agree after removing the rear calipers on your back is a challenge. Therefore can I ask the difficulty of removing the diff? The reason being I still have this mechanimal noise from the transmission. It sounds like a front wheel bearing, both replaced. To aid diagnosing I've put additives into both gearbox and diff, which made no difference to the noise. My thoughts now turn to the rear wheel bearings. A task for the winter unless it gets really bad. So if I go for the rear wheel bearings would removing the differential be feasible on axle stands? Cheers J C.
John042 said:
Hi, a little off topic although "Wesleys" brakes did have a similar problem and was a result of a binding rear brake caliper. Andy I agree after removing the rear calipers on your back is a challenge. Therefore can I ask the difficulty of removing the diff? The reason being I still have this mechanimal noise from the transmission. It sounds like a front wheel bearing, both replaced. To aid diagnosing I've put additives into both gearbox and diff, which made no difference to the noise. My thoughts now turn to the rear wheel bearings. A task for the winter unless it gets really bad. So if I go for the rear wheel bearings would removing the differential be feasible on axle stands? Cheers J C.
If your using stands, is better to leave the diff in place and remove the hubs and drive shafts.You can then easily remove and service the breaks, and the wheel bearings and the UJ. its worth doing all 3 while they are off.
Best to fit new bolts also with copper slip, also look at bushes, as easier to do while it's all apart.
I agree that the brakes are binding and heating/boiling the brake fluid. If the front brakes are binding you'll be able to feel one of the front wheels is much hotter than the other; if it's the rear brakes you'll be able to smell burning under the rear wheelarches.
You'll also smell burning if it's the front wheels. Be suspicious if a burning smell is following you around...
You'll also smell burning if it's the front wheels. Be suspicious if a burning smell is following you around...
Hi mate
If its stuck then there could be rust in there...If water has got into the fluid at any point...
There is a section in this very useful site....Rebuilding rear brakes.
Wedgeneering
https://www.google.co.uk/url?sa=t&rct=j&q=...
Although there is no explanation as regards to removing the offending item, Perhaps the man himself will be along to explain...
If its stuck then there could be rust in there...If water has got into the fluid at any point...
There is a section in this very useful site....Rebuilding rear brakes.
Wedgeneering
https://www.google.co.uk/url?sa=t&rct=j&q=...
Although there is no explanation as regards to removing the offending item, Perhaps the man himself will be along to explain...
280iUSA said:
Appreciate the info brother.
I hit it again with air and it moved a little, very little. I get about 125 psi on my compressor. Maybe a higher psi will blow it out.
BTW, great handle.
Be careful ...That thing is bigger than an Anti-aircraft shell....I hit it again with air and it moved a little, very little. I get about 125 psi on my compressor. Maybe a higher psi will blow it out.
BTW, great handle.
Maybe some penetrating oil to help liberate it......
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